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Register a new userInfrared variable stars in the compact elliptical galaxy M32
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Variable stars in the compact elliptical galaxy M32 are identified, using three epochs of photometry from the Spitzer Space Telescope at 3.6 and 4.5 $mu$m, separated by 32 to 381 days. We present a high-fidelity catalogue of sources detected in multiple epochs at both 3.6 and 4.5 $mu$m, which we analysed for stellar variability using a joint probability error-weighted flux difference. Of these, 83 stars are identified as candidate large-amplitude, long-period variables, with 28 considered high-confidence variables. The majority of the variable stars are classified as asymptotic giant branch star candidates using colour-magnitude diagrams. We find no evidence supporting a younger, infrared-bright stellar population in our M32 field.
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A large extension of the Sextans dwarf spheroidal galaxy, 7 sq degrees, has been surveyed for variable stars using the Dark Energy Camera at the Blanco Telescope in Cerro Tololo Inter-American Observatory, Chile. We report 7 Anomalous Cepheids, 199 RR Lyrae stars and 16 dwarf Cepheids in the field. This is only the fifth extra-galactic systems 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 days, and a mean $g$ amplitude of 0.87 mags. They are located below the horizontal branch spanning a range of 0.8 mag, between $21.9 < g < 22.7$. The number of dwarf Cepheids in Sextans is low compared with other galaxies such as Carina, which have a strong intermediate-age population. On the other hand, the number and ratio of RR Lyrae stars to dwarf Cepheids is quite similar to 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 2 RR Lyrae stars and 1 Anomalous Cepheid in the outskirts of the galaxy, which may be extra-tidal stars and suggest this galaxy may be undergoing tidal destruction. These possible extra-tidal variable stars share the same proper motions as Sextans, as seen by recent Gaia measurements.
Context. The Vista Variables in the Via Lactea (VVV) near-infrared variability survey explores some of the most complex regions of the Milky Way bulge and disk in terms of high extinction and high crowding. Aims. We add a new wavelength dimension to the optical information available at the American Association of Variable Star Observers International Variable Star Index (VSX-AAVSO) catalogue to test the VVV survey near-infrared photometry to better characterise these objects. Methods. We cross-matched the VVV and the VSX-AAVSO catalogues along with Gaia Data Release 2 photometry and parallax. Results. We present a catalogue that includes accurate individual coordinates, near-infrared magnitudes (ZY JHKs), extinctions Aks, and distances based on Gaia parallaxes. We also show the near-infrared CMDs and spatial distributions for the different VSX types of variable stars, including important distance indicators, such as RR Lyrae, Cepheids, and Miras. By analysing the photometric flags in our catalogue, we found that about 20% of the stars with measured and verified variability are flagged as non-stellar sources, even when they are outside of the saturation and/or noise regimes. Additionally, we pair-matched our sample with the VIVA catalogue and found that more than half of our sources are missing from the VVV variability list, mostly due to observations with low signal-to-noise ratio or photometric problems with a low percentage due to failures in the selection process. Conclusions. Our results suggest that the current knowledge of the variability in the Galaxy is biased to nearby stars with low extinction. The present catalogue also provides the groundwork for characterising the results of future large variability surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time in the highly crowded and reddened regions of the Galactic plane, as well as follow-up campaigns for
We have compiled the first all-sky mid-infrared variable-star catalog based on Wide-field Infrared Survey Explorer (WISE) five-year survey data. Requiring more than 100 detections for a given object, 50,282 carefully and robustly selected periodic variables are discovered, of which 34,769 (69%) are new. Most are located in the Galactic plane and near the equatorial poles. A method to classify variables based on their mid-infrared light curves is established using known variable types in the General Catalog of Variable Stars. Careful classification of the new variables results in a tally of 21,427 new EW-type eclipsing binaries, 5654 EA-type eclipsing binaries, 1312 Cepheids, and 1231 RR Lyraes. By comparison with known variables available in the literature, we estimate that the misclassification rate is 5% and 10% for short- and long-period variables, respectively. A detailed comparison of the types, periods, and amplitudes with variables in the Catalina catalog shows that the independently obtained classifications parameters are in excellent agreement. This enlarged sample of variable stars will not only be helpful to study Galactic structure and extinction properties, they can also be used to constrain stellar evolution theory and as potential candidates for the James Webb Space Telescope.
We present preliminary results of the photometric variability search in the field of view of the young open cluster NGC 457. We find over 60 variable stars in the field, including 25 pulsating or candidate pulsating stars.
Recent observations and a photometric search for variable stars in the Ursa Minor dwarf spheroidal galaxy (UMi dSph) are presented. Our observations were taken at Apache Point Observatory in 2014 and 2016 using the 0.5m ARCSAT telescope and the West Mountain Observatory 0.9m telescope of Brigham Young University in 2016. Previously known RR Lyrae stars in our field of view of the UMi dSph are identified, and we also catalog new variable star candidates. Tentative classifications are given for some of the new variable stars. We have conducted period searches with the data collected with the WMO telescope. Our ultimate goal is to create an updated catalog of variable stars in the UMi dSph and to compare the RR Lyrae stellar characteristics to other RR Lyrae stars found in the Local Group dSph galaxies.
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