Search Publications
Dynamical properties and acceleration of hierarchical dust in the vicinity of comet 67P/Churyumov-Gerasimenko
Blum, J.; Hartogh, P.; Rezac, L. +4 more
A significant fraction of cometary dust grains leaving the nucleus surface are extremely porous and fluffy particles as revealed by recent observation from the Rosetta mission. In this paper our aim is to investigate the dynamics of such grains when subjected to a gas flow, representing the cometary outgassing. We perform numerical experiments to …
Eta Carinae’s Declining Outflow Seen in the UV, 2002-2015
Humphreys, Roberta M.; Davidson, Kris; Martin, John C. +1 more
Existing Hubble Space Telescope UV data offer many previously neglected clues to η Car’s behavior since 2000. Here we examine a subset of observations with diverse results. (1) The star’s rapid change of state is confirmed by major changes in UV absorption lines, circumstellar extinction, and other features. (2) N III] λ1750 is one of the two most…
Physical and geometrical parameters of VCBS XIII: HIP 105947
Masda, Suhail Gumaan; Al-Wardat, Mashhoor Ahmed; Pathan, Jiyaulla Khan Moula Khan
The best physical and geometrical parameters of the main sequence close visual binary system (CVBS), HIP 105947, are presented. These parameters have been constructed conclusively using Al-Wardat’s complex method for analyzing CVBSs, which is a method for constructing a synthetic spectral energy distribution (SED) for the entire binary system usin…
A Candidate Tidal Disruption Event in a Quasar at z = 2.359 from Abundance Ratio Variability
Shen, Yue; Jiang, Linhua; Liu, Xin +1 more
A small fraction of quasars show an unusually high nitrogen-to-carbon ratio (N/C) in their spectra. These “nitrogen-rich” (N-rich) quasars are a long-standing puzzle because their interstellar medium implies stellar populations with abnormally high metallicities. It has recently been proposed that N-rich quasars may result from tidal disruption ev…
The Origin of the 300 km s-1 Stream near Segue 1
Bovy, Jo; Beers, Timothy C.; Placco, Vinicius M. +13 more
We present a search for new members of the 300 km s-1 stream (300S) near the dwarf galaxy Segue 1 using wide-field survey data. We identify 11 previously unknown bright stream members in the APOGEE-2 and SEGUE-1 and 2 spectroscopic surveys. Based on the spatial distribution of the high-velocity stars, we confirm for the first time that …
A Study of Magnetic Field Characteristics of the Flaring Active Region Based on Nonlinear Force-free Field Extrapolation
Kusano, Kanya; Inoue, Satoshi; Bamba, Yumi +1 more
Coronal magnetic fields are responsible for the onset of solar flares and solar eruptions. However, the type of magnetic field parameters that can be used to measure the critical condition for a solar eruption is still unclear. As an effort to understand the possible condition for a solar flare, we have examined the nondimensional parameter κ intr…
An ultrafast inflow in the luminous Seyfert PG1211+143
King, A. R.; Pounds, K. A.; Lobban, A. +1 more
Blueshifted absorption lines in the X-ray spectra of an active galactic nucleus (AGN) show that ultrafast outflows with typical velocities v ∼ 0.1c are a common feature of these luminous objects. Such powerful AGN winds offer an explanation of the observed M-σ relation linking the mass of the supermassive black hole and the velocity dispersion in …
Identification of the Infrared Counterpart of SGR 1935+2154 with the Hubble Space Telescope
Kouveliotou, Chryssa; Levan, Andrew; Fruchter, Andrew
We present deep Hubble Space Telescope observations of a new magnetar source, the soft gamma-repeater SGR 1935+2154, discovered by Swift. We obtained three epochs of observations: while the source was active in 2015 March, during a quiescent period in 2015 August, and during a further active phase in 2016 May. Close to the center of the X-ray erro…
Low-mass star formation and subclustering in the H II regions RCW 32, 33, and 27 of the Vela Molecular Ridge. A photometric diagnostics for identifying M-type stars
Micela, G.; Sciortino, S.; Guarcello, M. G. +4 more
Context. Most stars are born in clusters, and recent results suggest that star formation (SF) preferentially occurs in subclusters. Studying the morphology and SF history of young clusters is crucial for understanding early cluster formation processes.
Aims: We aim to identify the embedded population of young stellar objects (YSOs) down to th…
Gas flow in near surface comet like porous structures: Application to 67P/Churyumov-Gerasimenko
Hartogh, Paul; Thomas, Nicolas; Kührt, Ekkehard +6 more
We performed an investigation of a comet like porous surface to study how sub-surface sublimation with subsequent flow through the porous medium can lead to higher gas temperatures at the surface. A higher gas temperature of the emitted gas at the surface layer, compared to the sublimation temperature, will lead to higher gas speeds as the gas exp…