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981. Period-mass-loss rate relation of Miras
ID:
ivo://CDS.VizieR/J/A+A/556/A38
Title:
Period-mass-loss rate relation of Miras
Short Name:
J/A+A/556/A38
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery that Mira variables with and without absorption lines of the element technetium (Tc) occupy two different regions in a diagram of near- to mid-IR colour versus pulsation period. Tc is an indicator of a recent or ongoing mixing event called the third dredge-up (3DUP), and the near- to mid-IR colour, such as the (K-[22]) colour where [22] is the the 22um band of the WISE space observatory, is an indicator of the dust mass-loss rate of a star. We collected data from the literature about the Tc content, pulsation period, and near- and mid-IR magnitudes of more than 190 variable stars on the asymptotic giant branch (AGB) to which Miras belong. The sample is naturally biased towards optical AGB stars, which have low to intermediate (dust) mass-loss rates.
982. Period of Cepheids in M 83
ID:
ivo://CDS.VizieR/J/ApJ/591/L111
Title:
Period of Cepheids in M 83
Short Name:
J/ApJ/591/L111
Date:
21 Oct 2021
Publisher:
CDS
Description:
We apply the image-subtraction method in order to reanalyze the ESO Very Large Telescope data on M83 (NGC 5236), obtained and analyzed by Thim et al. (2003ApJ...590..256T). Whereas Thim et al. (2003ApJ...590..256T) found 12 Cepheids with periods between 12 and 55 days, we find 112 Cepheids with periods ranging from 7 to 91 days as well as 60 other variables. These include two candidate eclipsing binaries, which, if confirmed, would be the first optically discovered outside the Local Group. We thus demonstrate that the image-subtraction method is much more powerful for detecting variability, especially in crowded fields. However, Hubble Space Telescope observations are necessary to obtain a Cepheid period-luminosity distance not dominated by blending and crowding. We propose a "hybrid" approach, in which numerous Cepheids are discovered and characterized using large ground-based telescopes and then followed up with the Hubble Space Telescope to obtain precise distances.
983. Period of M15 variable stars
ID:
ivo://CDS.VizieR/J/AJ/135/1459
Title:
Period of M15 variable stars
Short Name:
J/AJ/135/1459
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new BVI CCD photometry for variables in the globular cluster M15. Our photometry was obtained using both the image subtraction package ISIS and DAOPHOT/ALLFRAME. The data were acquired in 2001 on two observing runs on 11 observing nights using the 2m telescope of the Bulgarian National Astronomical Observatory "Rozhen" with a Photometrics CCD camera. For 39 previously known variables, we present a period for the first time, and improved periods were obtained for many previously known variables. Fourteen new variables are reported. We present updated Bailey diagrams for the cluster, and discuss its Oosterhoff classification. Although many of M15's RRab pulsators fall at an intermediate locus between Oosterhoff types I and II (OoII) in the Bailey diagram, we argue that M15 is indeed a bona fide OoII globular cluster.
984. Period spacings in gamma Dor stars
ID:
ivo://CDS.VizieR/J/A+A/574/A17
Title:
Period spacings in gamma Dor stars
Short Name:
J/A+A/574/A17
Date:
21 Oct 2021
Publisher:
CDS
Description:
The analysis of stellar oscillations is one of the most reliable ways to probe stellar interiors. Recent space missions such as Kepler have provided us with an opportunity to study these oscillations with unprecedented detail. For many multi-periodic pulsators such as gamma Doradus stars, this led to the detection of dozens to hundreds of oscillation frequencies that could not be found from ground-based observations. We aim to detect non-uniform period spacings in the Fourier spectra of a sample of gamma Doradus stars observed by Kepler. Such detection is complicated by both the large number of significant frequencies in the space photometry and by overlapping non-equidistant rotationally split multiplets. Guided by theoretical properties of gravity-mode oscillation of gamma Doradus stars, we developed a period-spacing detection method and applied it to Kepler observations of a few stars, after having tested the performance from simulations. The application of the technique resulted in the clear detection of non-uniform period spacing series for three out of the five treated Kepler targets. Disadvantages of the technique are also discussed, and include the disability to distinguish between different values of the spherical degree and azimuthal order of the oscillation modes, without additional theoretical modelling. Despite the shortcomings, the method is shown to enable solid detections of period spacings for gamma Doradus stars, which will allow future asteroseismic analyses of these stars.
985. Period variation in BW Vulpeculae redux
ID:
ivo://CDS.VizieR/J/A+A/544/A28
Title:
Period variation in BW Vulpeculae redux
Short Name:
J/A+A/544/A28
Date:
21 Oct 2021
Publisher:
CDS
Description:
For the past 25 years, BW Vulpeculae has been the topic of period analyses centered on a secular period change with a periodic variation superposed, presumed to be due to light time effects in a binary system. According to this paradigm, one would expect what seems like a period increase of about 0.5s during or soon after the year 2001. I have continued photometric monitoring through the year 2012, adding 40 new timings of maximum and minimum light. This expected change in period did not occur, which rules out that interpretation of the period variation. As of 2012, the observed timings are about two hours early compared to those predicted by the quadratic ephemeris, but are very close to those predicted by the linear ephemeris. In fact, the period has remained constant for the last 32 years, indicating that the previous epochs of constant period are almost certainly the correct interpretation, though the cause of the period changes is still not clear. Continued photometric monitoring of BW Vul leads to the conclusion that the period changes are abrupt, followed by epochs of constant period lasting between 12 and at least 32 years.
986. Period variations for the Cepheid VZ Cyg
ID:
ivo://CDS.VizieR/J/AJ/154/217
Title:
Period variations for the Cepheid VZ Cyg
Short Name:
J/AJ/154/217
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Cepheid Period-Luminosity law is a key rung on the extragalactic distance ladder. However, numerous Cepheids are known to undergo period variations. Monitoring, refining, and understanding these period variations allows us to better determine the parameters of the Cepheids themselves and of the instability strip in which they reside, and to test models of stellar evolution. VZ Cyg, a classical Cepheid pulsating at ~4.864 days, has been observed for over 100 years. Combining data from literature observations, the Kilodegree Extremely Little Telescope (KELT) transit survey, and new targeted observations with the Robotically Controlled Telescope (RCT) at Kitt Peak, we find a period change rate of dP/dt=-0.0642+/-0.0018 s/yr. However, when only the recent observations are examined, we find a much higher period change rate of dP/dt=-0.0923+/-0.0110 s/yr. This higher rate could be due to an apparent long-term (P~26.5 years) cyclic period variation. The possible interpretations of this single Cepheid's complex period variations underscore both the need to regularly monitor pulsating variables and the important benefits that photometric surveys such as KELT can have on the field. Further monitoring of this interesting example of Cepheid variability is recommended to confirm and better understand the possible cyclic period variations. Further, Cepheid timing analyses are necessary to fully understand their current behaviors and parameters, as well as their evolutionary histories.
987. Period variations in galactic RRab stars
ID:
ivo://CDS.VizieR/J/A+A/476/307
Title:
Period variations in galactic RRab stars
Short Name:
J/A+A/476/307
Date:
21 Oct 2021
Publisher:
CDS
Description:
The theory of stellar evolution can be more closely tested if we have the opportunity to measure new quantities. Nowadays, observations of galactic RR Lyr stars are available on a time baseline exceeding 100 years. Therefore, we can exploit the possibility of investigating period changes, continuing the pioneering work started by V.P. Tsesevich in 1969. We collected the available times of maximum brightness of the galactic RR Lyr stars in the GEOS RR Lyr database (http://dbrr.ast.obs-mip.fr/). Moreover, we also started new observational projects, including surveys with automated telescopes, to characterise the O-C diagrams better. The database we built has proved to be a very powerful tool for tracing the period variations through the ages. We analyzed 123 stars showing a clear O-C pattern (constant, parabolic or erratic) by means of different least-squares methods.
988. Period variations in SuperWASP PCEB
ID:
ivo://CDS.VizieR/J/A+A/566/A128
Title:
Period variations in SuperWASP PCEB
Short Name:
J/A+A/566/A128
Date:
21 Oct 2021
Publisher:
CDS
Description:
Period or amplitude variations in eclipsing binaries may reveal the presence of additional massive bodies in the system, such as circumbinary planets. Here, we have studied twelve previously-known eclipsing post-common-envelope binaries for evidence of such light curve variations, on the basis of multi-year observations in the SuperWASP archive. The results for HW Vir provided strong evidence for period changes consistent with those measured by previous studies, and help support a two-planet model for the system. ASAS J102322-3737.0 exhibited plausible evidence for a period increase not previously suggested; while NY Vir, QS Vir and NSVS 14256825 afforded less significant support for period change, providing some confirmation to earlier claims. In other cases, period change was not convincingly observed; for AA Dor and NSVS 07826147, previous findings of constant period were confirmed. This study allows us to present hundreds of new primary eclipse timings for these systems, and further demonstrates the value of wide-field high-cadence surveys like SuperWASP for the investigation of variable stars.
989. PHAT. XIII. M31 Cepheid P-L relation
ID:
ivo://CDS.VizieR/J/MNRAS/451/724
Title:
PHAT. XIII. M31 Cepheid P-L relation
Short Name:
J/MNRAS/451/724
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) and Wide Field Camera 3 (WFC3) observations from the Panchromatic Hubble Andromeda Treasury (PHAT), we present new period-luminosity (P-L) relations for Cepheid variables in M31. Cepheids from several ground-based studies are identified in the PHAT photometry to derive new P-L and Wesenheit P-L relations in the near infrared and visual filters. We derive a distance modulus to M31 of 24.51+/-0.08 in the IR bands and 24.32+/-0.09 in the visual bands, including the first P-L relations in the F_475W_ and F_814W_ filters for M31. Our derived visual and IR distance moduli disagree at slightly more than a 1{sigma} level. Differences in the P-L relations between ground-based and HST observations are investigated for a subset of Cepheids. We find a significant discrepancy between ground-based and HST P-L relations with the same Cepheids, suggesting adverse effects from photometric contamination in ground-based Cepheid observations. Additionally, a statistically significant radial trend in the P-L relation is found which does not appear to be explained by metallicity.
990. phi Dra BVRI light curves
ID:
ivo://CDS.VizieR/J/A+A/584/A17
Title:
phi Dra BVRI light curves
Short Name:
J/A+A/584/A17
Date:
21 Oct 2021
Publisher:
CDS
Description:
The presence of heavier chemical elements in stellar atmospheres influences the spectral energy distribution of stars. An uneven surface distribution of these elements, together with flux redistribution and stellar rotation, are commonly believed to be the primary causes of the variability of chemically peculiar (CP) stars. We aim to model the photometric variability of the CP star phi Dra based on the assumption of inhomogeneous surface distribution of heavier elements and compare it to the observed variability of the star. We also intend to identify the processes that contribute most significantly to its photometric variability. We use a grid of TLUSTY model atmospheres and the SYNSPEC code to model the radiative flux emerging from the individual surface elements of phi Dra with different chemical compositions. We integrate the emerging flux over the visible surface of the star at different phases throughout the entire rotational period to synthesise theoretical light curves of the star in several spectral bands.