Search Publications
The Ultraluminous X-Ray Sources Population of the Galaxy NGC 7456
Salvaterra, R.; Haberl, F.; Tiengo, A. +28 more
Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with X-ray luminosities above 1039 erg s-1. The ULX population counts several hundred objects but only a fraction are well studied. Here we present a detailed analysis of all ULXs hosted in the galaxy NGC 7456. It was observed in X-rays only once in t…
A More Efficient Search for H2O Megamaser Galaxies: The Power of X-Ray and Mid-infrared Photometry
Chang, Y. -Y.; Cunha, E. da; Matsushita, S. +10 more
We present an investigation of the dependence of H2O maser detection rates and properties on the mid-IR active galactic nucleus (AGN) luminosity, LAGN, and the obscuring column density, NH, based on mid-IR and hard X-ray photometry. Based on spectral energy distribution fitting that allows for decomposition of the …
Newly Improved Ionization Corrections for the Neutral Interstellar Medium: Enabling Accurate Abundance Determinations in Star-forming Galaxies throughout the Universe
Hernandez, Svea; Aloisi, Alessandra; James, Bethan L. +4 more
Studies measuring the chemical abundances of the neutral gas in star-forming galaxies (SFGs) require ionization correction factors (ICFs) to accurately measure their metal contents. In the work presented here, we calculate newly improved ICFs for a sample of SFGs. These new corrections include both the contaminating ionized gas along the line of s…
The High Helium Abundance and Charge States of the Interplanetary CME and Its Material Source on the Sun
Harrison, R. A.; Davies, J. A.; Barnes, D. +5 more
Identifying the source of the material within coronal mass ejections (CMEs) and understanding CME onset mechanisms are fundamental issues in solar and space physics. Parameters relating to plasma composition, such as charge states and He abundance (AHe), may be different for plasmas originating from differing processes or regions on the…
Hot Subdwarf All Southern Sky Fast Transit Survey with the Evryscope
Law, Nicholas M.; Németh, Péter; Glazier, Amy +6 more
We have conducted a survey of candidate hot subdwarf (HSD) stars in the southern sky searching for fast transits, eclipses, and sinusoidal-like variability in the Evryscope light curves. The survey aims to detect transit signals from Neptune-size planets to gas giants, and eclipses from M-dwarfs and brown dwarfs. The other variability signals are …
On the Production of He+ of Solar Origin in the Solar Wind
Landi, Enrico; Rivera, Yeimy J.; Lepri, Susan T. +1 more
Solar wind measurements in the heliosphere predominantly comprise protons, alphas, and minor elements in a highly ionized state. The majority of low-charge states, such as He+, measured in situ are often attributed to pick-up ions of nonsolar origin. However, through inspection of the velocity distribution functions of near-Earth measur…
Detection of Pb II in the Ultraviolet Spectra of Three Metal-poor Stars
Beers, Timothy C.; Placco, Vinicius M.; Holmbeck, Erika M. +8 more
We report the first detection of the Pb II line at 2203.534 Šin three metal-poor stars, using ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We perform a standard abundance analysis assuming local thermodynamic equilibrium (LTE) to derive lead (Pb, Z = 82) abundances. The Pb II line …
The Archetypal Ultra-diffuse Galaxy, Dragonfly 44, Is not a Dark Milky Way
Bogdán, Ákos
Due to the peculiar properties of ultra-diffuse galaxies (UDGs), understanding their origin presents a major challenge. Previous X-ray studies demonstrated that the bulk of UDGs lack substantial X-ray emission, implying that they reside in low-mass dark matter halos. This result, in concert with other observational and theoretical studies, pointed…
The Large-scale Behavior in the Disk of δ Scorpii from 2000 to 2018
Carciofi, A. C.; Mota, B. C.; Tycner, C. +4 more
We model the circumstellar disk of δ Sco using the three-dimensional Monte Carlo radiative transfer code HDUST in order to quantify the large-scale changes in the disk through the years 2000-2018, and to see if these changes can be attributed to the secondary star affecting the disk throughout its orbit. We determine our best-fitting models throug…
Multiwavelength Study of an X-Ray Tidal Disruption Event Candidate in NGC 5092
Komossa, S.; Jin, Chichuan; Saxton, R. D. +7 more
We present multiwavelength studies of a transient X-ray source, XMMSL1 J131952.3+225958, associated with the galaxy NGC 5092 at z = 0.023 detected in the XMM-Newton SLew survey (XMMSL). The source brightened in the 0.2-2 keV band by a factor of > 20 in 2005 as compared with previous flux limits and then faded by a factor of >200 as observed …