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421. BEST periodic variable stars in IR01 field
ID:
ivo://CDS.VizieR/J/AJ/134/1560
Title:
BEST periodic variable stars in IR01 field
Short Name:
J/AJ/134/1560
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on observations of the COROT IR01 field with the Berlin Exoplanet Search Telescope (BEST). BEST is a small-aperture telescope with a wide field of view (FOV). It is dedicated to searching for variable stars within the target fields of the COROT space mission to aid in minimizing false-alarm rates, and identifying potential targets for additional science. COROT's observational program started in 2007 February, with the "initial run" field (IR01) observed for about 2 months. BEST observed this field for 12 nights spread over 3 months in winter 2006. From the total of 30,426 stars observed in the IR01 field, 3769 were marked as suspected variable stars, and 54 of these showed clear periodicity. From these, 19 periodic stars are within the part of the COROT FOV covered in our data set.
422. BEST periodic variable stars in LRa1 field
ID:
ivo://CDS.VizieR/J/AJ/136/654
Title:
BEST periodic variable stars in LRa1 field
Short Name:
J/AJ/136/654
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we report on observations of the CoRoT LRa1 field with the Berlin Exoplanet Search Telescope (BEST). The current paper is part of a series of papers describing the results of our stellar variability survey. The BEST is a small aperture telescope with a wide field of view (FOV). It is dedicated to searching for stellar variability within the target fields of the CoRoT space mission to aid in minimizing false-alarm rates and identify potential targets for additional science. The LRa1 field is CoRoT's second long run field located in the galactic anticenter direction. We observed the LRa1 stellar field on 23 nights between November and March 2005/2006. From 6099 stars marked as variable, 39 were classified as periodic variable stars and 27 of them are within the CoRoT FOV. We also confirmed the variability for four stars listed in the General Catalogue of Variable Stars (GCVS).
423. BEST periodic variable stars in LRc2 field
ID:
ivo://CDS.VizieR/J/AJ/137/3911
Title:
BEST periodic variable stars in LRc2 field
Short Name:
J/AJ/137/3911
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on photometric observations of the CoRoT LRc2 field with the new robotic Berlin Exoplanet Search Telescope II (BEST II). The telescope system was installed and commissioned at the Observatorio Cerro Armazones, Chile, in 2007. BEST II is a small aperture telescope with a wide field of view dedicated to the characterization of the stellar variability primarily in CoRoT target fields with high stellar densities. The CoRoT stellar field LRc2 was observed with BEST II up to 20 nights in 2007 July and August. From the acquired data containing about 100,000 stars, 426 new periodic variable stars were identified and 90% of them are located within the CoRoT exoplanetary CCD segments and may be of further interest for CoRoT additional science programs.
424. BEST variable stars in LRc1 field
ID:
ivo://CDS.VizieR/J/AJ/134/766
Title:
BEST variable stars in LRc1 field
Short Name:
J/AJ/134/766
Date:
21 Oct 2021
Publisher:
CDS
Description:
The COROT space mission will monitor several target fields for up to 150 days to perform asteroseismology and to search for extrasolar planets by photometric transits. Variable stars in the target fields are important objects for additional scientific studies but can also disturb the search for planetary transits. A variability characterization of the target fields prior to COROT observations is therefore important for two reasons: to find interesting variable stars to monitor further and to make an analysis of the impact of the variable stars on detecting extrasolar planet transits with COROT. The Berlin Exoplanet Search Telescope (BEST) is a small wide-angle telescope dedicated to high-precision photometry. It has observed a 9deg^2^ field of view centered at (RA,DE)=(19:00:00.0+00:01:55.2) (J2000.0) over 98 nights to search for variable stars in the surroundings of the first long-run target field (LRc1) of the COROT space mission. In this data set we identified 92 periodic variable stars, 86 of which are new discoveries and 6 of which are known from the General Catalogue of Variable Stars (GCVS). For five of the GCVS stars, variability could not be confirmed. Forty-three of the 92 detected periodic variable stars are identified as eclipsing binaries. We have evaluated the completeness of our survey for eclipsing binaries by comparing it to the expected fraction of eclipsing binaries based on Hipparcos observations. From this evaluation we show that the BEST data set presented here has a completeness of 20%-30% for periods longer than 1 day and is complete relative to Hipparcos for short-period binaries.
425. Beta Cas
ID:
ivo://CDS.VizieR/J/A+AS/108/55
Title:
Beta Cas
Short Name:
J/A+AS/108/55
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
426. beta Cas BRITE and SMEI light curves
ID:
ivo://CDS.VizieR/J/A+A/643/A110
Title:
beta Cas BRITE and SMEI light curves
Short Name:
J/A+A/643/A110
Date:
21 Oct 2021
Publisher:
CDS
Description:
F type stars are characterised by several physical processes such as different pulsation mechanisms, rotation, convection, diffusion, and magnetic fields. The rapidly rotating delta Scuti star beta Cas can be considered as a benchmark star to study the interaction of several of these effects. We investigate the pulsational and magnetic field properties of beta Cas. We also determine the star's apparent fundamental parameters and chemical abundances. Based on photometric time series obtained from three different space missions (BRITE-Constellation, SMEI, and TESS), we conduct a frequency analysis and investigate the stability of the pulsation amplitudes over four years of observations. We investigate the presence of a magnetic field and its properties using spectropolarimetric observations taken with the Narval instrument by applying the Least Square Deconvolution and Zeeman Doppler Imaging techniques. beta Cas shows only three independent p-mode frequencies down to the few ppm-level; its highest amplitude frequency is suggested to be a n=3, l=2, m=0 mode. Its magnetic field structure is quite complex and almost certainly of a dynamo origin. beta Cas' atmosphere is slightly deficient in iron peak elements and slightly overabundant in C, O, and heavier elements. Atypically for delta Scuti stars, we can only detect three pulsation modes down to exceptionally low noise levels for beta Cas.The star is also one of very few delta Scuti pulsators known to date to show a measurable magnetic field, and the first delta Scuti star with a dynamo magnetic field. These characteristics make beta Cas an interesting target for future studies of dynamo processes in the thin convective envelopes of F-type stars, of the transition region between fossil and dynamo fields, and the interaction between pulsations and magnetic field.
427. beta Cephei light curves from KELT project
ID:
ivo://CDS.VizieR/J/AJ/160/32
Title:
beta Cephei light curves from KELT project
Short Name:
J/AJ/160/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a search for Galactic {beta} Cephei stars, which are massive pulsating stars with both pressure modes and mixed modes. Thus, these stars can serve as benchmarks for seismological studies of the interiors of massive stars. We conducted the search by performing a frequency analysis on the optical light curves of known O- and B-type stars with data from the Kilodegree Extremely Little Telescope exoplanet survey. We identify 113 {beta} Cephei stars, of which 86 are new discoveries, which altogether represent a 70% increase in the number currently known. An additional 97 candidates are identified. Among our targets, we find five new eclipsing binaries and 22 stars with equal frequency spacings suggestive of rotational splitting of nonradial pulsation modes. Candidates for runaway stars among our targets and a number of interesting individual objects are discussed. Most of the known and newly discovered {beta} Cephei stars will be observed by the Transiting Exoplanet Survey Satellite mission, providing by far the most comprehensive observational data set of massive main-sequence pulsating stars of sufficient quality for detailed asteroseismic studies. Future analysis of these light curves has the potential to dramatically increase our understanding of the structure of stellar interiors and the physical processes taking place therein.
428. Beta Lyrae light curve changes
ID:
ivo://CDS.VizieR/J/AJ/110/1350
Title:
Beta Lyrae light curve changes
Short Name:
J/AJ/110/1350
Date:
21 Oct 2021
Publisher:
CDS
Description:
We apply a variety of classical and recently developed periodicity analyses to light curves of Beta Lyrae in 9 eras that extend over a range of about 150 years. Some new data are tabulated. Most periodic variations that have been reported in the literature do not pass standard significance tests, according to our adopted criteria. Certain other periods do pass the tests, although most do so only for one, or at most two, data sets. Our main findings are that a period of about 9 months is present in all data sets and that it connects extremely well in phase from era to era, all the way back to Baxendell's observations of 1840-1877. The semiamplitude is small but reasonably consistent, averaging about 2% of the flux in the light curve maxima. Any substantially larger excursions that occur are nonperiodic. Phase coherence of the 9 month period is fairly good, even with a linear ephemeris, and becomes excellent if one allows for a slow sinusoidal variation of the 9 month periodicity. There is some evidence for a monotonic decrease in the amplitude of the 9 month periodicity with increasing wavelength.
429. {beta} Lyr light curves
ID:
ivo://CDS.VizieR/J/A+A/618/A112
Title:
{beta} Lyr light curves
Short Name:
J/A+A/618/A112
Date:
21 Oct 2021
Publisher:
CDS
Description:
Mass exchange and mass loss in close binaries can significantly affect their evolution, but a complete self-consistent theory of these processes is still to be developed. Processes such as radiative shielding due to a hot-spot region, or a hydrodynamical interaction of different parts of the gas stream have been studied previously. In order to test the respective predictions, it is necessary to carry out detailed observations of binaries undergoing the largescale mass exchange, especially for those that are in the rapid transfer phase. {beta} Lyr A is an archetype of such a system, having a long and rich observational history. Our goal for this first study is to quantitatively estimate the geometry and physical properties of the optically thick components, namely the Roche-lobe filling mass-losing star, and the accretion disk surrounding the mass-gaining star of {beta} Lyr A. A series of continuum visible and NIR spectro-interferometric observations by the NPOI, CHARA/MIRC and VEGA instruments covering the whole orbit of {beta} Lyr A acquired during a two-week campaign in 2013 were complemented with UBVR photometric observations acquired during a three-year monitoring of the system. We included NUV and FUV observations from OAO A-2, IUE, and Voyager satellites. All these observations were compared to a complex model of the system. It is based on the simple LTE radiative transfer code SHELLSPEC, which was substantially extended to compute all interferometric observables and to perform both global and local optimization of system parameters. Several shapes of the accretion disk were successfully tested - slab, wedge, and a disk with an exponential vertical profile - and the following properties were consistently found: the radius of the outer rim is 30.0+/-1.0R_{sun}_, the semithickness of the disk 6.5+/-1.0R_{sun}_, and the binary orbital inclination i=93.5+/-1.0deg. The temperature profile is a power-law or a steady-disk in case of the wedge geometry. The properties of the accretion disk indicate that it cannot be in a vertical hydrostatic equilibrium, which is in accord with the ongoing mass transfer. The hot spot was also detected in the continuum but is interpreted as a hotter part of the accretion disk illuminated by the donor. As a by-product, accurate kinematic and radiative properties of Lyr B were determined.
430. Beta Lyr radial velocities and UBV data
ID:
ivo://CDS.VizieR/J/A+A/312/879
Title:
Beta Lyr radial velocities and UBV data
Short Name:
J/A+A/312/879
Date:
21 Oct 2021
Publisher:
CDS
Description:
A preliminary analysis of an extensive collection of interferometric, spectroscopic and photometric observations of the bright Be star {beta} Lyr lead to the following main conclusions: (1) The bulk of the H{alpha} and He I 6678 emission seems to originate in jets of material perpendicular to the orbital plane of the binary. The jets are associated with the more massive component of the binary (star 1) and probably emanate from the `hot spot' in the disk, i.e. the region of interaction of the gas stream flowing from the Roche-lobe filling B6-8II component (star 2) toward star 1. Some contribution to the emission also comes from a region located between the two stars (the gas stream and the `hot spot') and from the `pseudoatmosphere' of the accretion disk around star 1. (2) The 282-d cyclic variation of the light curve of {beta} Lyr is confirmed on the basis of 2852 homogenized V-band observations covering an interval of 36yrs. We find, however, that the amplitude and phase of these variations vary with the orbital phase: the long-term modulation of the light curve almost disappears near orbital phases 0.25P and 0.50P (elongation and secondary eclipse). (3) Pronounced line-profile variations of the H{alpha} and He I 6678 lines on a time scale shorter than one orbital period were clearly detected. They may be periodic, with a period near 4.70-4.75d, and this periodicity may be related to the 282-d change via the orbital period.