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351. Distances to RRab stars from WISE and Gaia
ID:
ivo://CDS.VizieR/J/ApJ/838/107
Title:
Distances to RRab stars from WISE and Gaia
Short Name:
J/ApJ/838/107
Date:
21 Oct 2021
Publisher:
CDS
Description:
Pulsating stars, such as Cepheids, Miras, and RR Lyrae stars, are important distance indicators and calibrators of the "cosmic distance ladder," and yet their period-luminosity-metallicity (PLZ) relations are still constrained using simple statistical methods that cannot take full advantage of available data. To enable optimal usage of data provided by the Gaia mission, we present a probabilistic approach that simultaneously constrains parameters of PLZ relations and uncertainties in Gaia parallax measurements. We demonstrate this approach by constraining PLZ relations of type ab RR Lyrae stars in near-infrared W1 and W2 bands, using Tycho-Gaia Astrometric Solution (TGAS) parallax measurements for a sample of ~100 type ab RR Lyrae stars located within 2.5kpc of the Sun. The fitted PLZ relations are consistent with previous studies, and in combination with other data, deliver distances precise to 6% (once various sources of uncertainty are taken into account). To a precision of 0.05mas (1{sigma}), we do not find a statistically significant offset in TGAS parallaxes for this sample of distant RR Lyrae stars (median parallax of 0.8mas and distance of 1.4kpc). With only minor modifications, our probabilistic approach can be used to constrain PLZ relations of other pulsating stars, and we intend to apply it to Cepheid and Mira stars in the near future.
352. Distance to Cepheids using the Wesenheit function
ID:
ivo://CDS.VizieR/J/ApJ/747/50
Title:
Distance to Cepheids using the Wesenheit function
Short Name:
J/ApJ/747/50
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, we explore the possibility of using the Wesenheit function to derive individual distances to Galactic Cepheids, as the dispersion of the reddening-free Wesenheit function is smaller than the optical period-luminosity (P-L) relation. When compared to the distances from various methods, the averaged differences between our results and published distances range from -0.061 to 0.009, suggesting that the Wesenheit function can be used to derive individual Cepheid distances. We have also constructed Galactic P-L relations and selected Wesenheit functions based on the derived distances. A by-product from this work is the derivation of Large Magellanic Cloud distance modulus when calibrating the Wesenheit function. It is found to be 18.531+/-0.043 mag.
353. Distance to NGC6822 with Spitzer/FourStar Photometry
ID:
ivo://CDS.VizieR/J/ApJ/794/107
Title:
Distance to NGC6822 with Spitzer/FourStar Photometry
Short Name:
J/ApJ/794/107
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a revised distance to the nearby galaxy NGC 6822 using a new multi-band fit to both previously published and new optical, near-, and mid-infrared data for Cepheid variables. The new data presented in this study include multi-epoch observations obtained in 3.6 {mu}m and 4.5 {mu}m with the Spitzer Space Telescope taken for the Carnegie Hubble Program. We also present new observations in J, H, and K_s_ with FourStar on the Magellan Baade Telescope at Las Campanas Observatory. We determine mean magnitudes and present new period-luminosity relations in V, I, J, H, K_s_, Infrared Array Camera 3.6 {mu}m, and 4.5 {mu}m. In addition to using the multi-band distance moduli to calculate extinction and a true distance, we present a new method for determining an extinction-corrected distance modulus from multi-band data with varying sample sizes. We combine the distance moduli and extinction for individual stars to determine E(B-V)=0.35+/-0.04 and a true distance modulus {mu}_o_=23.38+/-0.02_stat_+/-0.04_sys_.
354. Distant RR Lyrae stars discovered with HiTS
ID:
ivo://CDS.VizieR/J/ApJ/855/43
Title:
Distant RR Lyrae stars discovered with HiTS
Short Name:
J/ApJ/855/43
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of distant RR Lyrae stars, including the most distant known in the Milky Way, using data taken in the g-band with the Dark Energy Camera as part of the High cadence Transient Survey (HiTS; 2014 campaign). We detect a total of 173 RR Lyrae stars over a ~120deg^2^ area, including both known RR Lyrae and new detections. The heliocentric distances dH of the full sample range from 9 to >200kpc, with 18 of them beyond 90kpc. We identify three sub-groups of RR Lyrae as members of known systems: the Sextans dwarf spheroidal galaxy, for which we report 46 new discoveries, and the ultra-faint dwarf galaxies Leo IV and Leo V. Following an MCMC methodology, we fit spherical and ellipsoidal profiles of the form {rho}(R)~Rn to the radial density distribution of RR Lyrae in the Galactic halo. The best fit corresponds to the spherical case, for which we obtain a simple power-law index of n=-4.17_-0.20_^+0.18^, consistent with recent studies made with samples covering shorter distances. The pulsational properties of the outermost RR Lyrae in the sample (dH>90kpc) differ from the ones in the halo population at closer distances. The distribution of the stars in a period-amplitude diagram suggest they belong to Oosterhoff-intermediate or Oosterhoff II groups, similar to what is found in the ultra-faint dwarf satellites around the Milky Way. The new distant stars discovered represent an important addition to the few existing tracers of the Milky Way potential in the outer halo.
355. Distribution of WR stars in 2 nearby galaxies
ID:
ivo://CDS.VizieR/J/A+A/518/A29
Title:
Distribution of WR stars in 2 nearby galaxies
Short Name:
J/A+A/518/A29
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the distribution of Wolf-Rayet (WR) stars and their subtypes with respect to their host galaxy light distribution. We thus want to investigate whether WR stars are potential progenitors of stripped-envelope core-collapse supernovae (SNe) and/or long-duration gamma-ray bursts (LGRBs).
356. DK Lac V light curves
ID:
ivo://CDS.VizieR/J/AJ/141/122
Title:
DK Lac V light curves
Short Name:
J/AJ/141/122
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on extensive photometry of DK Lac obtained during the interval 1990-2009, which includes a 2mag low state during 2001-2003. Much of the photometry consists of exposures obtained with a typical spacing of several days, but also includes 26 sequences of continuous photometry each lasting 2-7hr. We find no evidence for periodicities in our data.
357. DL Cas
ID:
ivo://CDS.VizieR/J/AJ/107/2093
Title:
DL Cas
Short Name:
J/AJ/107/2093
Date:
21 Oct 2021
Publisher:
CDS
Description:
As an eight-day Cepheid which is both a component of a spectroscopic binary and a member of the open cluster NGC 129, DL Cas is potentially a very accurate calibrator of the period-luminosity (PL) relation and Cepheid mass. From 160 high-precision (sigma<1.5km/s) radial velocity observations made with the CORAVEL and DAO spectrometers - including 67 new unpublished data - we have obtained both the orbital and pulsational velocity curves of this binary Cepheid. This body of RV data makes DL Cas one of the best observed Cepheids in our galaxy. Our analysis yields an orbital period of 684.4+/-0.4days which confirms DL Cas as one of the shortest-period binaries containing a Cepheid. We derive new precise orbital elements which replace earlier preliminary values found by Harris et al. Isochrone fitting to the V,B-V data points of Turner et al. yields an age of NGC 129 of (7.6+/-0.4)x10^7^yr and a Cepheid mass of 5.6M_{sun}_. Evidence from age, a possible period change, and strip crossing times suggest that DL Cas is a solar-abundance star making its third (redward) crossing through the Cepheid instability strip. Existing observational constraints from our mass function of the DL Cas system and an IUE spectrum suggest that the companion is a main sequence star in the mass range from 2.6 to 5.6M_{sun}_. We use the pulsational velocity curve and published photometry to derive the distance and mean radius of DL Cas with the surface brightness method, finding values of 2034+/-110pc and 66.0+/-3.5R_{sun}_, respectively. The radius we derive indicates that DL Cas is a fundamental-mode pulsator, removing any possible ambiguity in mode identification. The distance corresponds to a mean absolute visual magnitude of <Mv>=-4.2+/-0.3mag whose error is dominated by the uncertainty of the absorption correction. Since our very precise distance contributes only 0.12mag to the error in <Mv>, improved reddening studies of NGC 129 would make DL Cas a very tight calibrator of the PL relation. Our value of the gamma velocity of the DL Cas system is identical to the mean radial velocity of the stars in NGC 129, strengthening the case for cluster membership. However, our distance for DL Cas, and thus for NGC 129, is significantly larger than the 1670+/-13pc obtained by Turner et al. from ZAMS fitting of the cluster. Possible causes for this discrepancy, and their implications for Cepheid distance scale calibrations, are discussed.
358. DM Cyg BVIc light curves
ID:
ivo://CDS.VizieR/J/MNRAS/397/350
Title:
DM Cyg BVIc light curves
Short Name:
J/MNRAS/397/350
Date:
21 Oct 2021
Publisher:
CDS
Description:
DM Cyg, a fundamental mode RRab star, was observed in the 2007 and 2008 seasons in the framework of the Konkoly Blazhko Survey. Very small amplitude light-curve modulation was detected with 10.57d modulation period. The maximum brightness and phase variations do not exceed 0.07mag and 7min, respectively. In spite of the very small amplitude of the modulation, beside the frequency triplets characterizing the Fourier spectrum of the light curve, two quintuplet components were also identified. The accuracy and the good phase coverage of our observations made it possible to analyse the light curves at different phases of the modulation separately.
359. Double-mode radial-non-radial RR Lyrae stars
ID:
ivo://CDS.VizieR/J/MNRAS/453/2022
Title:
Double-mode radial-non-radial RR Lyrae stars
Short Name:
J/MNRAS/453/2022
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyse the OGLE-IV photometry of the first overtone and double-mode RR Lyrae stars (RRc/RRd) in the two fields towards the Galactic bulge observed with high cadence. In 27 per cent of RRc stars, we find additional non-radial mode, with characteristic period ratio, P_x_/P_1O_{include.in}(0.6, 0.64). It strongly corroborates the conclusion arising from the analysis of space photometry of RRc stars, that this form of pulsation must be common. In the Petersen diagram the stars form three sequences. In 20 stars, we find two or three close secondary modes simultaneously. The additional modes are clearly non-stationary. Their amplitude and/or phase vary in time. As a result, the patterns observed in the frequency spectra of these stars may be very complex. In some stars, the additional modes split into doublets, triplets or appear as a more complex bands of increased power. Subharmonics of additional modes are detected in 20 per cent of stars. They also display a complex structure. Including our previous study of the OGLE-III Galactic bulge data, we have discovered 260 RRc and 2 RRd stars with the additional non-radial mode, which is the largest sample of these stars so far. The additional mode is also detected in two Blazhko RRc stars, which shows that the modulation and additional non-radial mode are not exclusive.
360. Double-mode RR Lyrae stars in LINEAR
ID:
ivo://CDS.VizieR/J/PASP/126/509
Title:
Double-mode RR Lyrae stars in LINEAR
Short Name:
J/PASP/126/509
Date:
21 Oct 2021
Publisher:
CDS
Description:
Double-mode RR Lyr type stars are important for studies of properties of horizontal-branch stars. In particular, two periods coupled with spectral properties give a mass estimate that is independent of evolutionary models. Here, we present 59 new Galactic double-mode RR Lyr stars found in the LINEAR survey data with the fundamental radial mode and the first overtone exited (RRd stars). These stars may be useful for constraining the mass-metallicity relation for field horizontal-branch stars. Also, new RRd stars found in the LMC by EROS-II are verified. We present the updated Petersen diagram and the distribution of the fundamental mode periods. Comments on selected variable stars from LINEAR and LMC EROS-II surveys are also presented, including very rare objects: the third known mode-switching RR Lyr and a Cepheid pulsating simultaneously in three radial modes.