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40
Sep 18, 2013
09/13
by
F. Massaro; M. Ajello
texts
eye 40
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The recent discovery of the gamma-ray emission from the lobes of the closest radio galaxy Centaurus A by Fermi implies the presence of high-energy electrons at least up to gamma ~ 10^5 - 10^6. These high-energy electrons are required to interpret the observed gamma-ray radiation in terms of inverse Compton emission off the cosmic microwave background (IC/CMB); the widely accepted scenario to describe the X-ray emission of radio galaxy lobes. In this Letter, we consider the giant radio lobes of...
Source: http://arxiv.org/abs/1102.0774v1
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31
Sep 19, 2013
09/13
by
R. Voss; M. Ajello
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eye 31
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We study the populations of X-ray sources in the Milky Way in the 15-55 keV band using a deep survey with the BAT instrument aboard the Swift observatory. We present the logN-logS distributions of the various source types and we analyze their variability and spectra. For the low-mass X-ray binaries (LMXBs) and the high-mass X-ray binaries (HMXBs) we derive the luminosity functions to a limiting luminosity of L_X~7 times10^{34} erg s/s. Our results confirm the previously found flattening of the...
Source: http://arxiv.org/abs/1009.1397v1
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104
Sep 21, 2013
09/13
by
J. Singal; V. Petrosian; M. Ajello
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eye 104
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We present a determination of the distributions of photon spectral index and gamma-ray flux - the so called LogN-LogS relation - for the 352 blazars detected with a greater than approximately seven sigma detection threshold and located above +/- 20 degrees Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true LogN-LogS...
Source: http://arxiv.org/abs/1106.3111v4
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135
Sep 23, 2013
09/13
by
G. Sala; J. Greiner; M. Ajello; N. Primak
texts
eye 135
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On 28 February 2007 a new outburst of the previously known transient source XTE J1856+053 was detected with RXTE/ASM. We present here the results of an XMM-Newton (0.5-10.0 keV) Target of Opportunity observation performed on 14 March 2007, aimed at constraining the mass of the compact object in this X-ray binary and determining its main properties. The EPIC-pn camera was used in Timing mode and its spectrum fit together with the RGS data. IR observations with GROND at the 2.2 m telescope in La...
Source: http://arxiv.org/abs/0810.1523v1
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86
Sep 21, 2013
09/13
by
M. D. Caballero-Garcia; I. E. Papadakis; F. Nicastro; M. Ajello
texts
eye 86
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Aims: We used data from the 58 month long, continuous Swift/Burst Alert Telescope (BAT) observations of the five brightest Seyfert galaxies at hard X-rays, to study their flux and spectral variability in the 20-100 keV energy band. The column density in these objects is less than 10^24 cm-2, which implies that the Swift/BAT data allow us to study the "true" variability of the central source. Results: All objects show significant variations, with an amplitude which is similar to the...
Source: http://arxiv.org/abs/1108.6017v2
114
114
Jul 20, 2013
07/13
by
M. Di Mauro; F. Calore; F. Donato; M. Ajello; L. Latronico
texts
eye 114
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Active galactic nuclei (AGN) with jets seen at small viewing angles are the most luminous and abundant objects in the $\gamma$-ray sky. AGN with jets misaligned along the line-of-sight appear fainter in the sky, but are more numerous than the brighter blazars. We calculate the diffuse $\gamma$-ray emission due to the population of misaligned AGN (MAGN) unresolved by the Large Area Telescope (LAT) on the {\it Fermi} Gamma-ray Space Telescope ({\it Fermi}). A correlation between the $\gamma$-ray...
Source: http://arxiv.org/abs/1304.0908v1
103
103
Jul 20, 2013
07/13
by
F. Massaro; R. D'Abrusco; M. Ajello; J. E. Grindlay; Howard A. Smith
texts
eye 103
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Blazars constitute the most interesting and enigmatic class of extragalactic gamma-ray sources dominated by non-thermal emission. In this Letter, we show how the WISE infrared data make possible to identify a distinct region of the [3.4]-[4.6]-[12] micron color-color diagram where the sources dominated by the the thermal radiation are separated from those dominated by non-thermal emission, in particular the blazar population. This infrared non-thermal region delineated as the WISE Blazar Strip...
Source: http://arxiv.org/abs/1203.0304v1
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55
Sep 23, 2013
09/13
by
D. Burlon; M. Ajello; J. Greiner; A. Comastri; A. Merloni; N. Gehrels; .
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eye 55
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It is well accepted that unabsorbed as well as absorbed AGN are needed to explain the nature and the shape of the Cosmic X-ray background, even if the fraction of highly absorbed objects (dubbed Compton-thick sources) substantially still escapes detection. We derive and analyze the absorption distribution using a complete sample of AGN detected by Swift-BAT in the first three years of the survey. The fraction of Compton-thick AGN represents only 4.6% of the total AGN population detected by...
Source: http://arxiv.org/abs/1012.0302v1
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64
Jul 20, 2013
07/13
by
D. Burlon; G. Ghirlanda; T. Murphy; R. Chhetri; E. Sadler; M. Ajello
texts
eye 64
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We cross-matched the 6-year Swift/Burst Alert Telescope (BAT) survey of active galactic nuclei (AGN) with the AT20G radio survey of the southern sky, which is one of the largest high-frequency radio surveys available. With these data we investigated the possible correlation between the radio and the X-ray emission at the highest radio and X-ray frequencies. We found 37 AGN with a high probability of association (>80 per cent), among which 19 are local Seyfert galaxies (with median redshift z...
Source: http://arxiv.org/abs/1304.1258v1
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87
Jul 20, 2013
07/13
by
F. Massaro; R. D'Abrusco; G. Tosti; M. Ajello; A. Paggi. D. Gasparrini
texts
eye 87
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One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified gamma-ray sources (UGSs). Despite the large improvements of Fermi in the localization of gamma-ray sources with respect to the past gamma-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-Field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic...
Source: http://arxiv.org/abs/1203.3801v1
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53
Sep 17, 2013
09/13
by
R. M. Sambruna; D. Donato; M. Ajello; L. Maraschi; the GSFC BAT Team
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eye 53
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Using public \fermi LAT and \swift BAT observations, we constructed the first sample of blazars selected at both hard X-rays and gamma-rays. Studying its spectral properties, we find a luminosity dependence of the spectral slopes at both energies. Specifically, luminous blazars, generally classified as FSRQs, have {\it hard} continua in the medium-hard X-ray range but {\it soft} continua in the LAT gamma-ray range (photon indices $\Gamma_X$ \ltsima 2 and $\Gamma_G$ \gtsima 2), while lower...
Source: http://arxiv.org/abs/0912.2721v1
13
13
Jun 27, 2018
06/18
by
M. Ajello; A. Domínguez; D. Gasparrini; S. Cutini; for the Fermi-LAT Collaboration
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eye 13
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The {\it Fermi} Large Area Telescope (LAT) has been routinely gathering science data since August 2008, surveying the full sky every three hours. The first Fermi-LAT catalog of sources detected above 10 GeV (1FHL) relied on three years of data to characterize the $>$10 GeV sky. The improved acceptance and point-spread function of the new Pass 8 event reconstruction and classification together with six years of observations now available allow the detection and characterization of sources...
Topics: High Energy Astrophysical Phenomena, Astrophysics
Source: http://arxiv.org/abs/1503.02664
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98
Jul 19, 2013
07/13
by
N. Cappelluti; M. Ajello; D. Burlon; M. Krumpe; T. Miyaji; S. Bonoli; J. Greiner
texts
eye 98
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We present the clustering measurement of hard X-ray selected AGN in the local Universe. We used a sample of 199 sources spectroscopically confirmed detected by Swift-BAT in its 15-55 keV all-sky survey. We measured the real space projected auto-correlation function and detected a signal significant on projected scales lower than 200 Mpc/h. We measured a correlation length of r0=5.56+0.49-0.43 Mpc/h and a slope {\gamma}=1.64-0.08 -0.07. We also measured the auto-correlation function of Type I...
Source: http://arxiv.org/abs/1005.4968v1
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7.0
Jun 27, 2018
06/18
by
M. Orienti; F. D'Ammando; M. Giroletti; D. Dallacasa; T. Venturi; J. Finke; M. Ajello
texts
eye 7
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High redshift blazars are among the most powerful objects in the Universe. Although they represent a significant fraction of the extragalactic hard X-ray sky, they are not commonly detected in gamma-rays. High redshift (z>2) objects represent
Topics: High Energy Astrophysical Phenomena, Astrophysics
Source: http://arxiv.org/abs/1503.00480
3
3.0
Jun 30, 2018
06/18
by
M. Orienti; F. D'Ammando; M. Giroletti; J. Finke; M. Ajello; D. Dallacasa; T. Venturi
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eye 3
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We report results of a multiband monitoring campaign of the flat spectrum radio quasar TXS 0536+145 at redshift 2.69. This source was detected during a very high gamma-ray activity state in 2012 March by the Large Area Telescope on board Fermi, becoming the gamma-ray flaring blazar at the highest redshift detected so far. At the peak of the flare the source reached an apparent isotropic gamma-ray luminosity of 6.6 x 10^49 erg/s which is comparable to the values achieved by the most luminous...
Topics: High Energy Astrophysical Phenomena, Astrophysics
Source: http://arxiv.org/abs/1409.0392
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68
Sep 21, 2013
09/13
by
M. Ajello; J. Greiner; G. Kanbach; A. Rau; A. W. Strong; J. A. Kennea
texts
eye 68
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We applied the Maximum Likelihood method, as an image reconstruction algorithm, to the BAT X-ray Survey (BXS). This method was specifically designed to preserve the full statistical information in the data and to avoid mosaicking of many exposures with different pointing directions, thus reducing systematic errors when co-adding images. We reconstructed, in the 14-170 keV energy band, the image of a 90x90 deg$^2$ sky region, centered on (RA,DEC)=105$^{\circ}$,-25$^{\circ}$, which BAT surveyed...
Source: http://arxiv.org/abs/0712.2885v1
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124
Jul 20, 2013
07/13
by
R. D'Abrusco; F. Massaro. M. Ajello; J. E. Grindlay; H. A. Smith; G. Tosti
texts
eye 124
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Blazars constitute the most enigmatic class of extragalactic gamma-ray sources, and their observational features have been ascribed to a relativistic jet closely aligned to the line of sight. They are generally divided in two main classes: the BL Lac objects (BL Lacs) and the Flat Spectrum Radio Quasars (FSRQs). In the case of BL Lacs the double bumped spectral energy distribution (SED) is generally described by the Synchrotron Self Compton (SSC) emission, while for the FSRQs it is interpreted...
Source: http://arxiv.org/abs/1203.0568v1
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51
Sep 23, 2013
09/13
by
M. Ajello; D. M. Alexander; J. Greiner; G. M. Madejski; N. Gehrels; D. Burlon
texts
eye 51
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Surveys above 10 keV represent one of the the best resources to provide an unbiased census of the population of Active Galactic Nuclei (AGN). We present the results of 60 months of observation of the hard X-ray sky with Swift/BAT. In this timeframe, BAT detected (in the 15--55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGN, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of \sim2 larger over similarly complete sets of...
Source: http://arxiv.org/abs/1202.3137v1
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62
Sep 19, 2013
09/13
by
M. Ajello; P. Rebusco; N. Cappelluti; O. Reimer; H. Boehringer; V. La Parola; G. Cusumano
texts
eye 62
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We report on the discovery of 10 additional galaxy clusters detected in the ongoing Swift/BAT all-sky survey. Among the newly BAT-discovered clusters there are: Bullet, Abell 85, Norma, and PKS 0745-19. Norma is the only cluster, among those presented here, which is resolved by BAT. For all the clusters we perform a detailed spectral analysis using XMM-Newton and Swift/BAT data to investigate the presence of a hard (non-thermal) X-ray excess. We find that in most cases the clusters' emission in...
Source: http://arxiv.org/abs/1009.4699v1
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52
Jul 20, 2013
07/13
by
A. Rau; E. O. Ofek; S. R. Kulkarni; B. F. Madore; O. Pevunova; M. Ajello
texts
eye 52
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The luminosity gap between novae (M_R < -10) and supernovae (M_R > -14) is well known since the pioneering research of Zwicky and Hubble. Nearby galaxy clusters and concentrations offer an excellent opportunity to search for explosions brighter than classical novae and fainter than supernovae. Here, we present the results of a B-band survey of 23 member galaxies of the Fornax cluster, performed at the Las Campanas 2.5-m Irene duPont telescope. Observations with a cadence of 32 minutes...
Source: http://arxiv.org/abs/0804.4482v2
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80
Sep 23, 2013
09/13
by
F. Volpe; S. Ohm; M. Hauser; S. Kaufmann; L. Gérard; L. Costamante; S. Fegan; M. Ajello
texts
eye 80
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The high energy peaked BL Lac (HBL) object 1ES 0414+009 (z=0.287) is a distant very high-energy (VHE, E > 100 GeV) blazars with well-determined redshift. This source was detected with the High Energy Stereoscopic System (H.E.S.S.) between October 2005 and September 2009. It was also detected with the Fermi Large Area Telescope (LAT) in 21 months of data. The combined high energy (HE) and VHE spectra, once corrected for gamma-gamma absorption on the extragalactic background light (EBL),...
Source: http://arxiv.org/abs/1105.5114v1
107
107
Jul 20, 2013
07/13
by
F. Massaro; R. D'Abrusco; G. Tosti; M. Ajello; D. Gasparrini; J. E. Grindlay; Howard A. Smith
texts
eye 107
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Despite the large number of discoveries made recently by Fermi, the origins of the so called unidentified gamma-ray sources remain unknown. The large number of these sources suggests that among them there could be a population that significantly contributes to the isotropic gamma-ray background and is therefore crucial to understand their nature. The first step toward a complete comprehension of the unidentified gamma-ray source population is to identify those that can be associated with...
Source: http://arxiv.org/abs/1203.1330v1
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42
Sep 19, 2013
09/13
by
E. Bottacini; M. Böttcher; P. Schady; A. Rau; X. -L. Zhang; M. Ajello; C. Fendt; J. Greiner
texts
eye 42
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1ES 1959+650 is one of the most remarkable high-peaked BL Lacertae objects (HBL). In 2002, it exhibited a TeV gamma-ray flare without a similar brightening of the synchrotron component at lower energies. We present the results of a multifrequency campaign, triggered by the INTEGRAL IBIS detection of 1ES 1959+650. Our data range from the optical to hard X-ray energies, thus covering the synchrotron and inverse-Compton components simultaneously. We observed the source with INTEGRAL, the Swift...
Source: http://arxiv.org/abs/1010.3259v1
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68
Sep 18, 2013
09/13
by
M. Ajello; P. Rebusco; N. Cappelluti; O. Reimer; H. Boehringer; J. Greiner; N. Gehrels; J. Tueller; A. Moretti
texts
eye 68
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We report about the detection of 10 clusters of galaxies in the ongoing Swift/BAT all-sky survey. This sample, which comprises mostly merging clusters, was serendipitously detected in the 15--55 keV band. We use the BAT sample to investigate the presence of excess hard X-rays above the thermal emission. The BAT clusters do not show significant (e.g. >2 $\sigma$) non-thermal hard X-ray emission. The only exception is represented by Perseus whose high-energy emission is likely due to NGC 1275....
Source: http://arxiv.org/abs/0809.0006v1
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55
Sep 24, 2013
09/13
by
G. Lanzuisi; A. De Rosa; G. Ghisellini; P. Ubertini; F. Panessa; M. Ajello; L. Bassani; Y. Fukazawa; F. D'Ammando
texts
eye 55
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We present new Suzaku and Fermi data, and re-analyzed archival hard X-ray data from INTEGRAL and Swift-BAT survey, to investigate the physical properties of the luminous, high-redshift, hard X-ray selected blazar IGR J22517+2217, through the modelization of its broad band spectral energy distribution (SED) in two different activity states. Through the analysis of the new Suzaku data and the flux selected data from archival hard X-ray observations, we build the source SED in two different...
Source: http://arxiv.org/abs/1112.0472v1
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6.0
Jun 29, 2018
06/18
by
A. Kaur; A. Rau; M. Ajello; J. Greiner; D. H. Hartmann; V. S. Paliya; A. Dominguez; J. Bolmer; P. Schady
texts
eye 6
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Determining redshifts for BL Lacertae (BL Lac) objects using the traditional spectroscopic method is challenging due to the absence of strong emission lines in their optical spectra. We employ the photometric dropout technique to determine redshifts for this class of blazars using the combined 13 broad-band filters from Swift-UVOT and the multi-channel imager GROND at the MPG 2.2 m telescope at ESO's La Silla Observatory. The wavelength range covered by these 13 filters extends from far...
Topics: Astrophysics, High Energy Astrophysical Phenomena
Source: http://arxiv.org/abs/1611.03878
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67
Sep 21, 2013
09/13
by
N. Cappelluti; M. Ajello; P. Rebusco; S. Komossa; A. Bongiorno; C. Clemens; M. Salvato; P. Esquej; T. Aldcroft; J. Greiner; H. Quintana
texts
eye 67
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Tidal disruption events are possible sources of temporary nuclear activity in galactic nuclei and can be considered as good indicators of the existence of super massive black holes in the centers of galaxies. A new X-ray source has been serendipitously detected with ROSAT in a PSPC pointed observation of the galaxy cluster A3571. Given the strong flux decay of the object in subsequent detections, the tidal disruption scenario is investigated as possible explanationof the event. We followed up...
Source: http://arxiv.org/abs/0901.3357v2
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56
Sep 21, 2013
09/13
by
M. Ajello; A. Rau; J. Greiner; G. Kanbach; M. Salvato; A. W. Strong; S. D. Barthelmy; N. Gehrels; C. B. Markwardt; J. Tueller
texts
eye 56
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In this concluding part of the series of three papers dedicated to the Swift/BAT hard X-ray survey (BXS), we focus on the X-ray spectral analysis and statistical properties of the source sample. Using a dedicated method to extract time-averaged spectra of BAT sources we show that Galactic sources have, generally, softer spectra than extragalactic objects and that Seyfert 2 galaxies are harder than Seyfert 1s. The averaged spectrum of all Seyfert galaxies is consistent with a power-law with...
Source: http://arxiv.org/abs/0709.4333v1
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49
Jul 20, 2013
07/13
by
S. Komossa; H. Zhou; T. Wang; M. Ajello; J. Ge; J. Greiner; H. Lu; M. Salvato; R. Saxton; H. Shan; D. Xu; W. Yuan
texts
eye 49
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We report the discovery of superstrong, fading, high-ionization iron line emission in the galaxy SDSSJ095209.56+214313.3 (SDSSJ0952+2143 hereafter), which must have been caused by an X-ray outburst of large amplitude. SDSSJ0952+2143 is unique in its strong multiwavelength variability; such a broadband emission-line and continuum response has not been observed before. The strong iron line emission is accompanied by unusual Balmer line emission with a broad base, narrow core and double-peaked...
Source: http://arxiv.org/abs/0804.2670v1
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49
Sep 21, 2013
09/13
by
M. Ajello; J. Greiner; G. Sato; D. R. Willis; G. Kanbach; A. W. Strong; R. Diehl; G. Hasinger; N. Gehrels; C. B. Markwardt; J. Tueller
texts
eye 49
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We use Swift/BAT Earth occultation data at different geomagnetic latitudes to derive a sensitive measurement of the Cosmic X-ray background (CXB) and of the Earth albedo emission in the 15--200 keV band. We compare our CXB spectrum with recent (INTEGRAL, BeppoSAX) and past results (HEAO-1) and find good agreement. Using an independent measurement of the CXB spectrum we are able to confirm our results. This study shows that the BAT CXB spectrum has a normalization ~8(+/-3)% larger than the...
Source: http://arxiv.org/abs/0808.3377v1
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44
Sep 19, 2013
09/13
by
E. Bottacini; M. Ajello; J. Greiner; E. Pian; A. Rau; E. Palazzi; S. Covin; G. Ghisellini; T. Krühler; A. Küpcü Yoldas; N. Cappelluti; P. Afonso
texts
eye 44
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We present the results of a multifrequency campaign on the high-redshift (z = 3.1) blazar PKS 0537-286. The source was observed at different epochs from 2006 to 2008 with INTEGRAL and Swift, and nearly simultaneously with ground-based near-IR/optical telescopes. The SEDs are compatible with a model based on synchrotron radiation and external inverse Compton scattering. The campaign gives an insight into the physical environment of the blazar.
Source: http://arxiv.org/abs/0910.2463v1
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45
Sep 21, 2013
09/13
by
M. Ajello; L. Costamante; R. M. Sambruna; N. Gehrels; J. Chiang; A. Rau; A. Escala; J. Greiner; J. Tueller; J. V. Wall; R. F. Mushotzky
texts
eye 45
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We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03
Source: http://arxiv.org/abs/0905.0472v1
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47
Sep 21, 2013
09/13
by
S. Komossa; H. Zhou; A. Rau; M. Dopita; A. Gal-Yam; J. Greiner; J. Zuther; M. Salvato; D. Xu; H. Lu; R. Saxton; M. Ajello
texts
eye 47
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The galaxy SDSSJ0952+2143 showed remarkable emission-line properties first reported in 2008 (paper I), which are the consequence of a powerful high-energy flare. Here we report follow-up observations of SDSSJ0952+2143, and discuss outburst scenarios in terms of stellar tidal disruption by a SMBH, peculiar variability of an AGN, and a supernova explosion. The optical spectrum of SDSSJ0952+2143 exhibits several peculiarities: an exceptional ratio of [FeVII] transitions over [OIII], a dramatic...
Source: http://arxiv.org/abs/0902.3248v2
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4.0
Jun 30, 2018
06/18
by
L. Marcotulli; V. S. Paliya; M. Ajello; A. Kaur; D. H. Hartmann; D. Gasparrini; J. Greiner; A. Rau; P. Schady; M. Balokovic; D. Stern; G. Madejski
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eye 4
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The most powerful sources among the blazar family are MeV blazars. Often detected at $z>2$, they usually display high X- and \gm-ray luminosities, larger-than-average jet powers and black hole masses $\gtrsim 10^9 M_{\odot}$. In the present work we perform a multiwavelength study of three high redshift blazars: 3FGL J0325.5+2223 ($z=2.06$), 3FGL J0449.0+1121 ($z= 2.15$), and 3FGL J0453.2$-$2808 ($z=2.56$), analysing quasi simultaneous data from GROND, \swift-UVOT and XRT, \nustar, and...
Topics: Astrophysics, High Energy Astrophysical Phenomena
Source: http://arxiv.org/abs/1703.10657
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54
Sep 23, 2013
09/13
by
M. Ajello; M. S. Shaw; R. W. Romani; C. D. Dermer; L. Costamante; O. G. King; W. Max-Moerbeck; A. Readhead; A. Reimer; J. L. Richards; M. Stevenson
texts
eye 54
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Fermi has provided the largest sample of {\gamma}-ray selected blazars to date. In this work we use a complete sample of FSRQs detected during the first year of operation to determine the luminosity function (LF) and its evolution with cosmic time. The number density of FSRQs grows dramatically up to redshift \sim0.5-2.0 and declines thereafter. The redshift of the peak in the density is luminosity dependent, with more luminous sources peaking at earlier times; thus the LF of {\gamma}-ray FSRQs...
Source: http://arxiv.org/abs/1110.3787v1
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53
Sep 22, 2013
09/13
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J. Greiner; T. Krühler; S. McBreen; M. Ajello; D. Giannos; R. Schwarz; S. Savaglio; A. Küpcü Yoldas; C. Clemens; A. Stefanescu; G. Sala; F. Bertoldi; G. Szokoly; S. Klose
texts
eye 53
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We report on GROND observations of a 40 sec duration (rest-frame) optical flare from GRB 080129 at redshift 4.349. The rise- and decay time follow a power law with indices +12 and -8, respectively, inconsistent with a reverse shock and a factor 10$^5$ faster than variability caused by ISM interaction. While optical flares have been seen in the past (e.g. GRB 990123, 041219B, 060111B and 080319B), for the first time, our observations not only resolve the optical flare into sub-components, but...
Source: http://arxiv.org/abs/0811.4291v1
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25
Jun 26, 2018
06/18
by
M. Ajello; D. Gasparrini; M. Sanchez-Conde; G. Zaharijas; M. Gustafsson; J. Cohen-Tanugi; C. D. Dermer; Y. Inoue; D. Hartmann; M. Ackermann; K. Bechtol; A. Franckowiak; A. Reimer; R. W. Romani; A. W. Strong
texts
eye 25
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The origin of the extragalactic $\gamma$-ray background (EGB) has been debated for some time. { The EGB comprises the $\gamma$-ray emission from resolved and unresolved extragalactic sources, such as blazars, star-forming galaxies and radio galaxies, as well as radiation from truly diffuse processes.} This letter focuses on the blazar source class, the most numerous detected population, and presents an updated luminosity function and spectral energy distribution model consistent with the blazar...
Topics: High Energy Astrophysical Phenomena, Astrophysics, Cosmology and Nongalactic Astrophysics
Source: http://arxiv.org/abs/1501.05301
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58
Sep 22, 2013
09/13
by
A. Moretti; C. Pagani; G. Cusumano; S. Campana; M. Perri; A. Abbey; M. Ajello; A. P. Beardmore; D. Burrows; G. Chincarini; O. Godet; C. Guidorzi; J. E. Hill; J. Kennea; J. Nousek; J. P. Osborne; G. Tagliaferri
texts
eye 58
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We present a new measurement of the cosmic X-ray background (CXRB) in the 1.5-7 keV energy band, performed by exploiting the Swift X-ray telescope (XRT) data archive. We also present a CXRB spectral model in a wider energy band (1.5-200 keV), obtained by combining these data with the recently published Swift-BAT measurement. From the XRT archive we collect a complete sample of 126 high Galactic latitude gamma-ray burst (GRB) follow-up observations. This provides a total exposure of 7.5 Ms and a...
Source: http://arxiv.org/abs/0811.1444v2
15
15
Jun 28, 2018
06/18
by
A. A. Moiseev; M. Ajello; J. H. Buckley; R. Caputo; E. C. Ferrara; D. H. Hartmann; E. Hays; J. E. McEnery; J. W. Mitchell; R. Ojha; J. S. Perkins; J. L. Racusin; A. W. Smith; D. J. Thompson
texts
eye 15
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The gamma-ray energy range from a few hundred keV to a few hundred MeV has remained largely unexplored, mainly due to the challenging nature of the measurements, since the pi- oneering, but limited, observations by COMPTEL on the Compton Gamma-Ray Observatory (1991-2000). This energy range is a transition region between thermal and nonthermal processes, and accurate measurements are critical for answering a broad range of astrophysical questions. We are developing a MIDEX-scale wide-aperture...
Topics: High Energy Astrophysical Phenomena, Instrumentation and Methods for Astrophysics, Astrophysics
Source: http://arxiv.org/abs/1508.07349
53
53
Sep 22, 2013
09/13
by
G. G. Lichti; E. Bottacini; M. Ajello; P. Charlot; W. Collmar; A. Falcone; D. Horan; S. Huber; A. von Kienlin; A. Lähteenmäki; E. Lindfors; D. Morris; K. Nilsson; D. Petry; M. Rüger; A. Sillanpää; F. Spanier; M. Tornikoski
texts
eye 53
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We report the results of a multi-wavelength campaign on the blazar Mrk 421 during outburst. We observed four strong flares at X-ray energies that were not seen at other wavelengths (partially because of missing data). From the fastest rise in the X-rays, an upper limit could be derived on the extension of the emission region. A time lag between high-energy and low-energy X-rays was observed, which allowed an estimation of the magnetic-field strength. The spectral analysis of the X-rays revealed...
Source: http://arxiv.org/abs/0805.2577v1
75
75
Jul 20, 2013
07/13
by
W. McConville; L. Ostorero; R. Moderski; Ł. Stawarz; C. C. Cheung; M. Ajello; A. Bouvier; J. Bregeon; D. Donato; J. Finke; A. Furniss; J. E. McEnery; M. E. Monzani; M. Orienti; L. C. Reyes; A. Rossetti; D. A. Williams
texts
eye 75
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We report Fermi/LAT observations and broad-band spectral modeling of the radio-loud active galaxy 4C +55.17 (z=0.896), formally classified as a flat-spectrum radio quasar. Using 19 months of all-sky survey Fermi/LAT data, we detect a gamma-ray continuum extending up to an observed energy of 145 GeV, and furthermore we find no evidence of gamma-ray variability in the source over its observed history. We illustrate the implications of these results in two different domains. First, we investigate...
Source: http://arxiv.org/abs/1107.1471v1
55
55
Sep 24, 2013
09/13
by
Arne Rau; P. Schady; J. Greiner; M. Salvato; M. Ajello; E. Bottacini; N. Gehrels; P. M. J. Afonso; J. Elliott; R. Filgas; D. A. Kann; S. Klose; Thomas Kruehler; M. Nardini; A. Nicuesa Guelbenzu; F. Olivares E.; A. Rossi; V. Sudilovsky; A. C. Updike; D. H. Hartmann
texts
eye 55
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Observations of the gamma-ray sky with Fermi led to significant advances towards understanding blazars, the most extreme class of Active Galactic Nuclei. A large fraction of the population detected by Fermi is formed by BL Lacertae (BL Lac) objects, whose sample has always suffered from a severe redshift incompleteness due to the quasi-featureless optical spectra. Our goal is to provide a significant increase of the number of confirmed high-redshift BL Lac objects contained in the 2 LAC...
Source: http://arxiv.org/abs/1112.0025v2
35
35
Sep 22, 2013
09/13
by
F. D'Ammando; E. Antolini; G. Tosti; J. Finke; S. Ciprini; S. Larsson; M. Ajello; S. Covino; D. Gasparrini; M. Gurwell; M. Hauser; P. Romano; F. Schinzel; S. J. Wagner; D. Impiombato; M. Perri; M. Persic; E. Pian; G. Polenta; B. Sbarufatti; A. Treves; S. Vercellone; A. Wehrle; A. Zook
texts
eye 35
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We report on multiwavelength observations of the blazar PKS 0537-441 (z = 0.896) obtained from microwaves through gamma rays by SMA, REM, ATOM, Swift and Fermi during 2008 August-2010 April. Strong variability has been observed in gamma rays, with two major flaring episodes (2009 July and 2010 March) and a harder-when-brighter behaviour, quite common for FSRQs and low-synchrotron-peaked BL Lacs, in 2010 March. In the same way the SED of the source cannot be modelled by a simple synchrotron...
Source: http://arxiv.org/abs/1302.5439v2
3
3.0
Jun 29, 2018
06/18
by
M. Ajello; G. Ghisellini; V. S. Paliya; D. Kocevski; G. Tagliaferri; G. Madejski; A. Rau; P. Schady; J. Greiner; F. Massaro; M. Bakolovic; R. Buehler; M. Giomi; L. Marcotulli; F. D'Ammando; D. Stern; S. E. Boggs; F. E. Christensen; W. W. Craig; C. J. Hailey; F. A. Harrison; W. W. Zhang
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eye 3
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MeV blazars are a sub--population of the blazar family, exhibiting larger--than--average jet powers, accretion luminosities and black hole masses. Because of their extremely hard X--ray continua, these objects are best studied in the X-ray domain. Here, we report on the discovery by the $Fermi$ Large Area Telescope and subsequent follow-up observations with $NuSTAR$, $Swift$ and GROND of a new member of the MeV blazar family: PMN J0641$-$0320. Our optical spectroscopy provides confirmation that...
Topics: Astrophysics, High Energy Astrophysical Phenomena, Cosmology and Nongalactic Astrophysics
Source: http://arxiv.org/abs/1602.06446
37
37
Sep 22, 2013
09/13
by
J. Vandenbroucke; R. Buehler; M. Ajello; K. Bechtol; A. Bellini; M. Bolte; C. C. Cheung; F. Civano; D. Donato; L. Fuhrmann; S. Funk; S. E. Healey; A. B. Hill; C. Knigge; G. M. Madejski; R. W. Romani; M. Santander-García; M. S. Shaw; D. Steeghs; M. A. P. Torres; A. Van Etten; K. A. Williams
texts
eye 37
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The \emph{Fermi} Large Area Telescope (LAT) discovered a new gamma-ray source near the Galactic plane, \object{Fermi J0109+6134}, when it flared brightly in 2010 February. The low Galactic latitude (b =-1.2\degr) indicated that the source could be located within the Galaxy, which motivated rapid multi-wavelength follow-up including radio, optical, and X-ray observations. We report the results of analyzing all 19 months of LAT data for the source, and of X-ray observations with both \emph{Swift}...
Source: http://arxiv.org/abs/1004.1413v1
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54
Sep 21, 2013
09/13
by
J. Greiner; C. Clemens; T. Kruehler; A. v. Kienlin; A. Rau; R. Sari; D. B. Fox; N. Kawai; P. Afonso; M. Ajello; E. Berger; S. B. Cenko; A. Cucchiara; R. Filgas; S. Klose; A. Kuepue Yoldas; G. G. Lichti; S. Loew; S. McBreen; T. Nagayama; A. Rossi; S. Sato; G. Szokoly; A. Yoldas; X. -L. Zhang
texts
eye 54
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The detection of GeV photons from gamma-ray bursts (GRBs) has important consequences for the interpretation and modelling of these most-energetic cosmological explosions. The full exploitation of the high-energy measurements relies, however, on the accurate knowledge of the distance to the events. Here we report on the discovery of the afterglow and subsequent redshift determination of GRB 080916C, the first GRB detected by the Fermi Gamma-Ray Space Telescope with high significance detection of...
Source: http://arxiv.org/abs/0902.0761v1
7
7.0
Jun 30, 2018
06/18
by
C. C. Cheung; S. Larsson; J. D. Scargle; M. A. Amin; R. D. Blandford; D. Bulmash; J. Chiang; S. Ciprini; R. H. D. Corbet; E. E. Falco; P. J. Marshall; D. L. Wood; M. Ajello; D. Bastieri; A. Chekhtman; F. D'Ammando; M. Giroletti; J. E. Grove; B. Lott; R. Ojha; M. Orienti; J. S. Perkins; M. Razzano; A. W. Smith; D. J. Thompson; K. S. Wood
texts
eye 7
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Using data from the Fermi Large Area Telescope (LAT), we report the first clear gamma-ray measurement of a delay between flares from the gravitationally lensed images of a blazar. The delay was detected in B0218+357, a known double-image lensed system, during a period of enhanced gamma-ray activity with peak fluxes consistently observed to reach >20-50 times its previous average flux. An auto-correlation function analysis identified a delay in the gamma-ray data of 11.46 +/- 0.16 days (1...
Topics: High Energy Astrophysical Phenomena, Astrophysics
Source: http://arxiv.org/abs/1401.0548
40
40
Sep 23, 2013
09/13
by
J. Tueller; W. H. Baumgartner; C. B. Markwardt; G. K. Skinner; R. F. Mushotzky; M. Ajello; S. Barthelmy; A. Beardmore; W. N. Brandt; D. Burrows; G. Chincarini; S. Campana; J. Cummings; G. Cusumano; P. Evans; E. Fenimore; N. Gehrels; O. Godet; D. Grupe; S. Holland; J. Kennea; H. A. Krimm; M. Koss; A. Moretti; K. Mukai; J. P. Osborne; T. Okajima; C. Pagani; K. Page; D. Palmer; A. Parsons; D. P. Schneider; T. Sakamoto; R. Sambruna; G. Sato; M. Stamatikos; M. Stroh; T. N. Ukwatta; L. Winter
texts
eye 40
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We present the catalog of sources detected in the first 22 months of data from the hard X-ray survey (14--195 keV) conducted with the BAT coded mask imager on the \swift satellite. The catalog contains 461 sources detected above the 4.8 sigma level with BAT. High angular resolution X-ray data for every source from Swift XRT or archival data have allowed associations to be made with known counterparts in other wavelength bands for over 97% of the detections, including the discovery of ~30...
Source: http://arxiv.org/abs/0903.3037v2
7
7.0
Jun 29, 2018
06/18
by
G. M. Madejski; K. Nalewajko; K. K. Madsen; J. Chiang; M. Baloković; D. Paneque; A. K. Furniss; M. Hayashida; C. M. Urry; M. Sikora; M. Ajello; R. D. Blandford; F. A. Harrison; D. Sanchez; B. Giebels; D. Stern; D. M. Alexander; D. Barret; S. E. Boggs; F. E. Christensen; W. W. Craig; K. Forster; P. Giommi; B. Grefenstette; C. Hailey; A. Hornstrup; T. Kitaguchi; J. E. Koglin; P. H. Mao; H. Miyasaka; K. Mori; M. Perri; M. J. Pivovaroff; S. Puccetti; V. Rana; N. J. Westergaard; W. W. Zhang; A....
texts
eye 7
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We report the first hard X-ray observations with NuSTAR of the BL Lac type blazar PKS 2155-304, augmented with soft X-ray data from XMM-Newton and gamma-ray data from the Fermi Large Area Telescope, obtained in April 2013 when the source was in a very low flux state. A joint NuSTAR and XMM spectrum, covering the energy range 0.5 - 60 keV, is best described by a model consisting of a log-parabola component with curvature beta = 0.3(+0.2,-0.1) and a (local) photon index 3.04 +/- 0.15 at photon...
Topics: Astrophysics, High Energy Astrophysical Phenomena
Source: http://arxiv.org/abs/1609.02203
3
3.0
Jun 29, 2018
06/18
by
G. B. Lansbury; D. Stern; J. Aird; D. M. Alexander; C. Fuentes; F. A. Harrison; E. Treister; F. E. Bauer; J. A. Tomsick; M. Balokovic; A. Del Moro; P. Gandhi; M. Ajello; A. Annuar; D. R. Ballantyne; S. E. Boggs; N. Brandt; M. Brightman; C. J. Chen; F. E. Christensen; F. Civano; A. Comastri; W. W. Craig; K. Forster; B. W. Grefenstette; C. J. Hailey; R. Hickox; B. Jiang; H. Jun; M. Koss; S. Marchesi; A. D. Melo; J. R. Mullaney; G. Noirot; S. Schulze; D. J. Walton; L. Zappacosta; W. Zhang
texts
eye 3
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We present the first full catalog and science results for the NuSTAR serendipitous survey. The catalog incorporates data taken during the first 40 months of NuSTAR operation, which provide ~20Ms of effective exposure time over 331 fields, with an areal coverage of 13 sq deg, and 497 sources detected in total over the 3-24 keV energy range. There are 276 sources with spectroscopic redshifts and classifications, largely resulting from our extensive campaign of ground-based spectroscopic followup....
Topics: Astrophysics, High Energy Astrophysical Phenomena, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1612.06389
