Issue |
A&A
Volume 520, September-October 2010
|
|
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Article Number | A74 | |
Number of page(s) | 57 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/200810284 | |
Published online | 05 October 2010 |
Online Material
Table 11: Orbital parameters.
Table 12: Wilson-Devinney analysis, as obtained on the basis of both photometry and spectroscopy.
Table 13: Astrophysical parameters for the primary components.
Table 14: Astrophysical parameters for the secondary components.
Table 15: Distance determination.
Table 16: Light curves: ratio of the primary minimum to the rms (I-band), rms scatters and minimum chi-squared values from WD/PHOEBE code.
Table 17: Radial velocity curves: rms scatters.
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Figure 17:
I-band light curves with |
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Figure 18: Same as Fig. 17, for 12 more stars. |
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Figure 19: Same as Fig. 17, for nine more stars. |
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Figure 20:
Radial velocity data and best-fitting RV curves.The |
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Figure 21: Same as Fig. 20, for 12 more stars. |
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Figure 22: Same as Fig. 20, for nine more stars. |
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Figure 23: Mass-surface gravity diagrams: the positions of the primary and the secondary components are indicated by filled and open symboles, respectively. The lines ares isochrones from Charbonnel et al. (1993) at Z = 0.004, with ages of 3, 5, 10, 20, 30, 40, 50 and 100 Myr. See text for comments on individual stars. |
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Figure 24: Same as Fig. 23, for 12 more stars. |
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Figure 25: Same as Fig. 23, for nine more stars. |
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Figure 26:
HR diagrams: the positions of the primary and the secondary components
are indicated by filled and open symbols, respectively. The primary is
the component with the larger mass. The evolutionary tracks from
Charbonnel et al. (1993)
at Z = 0.004, corresponding to the observed masses,
are indicated by solid (primary) and dashed black lines (secondary).
Since
these authors adopt a helium content Y=0.24+3 |
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Figure 27: Same as Fig. 26, for 12 more stars. |
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Figure 28: Same as Fig. 26, for nine more stars. |
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Appendix A: The individual binaries
Each system is discussed thoroughly in this section. We give details concerning the light-curve solution, the radial-velocity solution, the temperature and luminosity-ratio determinations and the characteristics of the spectra. Also discussed are the positions of the components in the mass-surface gravity plane and the temperature-luminosity (HR) diagram. A review of the distances and collective properties of the whole sample of 33 binaries is given in Sect. 4. Except where otherwise stated, we mean the I-band light curve when we refer to the light curve of a specific system.
A.1 4 110409
With a difference of 0.04 mag in the brightness level between
phase 0.25 and phase 0.75, this semi-detached system
displays the most asymmetric light curve among all systems studied
here.
The light curve is bright (
mag) and of high
quality, with a low rms scatter combined with a deep primary eclipse (
65).
This EB-type light curve shows a relatively strong depression occurring
just before the primary minimum. Actually, this is strong evidence for
absorption by a gas stream stemming from the (inner) L1 Lagrangian
point and seen in projection against the primary surface (HHH05).
As a consequence, the use of a ``simple'' symmetric model for
the light-curve fit is not satisfactory, resulting in a rather poor fit
despite the intrinsic quality of the observations. Therefore, this
solution was subsequently improved by adding a cool spot on the equator
of the primary component (see Sect. 3.7). The
parameters of the spot are: a colatitude of
rad (fixed),
a longitude of 0.569 rad, an angular radius of
0.3 rad and a temperature factor of 0.6,
i.e. the effective temperature of the spot is 0.6
that of the rest of the stellar surface. Although this
new synthetic light curve gives a far more satisfactory fit, the
curve
reveals that this system is certainly more complex than this ``one
circular cool spot'' model. Actually, there are still some
discrepancies at the bottom of the eclipses and just after the
secondary minimum. Nevertheless, this model is certainly sufficient to
reliably set the inclination, the brightness
ratio of the components and the maximum out-of-eclipse flux. On the
finding chart, the image of this star is slightly elongated in the
EW direction, suggesting a blend with another, fainter star,
which would lie
or slightly farther away to the West. Nevertheless, no clear sign
of a third light is seen in the lightcurve.
The RV curves are well constrained with 11 out-of-eclipse spectra and notably observations close to phase 0.75. This system was previously studied by HHH05. There are significant differences between their RV parameters and ours. Our RV semi-amplitudes are 135 and 259 km s-1, to be compared to their values of 160 and 247 km s-1. Besides a lower S/N and resolving power than us, in this particular case the discrepancy is certainly due to their admitted lack of observations close to the quadratures. Consequently, our value for the mass ratio, q = 0.52, is certainly more secure than theirs (0.65).
We found a spectroscopic B luminosity ratio of 1.45. This is higher than the photometric value (1.29), perhaps because of the large distortion of the Roche lobe filling companion. Interestingly, the brighter, i.e. primary, component has lower monochromatic luminosities than the secondary component: even though the primary has a higher bolometric luminosity, it emits mostly in the UV part of the spectrum, so that its I luminosity, for instance, is lower than for the secondary.
The most interesting parts of the separated spectra of both
components are presented in Fig. A.1.
As a consequence of the low B luminosity
of the primary, the spectrum of the latter is the noisier of the pair.
Not surprisingly, in both spectra the most prominent features are the H
I and He I lines.
It is tempting to identify a number of features in the primary
spectrum with the C II 4267, O II 4276-4277,
Si III 4553, Si IV 4089
and Si IV 4116 lines.
Nevertheless, both the lack of positive identification of the He II 4542
line for a 14
star
and the noisy profile of the He I lines
mean that one must be careful in not over-interpreting a spectrum of
rather poor quality. The better secondary spectrum displays cleaner
features. The He I 4471 and Mg II 4481
lines allow us to secure the temperature of the secondary.
By fixing the photometric temperature and B luminosity ratios, a least-squares fit of the 11 out-of-eclipse spectra provided a primary temperature very close to 32 500 K, that is to say 7000 K more than what was determined by HHH05.
Both mass-
and the HR diagrams are typical of a massive Algol-type binary. The
brighter and more massive component of the system appears to be close
to the zero-age main sequence (ZAMS), while the secondary component is
larger and far more luminous than a non-evolved star of the same mass.
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Figure A.1:
Sections of the separated spectra of the primary and secondary
components of the binary 4 110409. The scale on the
vertical axis is adapted to the size of the features in each section.
The red line represents the best-fit synthetic spectrum shifted to the
systemic velocity. Besides prominent H I
and He I lines, Mg II
and Si III lines are visible in
the spectrum of the secondary. The spectrum of the primary is far less
convincing; nevertheless Si IV lines
seem to be present next to H |
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A.2 4 113853
The best fit was obtained with a semi-detached model. Because of a
moderate rms scatter (0.017) combined with shallow eclipses (0.18 mag)
if not purely ellipsoidal variations, the light curve of this binary is
one of the poorest of the whole sample. This low amplitude is due to a
low inclination (
60
).
The
curve
reveals that the profiles of the eclipses are not perfectly
symmetrical. The quality of the data is not sufficient, though, to
trace the possible astrophysical cause of this asymmetry. On the
finding chart, the star seems fairly well isolated.
Despite only seven out-of-eclipse spectra, the RV curves are rather well constrained with observations close to both quadratures.
The S/N of the composite spectra are low (25-65) and there is a sizeable nebular emission in the Balmer lines. Because of the lack of metallic lines and the severe contamination of the Balmer lines by nebular emission, which hinders the ``disentangling'' procedure, the separated spectra of the components were not used. The least-squares fit was performed, letting both temperatures and the B luminosity ratio free to converge. It provided a temperature ratio remarkably close to the photometric one, and a spectroscopic B luminosity ratio of 0.68, which also perfectly agreed with the photometric ratio (0.68). Thus, fixing the temperature and luminosity ratios to the photometric values was unnecessary for determining a reliable temperature of the primary.
Both the mass-
and the HR diagrams show an evolved system with a primary component
seemingly half-way between the ZAMS and the terminal-age main sequence
(TAMS). On the HR diagram the primary lies much higher than
the evolutionary track corresponding to its mass. Whether this is due
to a temperature overestimate (linked e.g. with an
underestimated sky background) or to some evolutionary effect remains
to be examined. Besides, the distance modulus perfectly agrees with the
currently accepted value for the SMC.
A.3 4 117831
This faint system has a low-to-medium quality light curve of the
EA type. There is a slight ellipsoidal variation between the
eclipses, and the latter have a similar depth (0.4 mag). This is a
close detached system with similar components. The finding chart
suggests a possible slight blend with a fainter star located some
to the East of the system. No clear sign of a third light is
seen in the lightcurves though.
The RV curves are well constrained with 12 out-of-eclipse spectra and observations close to phase 0.25 and phase 0.75. The mass ratio close to one (q = 0.98) is indicative of a binary with ``twin'' components.
The separated spectra have a quality too poor to see any
useful metallic line. The Mg II 4481
and C II 4267 are barely visible.
The separation of the Balmer lines was hindered by the strong emission.
A first least-squares fit provided both temperatures and a
poorly constrained spectroscopic B luminosity
ratio of 0.97 0.11.
The WD code converged to a higher luminosity ratio
(1.17
0.05),
even when we tried to minimize it by fixing the potential of the
primary. The temperature of the primary was finally set by a fit where
the ratio of temperatures was fixed to the photometric value, and the
luminosity ratio assumed equal to one. The small number of photometric
data in the minima, especially the primary one, probably makes the
photometric
luminosity ratio unreliable and explains why the radius of the primary
component appears slightly smaller than that of the secondary one.
According to the mass-
diagram, the age of the system is about 50 Myr, assuming the
standard SMC metalicity Z=0.004. The positions of
both components in the HR diagram agree to within the error bars with
the evolutionary tracks.
This system was studied by Wyithe et al. 2002 (see Table 6). Their results were not constrained by spectroscopy, thus it is not surprising that they found a very different solution. They considered this system as a semi-detached binary with a photometric mass ratio of 0.157. Our spectroscopic results completely rule out that model.
A.4 4 121084
This system displays deep eclipses (>0.6 mag) of similar depth. A slight ellipsoidal variation is visible. This is clearly a close detached system with slightly distorted twin components. No clear sign of crowding is seen on the finding chart, except possibly with very faint neighbor stars.
The RV curves are well constrained with nine out-of-eclipse observations regularly distributed around the quadratures.
The composite spectra are polluted by strong nebular emission
in both H
and H
lines.
Nevertheless, the widely separated Balmer lines allow a reliable
temperature and luminosity ratio determination. The separated spectra
are useful to confirm the rather high
values
of the components. Not surprisingly, no metallic lines are visible
because of the moderate S/N
combined with fast rotational velocities. The potential of the primary
was fixed so that the luminosity ratio given by the WD code
matched the spectroscopic one. The temperature of the primary was
obtained by fixing the temperature ratio to the
photometric one.
Both stars lie on the ZAMS, both in the mass-
and HR diagrams. On the HR diagram, however, they are
clearly more luminous and hotter than their expected positions for a
metalicity Z=0.004. They would better agree with
the ZAMS and evolutionary tracks for Z=0.001,
as many other systems do. Moving the representative
points to the their expected positions for Z=0.004
would
require a 2000 K decrease in effective temperature; that seems
high, but the residuals between the observed and synthetic composite
spectra show only very subtle changes. Only a modest systematic effect
might be responsible.
A.5 4 121110
The medium-to-high quality light curve shows a deep (0.5 mag)
primary eclipse. A slight ellipsoidal variation is visible
between the eclipses. This is again a close detached system with
slightly distorted components. No star closer than
is seen on the finding chart, except for a very faint one lying about
away to the SW.
The RV curves are well constrained with 11 out-of-eclipse spectra.
There is strong nebular emission in both Balmer lines. The
spectroscopic B luminosity ratio
(0.415 0.047)
nicely agrees with the photometric one (0.424), without any
need for fixing the potential of the primary. The temperature of the
primary was fitted after fixing the temperature and luminosity ratios
to their photometric values, as ususal. The Si III 4553
line is clearly visible on the separated spectrum of the primary. The
lack of Mg II 4481 confirms the
relatively high temperature of the primary. The spectrum of the
secondary is too noisy for the
identification of metallic lines.
On the mass-
diagram, the stars match an isochrone corresponding to about
7-8 Myr. In the HR diagram, the positions of both
components are above the Z=0.004 evolutionary
tracks but are consistent with the lower metalicity ones (Z=0.001).
Increasing the helium content would also help to reconcile their
positions with the evolutionary tracks, unless a systematic effect
raises
the apparent effective temperatures.
A.6 4 121461
This is an eccentric system with two (relatively) widely separated
components. Both eclipses are very similar in depth and width. With mag,
this is one of the faintest systems in our sample. Nevertheless, the
finding chart indicates no crowding problem whatsoever.
No significant apsidal motion was found on the basis of
photometry. An analysis with the EBOP code shows that the
value
depends critically on the
quantity,
which is poorly constrained, while the more robust
quantity
is such that
and thus does not constrain
very tightly. Figure A.2
suggests a marginal decrease of
with time which, if real, could only be due to gravitational
perturbations from a third body, because
,
while pure tidal effects always result in
.
We have assumed no apsidal motion.
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Figure A.2:
Variation with time of the |
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This system is one of the two in our sample with 16 out-of-eclipse spectra, of which 15 were used (the eighth has too poor SNR). There is a sufficient number of observations close to the quadratures.
The composite spectra are very noisy. The separated spectra
are of a very poor quality, with no exploitable metallic lines. There
is strong nebular emission. Letting the temperature of both components
free to converge (together with the B luminosity
ratio) resulted in very uncertain
values, so we fixed the temperature ratio to the photometric
one to estimate the temperature of the primary. The rotational
velocities were fixed to the pseudosynchronized values.
A luminosity ratio of 0.95
0.06 was found on the basis of the spectra, which agrees well with the
photometric one (0.91
0.03) obtained without fixing the
potential of the primary. The photometric luminosity ratio was adopted,
which results in almost identical radii for the components. This
results in a slightly lower surface gravity for the secondary component
than for the primary because of the mass ratio, but this difference is
not significant.
On the mass-
diagram, this system lies close to the ZAMS but might be up to
15-20 Myr old. The positions of the stars in the
HR diagram agree within the error bars with the evolutionary
tracks, although they tend to lie too high, as is the case of
other systems.
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Figure A.3:
Example of observed spectra close to a quadrature. Both spectra are at
the same scale. The red line represents the composite synthetic
spectrum of the binary system, i.e. the addition of the scaled
and velocity-shifted synthetic spectra of the two components for the
corresponding orbital phase. Besides a low S/N,
the spectrum of 4 121461 shows strong nebular emission in the
Balmer lines. From the best fit the B luminosity
ratio was found to be |
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A.7 4 159928
This system presents low-to-medium quality light curves of the
EW type with eclipses of unequal depth. The rms scatter of the
light curve is rather low, but the minima are not very deep (
mag).
It can be inferred from this that the system comprises close,
strongly distorted components of unequal brightness. The best-fitting
model corresponds to a
semi-detached binary with a low inclination, close to
.
The finding chart shows a well isolated target, except for a quite
faint neighbor at about
to the NNE.
There are only eight out-of-eclipse spectra, but they are close to the two quadratures.
A spectroscopic luminosity ratio of 0.45 was found in the B band,
which is higher than the photometric value (0.36). The
temperature of the primary was determined by fixing the temperature and
luminosity ratios to the photometric values, after suppression of the
very strong nebular emission lines. The Si III 4553
line is the only metallic line clearly visible in the
separated spectrum of the primary. The spectrum of the secondary shows
no exploitable metallic line. The Mg II 4481
is barely visible. The synchronized values for
are close to 200 km s-1 and
therefore all but the strongest lines are buried in the noise.
Both the mass-
and HR diagrams show positions typical of a semi-detached system with
an evolved secondary component. The primary is slightly overluminous
relative to the evolutionary track of a single star.
A.8 4 160094
This detached system of moderate eccentricity presents low-to-medium
quality light curves with rather shallow eclipses (
mag).
Except for a few very faint neighbors, the target seems free from
crowding on the finding chart.
There are 11 out-of-eclipse spectra. Both quadratures are well covered by the observations.
The
of the primary was determined together with that of the secondary and
with the B luminosity ratio. The
temperature of the secondary proved rather ill-defined, so the
photometric temperature ratio was used to define it,
as usual. The potential of the primary was fixed to a value
that implies a luminosity ratio close to the spectroscopic one.
No metallic lines are visible in the very noisy separated
spectra. The nebular emission is strong in both H I lines.
Despite the moderate quality of the photometric and
spectroscopic data, the positions of both stars fall right on the ZAMS
in the mass- diagram.
In the HR diagram, their position agree well with the
evolutionary tracks, though they appear slightly overluminous.
A notable characteristic of this system is its fast apsidal
motion
1.9
yr-1.
Figure A.4
shows the
product as a function of time, as obtained using the EBOP
code. The solid line represents the WD solution, which appears
consistent with the EBOP results, even though the latter would be
compatible with a faster apsidal motion coupled with a slightly smaller
eccentricity. Further discussion of this result is deferred to
Sect. 4.
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Figure A.4:
Variation with time of the |
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A.9 4 163552
This is one of the five systems with mag,
displaying a high-quality light curve of the EB type. The eclipses have
very similar depths (
mag),
indicating that the temperature ratio is very close to unity. Some
faint neighbors are seen on the finding chart about
from the target, and it is difficult to judge whether closer neighbors
might lurk
within the relatively large spot left by this bright system. According
to the light curve, there is a substantial third-light contribution to
this system: we find
,
while Graczyk (2003,
hereafter dG03) found
.
A significant ellipsoidal variation is indicative of tidally distorted
components, though the system is still in a detached
configuration.
There are only nine out-of-eclipse spectra, but the RV curves are well constrained near quadratures.
The observed spectra of this binary were roughly corrected for
the presence of a third component, by subtracting a constant
from the normalized spectra. The value of the constant was adjusted
until the effective temperatures obtained from the least-squares fit to
the corrected spectra give a reasonable match to the evolutionary
tracks at the metalicity Z=0.004 in the
HR diagram. A constant of 0.1 only proved
sufficient to this purpose, which is widely different from
dG03's photometric estimate of the third light, .
On the other hand, our WD analysis resulted in
,
which is more consistent with our rough
spectroscopic estimate. Actually, a first attempt to analyze
this system resulted in highly overluminous components. This was
interpreted as a clear sign that the observed spectra were
severely contaminated by the object responsible for the photometric
third light.
The separated spectrum of the primary shows a faint Mg II 4481 line and a noisy Si III 4553 line. These lines were used to constrain the temperature of the primary. The Si III 4553 line is visible in the spectrum of the secondary too.
This system was studied by HHH05, dG03 (see his Fig. 6) and WW02. Only dG03 took the third-light contribution into account. Not surprisingly, our photometric solution is very close to theirs.
Since we adjusted the amount of third light so that the
primary component have a realistic luminosity, the HR diagram shows a
primary close to the stellar evolutionary track of a 9.6
star, and a secondary close to the evolutionary track of a
9.1
star. Their positions are clearly far from the zero-age main sequence.
From the mass-
diagram,
the age of the system is estimated to be 20 Myr.
As the position of the primary was inferred from the expected
position in the HR diagram, the proposed solution is not
entirely reliable and thus is not used for the determination of the
mean distance modulus of the
SMC (see Sect. 4.6).
A.10 4 175149
The medium-to-high quality light curve of this system is of the
EB type; unfortunately, most of the right part of each eclipse
is missing. That is due to a period very close to 2 days
exactly. The minima are fairly deep (
mag),
well-defined and of unequal depth. There is a strong ellipsoidal
variation. The binary is a semi-detached system, with distorted
components of different brightnesses. A slight depression
occurring before the primary eclipse is indicative of a gas stream.
However, we did not venture into adding a spot on the primary in order
to mimick this effect, because we felt that the large gaps in the light
curve already limit the reliability of the proposed solution.
This system is close to the edge of the CCD used in the OGLE II survey, so it was also listed under the designation 5 38079 in the OGLE database. Thanks to that circumstance, there are 574 photometric I magnitudes instead of less than 300. An examination of the OGLE finding chart reveals that this binary is clearly blended.
This is the second system with 16 out-of-eclipse spectroscopic observations. Because of the 2-day period, all these observations took place before the quadratures. Nevertheless, the RV curves seem to be sufficiently constrained.
A spectroscopic B luminosity ratio of 1.39
was found, though with a large scatter (
). This is higher than the
photometric value (1.18). The separated spectra are fairly
good.
The spectrum of the hot primary component displays the He II 4200
and 4542 lines. The Si III 4553
and a faint Si IV 4089 lines are
equally visible. These lines provide strong constraints for the
temperature of the primary. The best-fitting primary temperature was
obtained after fixing the temperature and luminosity ratios to the
photometric values.
The mass-
diagram shows the typical oblique orientation of the segment connecting
the components of an evolved binary. The HR diagram shows a
highly overluminous primary, relative to the evolutionary track of a
11.8
star, and an evolved secondary far more luminous than a main-sequence
star of 7.8
.
One may wonder whether the strange position of the primary is due to an
unrecognized third light, both in photometry and spectroscopy,
or to some evolutionary effect. In any case, there is no
obvious third light in the light curve.
A.11 4 175333
This slightly eccentric system presents low-to-medium quality light
curves of the EA type. This is one of the few systems with mag.
Consequently, the
curve
shows a relatively high scatter. The minima are of unequal depth.
A slight ellipsoidal variation is visible. This is clearly a
detached system with components of unequal brightness. The target
appears perfectly isolated on the finding chart.
There are 14 out-of-eclipse spectra. The observations well constrain the RV curves.
This system was studied by WW01. That they consider the eclipses as total (while we consider them as partial) and their lack of spectroscopic constraints on their ratio of radii account for the differences between their solution and ours. The evidence for total eclipses does not appear compelling, so additional photometry would be needed to settle the issue. We found a spectroscopic B luminosity ratio of 0.55, slightly lower than that finally adopted taking photometry into account. The separated spectrum of the primary shows a noisy Mg II 4481 line. The spectrum of the secondary is too noisy to detect any metallic line. The temperature of the primary was fitted with the temperature and luminosity ratios fixed to the photometric values. The fit with both temperatures free to converge, together with the luminosity ratio, gave a rather large scatter of about 1600 K and a secondary temperature about 900 K cooler. In spite of the partial eclipses, there was no need to fix the potential of the primary in order to find a B luminosity ratio that matches the spectroscopic value, so the photometric value of the luminosity ratio was adopted.
On the mass-
diagram, both stars fall right on the 20 Myr isochrone. On the
HR diagram, however, both stars appear significantly
overluminous relative to their evolutionary tracks, suggesting that the
effective temperatures may be overestimated by at least
2000 K! Strangely
enough, the color excess of this system appears to be small (
E(B-V)=0.07)
and the distance modulus (18.6) clearly smaller than the
accepted value for the SMC (
). If the effective
temperatures had indeed been overestimated, this would have implied
both an intrinsic color that is too blue and an intrinsic luminosity
that is too large (hence a more negative absolute
magnitude), so one would rather expect a high color excess and
a high distance modulus.
A.12 5 016658
This close detached system presents medium quality light curves with eclipses of equal depths, and is composed of tidally distorted twin components. The finding chart reveals no crowding problem.
There are 11 out-of-eclipse spectra. The RV curves are well constrained by the observations around phase 0.25.
This system was studied by WW01. As for the previous binary,
the differences observed between their (photometric) solution and ours
is due to their lack of a spectroscopic constraint on the ratio of
radii, and because they assume total eclipses. Evidence for the latter
is not compelling, however, and awaits further photometric measurements
for confirmation. A spectroscopic B luminosity
ratio of 0.60
was found, which guided the choice of the potential of the primary
component in the WD analysis. The Mg II 4481
line is clearly visible on the separated spectrum of the primary. The
spectrum of the secondary is too noisy to show any metallic line. The
best-fitting primary temperature was obtained simultaneously with the
temperature of the secondary, which appeared quite compatible (within
300 K) with the photometric one (i.e. given the
spectroscopic primary temperature and the photometric temperature
ratio), and with the luminosity ratio. The photometric temperature
ratio was adopted.
On the mass-
diagrams, both stars fall on the 30 Myr isochrone within the
errors. On the HR diagram, the primary has a position
compatible with its evolutionary track within errors, though it appears
slightly too luminous. The secondary is slightly hotter than the
primary, and is more overluminous; still, it remains
compatible with its evolutionary track if the errors on both luminosity
and mass are considered.
A.13 5 026631
This system presents a medium-quality light curve of the EW type with
minima of unequal depth. This is clearly a semi-detached system with
strongly distorted components of unequal brightness.
It presents the second-lowest inclination of the sample with ,
implied by the rather small amplitude of the light curve.
No blend is apparent on the finding chart, except
for two or three very faint neighbors at about
.
There are only eight out-of-eclipse spectra, but these are sufficiently constraining to get reliable RV curves.
A spectroscopic B luminosity ratio of 0.74
was found, while the photometric value is 0.50. The separated
spectra show no useful metallic lines. This is due notably to the high values
(
190 km s-1).
The temperature of the primary was obtained by fixing the temperature
and luminosity ratios to the photometric values.
The mass-
and HR diagrams show the typical positions for the components of a
semi-detached system, with the primary near its expected evolutionary
track and an overluminous secondary. The primary is slightly
overluminous relative to its track, as is often the case in
this work, while the secondary is slightly below its track,
a rare occurrence.
This binary was studied by HHH05. Their primary temperature
(25 500 K) and mass ratio (1) differ significantly from
our values.
A.14 5 032412
This wide, detached system presents medium-to-high quality light curves with minima of unequal depth, betraying components of unequal brightness. The target appears well isolated on the finding chart.
There are 13 out-of-eclipse spectra. The RV curves are very
well constrained and the rms scatters are low. Interestingly, both the
light and velocity curves indicate a negligible eccentricity,
in spite of the small relative radii of the components,
as if circularization had taken place during the protostellar
phase. Note that this is the most massive system of our whole sample:
its total mass reaches .
A spectroscopic B luminosity ratio of 0.55 was found. The separated spectra are of high quality (Fig. A.5), even for the H I lines. Beside the H I and He I lines, the following lines are visible in the spectrum of the primary: He II 4200 and 4542 (strong), Si IV 4089, Si IV 4116, O II 4185, Si IV 4212, O II 4276-7 and Si III 4553. An effective temperature of about 35 000 K was inferred from the best-fitting synthetic spectrum.
The following metallic lines are visible in the separated spectrum of the secondary: Si IV 4089, Si IV 4116, O II 4185, O II 4190, C II 4267, O II 4276-7, O II 4415-7, Mg II 4481 and Si III 4553. He II 4542 is clearly visible too. Comparing the relative depths of Mg II 4481 with He I 4472, He II 4542 with Si III 4553, C II 4267 with O II 4276-7, Si IV 4089 and Si IV 4116 with He I 4121 allows us to estimate an effective temperature close to 31 000 K. Thanks to the good SNR of the spectra, fitting simultaneously the temperatures of the components and the luminosity ratio resulted in a temperature ratio very close to the photometric one. Nevertheless, the adopted temperatures are those obtained by imposing the photometric ratio.
The mass-
diagram shows a very young binary with both components on the ZAMS. On
the HR diagram, the positions of both components agree fairly
well with the stellar evolutionary tracks of 17.1 and
13.1
stars. However, the primary appears slightly overluminous relative to
its track.
![]() |
Figure A.5:
Sections of the separated spectra of the primary and secondary
components of the binary 5 032412. The scale on the
vertical axis is adapted to the size of the features in each section.
The red line represents a velocity-shifted synthetic spectrum of the
star. Beside prominent H I and He I lines,
He II, O II, Mg
II, Si III
and Si IV lines are visible in
both spectra. The strong He II 4542,
next to a smaller Si III 4553 line,
and the He II 4200 line confirm
the high temperature of the primary ( |
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A.15 5 038089
This bright detached system presents medium-quality light curves with eclipses of very similar depth. Therefore, the components are very similar.
This system has abnormal color indices (see Table 3 and Fig. 3), which suggests the presence of a third light. An examination of the OGLE finding chart reveals that this binary is clearly blended, though with much fainter stars.
There are 11 out-of-eclipse spectra. The RV curves are very well constrained and the rms scatter is remarkably low.
A spectroscopic B luminosity ratio of 0.68 was found. The eclipses are not very deep, so we fixed the potential of the primary to reproduce this luminosity ratio. The separated spectra shown in Fig. A.6 are very similar. Strong He II 4200 and 4552 lines are visible in both spectra. The following metallic lines are equally identifiable (Fig. A.6): O II 4076, Si IV 4089, Si IV 4116, O II 4185, O II 4190, C II 4267, O II 4276, O II 4415-4417, Si III 4553. This wealth of lines allows us to determine the temperatures of both components with a great accuracy. From the best-fitting synthetic spectra, we found 30 400 K and 30 800 K for the effective temperature of the primary and secondary, respectively. This is very close (i.e. within 200 K) to the temperatures estimated from the composite spectra by imposing the photometric temperature and luminosity ratios; thus, one can safely conclude from this example that the two methods are equivalent.
![]() |
Figure A.6: Sections of the separated spectra of the primary and secondary components of the binary 5 038089. The scale on the vertical axis is adapted to the size of the features in each section. The red line represents a velocity-shifted synthetic spectrum of the star. Beside prominent H I and He I lines, He II and a number of fainter metallic lines (C II, O II, Si III, Si IV) are visible. The relative intensities of the He II 4542 and Si III 4553 are very useful to constrain the temperature of the two stars. |
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The high quality of the spectroscopic observations allowed us to
estimate the astrophysical parameters with a greater accuracy than for
most systems in our sample. On the mass- diagram, both
components lie just above the 10 Myr isochrone; their
respective positions suggest that the ratio of radii may be slightly
underestimated. The HR diagram shows that both stars are
significantly overluminous with respect to the evolutionary tracks
of 13.0 and 11.7
stars. Invoking the blending of the binary with a third-light
contributor does not seem to help much. No clear sign of a
third light can be seen in the lightcurve; this is admittedly a weak
argument, since the light curve of a detached system with weak
proximity effects cannot constrain a third light well. But,
in addition, a third light will not much change the
relative radii of the components, and the effective temperatures seem
well constrained by the relative intensities of several lines,
so that the luminosities should remain unaffected.
Furthermore, the quality of the radial velocity curves is so good, that
it is difficult to imagine how the masses could be biased otherwise
than through the inclination angle i.
A third light would
make the photometric minima less deep and so it would mimick a
lower i. Since the RV amplitudes
give the product
,
underestimating i is equivalent to overestimating
,
while we would need the reverse to explain the HR diagram we
see. A test with the EBOP code confirms this qualitative
argument: assuming a third light
changes the radius of the primary by -0.26% only (keeping the
ratio of radii constant), so that the luminosity decreases by
half a percent, while the inclination is increased by more than three
degrees, lowering the masses by 3.6%. That would imply
evolutionary tracks with a luminosity about 0.05 dex lower
(or 11%) in the HR diagram. Finally, the distance
modulus of this system is very close to that expected for the SMC.
Therefore, for a third light to be the cause of
the inconsistency, it can only be via the RV curves,
the amplitude of which should be biased to low values by a stationary
third spectrum.
This binary was part of the first release of 10 bright SMC systems by HHH03. Comparing our results with theirs, we see that we have similar estimates for the mass ratio and temperatures of the stars, but markedly different values for the masses and radius of the secondary. A photometric solution was proposed by dG03, who do not recommend it for distance determination because its components do not fall into their mass-luminosity relation.
A.16 5 095337
This is a close but detached system, with tidally distorted components
of unequal brightness. The curve suggests that
the primary eclipse is not perfectly reproduced by the synthetic light
curve, but there is no obvious third-light contribution. The finding
chart shows some blends with two or three fainter stars at
or so.
There are 10 out-of-eclipse spectra. The RV curves are well constrained with observations close to both quadratures.
A spectroscopic B luminosity ratio of 0.66
was found. The separated spectra are of poor quality. Because of the
low S/N and the high
(
200 km s-1),
no metallic line can be positively identified. There is some
nebular emission in the Balmer lines. The best-fitting synthetic
spectra allowed us to simultaneously estimate the temperatures of the
primary and the secondary, whose ratio agrees quite well with the
photometric one. In addition, the spectroscopic B luminosity
ratio perfectly matches the photometric one, so that the
potential of
both the primary and the secondary were left free to converge.
On the mass-
diagram, both components define a segment which is perfectly parallel
and very close to the 10 Myr isochrone. On the
HR diagram, however, both components appear strongly
overluminous compared to the evolutionary tracks of 8.7 and
7.6
stars. Decreasing the effective temperatures by about 1300 K
would reconcile the luminosities with the tracks. However, this looks
difficult. The emission in both Balmer lines was suppressed on
a 4 Å range centered on each emission line, and we
verified that increasing that range to 8 Å does not change the
estimated temperature in a significant way. Thus, either this system
suffers from some bias on the RV curves, or its metalicity is
closer to Z=0.001 than to Z=0.004.
A.17 5 095557
This is the system with the highest eccentricity, displaying a medium-quality light curve with minima of unequal depths. The target is perfectly isolated on the finding chart.
There are 11 out-of-eclipse spectra. The RV curves are well constrained with observations close to both quadratures, but the fit is not very good and, unfortunately, most spectra are grouped in the phase interval with the smaller amplitude.
A spectroscopic B luminosity ratio of 0.5 was
found when limiting the fit to the seven spectra for which the radial
velocity difference
.
This ratio increases to 0.63 if all eleven spectra are taken
into account, so that this quantity is rather poorly constrained. The
separated spectra are of very poor quality. This is probably partly
due to the low S/N of the
observed spectra, and partly to some inaccuracies in the orbital
parameters. The temperature of the secondary given by the fits to the
composite spectra is about 1000 K higher than the photometric
estimate, which was adopted. The pseudosynchronized values of
were adopted.
An apsidal motion is detected at the significance level,
and the WD result is confirmed by the variation of the
quantity
as given by the EBOP code. The photometric data were divided into four
sets and the fits were obtained by fixing the inclination, the ratio of
radii and the relative radius of the primary. The result is displayed
in Fig. A.7
and suggests that the apsidal motion is real. The adopted apsidal
motion seems underestimated in that figure, but the constraint imposed
by the RV curves has to be kept in mind. On the mass-
diagram,
the two components lie right on the 30 Myr isochrone, despite
the rather large uncertainty of the masses. In the
HR diagram both components appear clearly overluminous with
regard to their respective evolutionary tracks, as in many other
systems.
![]() |
Figure A.7:
Same as Fig. A.4,
but for the system 5 95557. The filled black dots
represent independent |
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A.18 5 100485
This is a detached system with ``twin'' components and a circular
orbit. The finding chart reveals no crowding problem, because the
closest neighbor is found at about
.
There are 13 out-of-eclipse spectra. The RV curves are well constrained, with observations close to both quadratures and small residuals.
A spectroscopic B luminosity ratio of 0.93
was found, which matches the photometric value (0.97) rather
well. The separated spectra are very similar. The following metallic
lines can positively be identified: C II 4267,
Mg II 4481 and Si III 4553.
These lines allowed us to estimate a temperature close to 22 000 K
for each component. The least-squares fit, performed with both
temperatures and the luminosity ratio free to converge, provided a
temperature ratio very close to the photometric one.
The two components lie right on the 20 Myr isochrone
on the mass- diagram,
and they are compatible within the errors with their respective
evolutionary tracks in the HR diagram. Here again, however,
they are slightly overluminous, unless their metalicity
is low.
A.19 5 100731
This system presents low-to-medium quality light curves of the
EW type, with the smallest amplitudes among those in our
sample. This is another case of a binary seen in an unfavourable
inclination (60
).
The finding chart shows a perfectly isolated target.
The most satisfying fit of the light curves was obtained with an overcontact model.
There are only eight out-of-eclipse spectra. Nevertheless, these observations are sufficiently constraining to get reliable RV curves.
Spectroscopy gives a B luminosity ratio of
,
while the photometric ratio amounts to
.
As usual, the latter was preferred, especially because of the
strong constraints provided by a Roche-lobe-filling pair. The separated
spectra have a low S/N, and a
least-squares fit to the composite spectra with both temperatures free
provided two temperatures close to 23 000 K.
However, the scatter of the secondary temperature was high,
so the photometric temperature ratio was adopted and fixed.
The mass-
diagram shows a secondary component more evolved than the primary,
as expected. On the HR diagram, both components
appear to be underluminous with respect to their evolutionary tracks,
though only by a little amount. This is an exceptional occurrence.
A.20 5 106039
This system is a typical semi-detached one. There is a small depression occurring just before the eclipse of the primary, which is strong evidence for a gas stream. We did not attempt to model that stream with a cool spot on the primary, because the distortion of the light curve remains relatively mild. The target appears perfectly isolated on the finding chart.
There are nine out-of-eclipse spectra. The RV curves are well constrained with observations close to both quadratures.
A spectroscopic B luminosity ratio of 1.03
was found, which excellently agrees with the photometric
value (1.01). The following metallic lines are visible in the
separated spectrum of the primary: C II 4267,
Mg II 4481 (faint) and Si III 4553.
A stronger Mg II 4481
line is equally visible in the spectrum of the secondary. From these
lines, the primary temperature was estimated to be close
to 25 500 K. The least-squares fit,
performed with temperature and luminosity ratios fixed to the
photometric values, provided a primary temperature
K
higher.
The position of the primary component in the
HR diagram is in fair agreement with the theoretical
evolutionary track of a 8.6
star, though it is slightly overluminous. The evolved secondary
component is overluminous with respect to the track of a single star of
the same mass.
A.21 5 111649
This is a detached system with very slightly distorted twin components.
There is a group of bright stars close to the target in the finding
chart, but they are remote enough (
)
that no third light should be expected from them.
There are 10 out-of-eclipse spectra. The RV curves are not well sampled because the period of 2.95955 days is very close to an integer number of days, but the scatter is small, thanks to the slow projected rotational velocities induced by the relatively long period.
A spectroscopic B luminosity ratio of 0.89
was found, which was imposed (via the potential of the primary) to
define the ratio of radii. Indeed, the small amplitude of the light
curve prevents a purely photometric ratio to be well constrained. Noisy
C II 4267 and Mg II 4481
lines are visible in the separated spectrum of the secondary. The
temperature of the primary was determined from a fit with fixed
temperature and luminosity ratios. According to both spectroscopy and
photometry, the secondary appears marginally hotter than the primary,
the temperature difference being about .
Both components have a very similar mass (5.4
),
and according to the mass-
diagram,
the empirical mass contrast appears a bit too high to match the
Myr
isochrone. Interestingly, both components lie right on the Terminal Age
Main Sequence (TAMS), where evolution is so fast that a theoretical
lower limit to the mass ratio can be settled.
Starting from the purely empirical surface gravities, and increasing
their difference by two sigma (so that
and
),
one can read the corresponding masses along the
isochrone. Assuming that both stars have not yet passed the ``hook''
that marks the end of the main sequence, the resulting mass ratio is q=0.98.
But it is quite possible that the primary has just passed the hook
while the secondary has not, in which case q=0.966.
In both cases, the mass ratio is closer to one than the value directly
obtained from the RV curves by 0.03 to 0.04.
Therefore, this system can be considered as hosting real twins.
The position of the primary in the HR diagram agrees almost perfectly with the theoretical evolutionary track, especially if the star has just evolved beyond the ``hook''. That of the secondary, however, is a bit too high, as if its mass were underestimated.
A.22 5 123390
This slightly eccentric system (e = 0.042) presents
low-to-medium quality light curves with a small amplitude. This is
clearly a detached system with components of unequal brightness. The
finding chart shows a neighbor at about
to the SW of the binary, which might have polluted the spectra
slightly.
There are 14 out-of-eclipse spectra. The RV curves have a small rms scatter and are very well constrained by the observations.
A spectroscopic B luminosity ratio of 0.58
was found. The separated spectra are of fairly good quality. The
following metallic lines are visible in both spectra: O II 4076,
C II 4267, O II 4276,
O II 4415-4417, Mg II 4481
and Si III 4553. For the primary,
the best-fitting temperature for these lines is 26 000 K.
The least-squares fit of the composite spectra gave temperatures of
28 400 and
26 260 K for the primary and secondary respectively,
but with a large scatter. A plot of the fitted temperatures
versus the unnormalized chi-square shows that in some cases the fit
switched components, i.e. attributed the high temperature to
the secondary and vice versa, which partly explains the large
scatter (see Fig. A.8).
Strangely enough, the photometric ratio of temperatures is close to
one, so that the temperatures become 27 840 and
28 320 K for the primary and secondary component
respectively when fitted while keeping this ratio fixed. Taken at face
value, however, Fig. A.8
rather suggests 29 000 and 25 000 K.
![]() |
Figure A.8: Temperature of the primary (black dots) and of the secondary (red dots) component of the system 5 123390, obtained by fitting composite synthetic spectra to the observed ones, versus the quality of the fit. The trends are roughly horizontal, at least for good fits, which inspires confidence. In a few cases, the components are exchanged (see text). |
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According to the mass-
diagram, this binary is
12 Myr
old. The position of the primary component in the HR diagram is a bit
too high with regard to its evolutionary track. The secondary component
is much too luminous, falling on the track of the primary!
If the purely spectroscopic temperatures were adopted, the
primary would be even more overluminous, but the secondary would fall
right on its track.
There is a marginally significant apsidal motion of
4.75
1.63
yr-1.
We show in Fig. A.9
the
quantity found with
the EBOP code on the basis of the I magnitudes.
There is indeed a slight trend corresponding to an increase of
with time.
![]() |
Figure A.9:
Same as Fig. A.4,
but for the system 5 123390. The filled black dots
represent independent |
Open with DEXTER |
A.23 5 180185
The EA-type light curves of this system are irregularly sampled,
because the period is close to 5.5 days, and there
are only very few data in the primary minimum. This is a typical
well-detached system with twin components and a small eccentricity. The
finding chart reveals a slightly fainter neighbor about
away from the target, i.e. far enough that its influence on
the spectra may be considered negligible.
This system has unreliable color indices (see Table 3 and Fig. 3).
There are 12 out-of-eclipse spectra. The RV curves are excellent and well constrained by the observations, with the smallest residuals seen in our sample. The formal errors on the resulting amplitudes are smaller than one percent, allowing mass estimates to within 2-3%.
A spectroscopic B luminosity ratio of 0.63
was found, which is close to the value given by the
WD analysis and finally adopted (0.71). This is the
system with the longest period ( days) in our sample.
The long period is responsible for the low
values
(
40 km s-1)
compatible with synchronous rotation. As a consequence, the
separated spectra of this binary show rather sharp lines. The following
metallic lines are visible in both spectra: C II 4267,
Mg II 4481 and Si III 4553.
The temperature of the primary was obtained as usual by fixing the
temperature and luminosity ratios to the photometric values, despite
the small number of points in the minima. The secondary has a slightly
hotter temperature than the primary.
Both components are fairly well aligned on the 50 Myr
isochrone in the mass- diagram,
although the primary should be slightly more evolved. On the
HR diagram, the secondary falls right on its track, while the
luminosity of the primary appears too low. This might be due to an
unreliable temperature ratio, because of the small number of
photometric points in the minima.
A.24 5 180576
This system presents low quality light curves of the EB type.
The depths of both minima are rather low and the rms scatter is high.
This is a detached system with components of unequal brightness and a
circular orbit. The finding chart shows a close neighbor at
about
to the NNW, which might have distorted the temperature estimate of the
binary components.
There are 12 out-of-eclipse spectra. The RVs curves are rather good and well constrained by the observations.
A spectroscopic B luminosity ratio of 0.42
was found. This is close to the value reached by the final
WD analysis. The observed composite spectra are very noisy (
)
and are
contaminated by nebular emission. The separated spectra are of a rather
poor quality. This is partly due to the low reliability of the
continuum placement. The C II 4267
and Mg II 4481 lines are visible
in the spectrum of the primary. The temperature of the primary,
determined from a least-squares fit where the temperature and
luminosity ratios were fixed, depends on the quality
of the fit, as shown by Fig. A.10. We
adopted the temperature of the primary corresponding to the
best
,
in view of the roughly linear correlation between
and
,
but without attempting to extrapolate the relation to
.
![]() |
Figure A.10: Effective temperatures of the system 5 180576 obtained from a fit to the composite spectra, keeping the temperature and luminosity ratios fixed. Black dots are for the primary, red dots for the secondary. Note that the two curves should be considered as one and the same, since their ratio is constant. |
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In the mass-
diagram, the components are perfectly aligned along the 15 Myr
isochrone. The position of the primary component in the
HR diagram appears slightly too high relative to the
corresponding evolutionary track, while the secondary falls right on
its track.
A.25 5 185408
This system presents medium quality light curves of the
EA type. The minima are of similar depth and there is some
ellipsoidal variation. This is a typical detached system with closely
similar components, with medium quality light curves and low amplitude
minima of similar depth. The orbit is
circular. The I-band light curve was cleaned from
five outliers before the PHOEBE/WD analysis. The finding chart shows a
well isolated target, the closest neighbor is found at about
to the WNW.
There are 12 out-of-eclipse spectra. The RV curves are excellent, especially in view of the faintness of the object, and well constrained by the observations.
A spectroscopic B luminosity ratio of 0.64 was
found. The WD analysis tended to raise this value and the
potential of the primary had to be fixed to keep it close to the
spectroscopic one. The C II 4267,
Mg II 4481 and Si III 4553
lines are visible in both separated spectra. The temperatures were
obtained by fixing the temperature and luminosity ratios to the
photometric values.
On the mass-
diagram, the components are fairly well aligned on the 10 Myr
isochrone. On the HR diagram, both components are
significantly overluminous with respect to their respective
evolutionary tracks, as is often the case.
A.26 5 196565
This detached eccentric system presents medium quality light curves
with eclipses of similar depth. The V and B data
are missing in the OGLE database. The finding chart shows a neighbor of
similar brightness as the target about
to the S, raising some concern regarding possible spectral
pollution. The results do not confirm these fears, though.
There are 13 out-of-eclipse spectra. The RV curves are very good and well constrained by the observations, in spite of a lack of observations where the expected amplitude reaches its maximum.
A spectroscopic B luminosity ratio of 0.41 was
found, and the potential of the primary was adjusted and fixed in the
WD analysis to maintain that value. The C II 4267
and Mg II 4481 lines are visible
in both separated spectra. The least-squares fit of composite synthetic
spectra to the observed ones provided a temperature ratio higher than
that provided by the photometry, and a primary temperature of
20 960
600 K. Fixing the temperature ratio to
the photometric value resulted in the slightly hotter primary
temperature that has been adopted.
The mass-
diagram suggests that the secondary has a radius too large with regard
to the primary, as if the luminosity ratio was overestimated:
while the primary lies close to the 40 Myr isochrone, the
secondary lies on the 50 Myr one. On the HR diagram,
however, each component has a position compatible with its respective
evolutionary track within the error bars, though the primary is
slightly overluminous while the secondary is slightly underluminous.
This system was studied by WW01. Their relative radius of the primary (0.204) is very close to ours (0.200) but their radius of the secondary (0.116) is smaller than ours (0.150). The difference arises because they consider the eclipses as total, while we consider them as partial. Additional accurate photometry in both minima would be welcome to settle the question.
A.27 5 261267
This is a typical semi-detached system with high-quality light curves
and eclipses of unequal depths. The curve shows no
detectable depression before the primary eclipse. Although the finding
chart shows a few neighbors, they all lie beyond
of the target.
This system has peculiar color indices (see Table 3 and Fig. 3). Since it lies near the edge of the CCD in the OGLE-II survey, it is also listed under the name 6 11806 in the corresponding database. Thus, there are more than 600 data points in the I-band light curve, instead of about 300.
There are 10 out-of-eclipse spectra, which constrain the RV curves relatively well.
Both photometric and spectroscopic ratios are very similar (0.4).
Because of the relatively high
(>150 km s-1) and
moderate S/N of the
observations, there are no exploitable metallic lines in the separated
spectra. The temperature of the primary was obtained,
as usual, by least-squares fit to the composite
spectra, after fixing the temperature and luminosity ratios to the
values given by a preliminary WD analysis.
The mass-
and HR diagrams are typical of a massive Algol-type binary. The primary
is overluminous relative to the evolutionary track of an isolated star
of the same mass, as are other semi-detached systems like
4 113853 and 5 277080.
A.28 5 265970
This slightly eccentric detached system has medium-to-high quality
light curves of the EA type. The sampling of the light-curve
is incomplete, due to an orbital period close to 3.5 days.
In particular, the depth of the secondary minimum is
ill-defined. Therefore, the photometric temperature ratio and
inclination are not very reliable. Actually, there is a correlation
between
these two parameters, in the sense that an increase of
inclination implies a decrease of the temperature ratio. The finding
chart shows a well defined target, but with an only slightly fainter
neighbor about
to the NW.
This system lies near the edge of the OGLE-II CCD, and so was measured also on the adjacent chip under the name 6 17345, so that there are as many as 586 data points in the I band. The two data sets were merged after applying a small magnitude offset to each. With the EBOP code the fitted magnitude at quadrature and its error were defined for each set, then the mean magnitude at quadrature weighted by the inverse of the variance was computed. Finally, the appropriate offset was applied to each of the two sets to adjust it to this mean magnitude.
There are 10 out-of-eclipse spectra. The RV curves are quite good and well constrained by the observations.
Because of the loose constraints on the light curves, the proposed solution for this system heavily relies on the spectroscopic observations. Nevertheless, the proposed solution meets the spectroscopic and photometric constraints very well, so we consider it as close to reality.
A spectroscopic B luminosity ratio of 0.23 was
found from the usual least-squares fit, which provides the temperature
of the primary with an excellent internal precision. The temperature of
the secondary is much less certain, because of the small luminosity
ratio. In order to maintain the
luminosity ratio to the spectroscopic value in the
WD analysis, one has to fix the potential of the primary to an
appropriate value, and the temperature ratio converges to a lower value
than the spectroscopic one, but still compatible with it given the
errors. Thus the photometric temperature ratio was adopted, and the
temperature of the primary was determined in the usual way.
A number of metallic lines are identifiable in both separated spectra: C II 4267, O II 4276, O II 4415-17, Mg II 4481 and Si III 4553. There is no emission in the Balmer lines.
The positions of the stars in the mass-
diagram are not quite mutually consistent: the ratio of radii should be
decreased in order to bring the two components on the same isochrone,
which would correspond to about 26 Myr. In the
HR diagram, the primary component matches its theoretical
evolutionary track surprisingly well, while the secondary has a
position consistent with its
track within the error bar. The spectroscopic constraints, which are
strong, are well fulfilled, but additional photometric data would be
useful to improve our solution. This system is especially interesting,
because the primary is very close to the TAMS while the secondary is
much less evolved.
We applied the EBOP code on four subset of the total time
series, after fixing all parameters to their average value, except
inclination, ,
,
magnitude at quadrature and phase shift. No significant trend
can be seen in Fig. A.11,
which does not prove, however, that
remains constant with time. The less reliable
quantity does not
differ significantly from zero according to the EBOP code. In the
WD solution, we have arbitrarily imposed a low value
which roughly corresponds to the theoretical prediction.
![]() |
Figure A.11:
Same as Fig. A.4,
but for the system 5 265970. The horizontal dashed
line shows the weighted average of the |
Open with DEXTER |
A.29 5 266015
This system presents high-quality light curves of the EB type with minima of unequal depth. Its bright I-band light curve is perfectly well sampled. The small depression occurring just before the primary eclipse is indicative of a semi-detached system with a secondary component filling its Roche lobe and pouring matter onto the primary component. However, the amplitude of this effect was judged too small to justify an attempt to model it through a spot.
There are 10 out-of-eclipse spectra. The RV curves are well constrained by the observations.
A spectroscopic B luminosity ratio of 0.61
was found, rather remote from the photometric value (0.49),
as is often the case in semi-detached systems. The separated
spectra of both components have a decent S/N
(Fig. A.12).
Nevertheless, the
being high (>150 km s-1),
the small metallic lines are not very conspicuous. The
He I 4120 and He II 4542 lines
are visible in the spectrum of the primary. The Si III line
appears in both spectra. This is one of the few systems with apparently
no significant nebular emission lines, therefore the separated Balmer
lines can be used to find the temperature of the primary. The spectral
features of the primary point to a 32 000 K
star, which is confirmed by the usual least-squares fit.
The positions of the stars in the mass-
and HR diagrams are coherent with an evolved system having
undergone mass exchange. The primary component is close to the track
corresponding to a 15.6
star.
This system was studied by WW02. As with most semi-detached systems they studied, their photometric mass ratio proved to be unreliable.
![]() |
Figure A.12:
Sections of the separated spectra of the primary and secondary
components of the binary 5 266015. The scale on the
vertical axis is adapted to the size of the features in each section.
The red line represents a velocity-shifted synthetic spectrum of the
star.
Beside prominent H I and He I lines,
He II, O II, Mg
II, Si III
and Si IV lines are visible in
both spectra. The strong He II 4542,
next to a smaller Si III 4553 line,
and the He II 4200 line
confirm the high temperature of the primary ( |
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A.30 5 266131
The most striking feature of this slightly eccentric detached system (
)
is its huge apsidal motion, which explains the apparently very bad I-band
curve.
An examination of the OGLE finding chart revealed that this
binary is slightly blended, but a posteriori, this does not
seem to have distorted the results.
This system lying close to the edge of the CCD in the OGLE-II survey, it also exists under the name 6 22883, which doubles the number of data points in the I band. The magnitude at quadrature was determined using the EBOP code for each of the two data sets; the two resulting values agreeing within one thousandth of a magnitude, the two data sets were merged without applying any magnitude offset.
There are 10 out-of-eclipse spectra, which constrain quite well the RV curves.
A spectroscopic B luminosity ratio of 0.65 was
found. As usual with the well detached systems, the potential
of the primary was fixed at a value which preserves this luminosity
ratio through the WD analysis. The S/N
of the separated spectra are too low to allow any useful metallic
line to be seen. Since the temperature ratio is well constrained by the
photometric data, the temperature of the primary was determined by
fixing this ratio at its photometric value. There is no nebular
emission in the Balmer lines.
The mass-
diagram suggests that the ratio of radii has been slightly
underestimated, since the secondary has a surface gravity too large
compared to the primary. Still, the positions of both components are
compatible, within the errors, with an isochrone
at 7-8 Myr. The HR diagram shows a good
match between the positions of both components and the evolutionary
tracks of single 9.0 and 7.7
stars. However, both components are slightly overluminous relative to
their respective tracks.
The apsidal motion amounts to
yr-1,
as shown by the
values
obtained with the EBOP code for four successive subsets of the whole
time serie in the I band. That value is
confirmed by the WD analysis. The run of
versus
time is shown in Fig. A.13,
together with the best-fit curve provided by the WD code. The
reality of a very fast apsidal motion is beyond any doubt.
It is further discussed in Sect. 4.
A.31 5 266513
This a close detached system with similar components, according to its
medium quality light curves with minima of similar depth. The finding
chart shows a slightly fainter star at
to the W of the target.
There are 10 out-of-eclipse spectra. The RV curves are well constrained by the observations, though the noise is rather large because this system is the faintest in our sample.
A spectroscopic B luminosity ratio of 0.73 was found, but with a large scatter of 0.09. The potential of the primary was fixed so that the WD analysis preserves a ratio close to that value. The separated spectra have a low S/N and no metallic lines are exploitable. Moreover, the Balmer lines are polluted by nebular emission. The photometric temperature ratio is rather well defined, thanks to the large depth of the minima, and was fixed for the determination of the temperature of the primary, as usual for most detached systems.
The mass-
diagram shows the two components fairly well aligned along the
Myr
isochrone. On the HR diagram, the primary lies almost exactly
on its evolutionary track, while the secondary is slightly
overluminous, though its position is quite compatible with the
evolutionary tracks within the errors. The luminosity ratio (hence the
ratio of radii) seems to have been slightly overestimated.
A.32 5 277080
This system is a typical semi-detached binary with high-quality light curves of the EB type. A small depression before the primary eclipse signals the possible presence of a mass-transfer stream. The effect is small enough for us not to deem it worth the effort to model it through a cool spot on the primary.
![]() |
Figure A.13: Same as Fig. A.4, but for the system 5 266131. The solid line is the best fit provided by the WD code. |
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This system has peculiar color indices (see Table 3 and
Fig. 3).
Indeed, an examination of the OGLE finding chart revealed that this
binary is strongly blended with a brighter star lying
to the SW of the target.
There are 11 out-of-eclipse spectra. Because of an orbital period close to two days, there are no observations before the quadratures. Yet the RV curves are rather well constrained. This is one of the few systems without nebular emission in the Balmer lines.
A spectroscopic B luminosity ratio of 0.7 was found. This is higher than the photometric ratio (0.57), as seems to be often the case of semi-detached systems. The separated spectra are fairly good. A number of metallic lines are visible in the spectrum of the primary: O II 4185, C II 4267, O II 4276-7, Mg II 4481 and Si III 4553. The Mg II 4481 line is the only metallic line detectable in the spectrum of the secondary. The temperature of the primary was determined after fixing the temperature and luminosity ratios to their photometric values.
The positions of the stars in the mass-
and HR diagrams are typical of Algol-type system with a
secondary more evolved than the primary. The primary component,
however, is much more luminous than expected from the
evolutionary track of a single star of the same mass, and we cannot
guarantee that its effective temperature has not been overestimated.
The peculiar HR diagram might
be the result of the blend mentioned above with a nearby bright star.
A.33 5 283079
This is a typical detached system with twin components and a circular
orbit. The target appears just isolated on the finding chart, with a
companion of similar brightness about
away from it to the SE.
There are 10 out-of-eclipse spectra. The RV curves
are well defined and constrained by the observations. There is probably
a faint nebular emission in both H
and H
lines.
With a spectroscopic B luminosity ratio close to 1.0, a mass ratio of 1.003 and a temperature ratio of 0.997, this is the system with the most similar components in our sample. Thus it is probably a real pair of ``twins'', i.e. it has a mass ratio higher than 0.95. This is why the choice of the primary is undecided in this system: which component is the primary was decided on the basis of an early iteration, and it is only in the last iteration that we obtained q=1.003 > 1. The potential of the primary was fixed in the WD analysis, in order to keep the B luminosity ratio close to 0.99. The separated spectra are noisy and the C II 4267 and Mg II 4481 are barely visible. The temperature of the primary was determined by fixing the temperature ratio to 0.997 and the luminosity ratio to 0.99.
On the mass-
diagram, both components lie on the 3 Myr isochrone,
so this system is very young. On the HR diagram, they
are slightly overluminous with respect to the evolutionary tracks, but
still within the error bars. On the other hand, the components lie
exactly on the metal-poor tracks (Z=0.001).
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