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1351. Theoretical framework for RR Lyrae. II. MIR data
ID:
ivo://CDS.VizieR/J/ApJ/841/84
Title:
Theoretical framework for RR Lyrae. II. MIR data
Short Name:
J/ApJ/841/84
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new theoretical period-luminosity-metallicity (PLZ) relations for RR Lyrae stars (RRLs) at Spitzer and WISE wavelengths. The PLZ relations were derived using nonlinear, time-dependent convective hydrodynamical models for a broad range of metal abundances (Z=0.0001-0.0198). In deriving the light curves, we tested two sets of atmospheric models and found no significant difference between the resulting mean magnitudes. We also compare our theoretical relations to empirical relations derived from RRLs in both the field and in the globular cluster M4. Our theoretical PLZ relations were combined with multi-wavelength observations to simultaneously fit the distance modulus, {mu}0, and extinction, A_V_, of both the individual Galactic RRL and of the cluster M4. The results for the Galactic RRL are consistent with trigonometric parallax measurements from Gaia's first data release. For M4, we find a distance modulus of {mu}0=11.257+/-0.035mag with A_V_=1.45+/-0.12mag, which is consistent with measurements from other distance indicators. This analysis has shown that, when considering a sample covering a range of iron abundances, the metallicity spread introduces a dispersion in the PL relation on the order of 0.13mag. However, if this metallicity component is accounted for in a PLZ relation, the dispersion is reduced to ~0.02mag at mid-infrared wavelengths.
1352. The population of pulsating variable stars in Sextans
ID:
ivo://CDS.VizieR/J/AJ/157/35
Title:
The population of pulsating variable stars in Sextans
Short Name:
J/AJ/157/35
Date:
21 Oct 2021
Publisher:
CDS
Description:
A large extension of the Sextans dwarf spheroidal galaxy, 7 deg^2^, has been surveyed for variable stars using the Dark Energy Camera at the Blanco Telescope at Cerro Tololo Inter-American Observatory, Chile. We report seven anomalous Cepheids, 199 RR Lyrae stars, and 16 dwarf Cepheids in the field. This is only the fifth extragalactic system in which dwarf Cepheids have been systematically searched. Henceforth, the new stars increase the census of stars coming from different environments that can be used to asses the advantages and limitations of using dwarf Cepheids as standard candles in populations for which the metallicity is not necessarily known. The dwarf Cepheids found in Sextans have a mean period of 0.066 day and a mean g amplitude of 0.87 mag. They are located below the horizontal branch, spanning a range of 0.8 mag: 21.9<g<22.7. The number of dwarf Cepheids in Sextans is low compared with other galaxies such as Carina, which has a strong intermediate-age population. On the other hand, the number and ratio of RR Lyrae stars to dwarf Cepheids are quite similar to those of Sculptor, a galaxy which, as Sextans, is dominated by an old stellar population. The dwarf Cepheid stars found in Sextans follow a well-constrained period-luminosity relationship with an rms=0.05 mag in the g band, which was set up by anchoring to the distance modulus given by the RR Lyrae stars. Although the majority of the variable stars in Sextans are located toward the center of the galaxy, we have found two RR Lyrae stars and one anomalous Cepheid in the outskirts of the galaxy that may be extratidal stars and suggest that this galaxy may be undergoing tidal destruction. These possible extratidal variable stars share the same proper motions as Sextans, as seen by recent Gaia measurements. Two additional stars that we initially classified as foreground RR Lyrae stars may actually be other examples of Sextans extratidal anomalous Cepheids, although radial velocities are needed to prove that scenario.
1353. The pulsations of G 207-9 and LP 133-144
ID:
ivo://CDS.VizieR/J/MNRAS/461/4059
Title:
The pulsations of G 207-9 and LP 133-144
Short Name:
J/MNRAS/461/4059
Date:
21 Oct 2021
Publisher:
CDS
Description:
G 207-9 and LP 133-144 are two rarely observed ZZ Ceti stars located in the middle and close to the blue edge of the ZZ Ceti instability domain, respectively. We aimed to observe them at least during one observing season at Konkoly Observatory with the purpose of extending the list of known pulsation modes for asteroseismic investigations and detect any significant changes in their pulsational behaviour. We determined five and three new normal modes of G 207-9 and LP 133-144, respectively. In LP 133-144, our frequency analysis also revealed that at least at three modes there are actually triplets with frequency separations of ~4Hz. The rotational period of LP 133-144 based on the triplets is ~=42h. The preliminary asteroseismic fits of G 207-9 predict Teff=12000 or 12400K and M=0.855--0.870M_{sun}_ values for the effective temperature and mass of the star, depending on the assumptions on the spherical degree (l) values of the modes. These results are in agreement with the spectroscopic determinations. In the case of LP 133-144, the best-fitting models prefer Teff=11800K in effective temperature and M*>=0.71M_{sun}_ stellar masses, which are more than 0.1M_{sun}_ larger than the spectroscopic value.
1354. The R CrB stars
ID:
ivo://CDS.VizieR/J/A+A/353/287
Title:
The R CrB stars
Short Name:
J/A+A/353/287
Date:
21 Oct 2021
Publisher:
CDS
Description:
Adopted line data, measured equivalent widths and derived elemental abundances for the individual lines observed in R Coronae Borealis and Extreme Helium stars.
1355. The RR Lyrae population of NGC 6101
ID:
ivo://CDS.VizieR/J/ApJ/727/9
Title:
The RR Lyrae population of NGC 6101
Short Name:
J/ApJ/727/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use V-band time-series data to analyze the RR Lyrae (RRL) population of the Galactic globular cluster NGC 6101. Using template fitting, we have discovered seven new RRL stars and confirmed 10 candidates. We find unusually long mean periods for the RRL of <P_ab_>=0.803 days and <P_c_>=0.393 days, and an atypically high ratio of n(c)/n(ab+c)=0.82. Based on our derived mean properties of the RRL, NGC 6101 is Oosterhoff type II, consistent with the cluster metallicity but intriguing with respect to its kinematics.
1356. The VMC survey. XIX. Classical Cepheids in SMC
ID:
ivo://CDS.VizieR/J/ApJS/224/21
Title:
The VMC survey. XIX. Classical Cepheids in SMC
Short Name:
J/ApJS/224/21
Date:
21 Oct 2021
Publisher:
CDS
Description:
The "VISTA near-infrared YJK_s_ survey of the Magellanic Clouds System" (VMC) is collecting deep K_s_-band time-series photometry of pulsating variable stars hosted by the two Magellanic Clouds and their connecting Bridge. In this paper, we present Y, J, K_s_ light curves for a sample of 4172 Small Magellanic Cloud (SMC) Classical Cepheids (CCs). These data, complemented with literature V values, allowed us to construct a variety of period-luminosity (PL), period-luminosity-color (PLC), and period-Wesenheit (PW) relationships, which are valid for Fundamental (F), First Overtone (FO), and Second Overtone (SO) pulsators. The relations involving the V, J, K_s_ bands are in agreement with their counterparts in the literature. As for the Y band, to our knowledge, we present the first CC PL, PW, and PLC relations ever derived using this filter. We also present the first near-infrared PL, PW, and PLC relations for SO pulsators to date. We used PW(V, K_s_) to estimate the relative SMC-LMC distance and, in turn, the absolute distance to the SMC. For the former quantity, we find a value of {Delta}{mu}=0.55+/-0.04mag, which is in rather good agreement with other evaluations based on CCs, but significantly larger than the results obtained from older population II distance indicators. This discrepancy might be due to the different geometric distributions of young and old tracers in both Clouds. As for the absolute distance to the SMC, our best estimates are {mu}_SMC_=19.01+/-0.05mag and {mu}_SMC_=19.04+/-0.06mag, based on two distance measurements to the LMC which rely on accurate CC and eclipsing Cepheid binary data, respectively.
1357. The VVV Variables (V^4^) catalog
ID:
ivo://CDS.VizieR/J/ApJ/864/11
Title:
The VVV Variables (V^4^) catalog
Short Name:
J/ApJ/864/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
Time-varying phenomena are one of the most substantial sources of astrophysical information, and their study has led to many fundamental discoveries in modern astronomy. We have developed an automated tool to search for and analyze variable sources in the near-infrared Ks band using the data from the VISTA Variables in the Via Lactea (VVV) ESO Public Large Survey. This process relies on the characterization of variable sources using different variability indices calculated from time series generated with point-spread function (PSF) photometry of sources under analysis. In particular, we used two main indices, the total amplitude {Delta}Ks and the eta index {eta}, to identify variable sources. Once the variable objects are identified, periods are determined with generalized Lomb-Scargle periodograms and the information potential metric. Variability classes are assigned according to a compromise between comparisons with VVV templates and the period of the variability. The automated tool is applied on VVV tiles d001 and d002 and led to the discovery of 200 variable sources. We detected 70 irregular variable sources and 130 periodic ones. In addition, nine open-cluster candidates projected in the region are analyzed, and the infrared variable candidates found around these clusters are further scrutinized by cross-matching their locations against emission star candidates from VPHAS+ survey H{alpha} color cuts.
1358. 78th name-list of variable stars
ID:
ivo://CDS.VizieR/J/other/IBVS/5721
Title:
78th name-list of variable stars
Short Name:
J/other/IBVS/572
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the next regular Name-List of variable stars containing information on 1706 variable stars recently designated in the system of the General Catalogue of Variable Stars.
1359. 79th Name-List of Variable Stars
ID:
ivo://CDS.VizieR/J/other/IBVS/5863
Title:
79th Name-List of Variable Stars
Short Name:
J/other/IBVS/586
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the special Name-List of variable stars containing information on 1270 variable stars recently designated in the system of the General Catalogue of Variable Stars, which are mostly former suspected variables from the NSV catalogue.
1360. 81th name-list of variable stars. I.
ID:
ivo://CDS.VizieR/J/other/IBVS/6151
Title:
81th name-list of variable stars. I.
Short Name:
J/other/IBVS/615
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first part of a new Name-List of variable stars containing information on 1951 variable stars recently designated in the system of the General Catalogue of Variable Stars. With the exception of Novae and other unusual variables named upon request from the IAU CBAT or by our initiative, these stars are in the range of J2000.0 right ascensions from 0 hours to 17 hours 30 minutes.