- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/831/89
- Title:
- Eclipsing LMXB at the center of 3FGL J0427.9-6704
- Short Name:
- J/ApJ/831/89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of an eclipsing low-mass X-ray binary at the center of the 3FGL error ellipse of the unassociated Fermi/Large Area Telescope {gamma}-ray source 3FGL J0427.9-6704. Photometry from OGLE and the SMARTS 1.3m telescope and spectroscopy from the SOAR telescope have allowed us to classify the system as an eclipsing low-mass X-ray binary (P=8.8hr) with a main-sequence donor and a neutron-star accretor. Broad double-peaked H and He emission lines suggest the ongoing presence of an accretion disk. Remarkably, the system shows separate sets of absorption lines associated with the accretion disk and the secondary, and we use their radial velocities to find evidence for a massive (~1.8-1.9M_{sun}_) neutron-star primary. In addition to a total X-ray eclipse with a duration of ~2200s observed with NuSTAR, the X-ray light curve also shows properties similar to those observed among known transitional millisecond pulsars: short-term variability, a hard power-law spectrum ({Gamma}~1.7), and a comparable 0.5-10keV luminosity (~2.4x10^33^erg/s). We find tentative evidence for a partial (~60%) {gamma}-ray eclipse at the same phase as the X-ray eclipse, suggesting the {gamma}-ray emission may not be confined to the immediate region of the compact object. The favorable inclination of this binary is promising for future efforts to determine the origin of {gamma}-rays among accreting neutron stars.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJS/247/16
- Title:
- Extreme high-frequency-peaked BL Lac objects
- Short Name:
- J/ApJS/247/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature nonthermal gamma-ray emission whose peak lies in the very high-energy (VHE, E>100GeV) range, and in some sources exceeds 1TeV: this is the case for hard-TeV EHBLs such as 1ES 0229+200. With the aim of increasing the EHBL population, 10 targets were observed with the MAGIC telescopes from 2010 to 2017, for a total of 265hr of good-quality data. The data were complemented by coordinated Swift observations. The X-ray data analysis confirms that all but two sources are EHBLs. The sources show only a modest variability and a harder-when-brighter behavior, typical for this class of objects. At VHE gamma-rays, three new sources were detected and a hint of a signal was found for another new source. In each case, the intrinsic spectrum is compatible with the hypothesis of a hard-TeV nature of these EHBLs. The broadband spectral energy distributions (SEDs) of all sources are built and modeled in the framework of a single-zone, purely leptonic model. The VHE gamma-ray-detected sources were also interpreted with a spine-layer model and a proton synchrotron model. The three models provide a good description of the SEDs. However, the resulting parameters differ substantially in the three scenarios, in particular the magnetization parameter. This work presents the first mini catalog of VHE gamma-ray and multiwavelength observations of EHBLs.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A100
- Title:
- Fermi and Swift GRBs E_peak_-E_iso_ relation
- Short Name:
- J/A+A/557/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used a sample of gamma-ray bursts (GRBs) detected by Fermi and Swift to reanalyze the correlation discovered by Amati et al. (2002A&A...390...81A) between E_pi_, the peak energy of the prompt GRB emission, and E_iso_, the energy released by the GRB assuming isotropic emission. This correlation has been disputed by various authors, and our aim is to assess whether it is an intrinsic GRB property or the consequence of selection effects. We constructed a sample of Fermi GRBs with homogeneous selection criteria, and we studied their distribution in the E_pi_-E_iso_ plane. Our sample is made of 43 GRBs with a redshift and 243 GRBs without a redshift. We show that GRBs with a redshift follow a broad E_pi_-E_iso_ relation, while GRBs without a redshift show several outliers. We use these samples to discuss the impact of selection effects associated with GRB detection and with redshift measurement.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/L38
- Title:
- Fermi blazars with Doppler factors
- Short Name:
- J/ApJ/835/L38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Blazars are an extreme subclass of active galactic nuclei. Their rapid variability, luminous brightness, superluminal motion, and high and variable polarization are probably due to a beaming effect. However, this beaming factor (or Doppler factor) is very difficult to measure. Currently, a good way to estimate it is to use the timescale of their radio flares. In this Letter, we use multiwavelength data and Doppler factors reported in the literature for a sample of 86 flaring blazars detected by Fermi to compute their intrinsic multiwavelength data and intrinsic spectral energy distributions and investigate the correlations among observed and intrinsic data. Quite interestingly, intrinsic data show a positive correlation between luminosity and peak frequency, in contrast with the behavior of observed data, and a tighter correlation between {gamma}-ray luminosity and the lower-energy ones. For flaring blazars detected by Fermi, we conclude that (1) observed emissions are strongly beamed; (2) the anti-correlation between luminosity and peak frequency from the observed data is an apparent result, the correlation between intrinsic data being positive; and (3) intrinsic {gamma}-ray luminosity is strongly correlated with other intrinsic luminosities.
- ID:
- ivo://CDS.VizieR/J/MNRAS/441/1899
- Title:
- Fermi bright blazars
- Short Name:
- J/MNRAS/441/1899
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The exact location of the {gamma}-ray emitting region in blazars is still controversial. In order to attack this problem we present first results of a cross-correlation analysis between radio (11cm to 0.8mm wavelength, F-GAMMA programme) and {gamma}-ray (0.1-300GeV) ~3.5yr light curves of 54 Fermi-bright blazars. We perform a source stacking analysis and estimate significances and chance correlations using mixed source correlations.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A64
- Title:
- Fermi detection of BL Lac objects
- Short Name:
- J/A+A/562/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By cross-correlating an archival sample of 170 BL Lacs with a 2 year Fermi/LAT AGN sample, we have compiled a sample of 100 BL Lacs with Fermi detection (FBLs) and a sample of 70 non-Fermi BL Lacs (NFBLs). We compared various parameters of FBLs with those of NFBLs, including the redshift, the low-frequency radio luminosity at 408MHz (L_408MHz_), the absolute magnitude of host galaxies (M_host_), the polarization fraction from the NVSS survey (P_NVSS_), the observed arcsecond scale radio core flux at 5GHz (F_core_), and the jet Doppler factor. All these parameters are directly measured or derived from available data in the literature. We found that the Doppler factor is on average greater in FBLs than in NFBLs, and the Fermi {gamma}-ray detection rate is higher in sources with higher Doppler factor. In contrast, there are no significant differences in terms of the intrinsic parameters of redshift, L_408MHz_, M_host_, and P_NVSS_. FBLs seem to have a higher probability of exhibiting measurable proper motion.
