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in subjects: "Wavelengths Astrophysics,Astro"

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Search for Spatially Extended Fermi-LAT Sources Using Two Years of Data

Spatial extension is an important characteristic for correctly associating {gamma}-ray-emitting sources with their counterparts at other wavelengths and for obtaining an unbiased model of their spectra. We present a new method for quantifying the spatial extension of sources detected by the Large Area Telescope (LAT), the primary science instrument on the Fermi Gamma-ray Space Telescope (Fermi). We perform a series of Monte Carlo simulations to validate this tool and calculate the LAT threshold… more

Date: July 13, 2012

Creator: Lande, Joshua; Ackermann, Markus; Allafort, Alice; Ballet, Jean; Bechtol, Keith; Burnett, Toby et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Status of Identification of VHE Gamma-Ray Sources

With the recent advances made by Cherenkov telescopes such as H.E.S.S. the field of very high-energy (VHE) {gamma}-ray astronomy has recently entered a new era in which for the first time populations of Galactic sources such as e.g. Pulsar wind nebulae (PWNe) or Supernova remnants (SNRs) can be studied. However, while some of the new sources can be associated by positional coincidence as well as by consistent multi-wavelength data to a known counterpart at other wavelengths, most of the sources… more

Date: September 28, 2006

Creator: Funk, Stefan

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

SDSS J131339.98+515128.3: A new GravitationallyLensed Quasar Selected Based on Near-infrared Excess

We report the discovery of a new gravitationally lensed quasar, SDSS J131339.98+515128.3, at a redshift of 1:875 with an image separation of 1: 0024. The lensing galaxy is clearly detected in visible-light follow-up observations. We also identify three absorption-line doublets in the spectra of the lensed quasar images, from which we measure the lens redshift to be 0:194. Like several other known lenses, the lensed quasar images have different continuum slopes. This difference is probably the r… more

Date: September 28, 2007

Creator: Ofek, Eran O.; Oguri, Masamune; Jackson, Neal; Inada, Naohisa & Kayo, Issha

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode As Deflagrations?

We present extensive u{prime}g{prime}r{prime}i{prime} BV RIY JHK{sub s} photometry and optical spectroscopy of SN 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called 'the most peculiar known type Ia supernova'. Both supernovae exhibited high ionization SN 1991T-like pre-maximum spectra, yet low peak luminosities like SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roug… more

Date: November 14, 2006

Creator: Phillips, M. M.; Li, W.; Frieman, J. A.; Blinnikov, S. I.; DePoy, D.; Prieto, J. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The DART Imaging And CaT Survey of the Fornax Dwarf Spheroidal Galaxy

As part of the DART project we have used the ESO/2.2m Wide Field Imager in conjunction with the VLT/FLAMES* GIRAFFE spectrograph to study the detailed properties of the resolved stellar population of the Fornax dwarf spheroidal galaxy out to and beyond its tidal radius. Fornax dSph has had a complicated evolution and contains significant numbers of young, intermediate age and old stars. We investigate the relation between these different components by studying their photometric, kinematic and a… more

Date: August 28, 2006

Creator: Battaglia, Giuseppina; Tolstoy, E.; Helmi, A.; Irwin, M. J.; Letarte, B.; Jablonka, P. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Multiwavelength Monitoring of the Enigmatic Narrow-Line Seyfert 1 PMN J0948 0022 in March-July 2009

Following the recent discovery of {gamma} rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z = 0.5846), we started a multiwavelength campaign from radio to {gamma} rays, which was carried out between the end of 2009 March and the beginning of July. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to {gamma}-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the {gamm… more

Date: March 29, 2012

Creator: Abdo, A. A.; Ackermann, M.; Ajello, M.; Axelsson, M.; Baldini, L.; Ballet, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Principles of X-ray Navigation

X-ray navigation is a new concept in satellite navigation in which orientation, position and time are measured by observing stellar emissions in x-ray wavelengths. X-ray navigation offers the opportunity for a single instrument to be used to measure these parameters autonomously. Furthermore, this concept is not limited to missions in close proximity to the earth. X-ray navigation can be used on a variety of missions from satellites in low earth orbit to spacecraft on interplanetary missions. I… more

Date: March 17, 2006

Creator: Hanson, John Eric

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Gamma-Ray Observations of the Supernova Remnant RX J0852.0-4622 with the Fermi LAT

We report on gamma-ray observations of the supernova remnant (SNR) RX J0852.0-4622 with the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope. In the Fermi LAT data, we find a spatially extended source at the location of the SNR. The extension is consistent with the SNR size seen in other wavelengths such as X-rays and TeV gamma rays, leading to the identification of the gamma-ray source with the SNR. The spectrum is well described as a power law with a photon index of {Lamb… more

Date: December 13, 2011

Creator: Tanaka, T.; Allafort, A.; /Stanford U., HEPL /KIPAC, Menlo Park; Ballet, J.; /Saclay; Funk, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

An Infrared Study of the Large-Scale Jet in Quasar PKS 1136-135

We present Spitzer IRAC imaging of the large-scale jet in the quasar PKS 1136-135 at wavelengths of 3.6 and 5.8 {micro}m, combined with previous VLA, HST, and Chandra observations. We clearly detect infrared emission from the jet, resulting in the most detailed multifrequency data among the jets in lobe-dominated quasars. The spectral energy distributions of the jet knots have significant variations along the jet, like the archetypal jet in 3C 273. The infrared measurements with IRAC are consis… more

Date: March 16, 2007

Creator: Uchiyama, Yasunobu; Urry, C.Megan; Coppi, Paolo; Van Duyne, Jeffrey; Cheung, C. C.; Sambruna, Rita M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Large Synoptic Survey Telescope: From Science Drivers to Reference Design

In the history of astronomy, major advances in our understanding of the Universe have come from dramatic improvements in our ability to accurately measure astronomical quantities. Aided by rapid progress in information technology, current sky surveys are changing the way we view and study the Universe. Next-generation surveys will maintain this revolutionary progress. We focus here on the most ambitious survey currently planned in the visible band, the Large Synoptic Survey Telescope (LSST). LS… more

Date: October 14, 2011

Creator: Ivezic, Z.; Axelrod, T.; Brandt, W. N.; Burke, D. L.; Claver, C. F.; Connolly, A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department