- 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.
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- 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.
- 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.
- 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.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/393/167
- Title:
- Mean Spectra for upper AGB stars
- Short Name:
- J/A+A/393/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Provided are average spectra extending from 510 to 2490nm for: - Oxygen rich, optically visible LPVs (temperature sequence based on the colour I-K); - Carbon rich, optically visible LPVs (temperature sequence based on the colour R-H, and C/O sequence); - Oxygen rich, dust-enshrouded LPVs (reddened versions of the coolest optically visible average); - Carbon rich, dust-enshrouded LPVs (reddened versions of the coolest optically visible average).
- ID:
- ivo://CDS.VizieR/J/A+A/421/937
- Title:
- Metal abundances of LMC RR Lyrae
- Short Name:
- J/A+A/421/937
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Metallicities ([Fe/H]) from low resolution spectroscopy obtained with the Very Large Telescope (VLT) are presented for 98 RR Lyrae and 3 short period Cepheids in the bar of the Large Magellanic Cloud. Our metal abundances have typical errors of +/-0.17dex. The average metallicity of the RR Lyrae stars is [Fe/H]=-1.48+/-0.03+/-0.06 on the scale of Harris (1996, Cat. <VII/202>). The star-to-star scatter (0.29dex) is larger than the observational errors, indicating a real spread in metal abundances. The derived metallicities cover the range -2.12<[Fe/H]<-0.27, but there are only a few stars having [Fe/H]>-1. For the ab-type variables we compared our spectroscopic abundances with those obtained from the Fourier decomposition of the light curves. We find good agreement between the two techniques, once the systematic offset of 0.2 dex between the metallicity scales used in the two methods is taken into account. The spectroscopic metallicities were combined with the dereddened apparent magnitudes of the variables to derive the slope of the luminosity-metallicity relation for the LMC RR Lyrae stars: the resulting value is 0.214+/-0.047mag/dex. Finally, the 3 short period Cepheids have [Fe/H] values in the range -2.0<[Fe/H]<-1.5. They are more metal-poor than typical LMC RR Lyrae stars, thus they are more likely to be Anomalous Cepheids rather than the short period Classical Cepheids that are often found in a number of dwarf Irregular galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/640/L43
- Title:
- Metallicities of RR Lyrae stars in Omega Cen
- Short Name:
- J/ApJ/640/L43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new spectroscopic metal abundances for 74 RR Lyrae (RRL) stars in {omega} Cen obtained with FLAMES. The well-known metallicity spread is visible among the RRL variables. The metal-intermediate (MI) RRL stars ([Fe/H]~-1.2) are fainter than the bulk of the dominant metal-poor population ([Fe/H]~-1.7), in good agreement with the corresponding zero-age horizontal-branch models with cosmological helium abundance Y=0.246.
- ID:
- ivo://CDS.VizieR/J/AJ/136/2441
- Title:
- Metallicity of RR0 Lyrae in the galactic bulge
- Short Name:
- J/AJ/136/2441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present metallicities of 2690 RR0 Lyrae stars observed toward the MACHO Survey fields in the Galactic bulge. These [Fe/H] values are based upon an empirically-calibrated relationship that uses the Fourier coefficients of the light curve and are accurate to +/-0.2dex. The majority of the RR0 Lyrae stars in our sample are located in the Galactic bulge, but 255 RR0 stars are associated with the Sagittarius (Sgr) dwarf galaxy.
