- ID:
- ivo://CDS.VizieR/J/A+AS/145/275
- Title:
- uvby phot. of suspected beta Pic-like stars
- Short Name:
- J/A+AS/145/275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out a Stroemgren photometric survey of thirteen southern bright stars, including {beta} Pictoris itself, during three years, d'Astrophysique de Paris, in order to detect possible weak photometric variations. {beta} Pictoris presents a small long-term variation with a change of brightness by -2.1x10^-3^mag per year, over about two years from beginning of 1996, a situation relatively similar to the one about 18 years ago. Among the other stars, only HD 38392 presents weak photometric variations with a period of 21.4 days, probably related to the star rotation period. The negative result concerning photometric variations of all other stars suggests that those stars are actually really stable and strengthens the reality of the variations discovered in the case of {beta} Pictoris and HD 38392.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/134/53
- Title:
- uvby photometry of 4 CP stars
- Short Name:
- J/A+AS/134/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Differential Stroemgren uvby photometry obtained with the Four College Automated Photoelectric Telescope shows that the hot HgMn star 33 Gem is photometrically constant. The Si star HD 15980 is found to be a variable whose period is significantly greater than 2 years. The unusual magnetic chemically peculiar Co star HR 1094 is discovered to be a low amplitude photometric variable with the magnetic field period of Hill & Blake (1996MNRAS.278..183H), 2.9761 days. The ephemeris for the magnetic chemically peculiar star HD 115708 of Wade et al. (1996A&A...307..500W) is confirmed with the error in its period of 5.07622 days being greatly reduced. The u, v, b, and y light curves for both HR 1094 and HD 115708 exhibit differences which indicate complex elemental photospheric abundance distributions.
- ID:
- ivo://CDS.VizieR/J/other/JAD/23.1
- Title:
- uvby photometry of theta Tucanae
- Short Name:
- J/other/JAD/23.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- theta Tucanae (HR 139, V=6.11, A7 IV) is a binary with a delta Scuti primary that was the subject of several photometric monitoring campaigns during the 1970s and again in the 1990s. The data presented in this paper were collected during an observing campaign from mid-September to the end of October 1993 at ESO La Silla, Chile, using the simultaneous Stroemgren uvby photometer at the SAT telescope during 25 partial nights. We present a time series of 1432 four-colour extinction-corrected magnitudes in the SAT instrumental system. This collection of data forms a homogeneous and contiguous dataset, obtained in one single instrumental setup, at one single observing site using one single observing protocol, and with centralized data reduction.
- ID:
- ivo://CDS.VizieR/J/ApJS/238/25
- Title:
- UV variability with GALEX gPhoton archive. I.
- Short Name:
- J/ApJS/238/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to develop and test a methodology to search for UV variability over the entire Galaxy Evolution Explorer (GALEX) database down to the shortest timescales, we analyzed time-domain photometry of ~5000 light curves of ~300 bright (mFUV, mNUV<=14) and blue (mFUV-mNUV<0) GALEX sources. Using the gPhoton database tool, we discovered and characterized instrumentally induced variabilities in time-resolved GALEX photometry that may severely impact automated searches for short-period variations. The most notable artifact is a quasi-sinusoidal variation mimicking light curves typical of pulsators, seen occasionally in either one or both detectors, with amplitudes of up to 0.3mag and periods corresponding to the periodicity of the spiral dithering pattern used during the observation (P~120s). Therefore, the artifact may arise from small-scale response variations. Other artifacts include visit-long "sagging" or "hump" in flux, occurring when the dithering pattern is not a spiral, or a one-time change in flux level during the exposure. These instrumentally caused variations were not reported before, and are not due to known (and flagged) artifacts such as hotspots, which can be easily eliminated. To characterize the frequency and causality of such artifacts, we apply Fourier transform analysis to both light curves and dithering patterns, and examine whether artificial brightness variations correlate with visit or instrumental parameters. Artifacts do not correlate with source position on the detector. We suggest methods to identify artifact variations and to correct them when possible.
- ID:
- ivo://CDS.VizieR/J/A+A/287/591
- Title:
- UV Variations in spectrum of Abell 35 c.star
- Short Name:
- J/A+A/287/591
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/550/A120
- Title:
- Variability classification of CoRoT targets
- Short Name:
- J/A+A/550/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an improved method for automated stellar variability classification, using fundamental parameters derived from high resolution spectra, with the goal to improve the variability classification obtained using information derived from CoRoT light curves only. Although we focus on Giraffe spectra and CoRoT light curves in this work, the methods are much more widely applicable. In order to improve the variability classification obtained from the photometric time series, only rough estimates of the stellar physical parameters (Teff and logg) are needed because most variability types that overlap in the space of time series parameters, are well separated in the space of physical parameters (e.g. {gamma} Dor/SPB or {delta} Sct/{beta} Cep). In this work, several state-of-the-art machine learning techniques are combined to estimate these fundamental parameters from high resolution Giraffe spectra. Next, these parameters are used in a multi-stage Gaussian-Mixture classifier to perform an improved supervised variability classification of CoRoT light curves. The variability classifier can be used independently of the regression module that estimates the physical parameters, so that non-spectroscopic estimates derived e.g. from photometric colour indices can be used instead. Teff and logg are derived from Giraffe spectra, for 6832 CoRoT targets. The use of those parameters in addition to information extracted from the CoRoT light curves, significantly improves the results of our previous automated stellar variability classification. Several new pulsating stars are identified with high confidence levels, including hot pulsators such as SPB and {beta} Cep, and several {gamma} Dor-{delta} Sct hybrids. From our samples of new {gamma} Dor and {delta} Sct stars, we find strong indications that the instability domains for both types of pulsators are larger than previously thought.
- ID:
- ivo://CDS.VizieR/J/AJ/147/70
- Title:
- Variability in TAOS I. 58 new variable stars
- Short Name:
- J/AJ/147/70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Taiwanese-American Occultation Survey project is designed for the detection of stellar occultations by small-size Kuiper Belt Objects, and it has monitored selected fields along the ecliptic plane by using four telescopes with a 3deg^2^ field of view on the sky since 2005. We have analyzed data accumulated during 2005-2012 to detect variable stars. Sixteen fields with observations of more than 100 epochs were examined. We recovered 85 variables among a total of 158 known variable stars in these 16 fields. Most of the unrecovered variables are located in the fields observed less frequently. We also detected 58 variable stars which are not listed in the International Variable Star Index of the American Association of Variable Star Observers. These variable stars are classified as 3 RR Lyrae, 4 Cepheid, 1 {delta} Scuti, 5 Mira, 15 semi-regular, and 27 eclipsing binaries based on the periodicity and the profile of the light curves.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A125
- Title:
- Variability of A- and F-stars from Kepler
- Short Name:
- J/A+A/534/A125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars, and observationally investigate the relation between {gamma} Doradus ({gamma} Dor), {delta} Scuti ({delta} Sct), and hybrid stars.
- 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/134/2099
- Title:
- Variability of point sources in infrared
- Short Name:
- J/AJ/134/2099
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a list of 552 sources with suspected variability, based on a comparison of mid-infrared photometry from the GLIMPSE I and Midcourse Space Experiment (MSX) surveys, which were carried out nearly a decade apart. We were careful to address issues such as the difference in resolution and sensitivity between the two surveys, as well as the differences in the spectral responses of the instruments. We selected only sources where the IRAC 8.0um and MSX 8.28um fluxes differ by more than a factor of 2, in order to minimize contamination from sources where the difference in fluxes at 8um is due to a strong 10um silicate feature. We present a subset of 40 sources for which additional evidence suggests variability, using 2MASS and MIPSGAL data. Based on a comparison with the variability flags in the IRAS and MSX point-source catalogs we estimate that at least a quarter of the 552 sources and at least half of the 40 sources in the subset are truly variable. In addition, we tentatively confirm the variability of one source using multiepoch IRAS LRS spectra. We suggest that most of the sources in our list are likely to be asymptotic giant branch stars.