- ID:
- ivo://CDS.VizieR/J/PASP/121/1188
- Title:
- Periodic variables in NGC 2301
- Short Name:
- J/PASP/121/1188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for periodic variables within 4078 time-series light curves and an analysis of the period-color plane for stars in the field of the open cluster NGC 2301. One hundred thirty-eight periodic variables were discovered, of which five are eclipsing binary candidates with unequal minima. The remaining 133 periodic variables appear to consist mainly of late-type stars whose variation is due to rotation modulated by star spot activity. The determined periods range from less than a day to over 14 days and have nearly unreddened B-R colors in the range of 0.8 to 2.8. The Barnes (2003ApJ...586..464B) interpretation of the period-color plane of late type stars is tested with our data. Our data did not show distinct I and C sequences, likely due to nonmember field stars contaminating in the background, as we estimate the total contamination to be 43%. Using different assumptions, the gyrochronological age of the cluster is calculated to be 210+/-25Myr, which falls in the range of age values (164-250Myr) determined by previous studies. Finally, we present evidence which nullifies the earlier suggestion that two of the variable stars in NGC 2301 might be white dwarfs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/554/A108
- Title:
- Periodic variables in NGC 3766
- Short Name:
- J/A+A/554/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the population of periodic variable stars in the open cluster NGC3766 based on a 7-year multiband monitoring campaign conducted on the 1.2m Swiss Euler telescope at La Silla, Chili. The data reduction, light curve cleaning, and period search procedures, combined with the long observation time line, allowed us to detect variability amplitudes down to the mmag level. The variability properties were complemented with the positions in the color-magnitude and color-color diagrams to classify periodic variable stars into distinct variability types. We find a large population (36 stars) of new variable stars between the red edge of slowly pulsating B (SPB) stars and the blue edge of delta Sct stars, a region in the Hertzsprung-Russell (HR) diagram where no pulsation is predicted to occur based on standard stellar models. The bulk of their periods ranges from 0.1 to 0.7d, with amplitudes between 1 and 4mmag for the majority of them. About 20% of stars in that region of the HR diagram are found to be variable, but the number of members of this new group is expected to be higher, with amplitudes below our mmag detection limit. The properties of this new group of variable stars are summarized and arguments set forth in favor of a pulsation origin of the variability, with g-modes sustained by stellar rotation. Potential members of this new class of low-amplitude periodic (most probably pulsating) A and late-B variables in the literature are discussed. We additionally identify 16 eclipsing binary, 13 SPB, 14 delta Sct, and 12 gamma Dor candidates, as well as 72 fainter periodic variables. All are new discoveries. We encourage searching for this new class of variables in other young open clusters, especially in those hosting a rich population of Be stars.
- 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.
- 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.
- 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.
- 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/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>)
