Issue |
A&A
Volume 379, Number 2, November IV 2001
|
|
---|---|---|
Page(s) | 482 - 495 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20011280 | |
Published online | 15 November 2001 |
Optical spectra of five UX Orionis-type stars *,**
1
Crimean Astrophysical Observatory, Crimea, 334413 Nauchny, Ukraine
2
Pulkovo Astronomical Observatory, 196140 St. Petersburgh, Russia
3
Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
4
Astronomy Division, PO Box 3000, 90014, University of Oulu, Finland
Corresponding author: A. Natta, natta@arcetri.astro.it
Received:
January
1900
Accepted:
7
September
2001
We present in this paper several high resolution ()
spectra of five UXORs (UX Ori, CQ Tau,
BF Ori, RR Tau, WW Vul), which cover
the entire visual range, from 3900 to about 8700 Å. There
are between 4 and 7 spectra per star,
obtained over a time interval of two years.
Simultaneous or quasi-simultaneous
photometric observations were also obtained
at the Crimean Astrophysical Observatory.
The complete, reduced and normalized spectra are available
in electronic form. We show for each
star a selection of the most interesting lines, and the full spectrum
of UX Ori computed by averaging the spectra
obtained when the star was at maximum light. For UX Ori
we show also the synthetic spectrum and provide an
identification of most of the lines.
The spectra are too sparse to form true time sequences; however, they provide
an extremely useful database for studies of UX Ori-type stars.
We discuss briefly the main features of the spectra.
We show that they contain many time-stable photospheric lines
that can be described
to a good approximation by the synthetic spectra of normal
A stars with
and we derive for each
star effective temperature, gravity and rotational velocity.
We examine the time variability of selected lines
and study their connection with the photometric activity of the stars.
Two different types of spectral variability are identified.
One is common to all stars with circumstellar (CS) gas
and is caused by perturbations of the physical and kinematic conditions
of the emitting region.
There is no correlation between this type of activity
and the brightness variations of the star.
On the contrary, a second type of spectral variability correlates
well with the brightness variations and is very likely
connected with the
screening effect of an opaque dust cloud which sporadically
intersects the line of sight.
This type
of variability has been observed in its simplest form in one of
the RR Tau spectra,
where
the equivalent width of the forbidden line [Oi] 6364 Å
increased by a factor of about three as the star faded
by approximately the same amount.
Key words: stars: individual: UX Ori, CQ Tau, BF Ori, RR Tau, WW Vul / stars: general
© ESO, 2001
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