- ID:
- ivo://CDS.VizieR/J/MNRAS/415/1061
- Title:
- Variability of FBS blue stellar objects
- Short Name:
- J/MNRAS/415/1061
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new method for combined calculations of magnitudes based on accurate measurements of POSS1 and POSS2 epoch plates is given. The photometric accuracy of various surveys and catalogs has been estimated and established and statistical weights for each of them have been calculated. To achieve the best possible magnitudes, weighted averaging of data from USNO-A2.0, APM, MAPS, USNO-B1.0, and GSC 2.3.2 catalogs have been used. The rms accuracy of magnitudes achieved for POSS1 is 0.184 mag for B and 0.173 mag for R and for POSS2 is 0.138 mag for B and 0.128 mag for R. We have derived the best POSS1 and POSS2 magnitudes for the FBS blue stellar objects. We have refined the transformation formulae between the POSS1 and POSS2 magnitudes and SDSS ones and standard UBV system. Using these accurate magnitudes, we have estimated the variability of the FBS blue stellar objects and revealed probable and possible variables. We have worked out methods to control and exclude accidental errors that appear in any survey. We have compared and combined our results with those given in NSVS database and obtained better candidates for variability. Having excluded variables, we have combined POSS1 and POSS2 data for the rest of objects to achieve even better magnitudes and colors; the rms being smaller than 0.1 mag both in B and R and for the B-R colors. This approach has been applied to the First Byurakan Survey blue stellar objects containing significant number of white dwarfs, cataclysmic variables, as well as extragalactic objects (quasars, Seyferts, BL Lac objects). Altogether 336 variable objects have been revealed with POSS2-POSS1 >= 3{sigma} of the errors. An electronic table of these objects is given. Candidate variables are divided into 4 classes: extreme, strong, probable and possible variables. For a more reliable sample of variable objects we excluded possible ones from the list and were left with 161 objects. Analyzing radio and X-ray properties of these objects, we have revealed their nature and re-discovered or revealed candidate AGN, CVs, WDs and other objects.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/731/17
- Title:
- Variability of low-mass stars in SDSS Stripe 82
- Short Name:
- J/ApJ/731/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of periodic stellar variability in the "Stripe 82" region of the Sloan Digital Sky Survey. After aggregating and re-calibrating catalog-level data from the survey, we ran a period-finding algorithm (Supersmoother) on all point-source light curves. We used color selection to identify systems that are likely to contain low-mass stars, in particular M dwarfs and white dwarfs. In total, we found 207 candidates, the vast majority of which appear to be in eclipsing binary systems. The catalog described in this paper includes 42 candidate M dwarf/white dwarf pairs, four white dwarf pairs, 59 systems whose colors indicate they are composed of two M dwarfs and whose light-curve shapes suggest they are in detached eclipsing binaries, and 28 M dwarf systems whose light-curve shapes suggest they are in contact binaries. We find no detached systems with periods longer than 3 days, thus the majority of our sources are likely to have experienced orbital spin-up and enhanced magnetic activity.
- ID:
- ivo://CDS.VizieR/J/AJ/132/1221
- Title:
- VJHK and SDSS photometry of DA white dwarfs
- Short Name:
- J/AJ/132/1221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have calibrated four major ground-based photometric systems with respect to the Hubble Space Telescope (HST) absolute flux scale, which is defined by Vega and four fundamental DA white dwarfs. These photometric systems include the Johnson-Kron-Cousins UBVRI, the Stroemgren uvby filters, the Two Micron All Sky Survey JHKs, and the Sloan Digital Sky Survey ugriz filters. Synthetic magnitudes are calculated from model white dwarf spectra folded through the published filter response functions; these magnitudes in turn are absolutely calibrated with respect to the HST flux scale. Effective zero-magnitude fluxes and zero-point offsets of each system are determined. In order to verify the external observational consistency, as well as to demonstrate the applicability of these definitions, the synthetic magnitudes are compared with the respective observed magnitudes of larger sets of DA white dwarfs that have well-determined effective temperatures and surface gravities and span a wide range in both of these parameters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/469/621
- Title:
- VST ATLAS white dwarf candidates cat.
- Short Name:
- J/MNRAS/469/621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey (SDSS) has created a knowledge gap between the Northern and the Southern hemispheres, which is very marked for white dwarfs: Only ~15 per cent of the known white dwarfs are south of the equator. Here, we make use of the VLT Survey Telescope (VST) ATLAS survey, one of the first surveys obtaining deep, optical, multiband photometry over a large area of the southern skies, to remedy this situation. Applying the colour and proper-motion selection developed in our previous work on SDSS to the most recent internal data release (2016 April 25) of VST ATLAS, we created a catalogue of ~4200 moderately bright (g<=19), high-confidence southern white dwarf candidates, which can be followed up individually with both the large array of southern telescopes or in bulk with ESO's forthcoming multi-object spectrograph 4MOST.
- ID:
- ivo://CDS.VizieR/J/AJ/154/118
- Title:
- WD+dMs from the SUPERBLINK proper motion survey
- Short Name:
- J/AJ/154/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an activity and kinematic analysis of high proper motion white dwarf-M dwarf binaries (WD+dMs) found in the SUPERBLINK survey, 178 of which are new identifications. To identify WD+dMs, we developed a UV-optical-IR color criterion and conducted a spectroscopic survey to confirm each candidate binary. For the newly identified systems, we fit the two components using model white dwarf spectra and M dwarf template spectra to determine physical parameters. We use H{alpha} chromospheric emission to examine the magnetic activity of the M dwarf in each system, and investigate how its activity is affected by the presence of a white dwarf companion. We find that the fraction of WD+dM binaries with active M dwarfs is significantly higher than their single M dwarf counterparts at early and mid-spectral types. We corroborate previous studies that find high activity fractions at both close and intermediate separations. At more distant separations, the binary fraction appears to approach the activity fraction for single M dwarfs. Using derived radial velocities and the proper motions, we calculate 3D space velocities for the WD+dMs in SUPERBLINK. For the entire SUPERBLINK WD+dMs, we find a large vertical velocity dispersion, indicating a dynamically hotter population compared to high proper motion samples of single M dwarfs. We compare the kinematics for systems with active M dwarfs and those with inactive M dwarfs, and find signatures of asymmetric drift in the inactive sample, indicating that they are drawn from an older population.
- ID:
- ivo://CDS.VizieR/J/MNRAS/482/715
- Title:
- WD luminosity functions from the PS1 3pi Survey
- Short Name:
- J/MNRAS/482/715
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A large sample of white dwarfs is selected by both proper motion and colours from the Pan-STARRS 1 3{pi} Steradian Survey Processing Version 2 to construct the white dwarf luminosity functions of the discs and halo in the solar neighbourhood. Four-parameter astrometric solutions were recomputed from the epoch data. The generalized maximum volume method is then used to calculate the density of the populations. After removal of crowded areas near the Galactic plane and centre, the final sky area used by this work is 7.833sr, which is 83 per cent of the 3{pi} sky and 62 per cent of the whole sky. By dividing the sky using Voronoi tessellation, photometric and astrometric uncertainties are recomputed at each step of the integration to improve the accuracy of the maximum volume. Interstellar reddening is considered throughout the work. We find a disc-to-halo white dwarf ratio of about 100.
167. WDMS from LAMOST DR1
- ID:
- ivo://CDS.VizieR/J/A+A/570/A107
- Title:
- WDMS from LAMOST DR1
- Short Name:
- J/A+A/570/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- White dwarf-main sequence (WDMS) binaries are used to study several different important open problems in modern astrophysics. The Sloan Digital Sky Survey (SDSS) identified the largest catalogue of WDMS binaries currently known. However, this sample is seriously affected by selection effects and the population of systems containing cool white dwarfs and early-type companions is under-represented. Here we search for WDMS binaries within the spectroscopic data release 1 of the LAMOST (Large sky Area Multi-Object fiber Spectroscopic Telescope) survey. LAMOST and SDSS follow different target selection algorithms. Hence, LAMOST WDMS binaries may be drawn from a different parent population and thus help in overcoming the selection effects incorporated by SDSS on the current observed population. We develop a fast and efficient routine based on the wavelet transform to identify LAMOST WDMS binaries containing a DA white dwarf and a M dwarf companion, and apply a decomposition/fitting routine to their LAMOST spectra to estimate their distances and measure their stellar parameters, namely the white dwarf effective temperatures, surface gravities and masses, and the secondary star spectral types. We identify 121 LAMOST WDMS binaries, 80 of which are new discoveries, and estimate the sample to be about 90 per cent complete. The LAMOST and SDSS WDMS binaries are found to be statistically different. However, this result is not due to the different target selection criteria of both surveys, but likely a simple consequence of the different observing conditions. Thus, the LAMOST population is found at considerably shorter distances (50-450pc) and is dominated by systems containing early-type companions and hot white dwarfs. Even though WDMS binaries containing cool white dwarfs are also missed by the LAMOST survey, the LAMOST WDMS binary sample dominated by systems containing early-type companions is an important addition to the current known spectroscopic catalogue. Future LAMOST observations however are required to increase the small number of LAMOST WDMS binaries.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1681
- Title:
- WD within 20pc of the Sun
- Short Name:
- J/AJ/138/1681
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the kinematical properties, distribution of spectroscopic subtypes, and stellar population subcomponents of the white dwarfs within 20pc of the Sun. We find no convincing evidence of halo white dwarfs in the total 20pc sample of 129 white dwarfs nor is there convincing evidence of genuine thick disk subcomponent members within 20 parsecs. Virtually, the entire 20pc sample likely belongs to the thin disk. The total DA to non-DA ratio of the 20pc sample is 1.6, a manifestation of deepening envelope convection which transforms DA stars with sufficiently thin H surface layers into non-DAs. The addition of five new stars to the 20pc sample yields a revised local space density of white dwarfs of (4.9+/-0.5)x10^-3^pc^-3^ and a corresponding mass density of (3.3+/-0.3)x10^-3^M_{sun}_pc^-3^. We find that at least 15% of the white dwarfs within 20 parsecs of the Sun (the DAZ and DZ stars) have photospheric metals that possibly originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, this suggests the possibility that the same percentage have planets or asteroid-like bodies orbiting them.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/2125
- Title:
- White dwarf binary pathways survey
- Short Name:
- J/MNRAS/463/2125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The number of spatially unresolved white dwarf plus main-sequence star binaries has increased rapidly in the last decade, jumping from only ~30 in 2003 to over 3000. However, in the majority of known systems the companion to the white dwarf is a low-mass M dwarf, since these are relatively easy to identify from optical colours and spectra. White dwarfs with more massive FGK type companions have remained elusive due to the large difference in optical brightness between the two stars. In this paper, we identify 934 main-sequence FGK stars from the Radial Velocity Experiment survey in the Southern hemisphere and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope survey in the Northern hemisphere, that show excess flux at ultraviolet wavelengths which we interpret as the likely presence of a white dwarf companion. We obtained Hubble Space Telescope ultraviolet spectra for nine systems which confirmed that the excess is indeed caused, in all cases, by a hot compact companion, eight being white dwarfs and one a hot subdwarf or pre-helium white dwarf, demonstrating that this sample is very clean. We also address the potential of this sample to test binary evolution models and Type Ia supernovae formation channels.
- ID:
- ivo://CDS.VizieR/J/MNRAS/462/2506
- Title:
- White dwarf candidates in DECam first field
- Short Name:
- J/MNRAS/462/2506
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from a minute cadence survey of a 3deg^2^ field obtained with the Dark Energy Camera. We imaged part of the Canada-France-Hawaii Telescope Legacy Survey area over eight half-nights. We use the stacked images to identify 111 high proper motion white dwarf candidates with g<=24.5mag and search for eclipse-like events and other sources of variability. We find a new g=20.64mag pulsating ZZ Ceti star with pulsation periods of 11-13min. However, we do not find any transiting planetary companions in the habitable zone of our target white dwarfs. Given the probability of eclipses of 1 per cent and our observing window from the ground, the non-detection of such companions in this first field is not surprising. Minute cadence DECam observations of additional fields will provide stringent constraints on the frequency of planets in the white dwarf habitable zone.
