Search Publications
Suzaku Observations of the HMXB 1A 1118-61
Makishima, Kazuo; Terada, Yukikatsu; Rothschild, Richard E. +12 more
We present broadband analysis of the Be/X-ray transient 1A 1118-61 by Suzaku at the peak of its third observed outburst in 2009 January and two weeks later when the source flux had decayed by an order of magnitude. The continuum was modeled with a cutoffpl model as well as a compTT model, with both cases requiring an additional blackbody component…
HST/NICMOS Imaging of Bright High-redshift 24 µm Selected Galaxies: Merging Properties
Helou, George; Surace, Jason; Yan, Lin +4 more
We present new results on the physical nature of infrared-luminous sources at 0.5 < z < 2.8 as revealed by HST/NICMOS imaging and Infrared Spectrograph mid-infrared spectroscopy. Our sample consists of 134 galaxies selected at 24 µm with a flux of S(24 µm)>0.9 mJy. We find many (~60%) of our sources to possess an important bul…
Broad Lyα Emission from Three Nearby BL Lacertae Objects
Perlman, Eric S.; Danforth, Charles W.; Stocke, John T.
We present far-UV HST/COS spectra of four nearby BL Lac objects. BL Lac spectra are dominated by a smooth, power-law continuum which arises in a relativistic jet. However, the spectra are not necessarily featureless; weak, broad- and/or narrow-line emission is sometimes seen in high-quality optical spectra. We present detections of Lyα emission in…
Chandra Detection of SN 2010da Four Months After Outburst: Evidence for a High-mass X-Ray Binary in NGC 300
Dalcanton, J. J.; Kong, A. K. H.; Weisz, D. R. +4 more
We present the results of a 63 ks Chandra observation of the "supernova impostor" SN 2010da four months after it was first observed on 2010 May 24. We detect an X-ray source at ~7σ confidence coincident with the optical location of the outburst. Our imaging analysis has revealed a hard central point source, surrounded by soft diffuse emission exte…
Dimming of the 17th Century Sun
Ortiz, Ada; Foukal, Peter; Schnerr, Roald
Reconstructions of total solar irradiance (TSI) rely mainly on linear relations between TSI variation and indices of facular area. When these are extrapolated to the prolonged 15th-17th century Spörer and Maunder solar activity minima, the estimated solar dimming is insufficient to explain the mid-millennial climate cooling of the Little Ice Age. …
The Optical Counterpart of NGC 1313 X-1
Feng, Hua; Kaaret, Philip; Yang, Lin
We identify the optical counterpart of the ultraluminous X-ray source (ULX) NGC 1313 X-1 and discuss constraints on its physical nature from multiband optical spectra. There is a single object on Hubble Space Telescope images within the aspect-corrected Chandra X-ray error circle; a fainter, possibly extended, feature lies near the edge of the err…
Chandra Evidence for Extended X-Ray Structure in RY Tau
Skinner, Stephen L.; Güdel, Manuel; Audard, Marc
We report results of a sensitive Chandra ACIS-S observation of the classical T Tauri star RY Tau. Previous studies have shown that it drives a spectacular bipolar jet whose blueshifted component is traced optically along P.A. ≈ 295° at separations of 1farcs5-31'' from the star. Complex X-ray emission is revealed, including a very soft non-variable…
Temperature Equilibration Behind the Shock Front: An Optical and X-Ray Study Of RCW 86
Vink, J.; Bassa, C. G.; Helder, E. A.
We study the electron-proton temperature equilibration behind several shocks of the RCW 86 supernova remnant. To measure the proton temperature, we use published and new optical spectra, all from different locations on the remnant. For each location, we determine the electron temperature from X-ray spectra, and correct for temperature equilibratio…
The Rotation of the White Light Solar Corona at Height 4 R sun from 1996 to 2010: A Tomographical Study of Large Angle and Spectrometric Coronagraph C2 Observations
Morgan, Huw
Solar rotational tomography is applied to Large Angle and Spectrometric Coronagraph (LASCO) C2/Solar and Heliospheric Observatory (SOHO) observations covering the period 1996-2010, resulting in a set of electron density maps at a height of 4 R sun from which rotation rates can be calculated. Large variation of rotation rates is measured…
Revisiting the Solar Tachocline: Average Properties and Temporal Variations
Basu, Sarbani; Antia, H. M.
The tachocline is believed to be the region where the solar dynamo operates. With over a solar cycle's worth of data available from the Michelson Doppler Imager and Global Oscillation Network Group instruments, we are in a position to investigate not merely the average structure of the solar tachocline, but also its time variations. We determine t…