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HST Low-resolution Stellar Library
Gregg, Michael D.; Worthey, Guy; Silva, David R. +2 more
In order to provide fundamental stellar spectra that extend into the UV, Hubble Space Telescope's Space Telescope Imaging Spectrograph targeted 556 stars via proposals GO9088, GO9786, GO10222, and GO13776. Exposures through three low-resolution gratings provide wavelength coverage from 0.2 < λ < 1 µm at λ/Δλ ~ 1000. The UV grating (G23…
On the nature of Tycho Brahe's supernova
Ruiz-Lapuente, Pilar
At the 450 years anniversary of its observation, the supernova named after Tycho Brahe, SN 1572, can be explained in the terms used nowadays to characterize Type Ia supernovae (SNe Ia). By assembling the records of the observations made in 1572–74 and evaluating their uncertainties, it is possible to recover the light curve and the color evolution…
Spectroscopic properties of stars in young binaries: fundamental data for understanding binary formation and disk evolution
Prato, Lisa
This contribution combines a relatively comprehensive review of the spectroscopic study of the individual component stars and their associated disks in young binary systems, outlines the need for more in-depth studies, and previews the results of a high-spectral and high-angular resolution survey of
Evidence for the Disruption of a Planetary System During the Formation of the Helix Nebula
Kemper, Francisca; Villaver, Eva; Ertel, Steve +5 more
The persistence of planetary systems after their host stars evolve into their post-main-sequence phase is poorly constrained by observations. Many young white dwarf systems exhibit infrared excess emission and/or spectral absorption lines associated with a reservoir of dust (or planetesimals) and its accretion. However, most white dwarfs are too c…
Multi-wavelength aperture polarimetry of debris disc host stars
Bailey, Jeremy; Cotton, Daniel V.; Kedziora-Chudczer, Lucyna +3 more
Debris discs around main sequence stars have been extensively characterized from infrared to millimetre wavelengths through imaging, spectroscopic, and total intensity (scattered light and/or thermal emission) measurements. Polarimetric observations have only been used sparingly to interpret the composition, structure, and size of dust grains in t…
The unaltered pulsar: GRO J1750-27, a supercritical X-ray neutron star that does not blink an eye
Altamirano, D.; Sanna, A.; Ducci, L. +11 more
When accreting X-ray pulsars (XRPs) undergo bright X-ray outbursts, their luminosity-dependent spectral and timing features can be analyzed in detail. The XRP GRO J1750-27 recently underwent one such episode, during which it was observed with NuSTAR and monitored with NICER. Such a data set is rarely available, as it samples the outburst over more…
The Shapes of Stellar Spectra
Allende Prieto, Carlos
Stellar atmospheres separate the hot and dense stellar interiors from the emptiness of space. Radiation escapes from the outermost layers of a star, carrying direct physical information. Underneath the atmosphere, the very high opacity keeps radiation thermalized and resembling a black body with the local temperature. In the atmosphere the opacity…
ULF Waves Propagating Through the Martian Magnetosheath into the Ionosphere: A Statistical Study Using Mars Express Observations
Fraenz, Markus; Echer, Ezequiel; Franco, Adriane Marques de Souza +1 more
The Martian magnetosphere is induced, and the low-energy ion escape is related to the extreme ultraviolet (EUV) solar radiation and to the solar wind pressure variations. The ion reflection at the bow shock is a permanent source of ultra-low frequency (ULF) waves. These are convected through the magnetosheath and can penetrate into the upper ionos…
A Simple Method for Predicting N H Variability in Active Galactic Nuclei
Marchesi, Stefano; Zhao, Xiurui; Ajello, Marco +4 more
The unified model of active galactic nuclei (AGNs) includes a geometrically thick obscuring medium to explain the differences between type I and type II AGNs as an effect of inclination angle. This medium is often referred to as the torus and is thought to be "clumpy" as the line-of-sight column density, N H, has been observed to vary i…
A Census of Archival X-Ray Spectra for Modeling Tidal Disruption Events
Wen, Sixiang; Jonker, Peter G.; Stone, Nicholas C. +3 more
Tidal disruption events (TDEs) are highly energetic phenomena that occur when a star is tidally disrupted by the central massive black hole in a galaxy. Fitting the observed X-ray spectra of TDEs with a first-principles, general-relativistic slim-disk model for the emission from the inner accretion disk can constrain the black hole mass M •