- ID:
- ivo://CDS.VizieR/J/AJ/146/139
- Title:
- 2010 photometry of variable stars from Dome A
- Short Name:
- J/AJ/146/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a season of observations with the Chinese Small Telescope ARray, obtained over 183 days of the 2010 Antarctic winter. We carried out high-cadence time-series aperture photometry of 9125 stars with i{<~}15.3mag located in a 23deg^2^ region centered on the south celestial pole. We identified 188 variable stars, including 67 new objects relative to our 2008 observations, thanks to broader synoptic coverage, a deeper magnitude limit, and a larger field of view. We used the photometric data set to derive site statistics from Dome A. Based on two years of observations, we find that extinction due to clouds at this site is less than 0.1 and 0.4mag during 45% and 75% of the dark time, respectively.
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- ID:
- ivo://CDS.VizieR/J/A+A/616/A82
- Title:
- Physical parameters of classical Cepheids
- Short Name:
- J/A+A/616/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We gathered more than 1130 high-resolution optical spectra for more than 250 Galactic classical Cepheids. The spectra were collected with different optical spectrographs: UVES at VLT, HARPS at 3.6m, FEROS at 2.2m MPG/ESO, and STELLA. To improve the effective temperature estimates, we present more than 150 new line depth ratio (LDR) calibrations that together with similar calibrations already available in the literature allowed us to cover a broad range in wavelength (between 5348 and 8427 angstrom) and in effective temperatures (between 3500 and 7700K). This means the unique opportunity to cover both the hottest and coolest phases along the Cepheid pulsation cycle and to limit the intrinsic error on individual measurements at the level of ~100K. Thanks to the high signal-to-noise ratio of individual spectra we identified and measured hundreds of neutral and ionized lines of heavy elements, and in turn, have the opportunity to trace the variation of both surface gravity and microturbulent velocity along the pulsation cycle. The accuracy of the physical parameters and the number of FeI (more than one hundred) and FeII (more than ten) lines measured allowed us to estimate mean iron abundances with a precision better than 0.1dex. Here we focus on 14 calibrating Cepheids for which the current spectra cover either the entire or a significant portion of the pulsation cycle. The current estimates of the variation of the physical parameters along the pulsation cycle and of the iron abundances agree quite well with similar estimates available in the literature. Independent homogeneous estimates of both physical parameters and metal abundances based on different approaches that can constrain possible systematics are highly encouraged.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A141
- Title:
- Physical properties of AM CVn stars
- Short Name:
- J/A+A/620/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- AM CVn binaries are hydrogen deficient compact binaries with an orbital period in the 5-65min range and are predicted to be strong sources of persistent gravitational wave radiation. Using Gaia, Data Release 2, we present the parallaxes and proper motions of 41 out of the 56 known systems. Compared to the parallax determined using the HST, Fine Guidance Sensor we find that the archetype star, AM CVn, is significantly closer than previously thought. This resolves the high luminosity and mass accretion rate which models had difficulty in explaining. Using Pan-STARRS1 data we determine the absolute magnitude of the AM CVn stars. There is some evidence that donor stars have a higher mass and radius than expected for white dwarfs or that the donors are not white dwarfs. Using the distances to the known AM CVn stars we find strong evidence that a large population of AM CVn stars has yet to be discovered. As this value sets the background to the gravitational wave signal of LISA, this is of wide interest. We determine the mass transfer rate for 15 AM CVn stars and find that the majority has a rate significantly greater than expected from standard models. This is further evidence that the donor star has a greater size than expected.
- ID:
- ivo://CDS.VizieR/J/MNRAS/351/1071
- Title:
- POINT-AGAPE Survey. M31 variables
- Short Name:
- J/MNRAS/351/1071
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For the purposes of identifying microlensing events, the POINT-AGAPE collaboration has been monitoring the Andromeda galaxy (M31) for three seasons (1999-2001) with the Wide Field Camera on the Isaac Newton Telescope. In each season, data are taken for one hour per night for roughly 60 nights during the six months that M31 is visible. The two 33x33arcmin^2^ fields of view straddle the central bulge, northwards and southwards. We have calculated the locations, periods and brightness of 35 414 variable stars in M31 as a by-product of the microlensing search. The variables are classified according to their period and brightness. Rough correspondences with classical types of variable star (such as Population I and II Cepheids, Miras and semiregular long-period variables) are established. The spatial distribution of Population I Cepheids is clearly associated with the spiral arms, while the central concentration of the Miras and long-period variables varies noticeably, the brighter and the shorter period Miras being much more centrally concentrated.
- ID:
- ivo://CDS.VizieR/J/A+A/489/911
- Title:
- Polarimetric measures of selected variable stars
- Short Name:
- J/A+A/489/911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The purpose of this paper is to summarize and interpret unpublished optical polarimetry for numerous program stars that were observed over the past decades at the Flower and Cook Observatory (FCO), University of Pennsylvania. We also make the individual calibrated measures available for long-term comparisons with new data. We employ three techniques to search for intrinsic variability within each dataset. First, when the observations for a given star and filter are numerous enough and when a period has been determined previously via photometry or spectroscopy, the polarimetric measures are plotted versus phase. If a statistically significant pattern appears, we attribute it to intrinsic variability. Second, we compare means of the FCO data to means from other workers. If they are statistically different, we conclude that the object exhibits long-term intrinsic variability. Third, we calculate the standard deviation for each program star and filter and compare it to the standard deviation estimated from comparable polarimetric standards. If the standard deviation of the program star is at least three times the value estimated from the polarimetric standards, the former is considered intrinsically variable. All of these statements are strengthened when variability appears in multiple filters.
- ID:
- ivo://CDS.VizieR/J/ApJ/598/L43
- Title:
- Polarimetry of V838 Mon and stars around
- Short Name:
- J/ApJ/598/L43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present imaging polarimetry observations of the eruptive variable V838 Monocerotis and its neighboring field obtained in 2002 October. The polarization of field stars confirms the previously determined interstellar polarization along the line of sight to V838 Mon. While V838 Mon showed intrinsic polarization shortly after its second outburst on 2002 February 8, all subsequent observations only showed a quiescent interstellar polarization component. We find that V838 Mon once again showed significant intrinsic polarization in 2002 October, suggesting the presence of an asymmetrical geometry of scattering material close to the star. Furthermore, an observed 90{deg} position angle flip in the intrinsic polarization from 2002 February to October suggests that the distribution of nearby circumstellar material has experienced significant changes. We discuss the opacity changes in the evolving circumstellar cloud around V838 Mon that may explain these observations.
- ID:
- ivo://CDS.VizieR/II/220
- Title:
- Polarisation of Be stars
- Short Name:
- II/220
- Date:
- 20 Dec 2021 15:54:35
- Publisher:
- CDS
- Description:
- The catalogue contains observations of the linear polarization in the UBVRI photometric system of 8 Northern Be stars; the observations are part of a long-term monitoring program begun in 1984.
- ID:
- ivo://CDS.VizieR/J/ApJ/793/135
- Title:
- Positions and distances of RR Lyrae stars
- Short Name:
- J/ApJ/793/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Almost every known low-luminosity Milky Way dwarf spheroidal (dSph) satellite galaxy contains at least one RR Lyrae star. Assuming that a fraction of distant (60<d_helio_<100 kpc) Galactic halo RR Lyrae stars are members of yet to be discovered low-luminosity dSph galaxies, we perform a guided search for these low-luminosity dSph galaxies. In order to detect the presence of dSph galaxies, we combine stars selected from more than 123 sightlines centered on RR Lyrae stars identified by the Palomar Transient Factory. We find that this method is sensitive enough to detect the presence of Segue 1-like galaxies (M_V_=-1.5_-0.8_^+0.6^, r_h_=30 pc) even if only ~20 sightlines were occupied by such dSph galaxies. Yet, when our method is applied to the Sloan Digital Sky Survey Data Release 10 imaging catalog, no signal is detected. An application of our method to sightlines occupied by pairs of close (<200 pc) horizontal branch stars, also did not yield a detection. Thus, we place upper limits on the number of low-luminosity dSph galaxies with half-light radii from 30 pc to 120 pc, and in the probed volume of the halo. Stronger constraints on the luminosity function may be obtained by applying our method to sightlines centered on RR Lyrae stars selected from the Pan-STARRS1 survey, and eventually, from the Large Synoptic Survey Telescope. In Appendix A, we present spectroscopic observations of an RRab star in the Bootes 3 dSph and a light curve of an RRab star near the Bootes 2 dSph.
- ID:
- ivo://CDS.VizieR/J/PASP/121/1378
- Title:
- Positions of variable stars in globular clusters
- Short Name:
- J/PASP/121/1378
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a catalog of equatorial coordinates for 3398 variable stars in those 103 globular clusters that, according to the most recent update of the Catalogue of Variable Stars in Globular Clusters (CVSGC) available in 2008 June (essentially that of 2002, with some more recent additions), had known variable stars. Our catalog is in the electronic attachment to this article. We found that 216 stars are also contained in the General Catalogue of Variable Stars (GCVS) or in the New Catalogue of Suspected Variable Stars (with Supplement); most of these identifications were not previously recognized. We also detected a number of previously unknown cross-identifications among stars of the CVSGC. Our results allow us to initiate compilation of name lists in order to add to the GCVS those stars from the CVSGC that satisfy GCVS naming criteria.
- ID:
- ivo://CDS.VizieR/J/ApJ/839/92
- Title:
- Praesepe members with K2 light curve data
- Short Name:
- J/ApJ/839/92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have Fourier-analyzed 941 K2 light curves (LCs) of likely members of Praesepe, measuring periods for 86% and increasing the number of rotation periods (P) by nearly a factor of four. The distribution of P versus (V-Ks), a mass proxy, has three different regimes: (V-Ks)<1.3, where the rotation rate rapidly slows as mass decreases; 1.3<(V-Ks)<4.5, where the rotation rate slows more gradually as mass decreases; and (V-Ks)>4.5, where the rotation rate rapidly increases as mass decreases. In this last regime, there is a bimodal distribution of periods, with few between ~2 and ~10 days. We interpret this to mean that once M stars start to slow down, they do so rapidly. The K2 period-color distribution in Praesepe (~790Myr) is much different than that in the Pleiades (~125Myr) for late F, G, K, and early-M stars; the overall distribution moves to longer periods and is better described by two line segments. For mid-M stars, the relationship has a similarly broad scatter and is steeper in Praesepe. The diversity of LCs and of periodogram types is similar in the two clusters; about a quarter of the periodic stars in both clusters have multiple significant periods. Multi- periodic stars dominate among the higher masses, starting at a bluer color in Praesepe ((V-Ks)~1.5) than in the Pleiades ((V-Ks)~2.6). In Praesepe, there are relatively more LCs that have two widely separated periods, {Delta}P>6days. Some of these could be examples of M star binaries where one star has spun down but the other has not.
