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A Direct Upper Limit on the Density of Cosmological Dust from the Absence of an X-ray Scattering Halo around the z=4.3 QSO 1508+5714
A. O. Petric, G. A. Telis, F. Paerels +1
We report on the results of a search for an intergalactic X-ray dust scattering halo in a deep observation of the bright, high-redshift quasar QSO 1508+5714 with the Chandra X-ray…
A Shell of Thermal X-ray Emission Associated with the Young Crab-like Remnant 3C58
E. V. Gotthelf, D. J. Helfand, L. Newburgh
Deep X-ray imaging spectroscopy of the bright pulsar wind nebula 3C58 confirms the existence of an embedded thermal X-ray shell surrounding the pulsar PSR J0205+6449. Radially reso…
On radio-bright Active Galactic Nuclei in a complete Spectroscopic Redshift Survey
Pietro Reviglio, David J. Helfand
Analysis of the frequency and physical properties of galaxies with star-formation and AGN activity in different environments in the local universe is a cornerstone for understandin…
Signals from the Noise: Image Stacking for Quasars in the FIRST Survey
Richard L. White, David J. Helfand, Robert H. Becker +2
We present a technique to explore the radio sky into the nanoJansky regime by employing image stacking using the FIRST survey. We first discuss the non-intuitive relationship betwe…
Transient pulsed radio emission from a magnetar
Fernando Camilo, Scott Ransom, Jules Halpern +4
Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields…
The Serendipitous Extragalactic X-Ray Source Identification (SEXSI) Program. III. Optical Spectroscopy
Megan E. Eckart, Daniel Stern, David J. Helfand +3
We present the catalog of 477 spectra from the Serendipitous Extragalactic X-ray Source Identification (SEXSI) program, a survey designed to probe the dominant contributors to the…