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1041. Physical properties of AM CVn stars
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.
1042. Planetary transit of TrES-1 and TrES-2
ID:
ivo://CDS.VizieR/J/A+A/508/1011
Title:
Planetary transit of TrES-1 and TrES-2
Short Name:
J/A+A/508/1011
Date:
21 Oct 2021
Publisher:
CDS
Description:
The aim of this work is a detailed analysis of transit light curves from TrES-1 and TrES-2, obtained over a period of three to four years, in order to search for variabilities in observed mid-transit times and to set limits for the presence of additional third bodies. Using the IAC 80cm telescope, we observed transits of TrES-1 and TrES-2 over several years. Based on these new data and previously published work, we studied the observed light curves and searched for variations in the difference between observed and calculated (based on a fixed ephemeris) transit times. To model possible transit timing variations, we used polynomials of different orders, simulated O-C diagrams corresponding to a perturbing third mass and sinusoidal fits. For each model we calculated the chi-squared residuals and the False Alarm Probability (FAP). For TrES-1 we can exclude planetary companions (>1M_{earth}_) in the 3:2 and 2:1 MMRs having high FAPs based on our transit observations from ground. Additionally, the presence of a light time effect caused by e.g. a 0.09M_{sun}_ mass star at a distance of 7.8AU is possible. As for TrES-2, we found a better ephemeris of Tc=2453957.63512(28)+2.4706101(18)xEpoch and a good fit for a sine function with a period of 0.2days, compatible with a moon around TrES-2 and an amplitude of 57s, but it was not a uniquely low chi-squared value that would indicate a clear signal. In both cases, TrES-1 and TrES-2, we were able to put upper limits on the presence of additional perturbers masses. We also conclude that any sinusoidal variations that might be indicative of exomoons need to be confirmed with higher statistical significance by further observations, noting that TrES-2 is in the field-of-view of the Kepler Space Telescope.
1043. Planetary transits of TrES-2 and TrES-3
ID:
ivo://CDS.VizieR/J/MNRAS/408/1494
Title:
Planetary transits of TrES-2 and TrES-3
Short Name:
J/MNRAS/408/1494
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first extrasolar planet observations from the 10.4-m Gran Telescopio Canarias (GTC). We used the Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) tunable filter imager on the GTC to acquire high-precision, narrow-band photometry of the transits of the giant exoplanets, TrES-2b and TrES-3b. We obtained near-simultaneous observations in two near-infrared wavelengths (790.2 and 794.4nm). We provide normalized flux ratios for each target, where the flux ratio is defined as the target flux divided by the total combined flux from several non-variable reference stars. The flux ratios have been normalized against the baseline (out-of-transit) flux ratio for each target. We provide normalized flux ratios for each target, where the flux ratio is defined as the target flux divided by the total combined flux from several non-variable reference stars. The flux ratios have been normalized against the baseline (out-of-transit) flux ratio for each target.
1044. PM J22299+3024 and LP 119-10 light curves
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.
1045. POINT-AGAPE Survey. M31 variables
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.
1046. Polarimetric asteroseismology of beta Crucis
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.
1047. Polarimetric measures of selected variable stars
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.
1048. Polarimetry of V838 Mon and stars around
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.
1049. 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.
1050. 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.