Search Publications
X-Ray Sources in the Dwarf Spheroidal Galaxy Draco
Sonbas, E.; Dhuga, K. S.; Kargaltsev, O. +3 more
We present the spectral analysis of an 87 ks XMM-Newton observation of Draco, a nearby dwarf spheroidal galaxy. Of the approximately 35 robust X-ray source detections, we focus our attention on the brightest of these sources, for which we report X-ray and multiwavelength parameters. While most of the sources exhibit properties consistent with acti…
Systematic Uncertainties in the Spectroscopic Measurements of Neutron-star Masses and Radii from Thermonuclear X-Ray Bursts. III. Absolute Flux Calibration
Marshall, Herman; Güver, Tolga; Özel, Feryal +3 more
Many techniques for measuring neutron star radii rely on absolute flux measurements in the X-rays. As a result, one of the fundamental uncertainties in these spectroscopic measurements arises from the absolute flux calibrations of the detectors being used. Using the stable X-ray burster, GS 1826-238, and its simultaneous observations by Chandra HE…
Spitzer IRAC Observations of IR Excess in Holmberg IX X-1: A Circumbinary Disk or a Variable Jet?
Roberts, T. P.; Berghea, C. T.; Dudik, R. P. +4 more
We present Spitzer Infrared Array Camera photometric observations of the ultraluminous X-ray source (ULX, X-1) in Holmberg IX. We construct a spectral energy distribution (SED) for Holmberg IX X-1 based on published optical, UV, and X-ray data combined with the IR data from this analysis. We modeled the X-ray and optical data with disk and stellar…
Foreground Bias from Parametric Models of Far-IR Dust Emission
Kogut, A.; Fixsen, D. J.
We use simple toy models of far-IR dust emission to estimate the accuracy to which the polarization of the cosmic microwave background can be recovered using multi-frequency fits, if the parametric form chosen for the fitted dust model differs from the actual dust emission. Commonly used approximations to the far-IR dust spectrum yield CMB residua…
After the Interaction: an Efficiently Star-forming Molecular Disk in NGC 5195
Aalto, Susanne; Nyland, Kristina; Gallagher, John S. +4 more
We present new molecular gas maps of NGC 5195 (alternatively known as M51b) from the Combined Array for Research in Millimeter Astronomy, including 12CO(1-0), 13CO(1-0), CN(1{}{0,2}-{0}{0,1}), CS(2-1), and 3 mm continuum. We also detected HCN(1-0) and HCO+(1-0) using the Onsala Space Observato…
Deep Optical Observations of Unusual Neutron Star Calvera with the GTC
Shibanov, Yury; Danilenko, Andrey; Zharikov, Sergey +2 more
Calvera is an unusual, isolated neutron star with a pure thermal X-ray spectrum typical of central compact objects in supernova remnants. On the other hand, its rotation period and spin-down rate are typical of ordinary rotation-powered pulsars. It was discovered and studied through X-rays, and has not yet been detected in other spectral domains. …
On the Relation between the Mysterious 21 µm Emission Feature of Post-asymptotic Giant Branch Stars and Their Mass-loss Rates
Li, Aigen; Jiang, B. W.; Mishra, Ajay
Over two decades ago, a prominent, mysterious emission band peaking at ∼20.1 µm was serendipitously detected in four preplanetary nebulae (PPNe; also known as “protoplanetary nebulae”). To date, this spectral feature, designated as the “21 µm” feature, has been seen in 27 carbon-rich PPNe in the Milky Way and the Magellanic Clouds. The…
A Star-forming Ring around κ Ori 250 pc from the Sun
Megeath, S. T.; Pillitteri, I.; Wolk, S. J.
X-rays are a powerful probe of activity in early stages of star formation. They allow us to identify young stars even after they have lost the IR signatures of circumstellar disks and provide constraints on their distance. Here, we report on XMM-Newton observations that detect 121 young stellar objects (YSOs) in two fields between L1641 S and κ Or…
A Multiwavelength Characterization of Proto-brown-dwarf Candidates in Serpens
Riaz, B.; Gonzalez-Martin, O.; Caselli, P. +3 more
We present results from a deep submillimeter survey in the Serpens Main and Serpens/G3-G6 clusters, conducted with the Submillimetre Common-User Bolometer Array (SCUBA-2) at the James Clerk Maxwell Telescope. We have combined near- and mid-infrared spectroscopy, Herschel PACS far-infrared photometry, submillimeter continuum, and molecular gas line…
Transverse Velocity Shifts in Protostellar Jets: Rotation or Velocity Asymmetries?
De Colle, Fabio; Riera, Angels; Cerqueira, Adriano H.
Observations of several protostellar jets show systematic differences in radial velocity transverse to the jet propagation direction that have been interpreted as evidence of rotation in the jets. In this paper we discuss the origin of these velocity shifts, and show that they could originate from rotation in the flow, or from side-to-side asymmet…