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The first Fermi-LAT High-energy source catalog (1FHL), containing gamma-ray sources detected above 10 GeV, is an ideal sample to characterize the physical properties of the most extreme gamma-ray sources. We investigate the pc scale…

High Energy Astrophysical Phenomena · Physics 2016-10-19 R. Lico , M. Giroletti , M. Orienti , F. D'Ammando

We report on a recent 90 cm wide-field VLBI survey of two 3.1 deg^2 fields using the VLBA, Westerbork and Jodrell Bank telescopes. In-beam calibration was used to calibrate each field, the process was simplified by imaging the calibrators…

Astrophysics · Physics 2007-05-23 Emil Lenc , Mike A. Garrett , Olaf Wucknitz , James M. Anderson , Steven J. Tingay

We consider standard and extended CMV matrices with small quasi-periodic Verblunsky coefficients and show that on their essential spectrum, all spectral measures are purely absolutely continuous. This answers a question of Barry Simon from…

Spectral Theory · Mathematics 2021-02-02 Long Li , David Damanik , Qi Zhou

We propose a novel statistical method to extend Fermi-LAT catalogues of high-latitude $\gamma$-ray sources below their nominal threshold. To do so, we rely on a recent determination of the differential source-count distribution of…

High Energy Astrophysical Phenomena · Physics 2024-05-16 Aurelio Amerio , Francesca Calore , Pasquale Dario Serpico , Bryan Zaldivar

An international project is underway to design and build a radio telescope with an effective collecting area two orders of magnitude greater than the largest existing instruments. One of the many scientific goals of this instrument will be…

Astrophysics · Physics 2009-09-25 A. Hopkins , R. Windhorst , L. Cram , R. Ekers

We present light curves for 149 sources monitored with the Green Bank Interferometer. The light curves are at two radio frequencies (approximately 2.5 and 8.2 GHz) and range from 3 to 15 yrs in length, covering the interval 1979--1996, and…

From an on-going survey of the Galactic bulge, we have discovered a number of compact, steep spectrum radio sources. In this present study we have carried out more detailed observations for two of these sources, located 43 arcmin and 12.7…

High Energy Astrophysical Phenomena · Physics 2021-07-21 S. D. Hyman , D. A. Frail , J. S. Deneva , N. E. Kassim , S. Giacintucci , J. E. Kooi , T. J. W. Lazio , I. Joyner , W. M. Peters , V. Gajjar , A. P. V. Siemion

A large number of deep and wide-field radio interferometric surveys are being designed to measure accurate statistics of faint source populations. Most require mosaic observations, and expect to benefit from the sensitivity provided by…

Instrumentation and Methods for Astrophysics · Physics 2014-03-21 Urvashi Rau , Sanjay Bhatnagar , Frazer N. Owen

Nowadays, compact sources like surfaces of nearby stars, circumstellar environments of stars from early stages to the most evolved ones and surroundings of active galactic nuclei can be investigated at milli-arcsecond scales only with the…

We use archival data from the Phoenix Deep Survey to investigate the variable radio source population above 1mJy/beam at 1.4GHz. Given the similarity of this survey to other such surveys we take the opportunity to investigate the…

Astrophysics of Galaxies · Physics 2016-08-03 Paul Hancock , Jason Drury , Martin Bell , Tara Murphy , Bryan Gaensler

We describe a program to identify optical counterparts to radio sources from the VLA FIRST survey using the Cambridge APM scans of the POSS-I plates. We use radio observations covering 4150 square degrees of the north Galactic cap to a 20…

Astrophysics · Physics 2009-11-07 Richard G. McMahon , Richard L. White , David J. Helfand , Robert H. Becker

In a previous paper, we proposed a new method to select low-power BL Lacs (LPBLs) based on mid-infrared emission and flux contrast through the Ca II spectral break; that study led to the selection of a complete sample formed by 34 LPBLs…

Astrophysics of Galaxies · Physics 2016-02-17 Claudia M. Raiteri , Alessandro Capetti

High red-shift radio galaxies are best searched at low radio frequencies, due to its steep radio spectra. Here we present preliminary results from our programme to search for high red-shift radio galaxies to ~ 10 to 100 times fainter than…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-30 Susanta Kumar Bisoi , C. H. Ishwara-Chandra , S. K. Sirothia , P. Janardhan

A compact steep spectrum radio source (J0535-0452) is located in the sky coincident with a bright optical rim in the HII region NGC1977. J0535-0452 is observed to be $\leq 100$ mas in angular size at 8.44 GHz. The spectrum for the radio…

Astrophysics of Galaxies · Physics 2012-09-17 D. Anish Roshi , Scott M. Ransom

We cross-identified the ROSAT Bright Source Catalog (RBSC) and the NRAO VLA Sky Survey (NVSS) to construct the RBSC-NVSS sample of the brightest X-ray sources (>= 0.1 counts/s or ~1E-12 ergs/cm/cm/s in the 0.1-2.4 keV band) that are also…

Astrophysics · Physics 2009-10-31 F. E. Bauer , J. J. Condon , T. X. Thuan , J. J. Broderick

We present here the results of a 325 MHz radio survey of M31, conducted with the A-configuration of the Very Large Array. The survey covered an area of 7.6 deg$^2$, and a total of 405 radio sources between $\la$6\arcsec and 170\arcsec in…

Astrophysics · Physics 2009-11-10 Joseph D. Gelfand , T. Joseph W. Lazio , B. M. Gaensler

Compact Steep Spectrum (CSS) sources are powerful extragalactic radio sources with angular dimensions of the order of a few arcseconds or less. Such a compactness is apparently linked to the youth of these objects. The majority of CSSs…

Astrophysics · Physics 2009-11-07 M. Kunert , A. Marecki , R. E. Spencer , A. J. Kus , J. Niezgoda

The Local Volume Mapper (LVM) project is one of three surveys that form the Sloan Digital Sky Survey V. It will map the interstellar gas emission in a large fraction of the southern sky using wide-field integral field spectroscopy. Four…

The radio properties of hard (2-8keV) X-ray selected sources are explored by combining a single 50ks XMM-Newton pointing with the ultra-deep and homogeneous Phoenix radio (1.4GHz) survey (Hopkins et al. 2003). A total of 43 sources are…

Astrophysics · Physics 2009-11-10 A. Georgakakis , A. M. Hopkins , J. Afonso , M. Sullivan , B. Mobasher , L. E. Cram

To fully exploit the scientific potential of the Fermi mission, we initiated the F-GAMMA program. Between 2007 and 2015 it was the prime provider of complementary multi-frequency monitoring in the radio regime. We quantify the radio…