- ID:
- ivo://CDS.VizieR/J/AJ/151/110
- Title:
- BEST-II catalog of variables: CoRoT SRc02 field
- Short Name:
- J/AJ/151/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Time-series photometry of the CoRoT field SRc02 was obtained by the Berlin Exoplanet Search Telescope II (BEST II) in 2009. The main aim was to conduct a ground-based follow-up of the CoRoT field in order to detect variable stars with better spatial resolution than what can be achieved with the CoRoT Space Telescope. A total of 1846 variable stars were detected, of which only 30 have been previously known. For nine eclipsing binaries the stellar parameters were determined by modeling their light curves.
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- ID:
- ivo://CDS.VizieR/J/AJ/156/204
- Title:
- BEST-II catalog of variables. III. Puppis field
- Short Name:
- J/AJ/156/204
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Berlin Exoplanet Search Telescope II (BEST II) is a ground-based, small aperture, wide-angle telescope used to search for stellar light variations in the southern hemisphere. We report the results of a monitoring campaign observing a field in the Puppis constellation in late 2011/early 2012. Light curves were obtained for 130472 stars, out of which we identify 2169 variables, including 1829 newly discovered, 26 previously known, and 314 suspected variable stars. We determine periods and variability class for two previously known, but only suspected to be, variable stars. For eight individual eclipsing binary stars, including the two previously known but unclassified binaries, the system parameters were derived at the epoch of the observation by modeling the light curves. Eventually, in a catalog for all variable stars, we present coordinates, magnitude, and elements of light variations, e.g., epoch, period, amplitude, type, and light curves. This catalog concludes the BEST/BEST II project.
- ID:
- ivo://CDS.VizieR/J/AJ/146/136
- Title:
- BEST-II catalog of variables. I. Southern fields
- Short Name:
- J/AJ/146/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A photometric survey of three southern target fields with BEST II yielded the detection of 2406 previously unknown variable stars and an additional 617 stars with suspected variability. This study presents a catalog including their coordinates, magnitudes, light curves, ephemerides, amplitudes, and type of variability. In addition, the variability of 17 known objects is confirmed, thus validating the results. The catalog contains a number of known and new variables that are of interest for further astrophysical investigations, in order to, e.g., search for additional bodies in eclipsing binary systems, or to test stellar interior models. Altogether, 209070 stars were monitored with BEST II during a total of 128 nights in 2009/2010. The overall variability fraction of 1.2%-1.5% in these target fields is well comparable to similar ground-based photometric surveys. Within the main magnitude range of R{isin}[11, 17], we identify 0.67(3)% of all stars to be eclipsing binaries, which indicates a completeness of about one third for this particular type in comparison to space surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/506/569
- Title:
- BEST-II periodic variables in CoRoT LRa02 field
- Short Name:
- J/A+A/506/569
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Berlin Exoplanet Search Telescope II (BEST II) is a small wide field-of-view photometric survey telescope system located at the Observatorio Cerro Armazones, Chile. The high duty cycle combined with excellent observing conditions and millimagnitude photometric precision makes this instrument suitable for ground based support observations for the CoRoT space mission. Photometric data of the CoRoT LRa02 target field collected between November 2008 and March 2009 were analysed for stellar variability. The presented results will help in the future analysis of the CoRoT data, particularly in additional science programs related to variable stars. BEST II observes selected CoRoT target fields ahead of the space mission. The photometric data acquired are searched for stellar variability, periodic variable stars are identified with time series analysis of the obtained stellar light curves. We obtained the light curves of 104335 stars in the CoRoT LRa02 field over 41 nights. Variability was detected in light curves of 3726 stars of which 350 showed a regular period. These stars are, with the exception of 5 previously known variable stars, new discoveries.
- ID:
- ivo://CDS.VizieR/J/AJ/143/140
- Title:
- BEST-II periodic variables in CoRoT LRa02 field. II.
- Short Name:
- J/AJ/143/140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CoRoT (Convection, Rotation and planetary Transit) field LRa02 has been observed with the Berlin Exoplanet Search Telescope II (BEST II) during the southern summer 2007/2008. A first analysis of stellar variability led to the publication of 345 newly discovered variable stars. Now, a deeper analysis of this data set was used to optimize the variability search procedure. Several methods and parameters have been tested in order to improve the selection process compared to the widely used J index for variability ranking. This paper describes an empirical approach to treat systematic trends in photometric data based upon the analysis of variance statistics that can significantly decrease the rate of false detections. Finally, the process of reanalysis and method improvement has virtually doubled the number of variable stars compared to the first analysis by Kabath et al. (Paper I, 2009, Cat. J/A+A/506/569). A supplementary catalog of 272 previously unknown periodic variables plus 52 stars with suspected variability is presented. Improved ephemerides are given for 19 known variables in the field. In addition, the BEST II results are compared with CoRoT data and its automatic variability classification.
- ID:
- ivo://CDS.VizieR/J/A+A/496/813
- Title:
- Binary PNe towards the Galactic bulge
- Short Name:
- J/A+A/496/813
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Binarity has been hypothesised to play an important, if not ubiquitous, role in the formation of planetary nebulae (PNe). Yet there remains a severe paucity of known binary central stars required to test the binary hypothesis and to place strong constraints on the physics of the common-envelope (CE) phase of binary stellar evolution. Large photometric surveys offer an unrivalled opportunity to efficiently discover many binary central stars. We have combined photometry from the OGLE microlensing survey with the largest sample of PNe towards the Galactic bulge to systematically search for new binaries. A total of 21 periodic binaries were found thereby more than doubling the known sample. The orbital period distribution was found to be best described by CE population synthesis models when no correlation between primary and secondary masses is assumed for the initial mass ratio distribution. A comparison with post-CE white dwarf binaries indicates both distributions are representative of the true post-CE period distribution with most binaries exhibiting periods less than one day. An estimated close binary fraction of 12-21% is derived and is the first robust and independent validation of the prevailing 10-15% fraction estimated by Bond (2000, in Asymmetrical Planetary Nebulae II: From Origins to Microstructures, 199, 115). This suggests that binarity is not a precondition for the formation of PNe and that close binaries do not play a dominant role in the shaping of nebular morphologies. Systematic effects and biases of the survey are discussed with implications for future photometric surveys.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/43
- Title:
- Binary stars parameters from LAMOST & Kepler obs.
- Short Name:
- J/ApJS/244/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The parameter distribution of binaries is a fundamental knowledge of the stellar systems. A statistical study on the binary stars is carried out based on the LAMOST spectral and Kepler photometric database. We presented a catalog of 1320 binary stars with plentiful parameters, including period, binary subtype, atmosphere parameters (Teff, [Fe/H], and logg), and the physical properties, such as mass, radius, and age, for the primary component stars. Based on this catalog, the unbiased distribution, rather than the observed distribution, was obtained after the correction of selection biases by the Monte Carlo method considering comprehensive affecting factors. For the first time, the orbital eccentricity distribution of the detached binaries is presented. The distribution differences between the three subtypes of binaries (detached, semidetached, and contact) are demonstrated, which can be explained by the generally accepted evolutional scenarios. Many characteristics of the binary stars, such as huge mass transfer on semidetached binaries, period cutoff on contact binaries, period-temperature relationship of contact binaries, and the evolved binaries, are reviewed by the new database. This work supports a common evolutionary scenario for all subtypes of binary stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/183
- Title:
- Binary stellar evolution data for Kepler systems
- Short Name:
- J/ApJ/832/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Inspired by the recent Kepler discoveries of circumbinary planets orbiting nine close binary stars, we explore the fate of the former as the latter evolve off the main sequence. We combine binary star evolution models with dynamical simulations to study the orbital evolution of these planets as their hosts undergo common-envelope (CE) stages, losing in the process a tremendous amount of mass on dynamical timescales. Five of the systems experience at least one Roche-lobe overflow and CE stage (Kepler-1647 experiences three), and the binary stars either shrink to very short orbits or coalesce; two systems trigger a double-degenerate supernova explosion. Kepler's circumbinary planets predominantly remain gravitationally bound at the end of the CE phase, migrate to larger orbits, and may gain significant eccentricity; their orbital expansion can be more than an order of magnitude and can occur over the course of a single planetary orbit. The orbits these planets can reach are qualitatively consistent with those of the currently known post-CE, eclipse-time variations circumbinary candidates. Our results also show that circumbinary planets can experience both modes of orbital expansion (adiabatic and nonadiabatic) if their host binaries undergo more than one CE stage; multiplanet circumbinary systems like Kepler-47 can experience both modes during the same CE stage. Additionally, unlike Mercury orbiting the Sun, a circumbinary planet with the same semimajor axis can survive the CE evolution of a close binary star with a total mass of 1M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/152/180
- Title:
- Bolometric fluxes of eclipsing binaries in Tycho-2
- Short Name:
- J/AJ/152/180
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present fits to the broadband photometric spectral energy distributions (SEDs) of 158 eclipsing binaries (EBs) in the Tycho-2 catalog. These EBs were selected because they have highly precise stellar radii, effective temperatures, and in many cases metallicities previously determined in the literature, and thus have bolometric luminosities that are typically good to <~10%. In most cases the available broadband photometry spans a wavelength range 0.4-10{mu}m, and in many cases spans 0.15-22{mu}m. The resulting SED fits, which have only extinction as a free parameter, provide a virtually model-independent measure of the bolometric flux at Earth. The SED fits are satisfactory for 156 of the EBs, for which we achieve typical precisions in the bolometric flux of {\simeq}3%. Combined with the accurately known bolometric luminosity, the result for each EB is a predicted parallax that is typically precise to <~5%. These predicted parallaxes-with typical uncertainties of 200{mu}as-are 4-5 times more precise than those determined by Hipparcos for 99 of the EBs in our sample, with which we find excellent agreement. There is no evidence among this sample for significant systematics in the Hipparcos parallaxes of the sort that notoriously afflicted the Pleiades measurement. The EBs are distributed over the entire sky, span more than 10mag in brightness, reach distances of more than 5kpc, and in many cases our predicted parallaxes should also be more precise than those expected from the Gaia first data release. The EBs studied here can thus serve as empirical, independent benchmarks for these upcoming fundamental parallax measurements.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A1
- Title:
- Bright B-type variables in Scorpius
- Short Name:
- J/A+A/557/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first two of a total of six nano-satellites that will constitute the BRITE-Constellation space photometry mission have recently been launched successfully. In preparation for this project, we carried out time-resolved colour photometry in a field that is an excellent candidate for BRITE measurements from space. We acquired 117h of Stromgren uvy data during 19 nights. Our targets comprised the {beta} Cephei stars {kappa} and {lambda} Sco, the eclipsing binary {mu}^1^ Sco, and the variable super/hypergiant {zeta}^1^ Sco. For {kappa} Sco, a photometric mode identification in combination with results from the spectroscopic literature suggests a dominant (l,m)=(1,-1) {beta} Cephei-type pulsation mode of the primary star. The longer period of the star may be a rotational variation or a g-mode pulsation. For {lambda} Sco, we recover the known dominant {beta} Cephei pulsation, a longer-period variation, and observed part of an eclipse. Lack of ultraviolet data precludes mode identification for this star. We noticed that the spectroscopic orbital ephemeris of the closer pair in this triple system is inconsistent with eclipse timings and propose a refined value for the orbital period of the closer pair of 5.95189+/-0.00003d. We also argue that the components of the {lambda} Sco system are some 30% more massive than previously thought. The binary light curve solution of {mu}^1^ Sco requires inclusion of the irradiation effect to explain the u light curve, and the system could show additional low amplitude variations on top of the orbital light changes. {zeta}^1^ Sco shows long-term variability on a time scale of at least two weeks that we prefer to interpret in terms of a variable wind or strange mode pulsations.
