Search Publications
Variability of optical and X-ray spectra of Gamma Cassiopeia stars
Yakunin, I. A.; Kholtygin, A. F.; Ryspaeva, E. B. +1 more
Stars of the γ Cas type (γ Cas analogs) belong to a small group of Be stars with a high X-ray luminosity of 10 31 ‑ 10 33 erg/s and an anomalously high temperature of the plasma emitting in the X-ray range of 10–20 keV or more, assuming a completely thermal X-ray emission. The results of the analysis of the optical spectra of γ Cas under the progr…
Multiwavelength Study of Dark Globule DC 314.8-5.1: Point-source Identification and Diffuse Emission Characterization
Cheung, C. C.; Stawarz, Ł.; Rocha, W. R. M. +3 more
We present an analysis of multiwavelength observations of the dark globule DC 314.8-5.1, using data from the Gaia optical, Two Micron All Star Survey near-infrared, and Wide-field Infrared Survey Explorer mid-infrared surveys, dedicated imaging with the Spitzer Space Telescope, and X-ray data obtained with the Swift X-Ray Telescope (XRT). The main…
New constraints on the presence of debris disks around G 196-3 B and VHS J125601.92-125723.9 b
Zakhozhay, Olga V.; Rebolo, Rafael; Semenov, Dmitry A. +10 more
Context. The existence of warm (protoplanetary) disks around very young isolated planetary and brown dwarf mass objects is known based on near- and mid-infrared flux excesses and millimeter observations. These disks may later evolve into debris disks or rings, although none have been observed or confirmed so far. Little is known about circum(sub)s…
Most Rotational Variables Dominated by a Single Bright Feature Are α 2 CVn Stars
Heinze, A. N.; Huber, Mark E.; Flewelling, Heather
We previously reported a rare class of variable star light curves isolated from a sample of 4.7 million candidate variables from the ATLAS survey. Dubbed "UCBH" light curves, they have broad minima and narrow, symmetrical maxima, with typical periods of 1-10 days and amplitudes of 0.05-0.20 mag. They maintain constant amplitude, shape, and phase c…
A non-detection of red supergiant convection in Gaia
Kochanek, C. S.
Large-scale surface convection on red supergiants (RSGs) can lead to shifts in the photocentre of the star that might be measured by Gaia and used as a new probe of the surface dynamics of these rare but important stars. Unlike brightness variations, photocentre motions would provide information on the physical scale of the convective cells. The s…
Electrostatic Plasma Wave Excitations at the Interplanetary Shocks
Giacalone, Joe; Fraschetti, Federico; Singh, Manpreet
Over the last few decades, different types of plasma waves (e.g., the ion acoustic waves (IAWs), electrostatic solitary waves, upper/lower hybrid waves, and Langmuir waves) have been observed in the upstream, downstream, and ramp regions of the collisionless interplanetary (IP) shocks. These waves may appear as short-duration (only a few milliseco…
Evolutionary history of western Eos Chaos of Valles Marineris, Mars: Insights from morphological characteristics
Sinha, Rishitosh K.; Rajesh, V. J.; Sajinkumar, K. S. +2 more
The dynamics of aqueous processes within the Eos Chasma region in the trough of Valles Marineris on Mars have been attributed to a variety of Hesperian-aged landforms. We aim to improve the understanding of the geological characteristics of the western part of the Eos Chaos by investigating the morphological, topographical, and thermo-physical cha…
The Nature of Blue Stars with Mid-infrared Excesses in the Large Magellanic Cloud
Chu, You-Hua; Gruendl, Robert A.; Ishioka, Ryoko +3 more
We present low-resolution optical spectra and classifications of 92 blue objects with mid-infrared excesses in the Large Magellanic Cloud. The majority of these objects were selected with the criteria of U - B < 0 and V < 17 from the potential young stellar object (YSO) candidates in Gruendl & Chu (GC09), which were identified based on S…
Fundamental parameters and stellar mass function of four open clusters close to the galactic plane
Kowshik, Krishna Kumar; Sujatha, S.; Routh, Swati
In the context of understanding star formation in the galactic plane, we present the results from the analysis of four young open clusters using archival data from Gaia Data Release 3, the Two-Micron All Sky Survey (2MASS) and Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). The open clusters—[BDB2003]G085.25‑00.02, [BDS2003]48, …
Space astrometry
Perryman, Michael
Astrometry, the measurement of accurate star positions and motions, was first carried out from space by the European Space Agency's Hipparcos mission in the 1990s. Today, it is undergoing a particularly dramatic advance with ESA's ongoing Gaia mission, launched in 2013. I explain why star positions are of such importance in astronomy, and outline …