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A Dynamically Distinct Stellar Population in the Leading Arm of the Sagittarius Stream
Beers, Timothy C.; Lee, Young Sun; Kang, Gwibong +1 more
We present a chemical and dynamical analysis of the leading arm (LA) and trailing arm (TA) of the Sagittarius (Sgr) stream, as well as for the Sgr dwarf galaxy core (SC), using red giant branch, main-sequence, and RR Lyrae stars from large spectroscopic survey data. The different chemical properties among the LA, TA, and SC generally agree with re…
Variability in NGC 3201 Giant Stars
Villanova, S.; Parisi, C.; Cortés, C. C. +2 more
We present the analysis of 510 light curves in V and I bands of 255 giant stars in the globular cluster NGC 3201. Our aim is to expand the sample of new types of variables reported in a previous study. These variables show a short period (P V < 0.6 day) and a low amplitude (A(V) < 0.06 mag.). We first searched for variability us…
Evolution of Magnetic Fields and Energy Release Processes during Homologous Eruptive Flares
Joshi, Bhuwan; Cho, Kyung-Suk; Sahu, Suraj +1 more
We explore the processes of the repetitive buildup and the explosive release of magnetic energy, together with the formation of magnetic flux ropes, which eventually resulted in three homologous eruptive flares of successively increasing intensities (i.e., M2.0, M2.6, and X1.0). The flares originated from NOAA active region 12017 between 2014 Marc…
Local Electron Density Depletions in the Martian Upper Ionosphere Obtained From MARSIS: Comparison With ASPERA-3, and MAVEN, and the Connection With Crustal Magnetic Fields
Frahm, R. A.; Duru, F.; Hughes, D. +3 more
Steep electron density depletions in the Martian ionosphere are important, especially because they could be regions of significant plasma escape. Local electron density profiles of the Martian ionosphere obtained from the radar sounder onboard the Mars Express spacecraft often show large fluctuations. In some cases, these fluctuations are observed…
A machine learning algorithm for reliably predicting active galactic nucleus absorbing column densities
Ajello, M.; Marchesi, S.; Torres-Albà, N. +4 more
We present a new method for predicting the line-of-sight column density (NH) values of active galactic nuclei (AGN) based on mid-infrared (MIR), soft X-ray, and hard X-ray data. We developed a multiple linear regression machine learning algorithm trained with WISE colors, Swift-BAT count rates, soft X-ray hardness ratios, and an MIR-sof…
Star-forming brightest cluster galaxies at z ∼ 0.4 in KiDS. Further studies of cold gas and stellar properties
Castignani, G.; Moscardini, L.; Radovich, M. +10 more
Brightest cluster galaxies (BCGs) at the centers of clusters are among the most massive galaxies in the Universe. Their star formation history and stellar mass assembly are highly debated. Recent studies suggest the presence of an emerging population of intermediate-z star-forming and gas-rich BCGs, whose molecular gas reservoirs that feed star fo…
Comet 108P/Ciffreo: The Blob
Mutchler, Max; Jewitt, David; Li, Jing +2 more
Short-period comet 108P/Ciffreo is known for its peculiar double morphology, in which the nucleus is accompanied by a comoving, detached, diffuse "blob." We report new observations of 108P/Ciffreo taken with the Hubble Space Telescope and the Nordic Optical Telescope and use them to determine the cause of this unusual morphology. The separation an…
Redshift-luminosity characterization of active galactic nucleus galaxies having obscuring dusty material using the spectral energy distribution from the X-ray to far-infrared
Gadallah, Kamel A. K.
The spectral energy distribution (SED) from the X-ray to far-IR is used to characterize active galactic nuclei (AGNs) having obscuring dusty material. A sample of 73 AGNs, with redshifts of z < 2.5, is subdivided based on the optical spectra into subgroups of type 1 and 2 AGNs and no-AGN. The X-CIGALE code is used to produce the SEDs of these g…
A NICER Viewing Angle on the Accretion Stream of Vela X-1
Behar, Ehud; Rahin, Roi
Vela X-1 is the archetypal eclipsing high-mass X-ray binary, composed of a neutron star (NS) accreting the B-star wind. It was observed by nearly all X-ray observatories, often multiple times, featuring a rich spectrum of variable emission lines. However, the precise origin of these lines in the binary system remains uncertain. We perform a system…
Detecting Long-period Variability in the SDSS Stripe 82 Standards Catalog
Ivezić, Željko; Ilić, Dragana; Kovačević, Andjelka B. +5 more
We report the results of a search for long-period (100 < P < 600 days) periodic variability in the SDSS Stripe 82 standards catalog. The SDSS coverage of Stripe 82 enables such a search because there are on average 20 observations per band in ugriz bands for about one million sources, collected over about 6 yr, with a faint limit of r ~ 22 m…