- ID:
- ivo://CDS.VizieR/J/ApJ/707/671
- Title:
- IM Vir BVRI photometry and radial velocities
- Short Name:
- J/ApJ/707/671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report extensive spectroscopic and differential photometric BVRI observations of the active, detached, 1.309-day double-lined eclipsing binary IM Vir, composed of a G7-type primary and a K7 secondary. With these observations, we derive accurate absolute masses and radii of M1=0.981+/-0.012M_{sun}_, M2=0.6644+/-0.0048M_{sun}_, R1=1.061+/-0.016R_{sun}_, and R2=0.681+/-0.013R_{sun}_ for the primary and secondary, with relative errors under 2%. The effective temperatures are 5570+/-100K and 4250+/-130K, respectively. The significant difference in mass makes this a favorable case for comparison with stellar evolution theory. We find that both stars are larger than the models predict, by 3.7% for the primary and 7.5% for the secondary, as well as cooler than expected, by 100K and 150K, respectively. These discrepancies are in line with previously reported differences in low-mass stars, and are believed to be caused by chromospheric activity, which is not accounted for in current models. The effect is not confined to low-mass stars: the rapidly rotating primary of IM Vir joins the growing list of objects of near-solar mass (but still with convective envelopes) that show similar anomalies. The comparison with the models suggests an age of 2.4Gyr for the system, and a metallicity of [Fe/H]~-0.3 that is consistent with other indications, but requires confirmation.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/430/2029
- Title:
- Initial masses of W UMa type contact binaries
- Short Name:
- J/MNRAS/430/2029
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- W UMa type binaries have two defining characteristics. These are (i) the effective temperatures of both components are very similar, and (ii) the secondary (currently less massive) component is overluminous for its current mass. We consider the latter to be an indication of its mass before the mass transfer event. For these stars, we define a mass difference ({delta}M) between the mass determined from its luminosity and the present mass determined from fitting the binary orbit. We compare the observed values of the mass difference to stellar models with mass-loss. The range of initial secondary masses that we find for observed W UMa type binaries is 1.3-2.6M_{sun}_. We discover that the A- and the W-subtype contact binaries have different ranges of initial secondary masses. Binary systems with an initial mass higher than 1.8+/-0.1M_{sun}_ become A-subtype while systems with initial masses lower than this become W-subtype. Only 6 per cent of systems violate this behaviour. We also obtain the initial masses of the primaries using the following constraint for the reciprocal of the initial mass ratio: 0<1/q_i_<1. The range of initial masses we find for the primaries is 0.2-1.5M_{sun}_, except for two systems. Finally in comparing our models to observed systems, we find evidence that the mass transfer process is not conservative. We find that only 34 per cent of the mass from the secondary is transferred to the primary. The remainder is lost from the system.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A71
- Title:
- IUE continuum fluxes of SY Mus
- Short Name:
- J/A+A/602/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Light curves (LCs) of some symbiotic stars show a different slope of the ascending and descending branch of their minimum profile. The origin of this asymmetry is not well understood. We explain this effect in the ultraviolet LCs of the symbiotic binary SY Mus. We model the continuum fluxes in the spectra obtained by the International Ultraviolet Explorer at ten wavelengths, from 1280 to 3080{AA}. We consider that the white dwarf radiation is attenuated by H^0^ atoms, H^-^ ions, and free electrons in the red giant wind. Variation in the nebular component is approximated by a sine wave along the orbit as suggested by spectral energy distribution models. The model includes asymmetric wind velocity distribution and the corresponding ionization structure of the binary. We determined distribution of the H^0^ and H^+^, as well as upper limits of H^-^ and H^0^ column densities in the neutral and ionized region at the selected wavelengths as functions of the orbital phase. Corresponding models of the LCs match well the observed continuum fluxes. In this way, we suggested the main UV continuum absorbing (scattering) processes in the circumbinary environment of S-type symbiotic stars. The asymmetric profile of the ultraviolet LCs of SY Mus is caused by the asymmetric distribution of the circumstellar matter at the near-orbital-plane area.
- ID:
- ivo://CDS.VizieR/J/AcA/54/347
- Title:
- IVB mag of LMC ellipsoidal variables
- Short Name:
- J/AcA/54/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the OGLE-II and OGLE-III photometry of red giants in the Large Magellanic Cloud to select and study objects revealing ellipsoidal variability. We detected 1546 candidates for long period ellipsoidal variables and 121 eclipsing binary systems with clear ellipsoidal modulation.
- ID:
- ivo://CDS.VizieR/J/AJ/149/125
- Title:
- Iybvu photometry and CCD spectroscopy of RX Gem
- Short Name:
- J/AJ/149/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained full-orbit Iybvu intermediate-band photometry and CCD spectroscopy of the long-period Algol eclipsing binary RX Geminorum. Photometric solutions using the Wilson-Devinney code give a gainer rotation (hotter, mass-accreting component) about 15 times the synchronous rate. We describe a simple technique to detect departures from uniform rotation of the hotter component. These binaries radiate double-peaked H{alpha} emission from a low-mass accretion disk around the gainer. We used an approximate non-LTE disk code to predict models in fair agreement with observations, except in the far wings of the emission profile, where the star-inner disk boundary layer emits extra radiation. Variations in H{alpha} emission derive from modulations in the transfer rate. A study of times of minima during the 20th century suggests that a perturbing third body is present near RX Gem.
- ID:
- ivo://CDS.VizieR/J/AJ/145/113
- Title:
- JHK photometry in Cyg OB7. II. Variable stars
- Short Name:
- J/AJ/145/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a subset of the results of a three-season, 124 nights, near-infrared monitoring campaign of the dark clouds Lynds 1003 and Lynds 1004 in the Cygnus OB7 star-forming region. In this paper, we focus on the field star population. Using three seasons of UKIRT J, H, and K-band observations spanning 1.5 years, we obtained high-quality photometry on 9200 stars down to J=17mag, with photometric uncertainty better than 0.04mag. After excluding known disk-bearing stars we identify 149 variables-1.6% of the sample. Of these, about 60 are strictly periodic, with periods predominantly <2days. We conclude this group is dominated by eclipsing binaries. A few stars have long period signals of between 20 and 60 days. About 25 stars have weak modulated signals, but it was not clear if these were periodic. Some of the stars in this group may be diskless young stellar objects with relatively large variability due to cool starspots. The remaining ~60 stars showed variations which appear to be purely stochastic.
- ID:
- ivo://CDS.VizieR/J/ApJ/699/1196
- Title:
- JHKs light curves of 2MASS J05352184-0546085
- Short Name:
- J/ApJ/699/1196
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared JHK_S_ light curves for the double-lined eclipsing binary system Two Micron All Sky Survey J05352184-0546085, in which both components have been shown to be brown dwarfs with an age of ~1Myr. We analyze these light curves together with the previously published I_C_-band light curve and radial velocities to provide refined measurements of the system's physical parameters. The component masses and radii are here determined with an accuracy of ~6.5% and ~1.5%, respectively. In addition, we confirm the previous surprising finding that the primary brown dwarf has a cooler effective temperature than its lower mass companion. Our analysis reveals two low-amplitude (~0.02mag) periodic signals, one attributable to the rotation of the primary with a period of 3.293+/-0.001d and the other to the rotation of the secondary with a period of 14.05+/-0.05d. Both periods are consistent with the measured vsin i and radii.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/3240
- Title:
- Ji photometry of WTS 19g-4-02069
- Short Name:
- J/MNRAS/431/3240
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star formation theory predicts that short-period M-dwarf binaries with highly unequal-mass components are rare. First, the mass ratio of close binary systems is driven to unity due to the secondary preferentially accreting gas with high angular momentum. Secondly, both dynamical decay of multiple systems and interactions with tertiary stars that tighten the binary orbit will eject the lowest mass member. Generally, only the two most massive stars are paired after such interactions, and the frequency of tight unequal-mass binaries is expected to decrease steeply with primary mass. In this paper, we present the discovery of a highly unequal-mass eclipsing M-dwarf binary, providing a unique constraint on binary star formation theory and on evolutionary models for low-mass binary stars. The binary is discovered using high-precision infrared light curves from the United Kingdom Infrared Telescope (UKIRT) Wide Field Camera (WFCAM) Transit Survey and has an orbital period of 2.44d. We find stellar masses of M_1_=0.53(+/-0.02)M_{sun}_ and M_2_=0.143(+/-0.006)M_{sun}_ (mass ratio 0.27), and radii of R_1_=0.51(+/-0.01)R_{sun}_ and R_2_=0.174(+/-0.006)R_{sun}_. This puts the companion in a very sparsely sampled and important late M-dwarf mass regime. Since both stars will share the same age and metallicity and straddle the theoretical boundary between fully and partially convective stellar interiors, a comparison can be made to model predictions over a large range of M-dwarf masses using the same model isochrone. Both stars appear to have a slightly inflated radius compared to 1Gyr` model predictions for their masses, but future work is needed to properly account for the effects of star spots on the light-curve solution. A significant, subsynchronous, ~2.56d signal with ~2% peak-to-peak amplitude is detected in the WFCAM light curve, which we attribute to rotational modulation of cool star spots. We propose that the subsynchronous rotation is either due to a stable star-spot complex at high latitude on the (magnetically active) primary (i.e. differential rotation), or additional magnetic braking, or interaction of the binary with a third body or circumbinary disc during its pre-main-sequence phase.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A50
- Title:
- J0113+31 light + velocity curves
- Short Name:
- J/A+A/572/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive the fundamental properties of 1SWASP J011351.29+314909.7 (J0113+31), a metal-poor (-0.40+/-0.04dex), eclipsing binary in an eccentric orbit (~0.3) with an orbital period of 14.277d. Eclipsing M dwarfs that orbit solar-type stars (EBLMs), like J0113+31, have been identified from their light curves and follow-up spectroscopy in the course of the WASP transiting planet search. We present the analysis of the first binary of the EBLM sample for which masses, radii and temperatures of both components are derived. The primary component with a mass of 0.945+/-0.045M_{sun}_ has a large radius (1.378+/-0.058R_{sun}_) indicating that the system is quite old, ~9.5Gyr. The M-dwarf secondary mass of 0.186+/-0.010M_{sun}_ and radius of 0.209+/-0.011R_{sun}_ are fully consistent with stellar evolutionary models. However, from the near-infrared secondary eclipse light curve, the M dwarf is found to have an effective temperature of 3922+/-42K, which is ~600K hotter than predicted by theoretical models. We present the WASP light curve, the optical follow-up light curves, the near-infrared light curve of the secondary eclipse, and the radial velocity measurements of J0113+31.
- ID:
- ivo://CDS.VizieR/J/AJ/106/2058
- Title:
- Karle observations of V505 Sgr
- Short Name:
- J/AJ/106/2058
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- V505 Sgr is a classical Algol system consisting of an A2 V primary and a G5 IV secondary that fills its Roche lobe. New times of minimum light are presented. The period of the eclipsing system (1.18287d) varies, due in part to an orbital light-time effect. A third component has been detected that orbits the eclipsing pair. This investigation uses the SIMPLEX algorithm [Kallrath & Linnell, ApJ, 313, 346 (1987)] and the Differential Correction code [Wilson, ApJ, 234, 1054 (1979)] to analyze two separate datasets. The results indicate the third component, an F8 V star, contributes about 5% of the light to the system. The minimum projected distance between the third component and the eclipsing pair is 37 AU. This implies an orbital period of about 105 years, a value that differs with the O-C data. The photometric solution, combined with recent spectroscopic data, yields R(1)=2.14R(Sun) and R(2)=2.24R(Sun) and M(1)=2.20M(Sun) and M(2)=1.15M(Sun).
