- ID:
- ivo://CDS.VizieR/J/MNRAS/470/1291
- Title:
- Classifying 3FGL with ANN
- Short Name:
- J/MNRAS/470/1291
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In its first four years of operation, the Fermi-Large Area Telescope (LAT) detected 3033 {gamma}-ray emitting sources. In the Fermi-LAT Third Source Catalogue (3FGL) about 50 per cent of the sources have no clear association with a likely {gamma}-ray emitter. We use an artificial neural network algorithm aimed at distinguishing BL Lacs from FSRQs to investigate the source subclass of 559 3FGL unassociated sources characterized by {gamma}-ray properties very similar to those of active galactic nuclei. Based on our method, we can classify 271 objects as BL Lac candidates, 185 as FSRQ candidates, leaving only 103 without a clear classification. We suggest a new zoo for {gamma}-ray objects, where the percentage of sources of uncertain type drops from 52 per cent to less than 10 per cent. The result of this study opens up new considerations on the population of the {gamma}-ray sky, and it will facilitate the planning of significant samples for rigorous analyses and multiwavelength observational campaigns.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/820/66
- Title:
- Cosmic evolution of long gamma-ray burst luminosity
- Short Name:
- J/ApJ/820/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The cosmic evolution of gamma-ray burst (GRB) luminosity is essential for revealing the GRB physics and for using GRBs as cosmological probes. We investigate the luminosity evolution of long GRBs with a large sample of 258 Swift/BAT GRBs. By describing the peak luminosity evolution of individual GRBs as L_p_{prop.to}(1+z)^k^, we get k=1.49+/-0.19 using the nonparametric {tau} statistics method without considering observational biases of GRB trigger and redshift measurement. By modeling these biases with the observed peak flux and characterizing the peak luminosity function of long GRBs as a smoothly broken power law with a break that evolves as L_b_{prop.to}(1+z)^kb^, we obtain k_b_=1.14^+0.99^_-0.47_ through simulations based on the assumption that the long GRB rate follows the star formation rate incorporating the cosmic metallicity history. The derived k and k_b_ values are systematically smaller than those reported in previous papers. By removing the observational biases of the GRB trigger and redshift measurement based on our simulation analysis, we generate mock complete samples of 258 and 1000 GRBs to examine how these biases affect the {tau} statistics method. We get k=0.94+/-0.14 and k=0.80+/-0.09 for the two samples, indicating that these observational biases may lead to overestimating the k value. With the large uncertainty of k_b_ derived from our simulation analysis, one cannot even convincingly argue for a robust evolution feature of the GRB luminosity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/425/477
- Title:
- Dark matter annihilation in galaxy clusters
- Short Name:
- J/MNRAS/425/477
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Clusters of galaxies are potentially important targets for indirect searches for dark matter (DM) annihilation. Here we reassess the detection prospects for annihilation in massive haloes, based on a statistical investigation of 1743 clusters in the new Meta-Catalogue of X-ray Clusters (MCXC). We derive a new limit for the extragalactic DM annihilation background of at least 20 per cent of that originating from the Galaxy for an integration angle of 0.1{deg}.
- ID:
- ivo://CDS.VizieR/J/other/RAA/14.1135
- Title:
- Doppler factor for a Fermi blazar sample
- Short Name:
- J/other/RAA/14.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected 457 blazars (193 flat spectrum radio quasars, 61 low-synchrotron peaked blazars, 69 intermediate-synchrotron peaked blazars and 134 high-synchrotron peaked blazars) from the second Fermi-LAT catalog (2FGL) of {gamma}-ray sources, which have X-ray observations. We calculated the lower limits for their Doppler factors, {delta}_{gamma}_, and compared the lower limits with the available Doppler factors and the apparent superluminal velocities in the literature.
- ID:
- ivo://CDS.VizieR/J/ApJ/711/495
- Title:
- Durations of Swift/BAT GRBs
- Short Name:
- J/ApJ/711/495
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculate durations and spectral parameters for 207 Swift bursts detected by the Burst Alert Telescope from 2007 April to 2009 August, including 67 events with measured redshifts. This is the first supplement to our catalog of 425 Swift gamma-ray bursts (GRBs; 147 with redshifts) starting from GRB 041220. This complete and extensive data set, analyzed with a unified methodology, allows us to conduct an accurate census of intrinsic GRB energetics, hardnesses, durations, and redshifts. The GRB world model we derive reproduces well the observables from both Swift and pre-Swift satellites. Comparing to the cosmic star formation rate, we estimate that only about 0.1% of massive stars explode as bright GRBs.
- ID:
- ivo://CDS.VizieR/J/ApJ/693/1484
- Title:
- Early optical afterglow catalog
- Short Name:
- J/ApJ/693/1484
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multicolor optical observations of long-duration {gamma}-ray bursts (GRBs) made over a three-year period with the robotic Palomar 60 inch telescope (P60). Our sample consists of all 29 events discovered by Swift for which P60 began observations less than 1hr after the burst trigger. We were able to recover 80% of the optical afterglows from this prompt sample, and we attribute this high efficiency to our red coverage. Like Melandri et al. (2008, Cat. J/ApJ/686/1209), we find that a significant fraction (~50%) of Swift events show a suppression of the optical flux with regard to the X-ray emission (the so-called "dark" bursts). Our multicolor photometry demonstrates this is likely due in large part to extinction in the host galaxy. We argue that previous studies, by selecting only the brightest and best-sampled optical afterglows, have significantly underestimated the amount of dust present in typical GRB environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/852/53
- Title:
- Early X-ray flares in GRBs
- Short Name:
- J/ApJ/852/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the early X-ray flares in the GRB "flare-plateau-afterglow" (FPA) phase observed by Swift-XRT. The FPA occurs only in one of the seven GRB subclasses: the binary-driven hypernovae (BdHNe). This subclass consists of long GRBs with a carbon-oxygen core and a neutron star (NS) binary companion as progenitors. The hypercritical accretion of the supernova (SN) ejecta onto the NS can lead to the gravitational collapse of the NS into a black hole. Consequently, one can observe a GRB emission with isotropic energy E_iso_>~10^52^erg, as well as the associated GeV emission and the FPA phase. Previous work had shown that gamma-ray spikes in the prompt emission occur at ~10^15^-10^17^cm with Lorentz Gamma factors {Gamma}~10^2^-10^3^. Using a novel data analysis, we show that the time of occurrence, duration, luminosity, and total energy of the X-ray flares correlate with Eiso. A crucial feature is the observation of thermal emission in the X-ray flares that we show occurs at radii ~10^12^cm with {Gamma}<~4. These model-independent observations cannot be explained by the "fireball" model, which postulates synchrotron and inverse-Compton radiation from a single ultrarelativistic jetted emission extending from the prompt to the late afterglow and GeV emission phases. We show that in BdHNe a collision between the GRB and the SN ejecta occurs at ~10^10^cm, reaching transparency at ~10^12^cm with {Gamma}<~4. The agreement between the thermal emission observations and these theoretically derived values validates our model and opens the possibility of testing each BdHN episode with the corresponding Lorentz Gamma factor.
- ID:
- ivo://CDS.VizieR/J/ApJ/657/706
- Title:
- EGRET blazar gamma-ray spectrum
- Short Name:
- J/ApJ/657/706
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO) discovered gamma-ray emission from more than 67 blazars during its 9yr lifetime. We conducted an exhaustive search of the EGRET archives and selected all the blazars that were observed multiple times and were bright enough to enable a spectral analysis using standard power-law models. The sample consists of 18 flat-spectrum radio quasars (FSRQs), 6 low-frequency peaked BL Lac objects (LBLs) and 2 high-frequency peaked BL Lac objects (HBLs). We do not detect any clear pattern in the variation of spectral index with flux. Some of the blazars do not show any statistical evidence for spectral variability.
- ID:
- ivo://CDS.VizieR/J/ApJS/157/324
- Title:
- EGRET high-energy cosmic photons (E>10GeV)
- Short Name:
- J/ApJS/157/324
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- During its 9 year lifetime, the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) detected 1506 cosmic photons with measured energy E>10GeV. Of this number, 187 are found within a 1{deg} of sources that are listed in the Third EGRET Catalog (Cat. <J/ApJS/123/79>) and were included in determining the detection likelihood, flux, and spectra of those sources. In particular, five detected EGRET pulsars are found to have events above 10GeV, and together they account for 37 events. A pulsar not included in the Third EGRET Catalog has two events, both with the same phase and in one peak of the lower energy gamma-ray light curve.
- ID:
- ivo://CDS.VizieR/VII/287
- Title:
- Extragalactic linear polarization meas. agglomeration
- Short Name:
- VII/287
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In the framework of the Standard Model Extension (SME), we present improved constraints on anisotropic Lorentz invariance and Charge-Parity-Time (CPT) violation by searching for astrophysical signals of cosmic vacuum birefringence with broadband optical polarimetry of high redshift astronomical sources, including Active Galactic Nuclei and Gamma-Ray Burst afterglows. We generalize Kislat (Constraints on lorentz invariance violation from optical polarimetry of astrophysical objects. Symmetry, 10(11), 2018. ISSN 2073-8994. doi:10.3390/sym10110596), which studied the SME mass dimension d=4 case, to arbitrary mass dimension for both the CPT-even and CPT-odd cases. We then present constraints on all 10, 16, and 42 anisotropic birefringent SME coefficients for dimension d=4, d=5, and d=6 models respectively, using 7554 observations for odd d and 7376 observations for even d of 1278 unique sources on the sky, which, to our knowledge comprises the most complete catalog of optical polarization from extragalactic sources in the literature to date. Compared to the smaller sample of 44 and 45 broadband optical polarimetry observations analyzed in Kislat (Constraints on lorentz invariance violation from optical polarimetry of astrophysical objects. Symmetry, 10(11), 2018. ISSN 2073-8994. doi:10.3390/sym10110596) and Kislat et al. (2017 Phys. Rev. D, 95(8):083013, doi: 10.1103/PhysRevD.95.083013), our dimension d=4 and d=5 average constraints are more sensitive by factors of 35 and 10, corresponding to a reduction in allowed SME parameter space volume for these studies of 15 and 16 orders of magnitude, respectively. Constraints from individual lines of sight can be significantly stronger using spectropolarimetry, due to the steep energy dependence of birefringence effects at increasing mass dimension. Nevertheless, due to the increased number of observations and lines of sight in our catalog, our average d=4 and d=5 broadband constraints are within factors of 2 and 12 of previous constraints using spectropolarimetry from Kislat (Constraints on lorentz invariance violation from optical polarimetry of astrophysical objects. Symmetry, 10(11), 2018. ISSN 2073-8994. doi:10.3390/sym10110596) and Kislat et al. (2017, Phys. Rev. D 95(8):083013, doi: 10.1103/PhysRevD.95.083013), respectively, using an independent data set and an improved analysis method. By contrast, our anisotropic constraints on all 42 birefringent SME coefficients for d=6 are the first to be presented in the literature.
