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1281. 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.
1282. 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.
1283. 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.
1284. Beta Cephei stars in the ASAS-3 data. I.
ID:
ivo://CDS.VizieR/J/A+A/477/907
Title:
Beta Cephei stars in the ASAS-3 data. I.
Short Name:
J/A+A/477/907
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyse V-filter photometry of 41 known Beta Cephei-type stars. The ASAS-3 photometry is combined with the archival data, if available, to determine long-term stability of periods and amplitudes of excited modes. We detected amplitude changes in three Beta Cephei stars, BW Cru, V836 Cen, and V348 Nor. Period changes were found in KK Vel and V836 Cen. Our analysis shows that intrinsic period changes are more common among multiperiodic stars, apparently because they are caused by some kind of mode interaction. In addition, we found new modes for seven stars, and for ten others we provide new solutions or remove ambiguities in the detected frequencies. One candidate hybrid Beta Cephei/SPB star, HD 133823, is discovered.
1285. Beta Cephei stars in the ASAS-3 data. II.
ID:
ivo://CDS.VizieR/J/A+A/477/917
Title:
Beta Cephei stars in the ASAS-3 data. II.
Short Name:
J/A+A/477/917
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analysed ASAS-3 photometry of bright early-type stars with the goal of finding new Beta Cephei stars. We were particularly interested in Beta Cephei stars that would be good for seismic analysis, i.e., stars that (i) have a large number of excited modes, (ii) show rotationally split modes, (iii) are components of eclipsing binary systems, (iv) have low-frequency modes, that is, are hybrid Beta Cephei/SPB stars. Our study was made with a homogeneous sample of over 4100 stars having MK spectral type B5 or earlier. For these stars, the ASAS-3 photometry was analysed by means of a Fourier periodogram. We have discovered 103 Beta Cephei stars, nearly doubling the number of previously known stars of this type. Among these stars, four are components of eclipsing binaries, seven have modes equidistant or nearly equidistant in frequency. In addition, we found five Beta Cephei stars that show low-frequency periodic variations, very likely due to pulsations. We therefore regard them as candidate hybrid Beta Cephei/SPB pulsators. All these stars are potentially very useful for seismic modeling. Moreover, we found Beta Cephei-type pulsations in three late O-type stars and fast period changes in one, HD 168050.
1286. {beta}Pic and AB Dor moving groups members
ID:
ivo://CDS.VizieR/J/AJ/140/119
Title:
{beta}Pic and AB Dor moving groups members
Short Name:
J/AJ/140/119
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from our continuing program to identify new, low-mass, members of the nearby young moving groups (NYMGs) using a proper motion selection algorithm and various observational techniques. We have three goals: (1) to provide high priority targets for exoplanet searches by direct imaging, (2) to complete the census of the membership in the NYMGs down to ~0.1M_{sun}_, and thus (3) provide a well-characterized sample of nearby (median distances at least twice as close as the Taurus and Ophiuchus star-forming regions), young (8-50Myr) stars for detailed study of their physical properties and multiplicity.
1287. beta Pic HARPS spectrum
ID:
ivo://CDS.VizieR/J/A+A/607/A25
Title:
beta Pic HARPS spectrum
Short Name:
J/A+A/607/A25
Date:
21 Oct 2021
Publisher:
CDS
Description:
The young planetary system beta Pictoris is surrounded by a circumstellar disk of dust and gas. Because both dust and gas have a lifetime shorter than the system age, they need to be replenished continuously. The gas composition is partly known, but its location and its origin are still a puzzle. The gas source could be the exocomets (or so-called falling and evaporating bodies, FEBs), which are observed as transient features in absorption lines of refractory elements (Mg, Ca, and Fe) when they transit in front of the star at several tens of stellar radii. Nearly 1700 high-resolution spectra of beta Pictoris have been obtained from 2003 to 2015 using the HARPS spectrograph. In these spectra, the circumstellar disk is always detected as a stable component among the numerous variable absorption signatures of transiting exocomets. Summing all the 1700 spectra allowed us to reach a signal-to-noise ratio higher than 1000, which is an unprecedentedly high number for a beta Pictoris spectrum. It revealed many weak Fe I absorption lines of the circumstellar gas in more than ten excited states. These weak lines bring new information on the physical properties of the neutral iron gas in the circumstellar disk. The population of the first excited levels follows a Boltzmann distribution with a slope consistent with a gas temperature of about 1300K; this temperature corresponds to a distance to the star of ~38 R_star_ and implies a turbulence of ksi~0.8km/s.
1288. beta Pictoris debris disk image
ID:
ivo://CDS.VizieR/J/A+A/646/A132
Title:
beta Pictoris debris disk image
Short Name:
J/A+A/646/A132
Date:
21 Oct 2021
Publisher:
CDS
Description:
The nearby young star beta Pictoris hosts a rich and complex planetary system, with at least two giant planets and a nearly edge-on debris disk that contains several dynamical subpopulations of planetesimals. While the inner ranges of the debris disk have been studied extensively, less information is known about the outer, fainter parts of the disk. Here we present an analysis of archival FORS V-band imaging data from 2003-2004, which have previously not been explored scientifically because the halo substructure of the bright stellar point spread function is complex. Here we present the deepest imaging yet for the outer range of the beta Pic disk.
1289. beta Pictoris moving group RV of 81 stars
ID:
ivo://CDS.VizieR/J/A+A/642/A179
Title:
beta Pictoris moving group RV of 81 stars
Short Name:
J/A+A/642/A179
Date:
21 Oct 2021
Publisher:
CDS
Description:
The {beta} Pictoris moving group is one of the most well-known young associations in the solar neighbourhood and several members are known to host circumstellar discs, planets, and comets. Measuring its age with precision is basic to study several astrophysical processes such as planet formation and disc evolution which are strongly age dependent. We aim to determine a precise and accurate dynamical traceback age for the {beta} Pictoris moving group. Our sample combines the extremely precise Gaia DR2 astrometry with ground-based radial velocities measured in an homogeneous manner. We use an updated version of our algorithm to determine dynamical ages. The new approach takes into account a robust estimate of the spatial and kinematic covariance matrices of the association to improve the sample selection process and to perform the traceback analysis. We estimate a dynamical age of 18.5_-2.4_^+2.0^Myr for the {beta} Pictoris moving group. We investigated the spatial substructure of the association at birth time and we propose the existence of a core of stars more concentrated. We also provide precise radial velocity measurements for 81 members of {beta} Pic, including ten stars with the first determination of their radial velocities. Our dynamical traceback age is three times more precise than previous traceback age estimates and, more important, for the first time, reconciles the traceback age with the most recent estimates of other dynamical, lithium depletion boundary, and isochronal ages. This has been possible thanks to the excellent astrometric and spectroscopic precisions, the homogeneity of our sample, and the detailed analysis of binaries and membership.
1290. BETA pilot multi-epoch continuum survey
ID:
ivo://CDS.VizieR/J/MNRAS/457/4160
Title:
BETA pilot multi-epoch continuum survey
Short Name:
J/MNRAS/457/4160
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Boolardy Engineering Test Array is a 6x12m dish interferometer and the prototype of the Australian Square Kilometre Array Pathfinder (ASKAP), equipped with the first generation of ASKAP's phased array feed (PAF) receivers. These facilitate rapid wide-area imaging via the deployment of simultaneous multiple beams within an ~30deg^2^ field of view. By cycling the array through 12 interleaved pointing positions and using nine digitally formed beams, we effectively mimic a traditional 1hx108 pointing survey, covering ~150deg^2^ over 711-1015MHz in 12h of observing time. Three such observations were executed over the course of a week. We verify the full bandwidth continuum imaging performance and stability of the system via self-consistency checks and comparisons to existing radio data. The combined three epoch image has arcminute resolution and a 1{sigma} thermal noise level of 375{mu}Jy/beam, although the effective noise is a factor of ~3 higher due to residual sidelobe confusion. From this we derive a catalogue of 3722 discrete radio components, using the 35 per cent fractional bandwidth to measure in-band spectral indices for 1037 of them. A search for transient events reveals one significantly variable source within the survey area. The survey covers approximately two-thirds of the Spitzer South Pole Telescope Deep Field. This pilot project demonstrates the viability and potential of using PAFs to rapidly and accurately survey the sky at radio wavelengths.