Search Publications
NuSTAR Detection of a Hard X-Ray Source in the Supernova Remnant-molecular Cloud Interaction Site of IC 443
Hailey, Charles J.; Mori, Kaya; Zhang, Shuo +10 more
We report on a broadband study of a complex X-ray source (1SAX J0618.0+2227) associated with the interaction site of the supernova remnant (SNR) IC 443 and ambient molecular cloud (MC) using NuSTAR, XMM-Newton, and Chandra observations. Its X-ray spectrum is composed of both thermal and nonthermal components. The thermal component can be equally w…
Composition and structure of fresh ammonia clouds on Jupiter based on quantitative analysis of Galileo/NIMS and New Horizons/LEISA spectra
Sromovsky, L. A.; Fry, P. M.
Ammonia gas has long been assumed to be the main source of condensables for the upper cloud layer on Jupiter, but distinctive spectral features associated with ammonia have been seen only rarely. Since both ammonia and NH4SH absorb in the 3 µm region, and widespread absorption in the 3 µm region was present (Sromovsky and Fr…
The Distance to the Galaxy Coma P
Anand, Gagandeep S.; Shaya, Edward J.; Tully, R. Brent +4 more
If the extremely low surface-brightness galaxy Coma P lies at 5.5 ± 0.3 Mpc, as recently proposed, then it would have an extraordinarily deviant peculiar velocity of ∼900 km s-1 at a location where differential velocities between galaxies are low. We have accessed the images from the Hubble Space Telescope (HST) archives used to derive …
Understanding Fundamental Properties and Atmospheric Features of Subdwarfs via a Case Study of SDSS J125637.13-022452.4
Gonzales, Eileen C.; Faherty, Jacqueline K.; Gagné, Jonathan +2 more
We present the distance-calibrated spectral energy distribution (SED) of the sdL3.5 subdwarf SDSS J125637.13-022452.4 (J1256-0224) using its Gaia DR2 parallax. We report the bolometric luminosity and semi-empirical fundamental parameters, as well as updated UVW velocities. The SED of J1256-0224 is compared to field-age and low-gravity dwarfs of th…
Must Star-forming Galaxies Rapidly Get Denser before They Quench?
Morishita, T.; Abramson, L. E.
Using the deepest data yet obtained, we find no evidence preferring compaction-triggered quenching—where rapid increases in galaxy density truncate star formation—over a null hypothesis in which galaxies age at constant surface density ({{{Σ }}}e\equiv {M}* /2π {r}e2). Results from two fully empirical an…
An Empirical Model of the Variation of the Solar Lyman-α Spectral Irradiance
Kretzschmar, Matthieu; Curdt, Werner; Snow, Martin
We propose a simple model that computes the spectral profile of the solar irradiance in the hydrogen Lyman alpha line, H Ly-α (121.567 nm), from 1947 to present. Such a model is relevant for the study of many astronomical environments, from planetary atmospheres to interplanetary medium. This empirical model is based on the SOlar Heliospheric Obse…
FTIR Laboratory Measurement of O I Spectra in the 0.77-12.5 µm Spectral Range: Rydberg States and Oscillator Strengths
Civiš, S.; Kubelík, P.; Ferus, M. +4 more
Precision laboratory measurements are presented for 135 O I lines in the infrared (including 51 lines not measured previously in the laboratory) using time-resolved Fourier transform infrared spectroscopy in the 800-13,000 cm-1 region. The fine structure of some lines is observed for the first time. Using our linelist together with all …
Fast plasma sheet flows and X line motion in the Earth's magnetotail: results from a global hybrid-Vlasov simulation
Jarvinen, Riku; Juusola, Liisa; Pfau-Kempf, Yann +6 more
Fast plasma flows produced as outflow jets from reconnection sites or X lines are a key feature of the dynamics in the Earth's magnetosphere. We have used a polar plane simulation of the hybrid-Vlasov model Vlasiator, driven by steady southward interplanetary magnetic field and fast solar wind, to study fast plasma sheet ion flows and related magn…
Estimate of the Upper Limit on Hot Plasma Differential Emission Measure (DEM) in Non-Flaring Active Regions and Nanoflare Frequency Based on the Mg XII Spectroheliograph Data from CORONAS-F/SPIRIT
Reva, Anton; Ulyanov, Artem; Kirichenko, Alexey +2 more
Nanoflare-heating theory predicts steady hot-plasma emission in non-flaring active regions. It is hard to find this emission with conventional non-monochromatic imagers (such as the Atmospheric Imaging Assembly or the X-Ray Telescope), because their images contain a cool-temperature background. In this work, we search for hot plasma in non-flaring…
Testing landslide and atmospheric-effects models for the formation of double-layered ejecta craters on Mars
Head, James W.; Weiss, David K.
Double-layered ejecta (DLE) craters are distinctive among the variety of crater morphologies observed on Mars, but the mechanism by which they form remains under debate. We assess two ejecta emplacement mechanisms: (1) atmospheric effects from ejecta curtain-induced vortices or a base surge and (2) ballistic emplacement followed by a landslide of …