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- ID:
- ivo://CDS.VizieR/J/AJ/160/175
- Title:
- BVRcIc light curve of eclisping binary V1023 Persei
- Short Name:
- J/AJ/160/175
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- V1023 Per is a polar spotted, but well-detached dwarf binary, very likely a Pre-WUMa eclipsing binary. It was observed on 11 nights in 2015 October, November, and December at Dark Sky Observatory in North Carolina with the 0.81m reflector of Appalachian State University. The period behavior is complex and may be increasing with a cubic or quadratic ephemeris. Its odd light curves are of high amplitude but have no totality and reach maximum light just before and following the secondary eclipse, indicating that it has polar spots similar to UV Leo. The 28yr orbital period study calls the attention of observers to further monitor this binary to understand the complex nature of the period evolution. Its presently fixed polar spot does indicate that it must have a strong magnetic field and that it is synchronously rotating. The BVRcIc simultaneous 2016 Wilson-Devinney program (W-D) solution gives fillouts of 68% and 75% for the primary and secondary components, respectively. The polar position of the spot, its radius (24{deg}), and T-fact (0.75) indicate that a strong magnetic field is present. The small {Delta}T in the components (~289K) show that the stars are similar in spectral type despite them being well detached. The inclination is high, ~85.19{deg}{+/-}0.04{deg}, but there is not a total eclipse due to the high mass ratio (~0.739{+/-}0.001). Due to the low galactic position (longitude=150.390{deg}, latitude=-1.023{deg}), its reddening is addressed. The primary components temperature is estimated to be 5250{+/-}250K.
- ID:
- ivo://CDS.VizieR/J/AJ/157/3
- Title:
- BVRI light curves of the binary QS Vir
- Short Name:
- J/AJ/157/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed the post-common-envelope eclipsing binary with a white dwarf component, QS Vir, using the 1.88 m telescope of Kotammia Observatory in Egypt. The new observations were analyzed together with all multicolor light curves available online (sampling a period of 25 yr), using a full-feature binary system modeling software based on Roche geometry. This is the first time complete photometric modeling was done with most of these data. QS Vir is a detached system, with the red dwarf component underfilling its Roche lobe by a small margin. All light curves feature out-of-eclipse variability that is associated with ellipsoidal variation, mutual irradiation and irregularities in surface brightness of the tidally distorted and magnetically active red dwarf. We tested models with one, two, and three dark spots and found that one spot is sufficient to account for the light curve asymmetry in all data sets, although this does not rule out the presence of multiple spots. We also found that a single spotted model cannot fit light curves observed simultaneously in different filters. Instead, each filter requires a different spot configuration. To thoroughly explore the parameter space of spot locations, we devised a grid-search procedure and used it to find consistent solutions. Based on this, we conclude that the dark spot responsible for light curve distortions has been stable for the past 15 yr, after a major migration that happened between 1993 and 2002, possibly due to a flip-flop event.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A11
- Title:
- BVRI light curves of V374 Peg
- Short Name:
- J/A+A/590/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ultrafast-rotating (Prot~0.44d) fully convective single M4 dwarf V374 Peg is a well-known laboratory for studying intense stellar activity in a stable magnetic topology. As an observable proxy for the stellar magnetic field, we study the stability of the light curve, hence the spot configuration. We also measure the occurrence rate of flares and coronal mass ejections (CMEs). We have analysed spectroscopic observations, BV(RI)C photometry covering 5yrs, and additional RC photometry that expands the temporal base over 16yr. The light curve suggests an almost rigid-body rotation and a spot configuration that is stable over about 16 yrs, confirming the previous indications of a very stable magnetic field. We observed small changes on a nightly timescale and frequent flaring, including a possible sympathetic flare. The strongest flares seem to be more concentrated around the phase where the light curve indicates a smaller active region. Spectral data suggest a complex CME with falling-back and re-ejected material with a maximal projected velocity of ~675km/s. We observed a CME rate that is much lower than expected from extrapolations of the solar flare-CME relation to active stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/3189
- Title:
- CaII and H{alpha} data for dK5/dM4 stars
- Short Name:
- J/MNRAS/421/3189
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use 665 high-resolution spectra for 60 different dM4 stars and 1088 high-resolution spectra for 97 different dK5 stars from the European Southern Observatory (ESO) and Observatoire de Haute Provence (OHP) data bases. We present 179 new measurements of the CaII resonance lines and 615 new measurements of the H{alpha} line for dM4 stars. We also present 701 new measurements of the CaII resonance lines and 1088 new measurements of the H{alpha} line for dK5 stars. We also compiled other measurements available in the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/177/131
- Title:
- CaII and MgII excess flux density in cool stars
- Short Name:
- J/A+A/177/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relation between the CaII H and K line-tore flux density and rotation period is studied for a sample of 313 cool stars of luminosity classes ranging from II-III to V, and compared to similar relations for MgII h and k and soft X-ray.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/1591
- Title:
- CaII equivalent widths of dM1 stars
- Short Name:
- J/MNRAS/426/1591
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 187 high-resolution spectra for 62 different M1 dwarfs from observations obtained with the FIbre-fed Echelle Spectrograph (FIES) on the Nordic Optical Telescope (NOT) and from observations with the Fibre-fed Extended Range Echelle Spectrograph (FEROS) from the European Southern Observatory (ESO) data base. We also compiled other measurements available in the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/339/858
- Title:
- Calibration of stellar parameters
- Short Name:
- J/A+A/339/858
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of calibration of the surface brightness, bolometric flux and effective temperature scales are presented for 537 dwarfs and giants selected as standards for the Infrared Space Observatory (ISO). Individual temperatures with small model-dependent corrections are derived at the target accuracy of 1%. The comparison with semiempirical values achieved by the Infrared Flux Method (IRFM) shows consistent results within the 1% level for F, G and K stars, but not for A-type stars.
- ID:
- ivo://CDS.VizieR/J/other/Sci/292.698
- Title:
- Candidate halo dark matter
- Short Name:
- J/other/Sci/292.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Milky Way galaxy contains a large, spherical component which is believed to harbor a substantial amount of unseen matter. Recent observations indirectly suggest that as much as half of this "dark matter" may be in the form of old, very cool white dwarfs, the remnants of an ancient population of stars as old as the galaxy itself. We conducted a survey to find faint, cool white dwarfs with large space velocities, indicative of their membership in the galaxy's spherical halo component. The survey reveals a substantial, directly observed population of old white dwarfs, too faint to be seen in previous surveys. This newly discovered population accounts for at least 2 percent of the halo dark matter. It provides a natural explanation for the indirect observations, and represents a direct detection of galactic halo dark matter.
- ID:
- ivo://CDS.VizieR/J/ApJ/497/330
- Title:
- Candidate main-sequence stars
- Short Name:
- J/ApJ/497/330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Vega-like sources are main-sequence stars that exhibit IR fluxes in excess of expectations for stellar photospheres, most likely due to reradiation of stellar emission intercepted by orbiting dust grains. We have identified a large sample of main-sequence stars with possible excess IR radiation by cross-correlating the Michigan Catalog of Two-dimensional Spectral Types for the HD Stars with the IRAS Faint Source Survey Catalog. Some 60 of these Vega-like sources were not found during previous surveys of the IRAS database, the majority of which employed the lower sensitivity Point Source Catalog. Here, we provide details of our search strategy, together with a preliminary examination of the full sample of Vega-like sources.
