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501. MC Cepheids, RR Lyrae stars and binaries
ID:
ivo://CDS.VizieR/J/MNRAS/437/2702
Title:
MC Cepheids, RR Lyrae stars and binaries
Short Name:
J/MNRAS/437/2702
Date:
21 Oct 2021
Publisher:
CDS
Description:
The VISTA near-infrared Y, J, Ks survey of the Magellanic System (VMC) survey is obtaining multi-epoch photometry in the Ks band of the Magellanic System down to a limiting magnitude of Ks~19.3 for individual epoch data. The observations are spaced in time such as to provide optimal sampling of the light curves for RR Lyrae stars and for Cepheids with periods up to 20-30d. We present examples of the Ks-band light curves of Classical Cepheids and RR Lyrae stars we are obtaining from the VMC data and outline the strategy we put in place to measure distances and infer the System three-dimensional geometry from the variable stars. For this purpose, the near-infrared Period-Luminosity, Period-Wesenheit and Period-Luminosity-Colour relations of the system RR Lyrae stars and Cepheids are used. We extensively exploit the catalogues of the Magellanic Clouds' variable stars provided by the EROS-2 and OGLE III/IV microlensing surveys. By combining these surveys, we present the currently widest-area view of the Large Magellanic Cloud as captured by the galaxy Cepheids, RR Lyrae stars and binaries. This reveals the full extent of the main structures (bar/s - spiral arms) that have only been vaguely guessed before. Our work strengthens the case for a detailed study of the Large Magellanic Cloud three-dimensional geometry.
502. M31C eclipsing binaries and Cepheids
ID:
ivo://CDS.VizieR/J/AJ/117/2810
Title:
M31C eclipsing binaries and Cepheids
Short Name:
J/AJ/117/2810
Date:
21 Oct 2021
Publisher:
CDS
Description:
We undertook a long-term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder - M31 and M33 - using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between 1996 September and 1997 October we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this third paper in the series, we present the catalog of variable stars, most of them newly detected, found in the field M31C [(RA, DE)=(11.10{deg}, 41.42{deg}), J2000.0]. We have found 115 variable stars: 12 eclipsing binaries, 35 Cepheids, and 68 other periodic, possible long-period or nonperiodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request.
503. M31 Cepheid disk sample of 1st year of PS1
ID:
ivo://CDS.VizieR/J/AJ/145/106
Title:
M31 Cepheid disk sample of 1st year of PS1
Short Name:
J/AJ/145/106
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of Cepheid variable stars towards M31 based on the first year of regular M31 observations of the PS1 survey in the r_P1 and i_P1 filters. We describe the selection procedure for Cepheid variable stars from the overall variable source sample and develop an automatic classification scheme using Fourier decomposition and the location of the instability strip. We find 1440 fundamental mode (classical {delta}) Cep stars, 126 Cepheids in the first overtone mode, and 147 belonging to the Population II types. 296 Cepheids could not be assigned to one of these classes and 354 Cepheids were found in other surveys. These 2009 Cepheids constitute the largest Cepheid sample in M31 known so far and the full catalog is presented in this paper. We briefly describe the properties of our sample in its spatial distribution throughout the M31 galaxy, in its age properties, and we derive an apparent period-luminosity relation (PLR) in our two bands. The Population I Cepheids nicely follow the dust pattern of the M31 disk, whereas the 147 Type II Cepheids are distributed throughout the halo of M31. We outline the time evolution of the star formation in the major ring found previously and find an age gradient. A comparison of our PLR to previous results indicates a curvature term in the PLR.
504. M101 Cepheids
ID:
ivo://CDS.VizieR/J/ApJ/508/491
Title:
M101 Cepheids
Short Name:
J/ApJ/508/491
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the identification of 255 candidate variable stars in a field located some 1.7' from the center of the late-type spiral galaxy M101 = NGC 5457, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Photometric measurements in the F555W and F814W filters - analyzed independently with the DAOPHOT/ALLFRAME and DoPHOT software suites - have been transformed to the Johnson V and Kron-Cousins I standard magnitude systems. Periods and intensity-averaged mean magnitudes for 61 carefully selected candidate Cepheid variables with periods in the range 10-48 days indicate a reddening-corrected mean distance modulus (m-M)_0_=29.05+/-0.14 (if the true modulus of the Large Magellanic Cloud is 18.50+/-0.10, and if there is no dependence of the period-luminosity relation on metal abundance); results consistent with this are obtained whether or not the sample is expanded to include a larger fraction of the candidates. Applying a metallicity-dependent correction of +0.16+/-0.10mag would increase this estimate to (m-M)_0_= 29.21+/-0.17mag.
505. M31 Cepheids in near-IR
ID:
ivo://CDS.VizieR/J/ApJ/799/144
Title:
M31 Cepheids in near-IR
Short Name:
J/ApJ/799/144
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the largest M31 near-infrared (F110W (close to J band), F160W (H band)) Cepheid sample so far. The sample consists of 371 Cepheids with photometry obtained from the HST PHAT program. The sample of 319 fundamental mode Cepheids, 16 first overtone Cepheids and 36 type II Cepheids, was identified using the median absolute deviation (MAD) outlier rejection method we develop here. This method does not rely on priors and allows us to obtain this clean Cepheid sample without rejecting a large fraction of Cepheids. The obtained Period-Luminosity relations (PLRs) have a very small dispersion, i.e. 0.155mag in F160W, despite using random phased observations. This remarkably small dispersion allows us to determine that the PLRs are significantly better described by a broken slope at ten days than a linear slope. The use of our sample as an anchor to determine the Hubble constant gives a 3.2% larger Hubble constant compared to the Riess et al. (2012ApJ...745..156R, Cat. J/ApJ/745/156) sample.
506. M 31 Cepheids periods
ID:
ivo://CDS.VizieR/J/A+AS/126/401
Title:
M 31 Cepheids periods
Short Name:
J/A+AS/126/401
Date:
21 Oct 2021
Publisher:
CDS
Description:
Cepheid variables can be used for more than just a distance indicator. Since the age can be determined from the period, they can be used to trace the star formation history of a galaxy. We have identified 130 new Cepheid variable candidates in M 31, particularly along the spiral arm regions in the north-east of the galaxy. These areas had not been searched for Cepheids in the previous study by Baade and collaborators. The contamination of our sample by other types of variables is low (<3%). For V<21, the completeness is =~53%. These Cepheids will be used to explore the star formation history in M 31.
507. M31 Cepheids with HST/WFC3
ID:
ivo://CDS.VizieR/J/ApJ/745/156
Title:
M31 Cepheids with HST/WFC3
Short Name:
J/ApJ/745/156
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present measurements of 68 classical Cepheids, most detected from the Canada-France-Hawaii Telescope POMME Survey, with periods from 10 to 78 days observed in the near-infrared by the Panchromatic Hubble Andromeda Treasury Program using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST). The combination of HST's resolution and the use of near-infrared measurements provide a dramatic reduction in the dispersion of the period-luminosity relation over the present optical, ground-based data. Even using random phase magnitudes we measure a dispersion of just 0.17mag, implying a dispersion of just 0.12mag for mean magnitudes. The error in the mean for this relation is 1% in distance. Combined with similar observations of Cepheids in other hosts and independent distance determinations, we measure a distance to M31 of {mu}_0_=24.38+/-0.06(statistical)+/-0.03(systematic), 752+/-27kpc, in good agreement with past measurements though with a better, 3% precision here. The result is also in good agreement with independent distance determinations from two detached eclipsing binaries allowing for an independent calibration of the Cepheid luminosities and a determination of the Hubble constant.
508. MC Type II and anomalous Cepheids PL and PR
ID:
ivo://CDS.VizieR/J/A+A/604/A29
Title:
MC Type II and anomalous Cepheids PL and PR
Short Name:
J/A+A/604/A29
Date:
21 Oct 2021
Publisher:
CDS
Description:
Type II Cepheids (T2Cs) and anomalous Cepheids (ACs) are pulsating stars that follow separate period-luminosity relations. We study the period-luminosity (PL) and period-radius (PR) relations for T2Cs and ACs in the Magellanic Clouds. In an accompanying paper we determined luminosity and effective temperature for the 335 T2Cs and ACs in the LMC and SMC discovered in the OGLE-III survey, by constructing the spectral energy distribution (SED) and fitting this with model atmospheres and a dust radiative transfer model (in the case of dust excess). Building on these results we study the PL- and PR relations. Using existing pulsation models for RR Lyrae and classical Cepheids we derive the period-luminosity-mass-temperature-metallicity relations, and then estimate the pulsation mass.
509. M31D eclipsing binaries and Cepheids
ID:
ivo://CDS.VizieR/J/AJ/118/346
Title:
M31D eclipsing binaries and Cepheids
Short Name:
J/AJ/118/346
Date:
21 Oct 2021
Publisher:
CDS
Description:
We undertook a long-term project, DIRECT, to obtain the direct distances to two important galaxies in the cosmological distance ladder - M31 and M33 - using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult to detect, DEBs provide us with the potential to determine these distances with an accuracy better than 5%. The extensive photometry obtained in order to detect DEBs provides us with good light curves for the Cepheid variables. These are essential to the parallel project to derive direct Baade-Wesselink distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries, the distance estimates will be free of any intermediate steps. As a first step in the DIRECT project, between 1996 September and 1997 October we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper, the fourth in the series, we present the catalog of variable stars, most of them newly detected, found in the field M31D [(RA, DE)=(11.03{deg}, 41.27{deg}), J2000.0]. We have found 71 variable stars: five eclipsing binaries, 38 Cepheids, and 28 other periodic, possible long-period or nonperiodic variables. The catalog of variables, as well as their photometry and finding charts, is available via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request.
510. M dwarf UV flares in GALEX
ID:
ivo://CDS.VizieR/J/ApJS/173/673
Title:
M dwarf UV flares in GALEX
Short Name:
J/ApJS/173/673
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the preliminary results from implementing a new software tool that enables inspection of time-tagged photon data for the astronomical sources contained within individual GALEX ultraviolet (UV) images of the sky. We have inspected the photon data contained within 1802 GALEX images to reveal rapid, short-term (<~500s) UV source variability in the form of stellar "flares." The mean associated change in near-UV (NUV) magnitude due to this flaring activity is 2.7+/-0.3mag. A list of 49 new UV variable star candidates is presented (associated with 52 separate flare events), together with their associated Sloan Digital Sky Survey (SDSS) photometric magnitudes. From these data we can associate the main source of these UV flare events with magnetic activity on M dwarf stars. Photometric parallaxes have been determined for 32 of these sources, placing them at distances ranging from approximately 25 to 1000pc. The average UV flare energy for these flare events is 2.5x10^30^ergs, which is of a similar energy to that of U-band, X-ray, and EUV flares observed on many local M dwarf stars. We have found that stars of classes M0 to M5 flare with energies spanning a far larger range and with an energy approximately 5 times greater than those of later (M6 to M8) spectral type.