Search Publications
Large-amplitude Rapid X-Ray Variability in the Narrow-line Seyfert 1 Galaxy PG 1404+226
Dewangan, G. C.; Mallick, L.
We present the first results from a detailed analysis of a new, long (∼100 ks) XMM-Newton observation of the narrow-line Seyfert 1 galaxy PG 1404+226, which showed a large-amplitude, rapid X-ray variability by a factor of ∼7 in ∼10 ks with an exponential rise and a sharp fall in the count rate. We investigate the origin of the soft X-ray excess em…
DirtyGrid I: 3D Dust Radiative Transfer Modeling of Spectral Energy Distributions of Dusty Stellar Populations
Gordon, Karl D.; Misselt, Karl A.; Law, Ka-Hei
Understanding the properties of stellar populations and interstellar dust has important implications for galaxy evolution. In normal star-forming galaxies, stars and the interstellar medium dominate the radiation from ultraviolet (UV) to infrared (IR). In particular, interstellar dust absorbs and scatters UV and optical light, re-emitting the abso…
The Far-UV Albedo of Europa From HST Observations
Hendrix, A. R.; Saur, J.; Roth, L. +3 more
We present an analysis of Europa's far-UV spectral albedo using observations during the 1999-2015 time period made by the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. Disk-integrated observations show that the far-UV spectrum in the 130 to 170-nm range is relatively flat or slightly blue (increasing albedo with decreasing wa…
Positional Offsets between SiO Masers in Evolved Stars and their Cross-matched Counterparts
Morris, Mark R.; Rich, R. Michael; Sjouwerman, Loránt O. +4 more
Observations of dust-enshrouded evolved stars selected from infrared catalogs requiring high positional accuracy, like infrared spectroscopy or long baseline radio interferometric observations, often require preparational observational steps determining a position with an accuracy much better than 1″. Using phase-referencing observations with the …
On the Nature of the X-Ray Emission from the Ultraluminous X-Ray Source, M33 X-8: New Constraints from NuSTAR and XMM-Newton
Williams, Benjamin F.; Zezas, Andreas; Maccarone, Thomas J. +12 more
We present nearly simultaneous NuSTAR and XMM-Newton observations of the nearby (832 kpc) ultraluminous X-ray source (ULX) M33 X-8. M33 X-8 has a 0.3-10 keV luminosity of L X ≈ 1.4 × 1039 erg s-1, near the boundary of the “ultraluminous” classification, making it an important source for understanding the link betwe…
Registration of H2O and SiO masers in the Calabash Nebula to confirm the planetary nebula paradigm
Kim, J.; Bujarrabal, V.; Dodson, R. +4 more
We report on the astrometric registration of very long baseline interferometry images of the SiO and H2O masers in OH 231.8+4.2, the iconic proto-planetary nebula also known as the Calabash nebula, using the Korean VLBI Network and source frequency phase referencing. This, for the first time, robustly confirms the alignment of the SiO m…
Interpreting the cosmic far-infrared background anisotropies using a gas regulator model
Wu, Hao-Yi; Doré, Olivier; Serra, Paolo +1 more
Cosmic far-infrared background (CFIRB) is a powerful probe of the history of star formation rate (SFR) and the connection between baryons and dark matter across cosmic time. In this work, we explore to which extent the CFIRB anisotropies can be reproduced by a simple physical framework for galaxy evolution, the gas regulator (bathtub) model. This …
Statistical Study of ICMEs with Low Mean Carbon Charge State Plasmas Detected from 1998 to 2011
Li, Gang; Yan, Xiaoli; Yao, Shuo +2 more
We present a statistical study of 219 ICMEs measured by both ACE and WIND from 1998 to 2011. ICME plasmas are defined as possessing cold materials if the carbon average charge states are lower than those of the preceding solar wind by three standard deviations and the carbon ionic temperature is lower than 106.05 K. A total of 69 ICMEs …
Multisatellite observations of the magnetosphere response to changes in the solar wind and interplanetary magnetic field
Angelopoulos, Vassilis; Sibeck, David; Thaller, Scott +5 more
We employ multipoint observations of the Van Allen Probes, THEMIS, GOES and Cluster to present case and statistical studies of the electromagnetic field, plasma and particle response to interplanetary (IP) shocks observed by the Wind satellite. On 27 February 2014 the initial encounter of an IP shock with the magnetopause occurred on the postnoon …
X-ray time lags in PG 1211+143
Vaughan, S.; Reeves, J. N.; Pounds, K. +1 more
We investigate the X-ray time lags of a recent ∼630 ks XMM-Newton observation of PG 1211+143. We find well-correlated variations across the XMM-Newton EPIC bandpass, with the first detection of a hard lag in this source with a mean time delay of up to ∼3 ks at the lowest frequencies. We find that the energy-dependence of the low-frequency hard lag…