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Start Over Subject gamma-ray astronomy Validation Level 2
431. X-ray, opt. & radio SEDs of Fermi blazars
ID:
ivo://CDS.VizieR/J/ApJS/226/20
Title:
X-ray, opt. & radio SEDs of Fermi blazars
Short Name:
J/ApJS/226/20
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper, multiwavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, log({nu}F_{nu}_)=P_1_(log{nu}-P_2_)^2^+P_3_, is used for SED fitting. Synchrotron peak frequency (log{nu}_p_), spectral curvature (P_1_), peak flux ({nu}_p_F_{nu}p_), and integrated flux ({nu}F_{nu}_) are successfully obtained for 1392 blazars (461 flat-spectrum radio quasars [FSRQs], 620 BL Lacs [BLs], and 311 blazars of uncertain type [BCUs]; 999 sources have known redshifts). Monochromatic luminosity at radio 1.4GHz, optical R band, X-ray at 1keV and {gamma}-ray at 1GeV, peak luminosity, integrated luminosity, and effective spectral indices of radio to optical ({alpha}_RO_) and optical to X-ray ({alpha}_OX_) are calculated. The "Bayesian classification" is employed to log{nu}_p_ in the rest frame for 999 blazars with available redshift, and the results show that three components are enough to fit the log{nu}_p_ distribution; there is no ultra-high peaked subclass. Based on the three components, the subclasses of blazars using the acronyms of Abdo+ (2010, J/ApJ/716/30) are classified, and some mutual correlations are also studied.
432. X-ray & radio fluxes of unassociated 2FGL sources
ID:
ivo://CDS.VizieR/J/ApJ/779/133
Title:
X-ray & radio fluxes of unassociated 2FGL sources
Short Name:
J/ApJ/779/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Fermi Gamma-Ray Space Telescope has been detecting a wealth of sources where the multiwavelength counterpart is either inconclusive or missing altogether. We present a combination of factors that can be used to identify multiwavelength counterparts to these Fermi unassociated sources. This approach was used to select and investigate seven bright, high-latitude unassociated sources with radio, UV, X-ray, and {gamma}-ray observations. As a result, four of these sources are candidates to be active galactic nuclei, and one to be a pulsar, while two do not fit easily into these known categories of sources. The latter pair of extraordinary sources might reveal a new category subclass or a new type of {gamma}-ray emitter. These results altogether demonstrate the power of a multiwavelength approach to illuminate the nature of unassociated Fermi sources.
433. X-ray sources near 2 bright {gamma}-ray sources
ID:
ivo://CDS.VizieR/J/ApJ/756/33
Title:
X-ray sources near 2 bright {gamma}-ray sources
Short Name:
J/ApJ/756/33
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Chandra ACIS-I X-ray observations of 0FGL J1311.9-3419 and 0FGL J1653.4-0200, the two brightest high Galactic latitude (|b|>10{deg}) {gamma}-ray sources from the three-month Fermi Large Area Telescope (LAT) bright source list that are still unidentified. Both were also detected previously by EGRET, and despite dedicated multi-wavelength follow-up, they are still not associated with established classes of {gamma}-ray emitters like pulsars or radio-loud active galactic nuclei. X-ray sources found in the ACIS-I fields of view are cataloged, and their basic properties are determined. These are discussed as candidate counterparts to 0FGL J1311.9-3419 and 0FGL J1653.4-0200, with particular emphasis on the brightest of the 9 and 13 Chandra sources detected within the respective Fermi-LAT 95% confidence regions. Further follow-up studies, including optical photometric and spectroscopic observations, are necessary to identify these X-ray candidate counterparts in order to ultimately reveal the nature of these enigmatic {gamma}-ray objects.
434. X-ray sources near soft gamma repeater in M31
ID:
ivo://CDS.VizieR/J/ApJ/681/1464
Title:
X-ray sources near soft gamma repeater in M31
Short Name:
J/ApJ/681/1464
Date:
21 Oct 2021
Publisher:
CDS
Description:
GRB 070201 was a bright, short-duration, hard-spectrum gamma-ray burst detected by the Interplanetary Network. Its error quadrilateral, which has an area of 0.124deg^2^, intersects some prominent spiral arms of the nearby M31 (Andromeda) galaxy. Given the properties of this GRB, along with the fact that LIGO data argue against a compact binary merger origin in M31, it is an excellent candidate to have been an extragalactic soft gamma-ray repeater (SGR) giant flare, with an energy of 1.4x1045ergs. However, we cannot rule out the possibility that it was a short-duration GRB in the background. Analysis of ROTSE-IIIb visible-light observations of M31, taken 10.6hr after the burst and covering 42% of the GRB error region, does not reveal any optical transient down to a limiting magnitude of 17.1. We inspected archival and proprietary XMM-Newton X-ray observations of the intersection of the GRB error region and M31, obtained about 4 weeks prior to the outburst, in order to look for periodic variable X-ray sources. No SGR or anomalous X-ray pulsar (AXP) candidates (periods in the range 1-20s) were detected. We discuss the possibility of detecting extragalactic SGRs/AXPs by identifying their periodic X-ray light curves. Our simulations suggest that the probability of detecting the periodic X-ray signal of one of the known Galactic SGRs/AXPs, if placed in M31, is about 10% using a 50ks XMM-Newton exposure, increasing to 50% for a 2Ms observation.
435. 10-year Fermi LAT results for the Crab pulsar
ID:
ivo://CDS.VizieR/J/A+A/640/A43
Title:
10-year Fermi LAT results for the Crab pulsar
Short Name:
J/A+A/640/A43
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Crab pulsar is a bright gamma-ray source, which has been detected at photon energies up to ~1TeV. Its phase-averaged and phase-resolved gamma-ray spectra below 10GeV exhibit exponential cutoffs, while those above 10GeV apparently follow simple power laws. We re-visit the gamma-ray properties of the Crab pulsar with ten-year Fermi Large Area Telescope (LAT) data in the range of 60MeV-500GeV. With the phase-resolved spectra, we investigate the origins and mechanisms responsible for the emissions. The phaseograms were reconstructed for different energy bands and further analysed using a wavelet decomposition. The phase-resolved energy spectra were combined with the observations of ground-based instruments, such as MAGIC and VERITAS, to achieve a larger energy converage. We fitted power-law models to the overlapping energy spectra from 10GeV to ~1TeV. In the fit, we included a relative cross-calibration of energy scales between air-shower-based gamma-ray telescopes with the orbital pair-production telescope from the Fermi mission. We confirm the energy-dependence of the gamma-ray pulse shape and, equivalently, the phase-dependence of the spectral shape for the Crab pulsar. A relatively sharp cutoff at a relatively high energy of ~8GeV is observed for the bridge-phase emission. The E>10 GeV spectrum observed for the second pulse peak is harder than those for other phases. In view of the diversity of phase-resolved spectral shapes of the Crab pulsar, we tentatively propose a multi-origin scenario where the polar-cap, outer-gap, and relativistic-wind regions are involved.
436. 7 year Swift-XRT point source catalog (1SWXRT)
ID:
ivo://CDS.VizieR/J/A+A/551/A142
Title:
7 year Swift-XRT point source catalog (1SWXRT)
Short Name:
J/A+A/551/A142
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Swift satellite is a multi-wavelength observatory specifically designed for gamma-ray burst (GRB) astronomy that is operational since 2004. Swift is also a very flexible multi-purpose facility that supports a wide range of scientific fields such as active galactic nuclei, supernovae, cataclysmic variables, Galactic transients, active stars and comets. The Swift X-ray Telescope (XRT) has collected more than 150Ms of observations in its first seven years of operations. The purpose of this work is to present to the scientific community the list of all the X-ray point sources detected in XRT imaging data taken in photon counting mode during the first seven years of Swift operations. All these point-like sources, excluding the Gamma-Ray Bursts (GRB), will be stored in a catalog publicly available (1SWXRT). We consider all the XRT observations with exposure time longer than 500 s taken in the period 2005-2011. Data were reduced and analyzed with standard techniques and a list of detected sources for each observation was produced. A careful visual inspection was performed to remove extended, spurious and piled-up sources. Finally, positions, count rates, fluxes and the corresponding uncertainties were computed.
437. 12Y-MST and 12Y-MSTw Catalogues
ID:
ivo://CDS.VizieR/J/A+A/652/A6
Title:
12Y-MST and 12Y-MSTw Catalogues
Short Name:
J/A+A/652/A6
Date:
22 Feb 2022
Publisher:
CDS
Description:
We present an updated version catalogue of gamma-ray source candidates, 12Y-MST, selected using the Minimum Spanning Tree (MST) algorithm on the 12-years Fermi/LAT sky (Pass 8) at energies higher than 10GeV. The high energy sky at absolute Galactic latitudes above 20 degrees has been investigated using rather restrictive selection criteria, resulting in a total sample of 1664 photon clusters, or candidate sources. Of these, 230 are new detections, i.e., candidate sources without any association in other gamma-ray catalogues. A large fraction of them have interesting counterparts, most likely blazars. In this paper the main results on the catalogue selection and search of counterparts are described. We also present an additional sample of 224 candidate sources (12Y-MSTw), which are clusters extracted applying weaker selection criteria: about 57% of them have not been reported in other catalogues.
438. 9Y-MST Catalogue
ID:
ivo://CDS.VizieR/J/A+A/619/A23
Title:
9Y-MST Catalogue
Short Name:
J/A+A/619/A23
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe a catalogue of gamma-ray source candidates selected using the minimum spanning tree (MST) algorithm on the nine year Fermi-LAT sky (Pass 8) at energies higher than 10GeV. The extragalactic sky at absolute Galactic latitudes above 20{deg} has been investigated using rather restrictive selection criteria, resulting in a total sample of 1342 sources. Of these, 249 are new detections that have not been previously associated with gamma-ray catalogues. A large portion of these candidates have interesting counterparts, which are most likely blazars. In this paper, we report the main results of the catalogue selection and search of counterparts.
439. 8yr INTEGRAL/IBIS soft gamma-ray source obs.
ID:
ivo://CDS.VizieR/J/ApJS/223/15
Title:
8yr INTEGRAL/IBIS soft gamma-ray source obs.
Short Name:
J/ApJS/223/15
Date:
21 Oct 2021
Publisher:
CDS
Description:
Here we report an all-sky soft gamma-ray source catalog based on IBIS observations performed during the first 1000 orbits of INTEGRAL. The database for the construction of the source list consists of all good-quality data available, from the launch in 2002, up to the end of 2010. This corresponds to ~110Ms of scientific public observations, with a concentrated coverage on the Galactic Plane and extragalactic deep exposures. This new catalog includes 939 sources above a 4.5{sigma} significance threshold detected in the 17-100keV energy band, of which 120 sources represent previously undiscovered soft gamma-ray emitters. The source positions are determined, mean fluxes are provided in two main energy bands, and these are both reported together with the overall source exposure. Indicative levels of variability are provided, and outburst times and durations are given for transient sources. A comparison is made with previous IBIS catalogs and catalogs from other similar missions.
440. 4.5yr obs. of Mrk421 with ARGO-YBJ & Fermi
ID:
ivo://CDS.VizieR/J/ApJS/222/6
Title:
4.5yr obs. of Mrk421 with ARGO-YBJ & Fermi
Short Name:
J/ApJS/222/6
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on the extensive multi-wavelength observations of the blazar Markarian 421 (Mrk 421) covering radio to {gamma}-rays, during the 4.5yr period of ARGO-YBJ and Fermi common operation time, from 2008 August to 2013 February. These long-term observations, extending over an energy range of 18 orders of magnitude, provide a unique chance to study the variable emission of Mrk 421. In particular, due to the ARGO-YBJ and Fermi data, the entire energy range from 100MeV to 10TeV is covered without any gap. In the observation period, Mrk 421 showed both low- and high-activity states at all wavebands. The correlations among flux variations in different wavebands were analyzed. The X-ray flux is clearly correlated with the TeV {gamma}-ray flux, while the GeV {gamma}-rays only show a partial correlation with the TeV {gamma}-rays. Radio and UV fluxes seem to be weakly or not correlated with the X-ray and {gamma}-ray fluxes. Seven large flares, including five X-ray flares and two GeV {gamma}-ray flares with variable durations (3-58d), and one X-ray outburst phase were identified and used to investigate the variation of the spectral energy distribution with respect to a relative quiescent phase. During the outburst phase and the seven flaring episodes, the peak energy in X-rays is observed to increase from sub-keV to a few keV. The TeV {gamma}-ray flux increases up to 0.9-7.2 times the flux of the Crab Nebula. The behavior of GeV {gamma}-rays is found to vary depending on the flare, a feature that leads us to classify flares into three groups according to the GeV flux variation. Finally, the one-zone synchrotron self-Compton model was adopted to describe the emission spectra. Two out of three groups can be satisfactorily described using injected electrons with a power-law spectral index around 2.2, as expected from relativistic diffuse shock acceleration, whereas the remaining group requires a harder injected spectrum. The underlying physical mechanisms responsible for different groups may be related to the acceleration process or to the environment properties.