- ID:
- ivo://CDS.VizieR/J/A+A/573/A103
- Title:
- Light curves for variables in 5 clusters
- Short Name:
- J/A+A/573/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the analysis of time-series observations from 2013 and 2014 of five metal rich ([Fe/H]>-1) globular clusters: NGC6388, NGC6441, NGC6528, NGC6638, and NGC6652. The data have been used to perform a census of the variable stars in the central parts of these clusters. The observations were made with the electron multiplying CCD (EMCCD) camera at the Danish 1.54m Telescope at La Silla, Chile, and they were analysed using difference image analysis (DIA) to obtain high-precision light curves of the variable stars. It was possible to identify and classify all of the previously known or suspected variable stars in the central regions of the five clusters. Furthermore, we were able to identify, and in most cases classify 48, 49, 7, 8, and 2 previously unknown variables in NGC 6388, NGC 6441, NGC 6528, NGC 6638, and NGC 6652, respectively. Especially interesting is the case of NGC 6441, for which the variable star population of about 150 stars has been thoroughly examined by previous studies, including a Hubble Space Telescope study. In this paper we are able to present 49 new variable stars for this cluster, of which one (possibly two) are RR Lyrae stars, two are W Virginis stars, and the rest are long period semi-regular or irregular variables on the red giant branch. We have also detected the first double mode RR Lyrae in the cluster.
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- ID:
- ivo://CDS.VizieR/J/ApJS/258/43
- Title:
- Light curves of AGBs in Galactic open clusters
- Short Name:
- J/ApJS/258/43
- Date:
- 15 Feb 2022 09:28:18
- Publisher:
- CDS
- Description:
- Benefiting from the GAIA second and early third releases of photometric and astrometric data we examine the population of asymptotic giant branch (AGB) stars that appear in the fields of intermediate-age and young open star clusters. We identify 49 AGB star candidates, brighter than the tip of the red giant branch, with a good-to-high cluster membership probability. Among them we find 19 TP-AGB stars with known spectral type: 4 M stars, 3 MS/S stars and 12 C stars. By combining observations, stellar models, and radiative transfer calculations that include the effect of circumstellar dust, we characterize each star in terms of initial mass, luminosity, mass-loss rate, core mass, period and mode of pulsation. The information collected helps us shed light on the TP-AGB evolution at solar-like metallicity, placing constraints on the third dredge-up process, the initial masses of carbon stars, stellar winds, and the initial-final mass relation (IFMR). In particular, we find that two bright carbon stars, MSB 75 and BM IV 90, members of the clusters NGC 7789 and NGC 2660 (with similar ages of about 1.2-1.6 Gyr and initial masses between 2.1 and 1.9 solar masses), have unusually high core masses, about 0.67-0.7 solar masses. These results support the findings of a recent work (Marigo et al., 2020NatAs...4.1102M) that identified a kink in the IFMR, which interrupts its monotonic trend just at the same initial masses. Finally, we investigate two competing scenarios to explain the Mc data: the role of stellar winds in single-star evolution, and binary interactions through the blue-straggler channel.
- ID:
- ivo://CDS.VizieR/J/A+A/456/599
- Title:
- Light curves of 5 cataclysmic variables
- Short Name:
- J/A+A/456/599
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time-resolved photometry of five relatively poorly-studied cataclysmic variables: V1193 Ori, LQ Peg, LD 317, V795 Her and MCT 2347-3144. The observations were made using four 1m-class telescopes for a total of more than 250h of observation and almost 16,000 data points. For LQ Peg WHT spectroscopic data have been analysed as well. The light curves show a whole range of variability on different time scales, from minutes to months. We detect for the first time a brightness variation of 0.05mag in amplitude in V1193 Ori on the same timescale as the orbital period, that we interpret as the result of the irradiation of the secondary. A 20-min Quasi-Periodic Oscillation is also detected. The mean brightness of the system has changed by 0.5mag on a three month interval, while the flickering was halved. In LQ Peg a 0.05mag modulation was revealed with a period of about 3h. The flickering was much smaller, of the order of 0.025mag. A possible Quasi-Periodic Oscillation could exist near 30min. For this object, the WHT spectra are single peaked and do not show any radial-velocity variations. The data of LD 317 show a decrease in the mean magnitude of the system. No periodic signal was detected but this is certainly attributable to the very large flickering observed: between 0.07 and 0.1mag. For V795 Her, the 2.8-hour modulation, thought to be a superhump arising from the precession of the disc, is present. We show this modulation not to be stable in terms of periodicity, amplitude and phase. Finally, for MCT 2347-3144, a clear modulation is seen in a first dataset obtained in October 2002. This modulation is absent in August 2003, when the system was brighter and showed much more flickering.
- ID:
- ivo://CDS.VizieR/J/other/PDDO/1.511
- Title:
- Light curves of M9 variables
- Short Name:
- J/other/PDDO/1.5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Time-series photographic photometry for the variable stars in M9.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A95
- Title:
- Light curves of NGC 6910 pulsating stars
- Short Name:
- J/A+A/632/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this study is to obtain the age of the open cluster NGC 6910 by means of ensemble asteroseismology of the early-type pulsating members, to derive their stellar parameters, and to classify the excited modes. We used time-series analysis, performed photometric and spectroscopic mode identification, and calculated grids of evolutionary and seismic models to apply the procedure of ensemble asteroseismology for nine pulsating members of NGC 6910. With two iterations of the procedure of ensemble asteroseismology we derived an age of 10.6^+0.9^_-0.8_Myr for NGC 6910. We also identified the degree l for 8 of 37 modes detected in these stars and classified all modes in terms of p, g, and mixed-mode pulsations. Of the nine pulsating stars examined in the paper, eight are {beta} Cep stars, including three that are hybrid {beta} Cep and slowly pulsating B-type (SPB) pulsators, and one is an SPB star. Interestingly, the least massive {beta} Cep star, NGC 6910-38, has a mass of about 5.6 solar masses. The present theory does not predict unstable p modes in B-type stars with such a low mass. The g modes with relatively high frequencies (>3.5d^-1^), observed in three members of the cluster, are also stable according to seismic modelling. Both findings pose a challenge for theoretical calculations and prompt a revision of the opacities. The procedure of ensemble asteroseismology was found to be successful for NGC 6910 and {chi} Per on the basis of pulsating B-type stars and can therefore be applied to other young open clusters that are rich in such stars.
- ID:
- ivo://CDS.VizieR/J/A+A/404/621
- Title:
- Light curves of ROTSE-I delta Scuti type stars
- Short Name:
- J/A+A/404/621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-passband CCD photometry of 20 ROTSE-I {delta} Scuti type pulsating stars and 1 RR Lyrae star to re-classify their variable types using the comparison of amplitudes between V and I passbands. For the re-classification, we used a criterion that pulsating stars have larger amplitude differences between passbands than eclipsing binaries because brightness changes of pulsating stars are mainly due to the temperature variations. As a result, only six stars were re-confirmed as {delta} Scuti variables and thirteen stars turned out to be W UMa type eclipsing binaries. The other two stars were identified as one cataclysmic variable and one non-variable, respectively. Our results suggest that a number of ROTSE-I {delta} Scuti type stars, which do not show typical pulsating light curves of high amplitude {delta} Scuti stars, are W UMa type eclipsing binaries.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/25
- Title:
- Light curves of RR Lyrae stars in M3 (NGC5272)
- Short Name:
- J/ApJS/219/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The overtone and multi-mode RR Lyrae stars in the globular cluster M3 are studied using a 200 day long, B,V, and l_c_ time-series photometry obtained in 2012. 70% of the 52 overtone variables observed show some kind of multi-periodicity (with additional frequency at f_0.61_=f_1O_/0.61 frequency ratio, Blazhko effect, double/multi-mode pulsation, and period doubling). A signal at the 0.587 frequency ratio to the fundamental-mode frequency is detected in the double-mode star, V13, which may be identified as the second radial overtone mode. If this mode identification is correct, then V13 is the first RR Lyrae star showing triple-mode pulsation of the first three radial modes. Either the Blazhko effect or the f_0,61_ frequency (or both of these phenomena) appears in seven double-mode stars. The P_1O_/P_F_ period ratio of RRd stars showing the Blazhko effect are anomalous. A displacement of the main frequency component at the fundamental mode with the value of modulation frequency (or its half), is detected in three Blazhko RRd stars that are parallel with the appearance of the overtone-mode pulsation. The f_0.61_ frequency appears in RRc stars that lie at the blue side of the double-mode region and in RRd stars, raising the suspicion that its occurrence may be connected to double-mode pulsation. The changes of the Blazhko and double-mode properties of the stars are also reviewed using the recent and archive photometric data.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/4590
- Title:
- Light curves of RR Lyrae variables in M31
- Short Name:
- J/MNRAS/478/4590
- Date:
- 10 Dec 2021 13:45:59
- Publisher:
- CDS
- Description:
- We present an analysis of M31 RR Lyrae stars in six different fields using archival imaging from the Hubble Space Telescope. Published data for M31, M33, and several M31 dwarf spheroidal galaxies are also used to study the global properties of RR Lyrae in these systems. From the properties of RR Lyrae stars, we found that the majority of M31 and M33 RRLs are of Oosterhoff I (OoI),while those in M31 dSphs are of Oosterhoff intermediate. The main parameter affecting these Oosterhoff types is likely to be metallicity. Metallicity also plays a role in the lack of RRLs in the high amplitude short period(HASP, defined as those with P<=0.48 and A_V_>=0.75mag) variables in M31 dSphs. This difference in the properties of RRLs between their parent galaxy and satellites, as well as the lack of RRLs in the HASP region in dSphs can also be observed in the Milky Way (MW). Therefore, systems like these dSphs are unlikely to be the main building blocks of the M31 and MW halo.
- ID:
- ivo://CDS.VizieR/J/PAZh/35/451
- Title:
- Light Curves of RS Pup
- Short Name:
- J/PAZh/35/451
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on photographic plates from the Harvard College Observatory, we have made 1492 magnitude estimates for the long-period classical Cepheid RS Pup (P=41.4d). Together with the observations taken from the literature, our data have allowed us to construct an O-C diagram spanning a time interval of 135-years.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A38
- Title:
- Light curves of spotted solar-type stars
- Short Name:
- J/A+A/588/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform detailed time series analysis for B- and V-band photometry of 21 young and active solar-type stars to study their spot structures, activity cycles, and differential rotation.
