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1041. Variable stars in IC 1613
ID:
ivo://CDS.VizieR/J/A+A/363/29
Title:
Variable stars in IC 1613
Short Name:
J/A+A/363/29
Date:
21 Oct 2021
Publisher:
CDS
Description:
Two nearby galaxies, IC 1613 and NGC 6822, were observed over four years to detect short period Cepheids and to obtain good light curves for Fourier decomposition. Since the program was carried out with a relatively small telescope, the Dutch 0.9-m at ESO-La Silla, the observations were performed without filter (white light), or Wh-band; the advantage of this technique is that the photon statistics correspond to those of V-band observations of similar exposure time obtained with a 2-m class telescope. In this paper we discuss some properties of Wh photometry and present the results of the observations of Field B in IC 1613 (3.8'x3.8'). A total of 65 images were obtained and the reduction was performed with DAOPHOT. The light curves of 4037 stars were measured, and the analysis using various techniques allowed the detection of 121 variable stars. We detected 51 population I Cepheids, while previously only 12 Cepheids were known in the same field. Most of these have short periods and some are first overtone mode pulsators. The other variable stars include one eclipsing binary, two suspected W Vir stars, 57 irregular and semi-regular red variables, 3 periodic red variables and 6 irregular blue variables.
1042. Variable stars in IC 1613
ID:
ivo://CDS.VizieR/J/A+A/367/759
Title:
Variable stars in IC 1613
Short Name:
J/A+A/367/759
Date:
21 Oct 2021
Publisher:
CDS
Description:
The nearby galaxies IC 1613 and NGC 6822 were observed over four years to detect short period Cepheids and to obtain good light curves for Fourier decomposition. The program was carried out with a relatively small telescope, the Dutch 0.9m at ESO-La Silla, and the observations were performed without filter (white light), or Wh-band. In this paper we present the results of the observations of Fields C and D in IC 1613 (3.8'x3.8' each). The analysis of the light curves of 3297 stars in the two fields has allowed the detection of 92 variable stars. A total of 34 Population I Cepheids have been found, while only 7 of these objects were previously known in these fields. Most of the stars have short periods and some of them are first overtone mode pulsators. Among the other variable stars there are one eclipsing binary and five W Vir candidates. A nova event was observed in Field D.
1043. Variable stars in instability strip
ID:
ivo://CDS.VizieR/J/A+AS/109/201
Title:
Variable stars in instability strip
Short Name:
J/A+AS/109/201
Date:
21 Oct 2021
Publisher:
CDS
Description:
Identifications, positions, photometry, spectra, some pulsational features, other astrophysical parameters and literature for 302 pulsating variable stars in the lower instability strip, near the ZAMS, are given. About 185 stars have near homogeneous photometric information in the Stroemgren's uvby-{beta} photometric system. This catalogue/database covers information published until November 1993.
1044. Variable stars in Leo I dSph
ID:
ivo://CDS.VizieR/J/PASP/126/616
Title:
Variable stars in Leo I dSph
Short Name:
J/PASP/126/616
Date:
21 Oct 2021
Publisher:
CDS
Description:
From archival ground-based images of the Leo I dwarf spheroidal galaxy, we have identified and characterized the pulsation properties of 164 candidate RR Lyrae variables and 55 candidate anomalous and/or short-period Cepheids. We have also identified 19 candidate long-period variable stars and 13 other candidate variables whose physical nature is unclear, but due to the limitations of our observational material we are unable to estimate reliable periods for them.
1045. Variable stars in LMC MACHO fields 1 & 79
ID:
ivo://CDS.VizieR/J/A+A/500/917
Title:
Variable stars in LMC MACHO fields 1 & 79
Short Name:
J/A+A/500/917
Date:
21 Oct 2021
Publisher:
CDS
Description:
Because of the strong effect of systematics/trends in variable star observations, we apply the Trend Filtering Algorithm (TFA) to a subset of the MACHO database and search for variable stars. TFA has been applied successfully in planetary transit searches, where weak, short-lasting periodic dimmings are sought in the presence of noise and various systematics (due to, e.g., imperfect flat fielding, crowding, etc). These latter effects introduce colored noise in the photometric time series that can completely overwhelm the signal. By using a large number of available photometric time series of a given field, TFA utilizes the fact that the same types of systematics appear in several/many time series of the same field. As a result, we attempt to reproduce each target time series by a linear combination of templates, optimized by least-squares. After a signal has been identified in the residuals between the original time series and the systematics computed by TFA, we reconstruct the signal by employing the full model, including the signal, systematics and noise. We apply TFA to the brightest ~5300 objects from subsets of each of the MACHO Large Magellanic Cloud fields #1 and #79. We find that the Fourier frequency analysis performed on the original data detects some 60% of the objects as trend-dominated. This figure decreases essentially to zero after using TFA. In total, we detect 387 variables in the two fields, 183 of which would have remained undetected without using TFA. Where possible, we give preliminary classification of the variables found.
1046. Variable stars in Logal Group galaxies. III.
ID:
ivo://CDS.VizieR/J/ApJ/842/60
Title:
Variable stars in Logal Group galaxies. III.
Short Name:
J/ApJ/842/60
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the discovery of 1568 RR Lyrae stars in three of the most luminous M31 satellites: And VII (573), NGC 147 (177), and NGC 185 (818). We use their properties to study the formation history of Local Group spiral haloes, and in particular, to infer about the nature of their possible building blocks by comparison with available data for RR Lyrae stars in the halo and in a sample of satellites of M31 and the Milky Way. We find that the brightest satellites and the halos of both galaxies host a number of High Amplitude Short Period (HASP) RR Lyrae variable stars, which are missing in the faintest satellites. HASP variable stars have been shown by Fiorentino+ (2015ApJ...798L..12F) to be tracers of a population of stars as metal-rich as [Fe/H]~-1.5 and older than ~10Gyr. This suggests that the metal-rich M31 and MW halo component, which manifests through the HASP phenomenon, comes from massive dwarf galaxy building blocks, as the low-mass dwarfs did not chemically enrich fast enough to produce them. All detected variable stars are new discoveries; in particular, this work presents the first detections of RR Lyrae stars in And VII. Moreover, a number of candidate Anomalous Cepheids, and binary and long-period variable stars have been detected. We provide pulsation properties (period, amplitude, mean magnitude), light curves, and time series photometry for all of the variable stars in the three galaxies.
1047. Variable stars in M54
ID:
ivo://CDS.VizieR/J/MNRAS/406/329
Title:
Variable stars in M54
Short Name:
J/MNRAS/406/329
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new B, V and I CCD time-series photometry for 177 variable stars in a 13x13arcmin^2^ field centred on the globular cluster M54 using the European Southern Observatory (ESO)-Danish 1.54-m telescope in La Silla, 94 of which are newly identified variables. The total sample is composed of two anomalous Cepheids, 144 RR Lyrae stars (108 RR0 and 36 RR1), three SX Phoenicis, seven eclipsing binaries (five W UMa and two Algol binaries), three variables of uncertain classification and 18 long-period variables. Ephemerides are provided for all the observed short-period variables. The positional accuracy is better than 0.2".
1048. Variable stars in M92
ID:
ivo://CDS.VizieR/J/ApJ/87/361
Title:
Variable stars in M92
Short Name:
J/ApJ/87/361
Date:
21 Oct 2021
Publisher:
CDS
Description:
The distance modulus of M92 is determined from the bright stars and the mean magnitude of 12 cluster-type variables. From the former, m-M=14.93; and from the latter, m-M=14.94+/-0.01. Two variables not belonging to the cluster are indicated, as well as two other stars with range in variation of 0.25mag, which are marked as probable variables. From star counts, the ratio of the minor to the major axis is found to be 0.85, with a position angle of the major axis of 28{deg}. Sensitometer tracings give 14' for the diameter of the cluster.
1049. Variable stars in M31 and M33. V. HR diagram
ID:
ivo://CDS.VizieR/J/ApJ/844/40
Title:
Variable stars in M31 and M33. V. HR diagram
Short Name:
J/ApJ/844/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present HR diagrams for the massive star populations in M31 and M33, including several different types of emission-line stars: the confirmed luminous blue variables (LBVs), candidate LBVs, B[e] supergiants, and the warm hypergiants. We estimate their apparent temperatures and luminosities for comparison with their respective massive star populations and evaluate the possible relationships of these different classes of evolved, massive stars, and their evolutionary state. Several of the LBV candidates lie near the LBV/S Dor instability strip that supports their classification. Most of the B[e] supergiants, however, are less luminous than the LBVs. Many are very dusty with the infrared flux contributing one-third or more to their total flux. They are also relatively isolated from other luminous OB stars. Overall, their spatial distribution suggests a more evolved state. Some may be post-RSGs (red supergiants) like the warm hypergiants, and there may be more than one path to becoming a B[e] star. There are sufficient differences in the spectra, luminosities, spatial distribution, and the presence or lack of dust between the LBVs and B[e] supergiants to conclude that one group does not evolve into the other.
1050. Variable stars in M31 & M33. II. LBVs
ID:
ivo://CDS.VizieR/J/ApJ/790/48
Title:
Variable stars in M31 & M33. II. LBVs
Short Name:
J/ApJ/790/48
Date:
21 Oct 2021
Publisher:
CDS
Description:
An increasing number of non-terminal eruptions are being found in the numerous surveys for optical transients. Very little is known about these giant eruptions, their progenitors and their evolutionary state. A greatly improved census of the likely progenitor class, including the most luminous evolved stars, the luminous blue variables (LBVs), and the warm and cool hypergiants is now needed for a complete picture of the final pre-supernova stages of very massive stars. We have begun a survey of the evolved and unstable luminous star populations in several nearby resolved galaxies. In this second paper on M31 and M33, we review the spectral characteristics, spectral energy distributions, circumstellar ejecta, and evidence for mass loss for 82 luminous and variable stars. We show that many of these stars have warm circumstellar dust including several of the Fe II emission line stars, but conclude that the confirmed LBVs in M31 and M33 do not. The confirmed LBVs have relatively low wind speeds even in their hot, quiescent or visual minimum state compared to the B-type supergiants and Of/WN stars which they spectroscopically resemble. The nature of the Fe II emission line stars and their relation to the LBV state remains uncertain, but some have properties in common with the warm hypergiants and the sgB[e] stars. Several individual stars are discussed in detail. We identify three possible candidate LBVs and three additional post-red supergiant candidates. We suggest that M33-013406.63 (UIT301,B416) is not an LBV/S Dor variable, but is a very luminous late O-type supergiant and one of the most luminous stars or pair of stars in M33.