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The Gaia-ASAS-SN Classical Cepheid Sample. I. Sample Selection
Rix, Hans-Walter; Drimmel, R.; Poggio, E. +4 more
We present a well-defined and characterized all-sky sample of classical Cepheids in the Milky Way, obtained by combining two time-domain all-sky surveys: Gaia DR2 (Gaia Collaboration et al. 2018) and All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al. 2014). We first use parallax and variability information from Gaia to select ~30,000…
High-resolution imaging follow-up of doubly imaged quasars
Treu, Tommaso; Wisotzki, Lutz; Fassnacht, Christopher D. +8 more
We report upon 3 years of follow-up and confirmation of doubly imaged quasar lenses through imaging campaigns from 2016 to 2018 with the Near-Infrared Camera2 (NIRC2) on the W. M. Keck Observatory. A sample of 57 quasar lens candidates are imaged in adaptive-optics-assisted or seeing-limited K'-band observations. Out of these 57 candida…
Red Be stars in the Magellanic Clouds?
Vieira, Katherine; Hernández, Jesús; García-Varela, Alejandro +2 more
We revisit the subject of Be candidate stars towards the Magellanic Clouds, previously studied by the authors using SPM4 proper motions. We obtain Gaia DR2 parallaxes and proper motions for 2357 and 994 LMC and SMC Be candidates, respectively. Parallaxes and proper motions versus colour V - I easily reveal the presence of the redder galactic conta…
A possible nonthermal X-ray emission from γ Cas analogues stars
Ryspaeva, Elizaveta B.; Kholtygin, Alexander F.
We analyze the archival XMM-Newton X-ray observations of 15 γ Cas analogue stars and two candidates for such objects. The EPIC spectra of the considered stars in the range of 0.2-8 keV were extracted and fitted by different models. Our estimates show that assuming the X-ray emission from γ Cas analogues to be totally thermal, their model plasma te…
Optical observations of near isotropic comet C/2006 OF2 (Broughton) at two different heliocentric distances
Lara, L.; Afanasiev, V.; Kulyk, I. +3 more
Spectra and images of comet C/2006 OF2 (Broughton) were obtained with the 4.2-m William Herschel Telescope (La Palma, Spain) and with the 6-m Big Telescope Alt-azimuth (SAO RAN, Russia) at two observing epochs on October 15, 2007 and December 05, 2008.The comet was at heliocentric distances of 4.24 au and 2.59 au before and after the perihelion, r…
Curiouser and curiouser: the peculiar chemical composition of the Li- and Na-rich star in ω Centauri
Salaris, M.; Bonifacio, P.; Momany, Y. +5 more
We present a multi-instrument spectroscopic analysis of the unique Li- and Na-rich giant star #25664 in ω Centauri, using spectra acquired with FLAMES-GIRAFFE, X-shooter, UVES, and HARPS. Li and Na abundances have been derived from the UVES spectrum using transitions weakly sensitive to non-local thermodynamic equilibrium and assumed isotopic rati…
Probing Gas Kinematics and PDR Structure around O-type Stars in the Sh 2-305 H II Region
Dewangan, L. K.; Ojha, D. K.; Sharma, Saurabh +3 more
We report an observational study of the Galactic H II region Sh 2-305/S305 using the [C II] 158 µm line data, which are used to examine the gas dynamics and structure of photodissociation regions. The integrated [C II] emission map at [39.4, 49.5] km s-1 spatially traces two shell-like structures (i.e., inner and outer neutral she…
Does ADS 9346 have a low-mass companion?
Kiyaeva, Olga V.; Khovritchev, Maxim Yu.; Kulikova, Agrippina M. +3 more
Based on the photographic and CCD observations of the relative motion of the A and B components of the binary system ADS 9346 obtained with the 26-inch refractor of Pulkovo Observatory during 1979-2019, we discover an invisible companion associated with star A. Comparison of the ephemerides with the positional and spectroscopic observations allowe…
Convex X-ray spectra of PKS 2155-304 and constraints on the minimum electron energy
Ravikumar, C. D.; Jagan, Sitha K.; Sahayanathan, S. +1 more
The convex (concave upward) high-energy X-ray spectra of the blazar PKS 2155-304, observed by XMM-Newton, is interpreted as the signature of subdominant inverse-Compton emission. The spectra can be well fitted by a superposition of two power-law contributions which imitate the emission due to synchrotron and inverse-Compton processes. The methodol…
High-cadence measurements of electron pitch-angle distributions from Solar Orbiter SWA-EAS burst mode operations
Lewis, G. R.; Kataria, D. O.; Livi, S. +17 more
Small-scale kinetic processes associated with turbulence, plasma instabilities, magnetic reconnection, etc., play a major role in dissipating energy and governing the large-scale evolution of the solar wind. However, a general impediment to improving the understanding of the kinetic physics of the solar wind is in the limitations on measurement ca…