Search Publications
Hard X-Ray Emission Associated with White Dwarfs. IV. Signs of Accretion from Substellar Companions
Toalá, Jesús A.; Guerrero, Martín A.; Chu, You-Hua +3 more
With an effective temperature of ≃200,000 K, KPD 0005+5106 is one of the hottest white dwarfs (WDs). ROSAT unexpectedly detected "hard" (∼1 keV) X-rays from this apparently single WD. We have obtained Chandra observations that confirm the spatial coincidence of this hard X-ray source with KPD 0005+5106. We have also obtained XMM-Newton observation…
On the Origin of Hard X-Ray Emissions from the Behind-the-limb Flare on 2014 September 1
Kouloumvakos, Athanasios; Rouillard, Alexis P.; Warmuth, Alexander +6 more
The origin of hard X-rays and γ-rays emitted from the solar atmosphere during occulted solar flares is still debated. The hard X-ray emissions could come from flaring loop tops rising above the limb or coronal mass ejection shock waves, two by-products of energetic solar storms. For the shock scenario to work, accelerated particles must be release…
Symbiotic Stars in the Apache Point Observatory Galactic Evolution Experiment Survey: The Case of LIN 358 and SMC N73 (LIN 445a)
Pan, Kaike; Cunha, Katia; Smith, Verne V. +9 more
LIN 358 and SMC N73 are two symbiotic binaries in the halo of the Small Magellanic Cloud, each composed of a hot white dwarf accreting from a cool giant companion. In this work, we characterize these systems using a combination of spectral energy distribution (SED)-fitting to the extant photometric data spanning a broad wavelength range (X-ray/ult…
An X-Ray Study of the White Dwarf Binary AR Scorpii
Takata, J.; Kong, A. K. H.; Li, K. L. +4 more
We report a study of X-ray emission from the white dwarf/M-type star binary system AR Scorpii using archival data taken in 2016-2020. It has been known that the X-ray emission is dominated by optically thin thermal plasma emission and its flux level varies significantly over the orbital phase. The X-ray emission also contains a component that modu…
Radio Spectral Index Analysis of Southern Hemisphere Symbiotic Stars
Sokoloski, J. L.; Vrtilek, S. D.; Dickey, John M. +2 more
Symbiotic stars show emission across the electromagnetic spectrum from a wide array of physical processes. At centimeter waves, both synchrotron and thermal emissions are seen, often highly variable and associated with outbursts in the optical and X-rays. Most models of the radio emission include an ionized region within the dense wind of the red …
Dynamics in the Transition Region beneath Active Region Upflows Viewed by IRIS
Fu, Hui; Xia, Lidong; Huang, Zhenghua +2 more
Coronal upflows at the edges of active regions (ARs), which are a possible source of slow solar wind, have been found to connect with dynamics in the transition region. To infer at what scale transition region dynamics connect to AR upflows, we investigate the statistical properties of the small-scale dynamics in the transition region underneath t…
A Complete 16 µm Selected Galaxy Sample at z ∼ 1: Mid-infrared Spectral Energy Distributions
Rigopoulou, D.; Cortzen, I.; Fazio, G. G. +21 more
We describe a complete, flux-density-limited sample of galaxies at redshift 0.8 < z < 1.3 selected at 16 µm. At the selection wavelength near 8 µm rest, the observed emission comes from both dust heated by intense star formation and active galactic nuclei (AGNs). Fitting the spectral energy distributions (SEDs) of the sample gala…
Comptonization as an Origin of the Continuum in Intermediate Polars
Maiolino, T.; Titarchuk, L.; Wang, W. +2 more
In this paper we test if the ∼0.3-15 keV XMM-Newton EPIC pn spectral continuum of IPs can be described by the thermal Comptonization COMPTT model. We used publicly observations of 12 IPs (AE Aqr, EX Hya, V1025 Cen, V2731 Oph, RX J2133.7+5107, PQ Gem, NY Lup, V2400 Oph, IGR J00234+6141, IGR J17195-4100, V1223 Sgr, and XY Ari). We find that our mode…
Evolution of the Ultraviolet Upturn at 0.3 < z < 1: Exploring Helium-rich Stellar Populations
De Propris, Roberto; Ali, Sadman S.; Chung, Chul +2 more
We measure the near-UV (rest-frame ~2400 Å) to optical color for early-type galaxies in 12 clusters at 0.3 < z < 1.0. We show that this is a suitable proxy for the more common far-ultraviolet bandpass used to measure the ultraviolet upturn and find that the upturn is detected to z = 0.6 in these data, in agreement with previous work. We find…
Stellar Feedback on the Earliest Stage of Massive Star Formation
Chevance, M.; Stutzki, J.; Nayak, O. +7 more
We report SOFIA/GREAT observations of high-J CO lines and [C II] observations of the super star cluster candidate H72.97-69.39 in the Large Magellanic Cloud (LMC), which is in its very early formation stage. We use our observations to determine if shocks are heating the gas or if photon-dominated regions (PDRs) are being heated by local far-UV rad…