- ID:
- ivo://CDS.VizieR/J/A+A/651/A14
- Title:
- PM J22299+3024 and LP 119-10 light curves
- Short Name:
- J/A+A/651/A14
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We continued our ground-based observing project with the season-long observations of ZZ Ceti stars at the Konkoly Observatory. Our present targets are the newly discovered PM J22299+3024 and the already known LP 119-10 variables. LP 119-10 was also observed by the TESS space telescope in 120-second cadence mode. Our main aims are to characterise the pulsation properties of the targets and extract pulsation modes from the data for asteroseismic investigations. We performed a standard Fourier analysis of the daily, weekly, and entire data sets, together with test data of different combinations of weekly observations. We then performed asteroseismic fits utilising the observed and the calculated pulsation periods. For the calculations of model grids necessary for the fits, we applied the 2018 version of the White Dwarf Evolution Code. We derived six possible pulsation modes for PM J22299+3024 and five plus two TESS pulsation frequencies for LP 119-10. We note that further pulsation frequencies may be present in the data sets, but we found their detection ambiguous, so we omitted them from the final frequency list. Our asteroseismic fits of PM J22299+3024 give 11400K and 0.46M_{sun}_ for the effective temperature and the stellar mass, respectively. The temperature is ~800K higher, while the mass of the model star is exactly the same as was earlier derived by spectroscopy. Our model fits of LP 119-10 put the effective temperature in the range of 11800-11900K, which is again higher than the spectroscopic 11290K value. Moreover, our best model solutions give M*=0.70M_{sun}_ mass for this target, which is near to the spectroscopic value of 0.65M_{sun}_ and likewise in the case of PM J22299+3024. The seismic distances of our best-fit model stars agree with the Gaia astrometric distances of PM J22299+3024 and LP 119-10 within the errors, validating our model results.
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Search Results
- 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/other/NatAs/6.154
- Title:
- Polarimetric asteroseismology of beta Crucis
- Short Name:
- J/other/NatAs/6.
- Date:
- 31 Jan 2022 09:03:48
- Publisher:
- CDS
- Description:
- Here we report the detection of polarization variations due to nonradial modes in the {beta} Cephei star {beta} Crucis. In so doing we confirm 40- year-old predictions of pulsation-induced polarization variability and its utility in asteroseismology for mode identification. In an approach suited to other {beta} Cephei stars, we combine polarimetry with space-based photometry and archival spectroscopy to identify the dominant nonradial mode in polarimetry, f2, as l=3, m=-3 (in the m-convention of Dziembowski, 1977AcA.....27..203D) and determine the stellar axis position angle as 25 (or 205) +/-8 degrees. The rotation axis inclination to the line of sight was derived as approx. 46 degrees from combined polarimetry and spectroscopy, facilitating identification of additional modes and allowing for asteroseismic modelling. This reveals a star of 14.5+/-0.5M_{sun}_ and a convective core containing approx. 28 percent of its mass - making {beta} Crucis the most massive star with an asteroseismic age.
- 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.
1036. Polarisation of Be stars
- 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.
1037. Polaris monitoring
- ID:
- ivo://CDS.VizieR/J/ApJ/683/433
- Title:
- Polaris monitoring
- Short Name:
- J/ApJ/683/433
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of 4.5 years of nearly continuous observations of the classical Cepheid Polaris, which comprise the most precise data available for this star. We have made spectroscopic measurements from ground and photometric measurements from the WIRE star tracker and the SMEI instrument on the Coriolis satellite. Measurements of the amplitude of the dominant oscillation (P=4days), which go back more than a century, show a decrease from A_V_=120 to 30mmag around the turn of the millennium. It has been speculated that the reason for the decrease in amplitude is the evolution of Polaris toward the edge of the instability strip. However, our new data reveal an increase in the amplitude by ~30% from 2003 to 2006. It now appears that the amplitude change is cyclic rather than monotonic and most likely the result of a pulsation phenomenon. In addition, previous radial velocity campaigns have claimed the detection of long-period variation in Polaris (P>40days). Our radial velocity data are more precise than previous data sets, and we find no evidence for additional variation for periods in the range 3-50days with an upper limit of 100m/s. However, in the WIRE data we find evidence of variation on timescales of 2-6days, which we interpret as being due to granulation.
- 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.
