- 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.
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- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/PAZh/35/348
- Title:
- Photoelectric observation of Cepheids
- Short Name:
- J/PAZh/35/348
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From December 2006 to January 2008, we performed 1699 BVIc observations for 46 low-amplitude Cepheids discovered in the course of the ASAS project using the 76-cm telescope of the South-African Astronomical Observatory (SAAO). We provide the tables of observations and V light and B-V and V-Ic color curves. These new observations, along with data from the ASAS-3 catalog, have been used to improve the elements of the light variations. Our data allow the number of known Galactic low-amplitude Cepheids to be almost doubled. This makes it possible to increase the number of distance indicators suitable for studying the structure of the inner Galactic arms by almost 15%.
- ID:
- ivo://CDS.VizieR/II/285
- Title:
- Photoelectric observations of Cepheids in UBV(RI)c
- Short Name:
- II/285
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog gathers the observation of 894 Cepheids made between 1986 to 2004. Observations are listed in alphabetical order of the constellations. The standard deviation for every magnitude and color is 0.01mag. This version supersedes the 1997 edition (Cat. <II/217>)
- ID:
- ivo://CDS.VizieR/II/217
- Title:
- Photoelectric observations of Cepheids in UBV(RI)c
- Short Name:
- II/217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations are listed in alphabetical order of the constellations. The standard deviation for every magnitude and color is 0.01 mag.
