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Start Over Subject gamma-ray astronomy Validation Level 2
261. Neutrinos from GRBs with ANTARES
ID:
ivo://CDS.VizieR/J/A+A/559/A9
Title:
Neutrinos from GRBs with ANTARES
Short Name:
J/A+A/559/A9
Date:
21 Oct 2021
Publisher:
CDS
Description:
A search for muon neutrinos in coincidence with gamma-ray bursts with the ANTARES neutrino detector using data from the end of 2007 to 2011 is performed. Expected neutrino fluxes are calculated for each burst individually. The most recent numerical calculations of the spectra using the NeuCosmA code are employed, which include Monte Carlo simulations of the full underlying photohadronic interaction processes. The discovery probability for a selection of 296 gamma-ray bursts in the given period is optimised using an extended maximum-likelihood strategy. No significant excess over background is found in the data, and 90% confidence level upper limits are placed on the total expected flux according to the model.
262. New Fermi/LAT extragalactic sources
ID:
ivo://CDS.VizieR/J/ApJ/742/66
Title:
New Fermi/LAT extragalactic sources
Short Name:
J/ApJ/742/66
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog (Abdo et al. 2010, Cat. J/ApJ/715/429), are detected. Using Swift/BAT and radio 20cm fluxes, we define a new radio-loudness parameter R_X,BAT_ where radio-loud objects have logR_X,BAT_> -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be ~2x10^-11^photons/cm^2^/s, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the {gamma}-ray (1-100GeV) luminosity of <~3x10^41^erg/s. In addition, we identified 120 new Fermi/LAT sources near the Swift/BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.
263. New redshifts of 357 GBBs
ID:
ivo://CDS.VizieR/J/A+A/584/A48
Title:
New redshifts of 357 GBBs
Short Name:
J/A+A/584/A48
Date:
21 Oct 2021
Publisher:
CDS
Description:
Several large structures, including the Sloan Great Wall, the Huge Large Quasar Group, and a large gamma-ray burst cluster referred to as the Hercules-Corona Borealis Great Wall, appear to exceed the maximum structural size predicted by Universal inflationary models. The existence of very large structures such as these might necessitate cosmological model modifications. Gamma-ray bursts are the most luminous sources found in nature. They are associated with the stellar endpoints of massive stars and are found in and near distant galaxies. Since they are viable indicators of the dense part of the Universe containing normal matter, the spatial distribution of gamma-ray bursts can serve as tracers of Universal large-scale structure. An increased sample size of gamma-ray bursts with known redshift provides us with the opportunity to validate or invalidate the existence of the Hercules-Corona Borealis Great Wall. Nearest-neighbour tests are used to search the larger sample for evidence of clustering and a bootstrap point-radius method is used to estimate the angular cluster size. The potential influence of angular sampling biasing is studied to determine the viability of the results. The larger gamma-ray burst database further supports the existence of a statistically significant gamma-ray burst cluster at 1.6<=z<2.1 with an estimated angular size of 2000-3000Mpc. Although small number statistics limit our angular resolution and do not rule out the existence of adjacent and/or line-of-sight smaller structures, these structures must still clump together in order for us to see the large gamma-ray burst cluster detected here. This cluster provides support for the existence of very large-scale universal heterogeneities.
264. New spectral lag measurements of 50 Fermi/GBM GRBs
ID:
ivo://CDS.VizieR/J/ApJ/844/126
Title:
New spectral lag measurements of 50 Fermi/GBM GRBs
Short Name:
J/ApJ/844/126
Date:
21 Oct 2021
Publisher:
CDS
Description:
We carry out a systematical study of the spectral lag properties of 50 single-pulsed gamma-ray bursts (GRBs) detected by the Fermi Gamma-Ray Burst Monitor. By dividing the light curves into multiple consecutive energy channels, we provide a new measurement of the spectral lag that is independent of energy channel selections. We perform a detailed statistical study of our new measurements. We find two similar power-law energy dependencies of both the pulse arrival time and pulse width. Our new results on the power-law indices would favor the relativistic geometric effects for the origin of spectral lag. However, a complete theoretical framework that can fully account for the diverse energy dependencies of both arrival time and pulse width revealed in this work is still lacking. We also study the spectral evolution behaviors of the GRB pulses. We find that a GRB pulse with negligible spectral lag would usually have a shorter pulse duration and would appear to have a "hardness-intensity tracking" behavior, and a GRB pulse with a significant spectral lag would usually have a longer pulse duration and would appear to have a "hard-to-soft" behavior.
265. Observation of first Fermi-LAT sources at Parkes
ID:
ivo://CDS.VizieR/J/ApJ/810/85
Title:
Observation of first Fermi-LAT sources at Parkes
Short Name:
J/ApJ/810/85
Date:
21 Oct 2021
Publisher:
CDS
Description:
In a search with the Parkes radio telescope of 56 unidentified Fermi-Large Area Telescope (LAT) gamma-ray sources, we have detected 11 millisecond pulsars (MSPs), 10 of them discoveries, of which five were reported by Kerr et al (2012ApJ...748L...2K). We did not detect radio pulsations from six other pulsars now known in these sources. We describe the completed survey, which included multiple observations of many targets conducted to minimize the impact of interstellar scintillation, acceleration effects in binary systems, and eclipses. We consider that 23 of the 39 remaining sources may still be viable pulsar candidates. We present timing solutions and polarimetry for five of the MSPs and gamma-ray pulsations for PSR J1903-7051 (pulsations for five others were reported in the second Fermi-LAT catalog of gamma-ray pulsars). Two of the new MSPs are isolated and five are in >1 day circular orbits with 0.2-0.3 M_{sun}_ presumed white dwarf companions. PSR J0955-6150, in a 24 day orbit with a 0.2-0.3 M_{sun}_ companion but eccentricity of 0.11, belongs to a recently identified class of eccentric MSPs. PSR J1036-8317 is in an 8 hr binary with a>0.14 M_{sun}_ companion that is probably a white dwarf. PSR J1946-5403 is in a 3 hr orbit with a>0.02 M_{sun}_ companion with no evidence of radio eclipses.
266. Observations of blazars at 15GHz
ID:
ivo://CDS.VizieR/J/ApJS/194/29
Title:
Observations of blazars at 15GHz
Short Name:
J/ApJS/194/29
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15GHz radio monitoring program with the 40m telescope at the Owens Valley Radio Observatory (OVRO). This program began with the 1158 northern ({delta}>-20{deg}) sources from the Candidate Gamma-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample.
267. Obs. of 2 Unidentified Gamma-ray Sources
ID:
ivo://CDS.VizieR/J/A+A/458/245
Title:
Obs. of 2 Unidentified Gamma-ray Sources
Short Name:
J/A+A/458/245
Date:
21 Oct 2021
Publisher:
CDS
Description:
The systematic X-ray and optical coverage of low-latitude unidentified gamma-ray sources, aiming at sources with high X-ray/optical flux ratio, seems one of the most promising ways to spot INS candidate counterparts. We have focussed on two middle-latitude, probably galactic, EGRET sources: 3EG J0616-3310 and 3EG J1249-8330. Here we report on X-ray observations of the two gamma-ray error boxes performed with XMM-Newton and on their optical follow-up carried on with the Wide Field Imager at the ESO/MPG 2.2m telescope. Less than half of the ~300 sources detected by the X-ray coverage have no optical counterparts. Among those, we have selected few interesting sources with f_X_/f_opt_>100, which we consider promising INS candidates.
268. Optical and X-ray light curves of BAT6 sample
ID:
ivo://CDS.VizieR/J/A+A/565/A72
Title:
Optical and X-ray light curves of BAT6 sample
Short Name:
J/A+A/565/A72
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the rest-frame light curves in the optical and X-ray bands of an unbiased and complete sample of the Swift long gamma-ray bursts (GRBs), namely, the BAT6 sample. The unbiased BAT6 sample (consisting of 58 events) has the highest level of completeness in redshift (~95%), allowing us to compute the rest-frame X-ray and optical light curves for 55 and 47 objects, respectively. We compute the X-ray and optical luminosities, which accounte for any possible source of absorption (Galactic and intrinsic) that could affect the observed fluxes in these two bands.
269. Optical/{gamma}-ray flares for Fermi-LAT blazars
ID:
ivo://CDS.VizieR/J/ApJ/880/32
Title:
Optical/{gamma}-ray flares for Fermi-LAT blazars
Short Name:
J/ApJ/880/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
Even with several thousand Fermi-Large Area Telescope (LAT) blazar detections, the {gamma}-ray emission mechanism is poorly understood. We explore correlated optical/{gamma}-ray flux variations for 178 Fermi-LAT blazars regularly monitored by the Katzman Automatic Imaging Telescope, the Small and Moderate Aperture Research Telescope System, and the Steward Observatory. Out of the 178 sources, 121 show a measurable (>1{sigma}) discrete correlation function peak. Using the derived time lags and Bayesian block light-curve decompositions, we measure the fraction of common and orphan flares between the two bands. After accounting for sampling and sensitivity limitations we quantify for the first time the true orphan flare rates of optical and {gamma}-ray flares: 54.5% of optical and 20% of {gamma}-ray flares are orphan events. Both the intraband temporal relation and the small orphan {gamma}-ray flare fraction point toward leptonic processes as the likely mechanisms for the high-energy emission. Motivated to discriminate between synchrotron self-Compton (SSC) and external-Compton dominance in individual sources, we use the flux-flux variations to determine the slope m of the log fopt-log f{gamma} dependence. The slope distribution suggests a bimodal population with high and intermediate synchrotron peak objects showing larger m than low synchrotron peak objects. We find that m is naturally decreased through pollution from the orphan (typically optical) flares and develop a method to statistically recover, given the sources' measured orphan flare rate, the intrinsic m. While source classes show composite behavior, the majority of BL Lac objects favor m=2, indicating an SSC origin for the {gamma}-rays. No preference for either m is found in flat spectrum radio quasars.
270. Optical/{gamma}-ray variability in blazars
ID:
ivo://CDS.VizieR/J/MNRAS/439/690
Title:
Optical/{gamma}-ray variability in blazars
Short Name:
J/MNRAS/439/690
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use optical data from the Palomar Transient Factory (PTF) and the Catalina Real-Time Transient Survey (CRTS) to study the variability of {gamma}-ray-detected and non-detected objects in a large population of active galactic nuclei selected from the Candidate Gamma-Ray Blazar Survey and Fermi Gamma-Ray Space Telescope catalogues. Our samples include 714 sources with PTF data and 1244 sources with CRTS data. We calculate the intrinsic modulation index to quantify the optical variability amplitude in these samples.