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A&A
Volume 619, November 2018
Article Number A32
Number of page(s) 17
Section Stellar structure and evolution
DOI https://doi.org/10.1051/0004-6361/201833440
Published online 07 November 2018

© ESO 2018

1. Introduction

Binary systems are essential for the study of stellar structure and evolution. Depending on their nature, they can yield fundamental properties such as the masses, radii, and luminosities of the components, independently from calibrations and stellar models and with very high precision. This enables critical comparisons with stellar model predictions and the determination of empirical calibrations that can be used for single stars (see Torres et al. 2010, for a review). Due to the increasing interest in the discovery of exoplanets, several instruments were developed to spectroscopically survey a large number of stars. In addition to planetary objects, these projects can also reveal new binary systems that are interesting on their own, because they can be used to constrain the stellar structure and evolution models and to improve the multiplicity statistics of late-type stars (Halbwachs et al. 2003; Mazeh et al. 2003).

This is the case of the CARMENES survey (Quirrenbach et al. 2016). This survey monitors about 300 M dwarf stars to uncover exoplanets in their habitable zones. Targets were selected from available M dwarf catalogues and photometric surveys, and were also carefully studied to discard unsuitable targets such as visual double systems, known spectroscopic binaries, and very faint stars (see e.g. Alonso-Floriano et al. 2015; Cortés-Contreras et al. 2017; Jeffers et al. 2018, for more details). The CARMENES collaboration has already announced its first planet detections (Reiners et al. 2018a; Sarkis et al. 2018; Trifonov et al. 2018). In addition to the new planets, several spectroscopic binary systems were identified with the first observations of the sample and they were followed-up to characterise them.

The binary systems discovered with CARMENES are especially interesting because the number of known M dwarf binary systems is still scarce (see e.g. the Ninth Catalogue of Spectroscopic Binary Orbits, hereafter SB91; Pourbaix et al. 2004). The distribution of mass ratios and orbital elements may help to understand the formation and evolution of low-mass stars, brown dwarfs, or giant planets in M dwarf stellar systems. Besides, they are also valuable for constraining the properties of M dwarfs, which still show some discrepancies with stellar model predictions (see e.g. Morales et al. 2010; Feiden & Chaboyer 2013; Feiden & Chaboyer 2014).

In this paper we present nine new double-line spectroscopic binary (SB2) systems discovered in the CARMENES survey. Orbital properties were derived for all of them, yielding their mass ratios and periods for the first time. In Sect. 2 we describe the observations for each system. In Sect. 3.1, the radial velocity analysis of each system is shown. Photometric light curves gathered from the literature and public databases are compiled and discussed in Sect. 3.2. Finally, the results are discussed in Sect. 4 and our conclusions are presented in Sect. 5. Figures of the radial velocity data and the photometric periodogram analysis are compiled in the Appendix.

2. Spectroscopic data

2.1. Spectroscopic observations

High-resolution spectroscopic observations of the targets were taken with the visual (VIS) and near-infrared (NIR) channels of the CARMENES spectrograph from January 2016 to March 2018, covering a wavelength range from 5200 to 9600 Å with a measured resolving power of R = 94 600 in the VIS, and from 9600 to 17100 Å with a measured resolving power of R = 80 400 in the NIR (Quirrenbach et al. 2016). For a few nights when the NIR channel was not available, only VIS spectra are used. From the over 300 studied stars (Reiners et al. 2018b), we have so far identified nine SB2 systems. Between 10 and ∼20 observations were taken sampling the orbital phases of short-period systems.

Table 1 lists some basic information for each target. Six publicly available additional HARPS-N (Cosentino et al. 2012) observations were found for one of the systems (Ross 59) and also included in our analysis.

Table 1.

Main properties and observing log of the spectroscopic binaries studied in this work.

2.2. Radial velocity determination

The candidate spectroscopic binary systems were identified by large variations in their radial velocities, which are routinely calculated by the CARMENES SERVAL pipeline (Caballero et al. 2016b); Zechmeister et al. 2018. This algorithm is based on least-squares fitting of the spectra, providing very accurate radial velocities for single stars (see Anglada-Escudé & Butler 2012). However, it does not yield the velocity of secondary components in binary systems. For that reason, radial velocities of both components were also determined using TODMOR (Zucker 2003), a modern implementation of the two-dimensional (2D) cross-correlation technique TODCOR (Zucker & Mazeh 1994) for multi-order spectra.

To derive the radial velocities of each component of the binary system, we used PHOENIX stellar models (Husser et al. 2013) as templates for the calculation of the cross-correlation functions (CCFs). Using TODMOR, we explored a grid of values for the effective temperatures, flux ratios in the observed wavelength band, and spectral-line broadening to fit all the spectra of each target. Spectral orders with low signal-to-noise ratio (S/N) or telluric contamination were discarded. To obtain the final radial velocity curves of each system in a consistent way, we selected as the template for each system the one that produces the highest CCF peak for spectra with radial velocities obtained close to quadratures. Orbital phases close to conjunction, where the radial velocities of the components cannot be disentangled due to rotational broadening and unfavourable flux ratio, were not considered in this analysis. For this reason, we discarded six spectra for GJ 1029, three for Ross 59, three for GJ 1182 and seven for GJ 810 A in both the VIS and NIR channels. In the case of the VIS spectra, all the parameters could be reliably optimised. However, the effective temperatures resulting from the optimisation process in the NIR spectra always led to unrealistic values at the edge of the grid. Therefore, for the NIR we adopted the values derived from the VIS data and the optimisation was performed on the flux ratio and broadening, which can differ in the NIR channel because of the different wavelength coverage and resolving power.

Only in the case of UU UMi did we use observed spectra as templates with TODMOR, which performed better than synthetic spectra due to the small radial velocity difference between the components and the long period of this system. The co-added spectra of an M2.5 star (Gl 436) and an M5 star (GJ 1253) obtained with CARMENES, were used for the primary and secondary components, respectively. Consequently, the systemic radial velocity derived for UU UMi depends on those of the templates; therefore its uncertainty might be larger. The use of observed spectra does not significantly change the parameters for the other binaries analysed in this work.

Table 2 shows the optimised parameters of the templates for each target, except for UU UMi, for which effective temperatures are obtained from Passegger et al. (2018). These are the parameters used to obtain the radial velocities of the systems with TODMOR, which are provided, together with their uncertainties, in Table A.1.

Table 2.

Spectral properties of the templates used to derive radial velocities with TODMOR in the VIS and NIR channel spectra.

3. Data analysis

3.1. Radial velocity analysis

The orbital parameters of each target were derived using the SBOP (Etzel 1985) code, which fits the seven parameters of a Keplerian orbit simultaneously to both components: the period (Porb), the time of periastron passage (T), the eccentricity (e), and argument of the periastron (ω), the radial velocity semi-amplitudes of each component of the system (K1 and K2 for the primary and secondary components, respectively), and the barycentric radial velocity of the system (γ). An initial estimate of the periods was obtained from a Lomb-Scargle periodogram analysis (Scargle 1982) of the radial velocities, and used as input parameter for SBOP.

Although NIR CARMENES measurements have lower precision than those from the VIS channel (Tal-Or et al. 2018), we fitted radial velocities from both channels simultaneously for consistency and considered the respective uncertainties. We also allowed for an adjustable radial velocity jitter (JitVIS/NIR, 1/2) in the fit, as defined by Baluev (2009), different for each channel and component. This jitter term represents unaccounted error sources in the estimation of the uncertainties of the measurements. The results show that the jitter parameter of the NIR channel radial velocity of the primary component is always above twice that of the VIS channel, except for LP 395-8. However, in this case, the dispersion of the VIS channel may be affected by the large residual of the observation close to conjunction at orbital phase ∼0.8 that does not have a NIR counterpart. Final parameters and uncertainties were computed running the Markov chain Monte Carlo (MCMC) sampler emcee (Foreman-Mackey et al. 2013) with a model based on SBOP with additional jitter terms. Parameter uncertainties were derived from the 68.3% credibility interval of the resulting posterior parameter distribution.

The fitted orbital parameters of all targets and their computed physical elements are given in Tables 3 and 4, respectively. Figure B.1 shows the radial velocity fits of all systems. We found three systems in close orbits with periods between 1 and 6 days (EZ Psc, NLTT 23956, and LP 395-8), three systems with intermediate periods between 70 and 160 days (GJ 1029, GJ 3612, and GJ 1182), and three systems with periods longer than about 2 years, for which further measurements are needed to better constrain the parameters (Ross 59, UU UMi, and GJ 810A). All systems show eccentric orbits, with smaller eccentricity in the case of short period binaries, except UU UMi. For this system, due to its long period and the short orbital phase sampled with CARMENES, a circular orbit was assumed in the present work.

Table 3.

Radial velocity parameters fitted for each binary system.

Table 4.

Physical parameters derived from the radial velocity fits.

3.2. Photometric analysis

To fully characterise our binary systems, we also carried out a bibliographic search for photometric light curves in public archives from surveys such as the Wide Angle Search for Planets (SuperWASP; Pollacco et al. 2006), The MEarth Project (MEarth; Charbonneau et al. 2008; Irwin et al. 2011a; Berta et al. 2012), the All-Sky Automated Survey (ASAS; Pojmański 1997) and the Northern Sky Variability Survey (NSVS; Woźniak et al. 2004). The aim was to search for eclipses in the light curves and the estimation of the rotation period of the systems. Before analysing the photometry we removed outliers as explained in Díez Alonso et al. (1999), iteratively rejecting datapoints deviating more than 2.5σ from the mean of the full photometric dataset for each target. However, outliers were further inspected by eye in order to make sure that possible eclipses were not removed.

The rotation period was determined by computing the Lomb-Scargle periodogram (Scargle 1981) of the photometric light curves, and then looking for strong signals between 1 and 200 days (Newton et al. 2016). Uncertainties are estimated as half the full width at half maximum of the periodogram peak, as a conservative approach. To evaluate the significance of the signals, we used the False Alarm Probability (FAP) as described in Scargle (1982), which measures the probability that the signal randomly arises from white noise. Periodic signals with FAP < 0.1% were defined as significant.

We searched for eclipses in the light curves using two different approaches: in the case of binary systems with well determined periods from radial velocities, we folded the light curve of each target in a phase-magnitude diagram using the orbital period found in Sect. 3.1, and checked for a decrease in brightness within a narrow phase region compatible with the radial velocity orbit. We also made use of the Box-fitting Least Squares code (hereafter BLS; Kovács et al. 2002) to identify eclipses with depth similar to the photometric scatter of each curve. BLS was also used in the case of binary systems with poorly constrained periods, although the eclipse probability is very small for long period systems. Both methodologies yielded negative results in all cases and, therefore, we concluded that none of our nine SB2s is an eclipsing binary within the limits of the sampling and measurement accuracy of the photometric data, which are given in Table 5.

Table 5.

Available photometry for the spectroscopic binaries analysed in this work.

Table 5 lists the significant photometric periods found for our targets and the Hα line pseudo-equivalent width resulting from the CARMENES pipeline (Zechmeister et al. 2018) as an indicator of stellar activity (Reid et al. 1995; Hawley et al. 1996). Figure C.1 shows the available photometry, the periodogram, and the light curves phase-folded to the best period found. Significant signals for seven of the systems studied here were found, which we identify as corresponding to the rotation period of the main component (the brightest star) of the systems, assuming that both components may have similar activity levels. Using the same data but with a more conservative approach, Díez Alonso et al. (1999) reported photometric periods for four of our stars (EZ Psc, GJ 3612, UU UMi and LP 395-8). In all cases, the measured Prot are identical within uncertainties.

Interestingly, the three short-period systems (EZ Psc, NLTT 23956, LP 395-8) all have rotation periods below 10 days, and they are active systems showing the Hα line in emission. Furthermore, in these cases the broadening of the spectral lines, which depends on the rotation period of the components and the instrumental resolution, is also larger (see Table 2). However, only in the case of LP 395-8, the binary system with the shortest orbital period, does rotation seem to be pseudo-synchronised with the orbital motion at periastron, although an alias period of ∼9 days cannot be excluded with the present data.

The systems EZ Psc and NLTT 23956 seem to be sub-synchronous, with rotation periods larger than their orbital period. This may indicate that these could be young binary systems still in the process of reaching synchronisation. However, synchronisation timescales are relatively short and even pre-main sequence stars are synchronised for orbital periods below 8–10 days (Mazeh 2008). By statistically analysing the Kepler eclipsing binary candidates, Lurie et al. (2017) suggested that differential rotation could also cause an apparent non-synchronisation of orbital and rotational periods if photospheric active regions are located at higher latitudes, as expected for fast rotation systems (Strassmeier 2002). In their study, they found that 13% of the FGK-type primaries with periods between 2 and 10 days, and with small expected mass ratios, are sub-synchronous, showing a ratio between orbital and rotational period of Porb/Prot ∼ 0.87. This is not far from the values we would expect for EZ Psc and NLTT 23956 assuming pseudo-synchronisation, Porb/Prot ∼ 0.82, although smaller.

Although synchronisation is not expected for long-period binary systems, GJ 3612 also shows significant variability with a semi-amplitude of ∼14 mmag and a period of ∼123 days, consistent with the orbital period within uncertainties. However, the rotation period determination may be affected by poor photometric sampling and the narrow time interval covered by the observations and, therefore, interaction between the components cannot be confirmed with the present data.

4. Results and discussion

4.1. Individual masses and radii

The analysis of the radial velocities of SB2 systems only yields the minimum masses of the components. However, it is possible to estimate absolute values using additional constraints such as mass-luminosity calibrations and mass ratios. We made use of the empirical mass-luminosity relationship (ℳ–MKs) in Benedict et al. (2016), which is based on mass measurements of astrometric M dwarf binaries. We assumed uncertainties of 0.02 M⊙ according to the scatter of the residuals of this relationship.

To estimate the individual masses, we used the systems’ Ks band magnitude of each binary system given in Table 1. From this magnitude and the flux ratio of the system, which we iteratively change between 0 and 1 in steps of 0.01, we computed a set of Ks, 1 and Ks, 2 values corresponding to each component of the system, and converted them to absolute magnitudes MKs, 1 and MKs, 2 using the distance of each system. We then determined ℳ1 and ℳ2 for each absolute magnitude using the ℳ–MKs relationship. From the set of possible values, we chose as individual masses those reproducing the mass ratio obtained from the radial velocity analysis, which are listed in Table 4. Alternatively, it is also possible to use the flux ratios derived from the spectral analysis with TODMOR, but in our case, they correspond to the flux ratio at the effective wavelengths of the VIS and NIR CARMENES channels, which have wavelengths shortwards of Ks used for the mass calibration. The second and third columns in Table 6 show the calculated individual masses for each system, with their uncertainties estimated as the standard deviation of 10 000 Monte Carlo realisations of the input parameter distribution.

Table 6.

Individual masses and absolute magnitudes computed with the mass-luminosity relation in Benedict et al. (2016) and the mass ratio in Table 4, and individual radii computed with the empirical mass-radius relation in Schweitzer et al. (in prep.).

To check the consistency of individual masses, we compared them with the minimum masses reported in Table 4, finding no discrepant values. Figure 1 shows the minimum masses found for our systems (see Table 4) compared with the ℳ–MKs calibration from Benedict et al. (2016). The arrows point towards the absolute masses derived from each component (see Table 6). Vertical arrows indicate large inclination angles between the visual and the normal to the orbital plane, while long horizontal arrows indicate systems with low inclination (i.e. small sini).

thumbnail Fig. 1.

Minimum masses, ℳ sin3 i, for the primary and secondary components of the SB2 binaries (squares). The magnitudes on the top and right axes are computed according to the ℳ–MKs relation in Benedict et al. (2016). Lines of constant mass ratio values are shown as dotted diagonals. Dashed contours correspond to the same total flux for pairs MKs, 1 and MKs, 2. The arrows point to the estimated absolute masses and magnitude MKs. Long arrows are indicative of low orbital inclinations.

Since none of the binary systems presented here are eclipsing, we computed individual radii from individual masses derived in this section and the empirical mass-radius relation in Schweitzer et al. (in prep.), R = aℳ + b, where a = 0.934  ±  0.015, b = 0.0286  ±  0.066, and R and M are in solar units. This relation is based on masses and radii of eclipsing binaries, and is valid on a mass range from 0.092 M⊙ to 0.73 M⊙. The last two columns in Table 6 provide the individual radii of the components. We have used the radii of the primary components of the binary systems to estimate the inclination of the targets showing rotation periods below 10 days, for which the spectral broadening may be close to the rotation velocity, vsini. However, only a consistent value of 38 deg was found for LP 395-8, compatible with the lack of eclipses.

4.2. Parameter distribution

We compared our M dwarf SB2 systems with those already reported. We considered the SB9 catalogue of spectroscopic binary orbits (Pourbaix et al. 2004, last update April 2018) which contains the orbital parameters of 3595 spectroscopic binaries, of which 1093 are SB2 systems. Only 18 of these systems correspond to SB2 M dwarf main sequence binary systems. A bibliographic search also results in 40 further known systems with published orbital parameters not included in SB9. Therefore, the nine systems studied in the present work bring the total number of M dwarf SB2 systems to 67, of which 29 are eclipsing, increasing the number of known SB2 systems by 15.5%. Table D.1 compiles the radial velocity parameters for all the 67 spectroscopic binary systems with M dwarf main sequence components we have found in the literature, including the systems analysed in this paper for completeness.

Figure 2 shows the parameter distribution of the SB2 systems in SB9, the M dwarf systems coming from both SB9 and the literature, and our reported new systems (red circles). The SB2s analysed in this work have typically smaller mass ratios than previously published M dwarf binaries. This results from a combination of several factors, including the high S/N and resolution of the CARMENES data, the lower semi-amplitudes induced by less massive components, and our previous literature compilation and preparatory observations, which discarded already-known binary systems from the CARMENES sample of targets (Caballero et al. 2016a; Cortés-Contreras et al. 2017; Jeffers et al. 2018). This initial cleaning also explains the apparently low binary fraction of the sample, with only 9 of the 342 surveyed stars found to be SB2s. In fact, Cortés-Contreras et al. (2017) analysed the CARMENES input catalogue and found a multiplicity fraction of 36.5  ±  2.6%.

thumbnail Fig. 2.

Parameter distribution of the SB2 spectroscopic binary systems in SB9 (black dots) and in this work (red circles). M dwarf spectroscopic binary systems in SB9 and coming from the literature are also shown as green squares. The upper panel of each column displays the one-dimensional distribution of each of parameter.

Given the orbital periods and separations of the binary systems studied here, it is worth estimating whether or not their orbits could be resolved by Gaia, since this would provide precise individual absolute masses independent from calibrations. Using the individual masses in Table 6 and the 1 Gyr stellar models in Baraffe et al. (2015), we estimated individual G-band magnitudes for each component of the systems, which are listed in Table 7. We then computed the semi-major axis of the photocenter motion in the G-band, αG, shown in the last column in Table 7. We found values ranging from 0.1 to 65 mas; therefore, given the Gaia astrometric precision of 50 μas (Lindegren et al. 2018), the astrometric orbits of all systems could be, in principle, resolved. Furthermore, all the binary systems analysed here show an astrometric excess noise (Lindegren et al. 2012) parameter above 0.25 mas, always above the median of all the Gaia sources (Lindegren et al. 2018). This may indicate that individual astrometric measurements are affected by the orbital motion of the system. Moreover, UU UMi and Ross 59 are flagged as duplicate sources in the second data release, indicating that they may be spatially resolved by Gaia.

Table 7.

Individual GaiaG-band magnitudes estimated using individual masses in Table 6 and the 1 Gyr stellar models in Baraffe et al. (2015), and motion of the semi-major axis of the photocentre in the G-band.

5. Conclusions

In this work we analysed nine new M dwarf SB2 systems found in the context of the CARMENES survey of exoplanets, increasing the number of known MM spectroscopic binaries by over 15%. Orbital parameters derived from the radial velocities, that is, period, eccentricity, argument of the periastron, radial velocity semi-amplitudes and mass ratios, are provided for these systems for the first time. Among them, three systems have periods shorter than 10 days, three have periods between 70 and 160 days, and three have periods longer than around 2 years for which additional observations may help to better constrain their properties.

Publicly available photometry for these targets was also analysed. Significant periodic signals attributed to the rotation period are found for seven of the systems. Unfortunately, no eclipses are found in any case. However, individual masses and radii were estimated using empirical calibrations for systems with parallactic distances, providing the fundamental properties of the components of the systems.

The comparison of the orbital properties of the systems studied here with those from the literature reveals that our set of low-mass binary systems have smaller mass ratios than more massive systems and those of known M dwarfs SB2s. This trend may arise from the better sensitivity of the CARMENES spectrograph towards longer wavelengths. This could also suggest that low-mass binary systems may have lower mass ratios, but more statistics are needed to confirm this trend.

Further observations of these systems will help to better constrain the properties of the long-period systems. Precise astrometric measurements from Gaia may also be very valuable to put additional constraints and derive absolute masses and inclinations. This will increase the sample of low-mass stars that can be used to refine the mass-luminosity relationship of these systems, independently of stellar models.

Acknowledgments

We are grateful to C. Jordi for useful discussions on Gaia data. We also thank the anonymous referee for a thorough and very helpful review of the paper. CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almería, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l’Espai, Insitut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. We acknowledge support from the Spanish Ministry of Economy and Competitiveness (MINECO) and the Fondo Europeo de Desarrollo Regional (FEDER) through grants ESP2013-48391-C4-1-R, ESP2014-57495-C2-2-R and AYA2015-69350-C3-2-P, AYA2016-79425–C3–1/2/3–P, ESP2016-80435-C2-1-R, as well as the support of the Generalitat de Catalunya/CERCA programme. We also acknowledge support from the Agència de Gestió d’Ajuts Universitaris i de Recerca of the Generalitat de Catalunya through grant 2018 FI_B_00188. This work makes use of data from the HARPS-N Project, a collaboration between the Astronomical Observatory of the Geneva University (lead), the CfA in Cambridge, the Universities of St. Andrews and Edinburgh, the Queens University of Belfast, and the TNG-INAF Observatory; from the public release of the WASP data as provided by the WASP consortium and services at the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program; from the MEarth Project, which is a collaboration between Harvard University and the Smithsonian Astrophysical Observatory; and from the Northern Sky Variability Survey created jointly by the Los Alamos National Laboratory and University of Michigan and funded by the Department of Energy, the National Aeronautics and Space Administration, and the National Science Foundation. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

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Appendix A: Radial velocity data

Table A.1.

Radial velocity measurements.

Appendix B: Radial velocity data fits

thumbnail Fig. B.1.

Radial velocity curves of our targets as a function of the orbital phase. VIS and NIR CARMENES data are shown in the left and right panels, respectively, for each target as labelled. The top plot in each panel displays the radial velocity data of the primary (blue circle) and secondary (red triangle) components, along with their best-fitting models (blue solid and red dashed lines, respectively). The bottom plot on each panel shows the residuals of the best fit. For Ross 59, HARPS data for the primary (green circles) and secondary (violet triangles) are also shown.

thumbnail Fig. B.1.

continued.

thumbnail Fig. B.1.

continued.

Appendix C: Photometric data and periodogram analysis

thumbnail Fig. C.1.

Photometry data and analysis for the stellar systems analysed in this work. Each panel corresponds to a binary system as labelled. For each system, top panel: light curve as a function of time and mean value of the uncertainty of the observations. Middle panel: light curve phase to the photometric period found and the best sinusoidal fit. Bottom panel: periodogram and window function of the data and the best period found (red dot-dashed line).

thumbnail Fig. C.1.

continued.

Appendix D: Known double-line spectroscopic binaries

Table D.1.

Known M dwarf SB2 systems with published orbital parameters.

All Tables

Table 1.

Main properties and observing log of the spectroscopic binaries studied in this work.

In the text
Table 2.

Spectral properties of the templates used to derive radial velocities with TODMOR in the VIS and NIR channel spectra.

In the text
Table 3.

Radial velocity parameters fitted for each binary system.

In the text
Table 4.

Physical parameters derived from the radial velocity fits.

In the text
Table 5.

Available photometry for the spectroscopic binaries analysed in this work.

In the text
Table 6.

Individual masses and absolute magnitudes computed with the mass-luminosity relation in Benedict et al. (2016) and the mass ratio in Table 4, and individual radii computed with the empirical mass-radius relation in Schweitzer et al. (in prep.).

In the text
Table 7.

Individual GaiaG-band magnitudes estimated using individual masses in Table 6 and the 1 Gyr stellar models in Baraffe et al. (2015), and motion of the semi-major axis of the photocentre in the G-band.

In the text
Table A.1.

Radial velocity measurements.

In the text
Table D.1.

Known M dwarf SB2 systems with published orbital parameters.

In the text

All Figures

thumbnail Fig. 1.

Minimum masses, ℳ sin3 i, for the primary and secondary components of the SB2 binaries (squares). The magnitudes on the top and right axes are computed according to the ℳ–MKs relation in Benedict et al. (2016). Lines of constant mass ratio values are shown as dotted diagonals. Dashed contours correspond to the same total flux for pairs MKs, 1 and MKs, 2. The arrows point to the estimated absolute masses and magnitude MKs. Long arrows are indicative of low orbital inclinations.
In the text
thumbnail Fig. 2.

Parameter distribution of the SB2 spectroscopic binary systems in SB9 (black dots) and in this work (red circles). M dwarf spectroscopic binary systems in SB9 and coming from the literature are also shown as green squares. The upper panel of each column displays the one-dimensional distribution of each of parameter.
In the text
thumbnail Fig. B.1.

Radial velocity curves of our targets as a function of the orbital phase. VIS and NIR CARMENES data are shown in the left and right panels, respectively, for each target as labelled. The top plot in each panel displays the radial velocity data of the primary (blue circle) and secondary (red triangle) components, along with their best-fitting models (blue solid and red dashed lines, respectively). The bottom plot on each panel shows the residuals of the best fit. For Ross 59, HARPS data for the primary (green circles) and secondary (violet triangles) are also shown.
In the text
thumbnail Fig. B.1.

continued.
In the text
thumbnail Fig. B.1.

continued.
In the text
thumbnail Fig. C.1.

Photometry data and analysis for the stellar systems analysed in this work. Each panel corresponds to a binary system as labelled. For each system, top panel: light curve as a function of time and mean value of the uncertainty of the observations. Middle panel: light curve phase to the photometric period found and the best sinusoidal fit. Bottom panel: periodogram and window function of the data and the best period found (red dot-dashed line).
In the text
thumbnail Fig. C.1.

continued.
In the text

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