- ID:
- ivo://CDS.VizieR/J/A+AS/131/119
- Title:
- Spectroscopy of irregular variables
- Short Name:
- J/A+AS/131/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of optical spectroscopy of 169 southern and equatorial objects previously known as irregular variables are presented. The targets were selected via photoelectric UBV photometry among objects classified as L, L:, I, I:, IS and IS: in the General Catalogue of Variable Stars and New Catalogue of Suspected Variable Stars. Among these objects we have identified 8 cataclysmic variables, 8 symbiotic stars and stars that belong to a variety of other classes.
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- ID:
- ivo://CDS.VizieR/J/AJ/144/88
- Title:
- Spectroscopy of 6 LMC RR Lyrae and 3 SMC RR Lyrae
- Short Name:
- J/AJ/144/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present for the first time a detailed spectroscopic study of chemical element abundances of metal-poor RR Lyrae stars in the Large and Small Magellanic Cloud (LMC and SMC). Using the MagE echelle spectrograph at the 6.5m Magellan telescopes, we obtain medium resolution (R~2000-6000) spectra of six RR Lyrae stars in the LMC and three RR Lyrae stars in the SMC. These stars were chosen because their previously determined photometric metallicities were among the lowest metallicities found for stars belonging to the old populations in the Magellanic Clouds. We find the spectroscopic metallicities of these stars to be as low as [Fe/H]_spec_=-2.7dex, the lowest metallicity yet measured for any star in the Magellanic Clouds. We confirm that for metal-poor stars, the photometric metallicities from the Fourier decomposition of the light curves are systematically too high compared to their spectroscopic counterparts. However, for even more metal-poor stars below [Fe/H]_phot_<-2.8dex this trend is reversed and the spectroscopic metallicities are systematically higher than the photometric estimates. We are able to determine abundance ratios for 10 chemical elements (Fe, Na, Mg, Al, Ca, Sc, Ti, Cr, Sr, and Ba), which extend the abundance measurements of chemical elements for RR Lyrae stars in the Clouds beyond [Fe/H] for the first time. For the overall [{alpha}/Fe] ratio, we obtain an overabundance of 0.36dex, which is in very good agreement with results from metal-poor stars in the Milky Way halo as well as from the metal-poor tail in dwarf spheroidal galaxies. Comparing the abundances with those of the stars in the Milky Way halo we find that the abundance ratios of stars of both populations are consistent with another. Therefore, we conclude that from a chemical point of view early contributions from Magellanic-type galaxies to the formation of the Galactic halo as claimed in cosmological models are plausible.
- ID:
- ivo://CDS.VizieR/J/PAZh/26/115
- Title:
- Spectrum of IRAS 23304+6147
- Short Name:
- J/PAZh/26/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on CCD-spectra obtain with the 6-m telescope, detailed chemical composition of the IR source IRAS 23304+6147 identified with the faint star is studied.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/110
- Title:
- SPIRITS catalog of IR long period variables
- Short Name:
- J/ApJ/877/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 417 luminous infrared variable stars with periods exceeding 250 days. These were identified in 20 nearby galaxies by the ongoing SPitzer InfraRed Intensive Transients Survey survey with the Spitzer Space Telescope. Of these, 359 variables have M_[4.5]_ (phase-weighted mean magnitudes) fainter than -12 and periods and luminosities consistent with previously reported variables in the Large Magellanic Cloud (LMC). However, 58 variables are more luminous than M_[4.5]_=-12, including 11 that are brighter than M_[4.5]_=-13, with the brightest having M_[4.5]_=-15.51. Most of these bright variable sources have quasi-periods longer than 1000 days, including four over 2000 days. We suggest that the fundamental period-luminosity relationship, previously measured for the LMC, extends to much higher luminosities and longer periods in this large galaxy sample. We posit that these variables include massive asymptotic giant branch (AGB) stars (possibly super-AGB stars), red supergiants experiencing exceptionally high mass-loss rates, and interacting binaries. We also present 3.6, 4.5, 5.8, and 8.0{mu}m photometric catalogs for all sources in these 20 galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/151/90
- Title:
- Spitzer and VRIJHK photometry of V582 Mon
- Short Name:
- J/AJ/151/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the light and color evolution of the T Tauri binary KH 15D through photometry obtained at wavelengths between 0.55 and 8.0{mu}m. The data were collected with A Novel Dual Imaging CAMera (ANDICAM) on the 1.3m SMARTS telescope at Cerro-Tololo Inter-American Observatory and with InfraRed Array Camera on the Spitzer Space Telescope. We show that the system's circumbinary ring, which acts as a screen that covers and uncovers different portions of the binary orbit as the ring precesses, has reached an orientation where the brighter component (star B) fully or nearly fully emerges during each orbital cycle. The fainter component (star A) remains fully occulted by the screen at all phases. The leading and trailing edges of the screen move across the sky at the same rate of ~15m/s, consistent with expectation for a ring with a radius and width of ~4 au and a precession period of ~6500 years. Light and color variations continue to indicate that the screen is sharp edged and opaque at VRIJH wavelengths. However, we find an increasing transparency of the ring edge at 2.2, 3.6, and 4.5{mu}m. Reddening seen at the beginning of the eclipse that occurred during the CSI 2264 campaign particularly suggests selective extinction by a population of large dust grains. Meanwhile, the gradual bluing observed while star B is setting is indicative of forward scattering effects at the edge of the ring. The spectral energy distribution of the system at its bright phase shows no evidence of infrared excess emission that can be attributed to radiation from the ring or other dust component out to 8{mu}m.
- ID:
- ivo://CDS.VizieR/J/ApJ/816/49
- Title:
- Spitzer/IRAC observations of SMC Cepheids
- Short Name:
- J/ApJ/816/49
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Spitzer observations of classical Cepheids we have measured the true average distance modulus of the Small Magellanic Cloud (SMC) to be 18.96+/-0.01_stat_+/-0.03_sys_mag (corresponding to 62+/-0.3kpc), which is 0.48+/-0.01mag more distant than the LMC. This is in agreement with previous results from Cepheid observations, as well as with measurements from other indicators such as RR Lyrae stars and the tip of the red giant branch. Utilizing the properties of the mid-infrared Leavitt Law we measured precise distances to individual Cepheids in the SMC, and have confirmed that the galaxy is tilted and elongated such that its eastern side is up to 20kpc closer than its western side. This is in agreement with the results from red clump stars and dynamical simulations of the Magellanic Clouds and Stream.
- ID:
- ivo://CDS.VizieR/J/ApJ/759/146
- Title:
- Spitzer/IRAC photometry for 37 Galactic Cepheids
- Short Name:
- J/ApJ/759/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Carnegie Hubble Program (CHP) is designed to calibrate the extragalactic distance scale using data from the post-cryogenic era of the Spitzer Space Telescope. The ultimate goal of the CHP is a systematic improvement in the distance scale leading to a determination of the Hubble constant to within an accuracy of 2%. This paper focuses on the measurement and calibration of the Galactic Cepheid period-luminosity (PL, Leavitt) relation using the warm Spitzer/IRAC 1 and 2 bands at 3.6 and 4.5{mu}m. We present photometric measurements covering the period range 4-70 days for 37 Galactic Cepheids. Data at 24 phase points were collected for each star. Three PL relations of the form M=a(log(P)-1)+b are derived. The method adopted here takes the slope a to be -3.31, as determined from the Spitzer Large Magellanic Cloud (LMC) data of Scowcroft et al. (Cat. J/ApJ/743/76). Using the geometric Hubble Space Telescope guide-star distances to 10 Galactic Cepheids, we find a calibrated 3.6{mu}m PL zero point of -5.80+/-0.03. Together with our value for the LMC zero point, we determine a reddening-corrected distance modulus of 18.48+/-0.04mag to the LMC. The mid-IR period-color diagram and the [3.6]-[4.5] color variation with phase are interpreted in terms of CO absorption at 4.5{mu}m. This situation compromises the use of the 4.5{mu}m data for distance determinations.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/76
- Title:
- Spitzer photometry of LMC Cepheids
- Short Name:
- J/ApJ/743/76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Carnegie Hubble Program is designed to improve the extragalactic distance scale using data from the post-cryogenic era of Spitzer. The ultimate goal is a determination of the Hubble constant to an accuracy of 2%. This paper is the first in a series on the Cepheid population of the Large Magellanic Cloud, and focusses on the period-luminosity (PL) relations (Leavitt laws) that will be used, in conjunction with observations of Milky Way Cepheids, to set the slope and zero point of the Cepheid distance scale in the mid-infrared. To this end, we have obtained uniformly sampled light curves for 85 LMC Cepheids, having periods between 6 and 140 days. PL and period-color relations are presented in the 3.6um and 4.5um bands. We demonstrate that the 3.6um band is a superb distance indicator. The cyclical variation of the [3.6]-[4.5] color has been measured for the first time. We attribute the amplitude and phase of the color curves to the dissociation and recombination of CO molecules in the Cepheid's atmosphere. The CO affects only the 4.5um flux making it a potential metallicity indicator.
- ID:
- ivo://CDS.VizieR/J/A+AS/106/397
- Title:
- Sra and Srb semiregular variables
- Short Name:
- J/A+AS/106/397
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/AJ/153/96
- Title:
- Standard Galactic field RR Lyrae. I. Photometry
- Short Name:
- J/AJ/153/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multi-wavelength compilation of new and previously published photometry for 55 Galactic field RR Lyrae variables. Individual studies, spanning a time baseline of up to 30 years, are self-consistently phased to produce light curves in 10 photometric bands covering the wavelength range from 0.4 to 4.5 microns. Data smoothing via the GLOESS technique is described and applied to generate high-fidelity light curves, from which mean magnitudes, amplitudes, rise times, and times of minimum and maximum light are derived. 60000 observations were acquired using the new robotic Three-hundred MilliMeter Telescope (TMMT), which was first deployed at the Carnegie Observatories in Pasadena, CA, and is now permanently installed and operating at Las Campanas Observatory in Chile. We provide a full description of the TMMT hardware, software, and data reduction pipeline. Archival photometry contributed approximately 31000 observations. Photometric data are given in the standard Johnson UBV, Kron-Cousins R_C_I_C_, 2MASS JHK, and Spitzer [3.6] and [4.5] bandpasses.
