- ID:
- ivo://CDS.VizieR/J/ApJ/807/169
- Title:
- SN IIn catalog with Fermi LAT
- Short Name:
- J/ApJ/807/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays in collisionless shocks and emit GeV {gamma}-rays and TeV neutrinos on a timescale of several months. We perform the first systematic search for {gamma}-ray emission in Fermi Large Area Telescope data in the energy range from 100MeV to 300GeV from the ensemble of 147 SNe Type IIn exploding in a dense CSM. We search for a {gamma}-ray excess at each SNe location in a one-year time window. In order to enhance a possible weak signal, we simultaneously study the closest and optically brightest sources of our sample in a joint-likelihood analysis in three different time windows (1 year, 6 months, and 3 months). For the most promising source of the sample, SN 2010jl (PTF 10aaxf), we repeat the analysis with an extended time window lasting 4.5 years. We do not find a significant excess in {gamma}-rays for any individual source nor for the combined sources and provide model-independent flux upper limits for both cases. In addition, we derive limits on the {gamma}-ray luminosity and the ratio of {gamma}-ray-to-optical luminosity ratio as a function of the index of the proton injection spectrum assuming a generic {gamma}-ray production model. Furthermore, we present detailed flux predictions based on multi-wavelength observations and the corresponding flux upper limit at a 95% confidence level (CL) for the source SN 2010jl (PTF 10aaxf).
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/631/A150
- Title:
- Softly X-raying the gamma-ray sky I.
- Short Name:
- J/A+A/631/A150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BL Lac objects are an extreme type of active galactic nuclei (AGNs) that belong to the largest population of gamma-ray sources: blazars. This class of AGNs shows a double-bumped spectral energy distribution that is commonly described in terms of a synchrotron self-Compton (SSC) emission process, whereas the low-energy component that dominates their emission between the infrared and the X-ray band is tightly connected to the high-energy component that peaks in the gamma-rays. Two strong connections that link radio and mid-infrared emission of blazars to the emission in the gamma-ray band are well established. They constitute the basis for associating gamma-ray sources with their low-energy counterparts. We searched for a possible link between X-ray and gamma-ray emissions for the subclass of BL Lacs using all archival Swift/XRT observations combined with Fermi data for a selected sample of 351 sources. Analyzing ~2400ks of Swift/XRT observations that were carried out until December 2018, we discovered that above the gamma-ray flux threshold Fgamma~=3x10^-12^erg/cm^2^/s, 96% of all Fermi BL Lacs have an X-ray counterpart that is detected with signal-to-noise ratio >3. We did not find any correlation or clear trend between X-ray and gamma-ray fluxes and/or spectral shapes, but we discovered a correlation between the X-ray flux and the mid-infrared color. Finally, we discuss on a possible interpretation of our results in the SSC framework.
- ID:
- ivo://CDS.VizieR/J/A+A/467/585
- Title:
- Sources detected by ISGRI
- Short Name:
- J/A+A/467/585
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In its first 4 years of observing the sky above 20keV, INTEGRAL-ISGRI has detected 500 sources, around half of which are new or unknown at these energies. Follow-up observations at other wavelengths revealed that some of these sources feature unusually large column densities, long pulsations, and other interesting characteristics. We investigate where new and previously-known sources detected by ISGRI fit in the parameter space of high-energy objects, and we use the parameters to test correlations expected from theoretical predictions. For example, the influence of the local absorbing matter on periodic modulations is studied for Galactic High-Mass X-ray Binaries (HMXBs) with OB supergiant and Be companions. We examine the spatial distribution of different types of sources in the Milky Way using various projections of the Galactic plane, in order to highlight signatures of stellar evolution and to speculate on the origin of the group of sources whose classifications are still uncertain.
- ID:
- ivo://CDS.VizieR/J/ApJ/720/1146
- Title:
- Spectral analysis of GRBs
- Short Name:
- J/ApJ/720/1146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A time-resolved spectral analysis for a sample of 22 intense, broad gamma-ray burst (GRB) pulses from the Compton Gamma Ray Observatory (CGRO)/BATSE GRB sample is presented. We fit the spectra with the Band function and investigate the correlation between the observed flux (F) and the peak energy (E_p_) of the {nu}f_{nu}_ spectrum in the rising and decaying phases of these pulses. Two kinds of E_p_ evolution trends, i.e., hard-to-soft (two-thirds of the pulses in our sample) and E_p_-tracing-F (one-third of the pulses in our sample), are observed in pulses from different GRBs and even from different pulses of the same burst. No dependence of spectral evolution feature on the pulse shape is found. A tight F-E_p_ positive correlation is observed in the decaying phases, with a power-law index ~2.2, which is much shallower than that expected from the curvature effect. In the rising phase, the observed F is either correlated or anti-correlated with E_p_, depending on the spectral evolution feature, and the power-law index of the correlation is dramatically different among pulses. More than 80% of the low-energy photon indices in the time-resolved spectra, whose E_p_'s are anti-correlated with F during the rising phase, violate the death line of the synchrotron radiation, disfavoring the synchrotron radiation model for these gamma rays. The F-E_p_ correlation, especially for those GRBs with E_p_-tracking-F spectral evolution, may be due to the viewing angle and jet structure effects. In this scenario, the observed F-E_p_ correlation in the rising phase may be due to the line of sight toward a structured jet (or jetter) moving from off-beam to on-beam, and both the on-beam emission and the delayed photons from high latitude of the GRB fireball contribute to the decaying phase, resulting in a shallower slope of the observed F-E_p_ correlation than that predicted by the pure curvature effect.
- ID:
- ivo://CDS.VizieR/J/ApJS/166/298
- Title:
- Spectral catalog of bright BATSE gamma-ray bursts
- Short Name:
- J/ApJS/166/298
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a systematic spectral analysis of 350 bright gamma-ray bursts (GRBs) observed with the Burst and Transient Source Experiment (BATSE; 30keV-2MeV) with high temporal and spectral resolution. Our sample was selected from the complete set of 2704 BATSE GRBs based on their energy fluence or peak photon flux values to assure good statistics and included 17 short GRBs. To obtain well-constrained spectral parameters, several photon models were used to fit each spectrum.
- ID:
- ivo://CDS.VizieR/J/ApJS/224/26
- Title:
- Spectral energy distributions of Roma BZCAT blazars
- Short Name:
- J/ApJS/224/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combined multi-wavelength data for blazars from the Roma-BZCAT catalog and analyzed hundreds of X-ray spectra. We present the fluxes and spectral energy distributions (SEDs), in 12 frequency bands from radio to {gamma}-rays, for a final sample of 2214 blazars. Using a model-independent statistical approach, we looked for systematic trends in the SEDs; the most significant trends involved the radio luminosities and X-ray spectral indices of the blazars. We used a principal component analysis (PCA) to determine the basis vectors of the blazar SEDs and, in order to maximize the size of the sample, imputed missing fluxes using the K-nearest neighbors method. Using more than an order of magnitude more data than was available when Fossati et al. first reported trends of SED shape with blazar luminosity, we confirmed the anti-correlation between radio luminosity and synchrotron peak frequency, although with greater scatter than was seen in the smaller sample. The same trend can be seen between bolometric luminosity and synchrotron peak frequency. Finally, we used all of the available blazar data to determine an empirical SED description that depends only on the radio luminosity at 1.4GHz and the redshift. We verified that this statistically significant relation was not a result of the luminosity-luminosity correlations that are natural in flux-limited samples (i.e., where the correlation is actually caused by the redshift rather than the luminosity).
- ID:
- ivo://CDS.VizieR/J/ApJ/756/44
- Title:
- Spectral lags and counts of the RHESSI GRBs
- Short Name:
- J/ApJ/756/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 427 gamma-ray bursts (GRBs) from a database (2002 February-2008 April) of the RHESSI satellite is analyzed statistically. The spectral lags and peak-count rates, which have been calculated for the first time in this paper, are studied, completing an earlier analysis of durations and hardness ratios. The analysis of the RHESSI database has already inferred the existence of a third group with intermediate duration, apart from the so-called short and long groups. The first aim of this article is to discuss the properties of these intermediate-duration bursts in terms of peak-count rates and spectral lags. The second aim is to discuss the number of GRB groups using another statistical method and by also employing the peak-count rates and spectral lags. The standard parametric (model-based clustering) and non-parametric (K-means clustering) statistical tests together with the Kolmogorov-Smirnov and Anderson-Darling tests are used. Two new results are obtained. (1) The intermediate-duration group has properties similar to those of the group of short bursts. Intermediate and long groups appear to be different. (2) The intermediate-duration GRBs in the RHESSI and Swift databases seem to be represented by different phenomena.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A81
- Title:
- Spectral properties of energetic GRBs
- Short Name:
- J/A+A/573/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the time-resolved spectral properties of energetic gamma-ray bursts (GRBs) with good high-energy photon statistics observed by the Gamma-Ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space Telescope. We aim to constrain in detail the spectral properties of GRB prompt emission on a time-resolved basis and to discuss the theoretical implications of the fitting results in the context of various prompt emission models. Our sample comprises eight GRBs observed by the Fermi GBM in its first five years of mission, with 1keV-1MeV fluence f>1.0x10^-4^erg/cm2 and a signal-to-noise ratio level of S/N>=10.0 above 900keV. We performed a time-resolved spectral analysis using a variable temporal binning technique according to optimal S/N criteria, resulting in a total of 299 time-resolved spectra. We performed Band function fits to all spectra and obtained the distributions for the low-energy power-law index {alpha}, the high-energy power-law index {beta}, the peak energy in the observed {nu}F_{nu}_ spectrum E_p_, and the difference between the low- and high-energy power-law indices {Delta}s={alpha}-{beta}. We also applied a physically motivated synchrotron model, which is a triple power-law with constrained power-law indices and a blackbody component, to test the prompt emission for consistency with a synchrotron origin and obtain the distributions for the two break energies E_b,1_ and E_b,2_, the middle segment power-law index {beta}, and the Planck function temperature kT.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A21
- Title:
- Spectral properties of 438 GRBs
- Short Name:
- J/A+A/530/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the spectral analysis of the public data of 438 gamma ray bursts (GRBs) detected by the Fermi Gamma ray Burst Monitor (GBM) up to March 2010. For 432 bursts we could fit the time-integrated spectrum. In 318 cases we could reliably constrain the peak energy E^obs^_peak_ of their {nu}F{nu} spectrum by analyzing their time-integrated spectrum between 8keV and 35MeV. Eighty percent of these spectra are fitted by a power-law with an exponential cutoff, and the remaining with the Band function. Among these 318 GRBs, 274 belong to the long GRB class and 44 to the short.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/108
- Title:
- Spectral properties of Type Ic & Ic-bl SNe
- Short Name:
- J/ApJ/832/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first systematic investigation of spectral properties of 17 Type Ic Supernovae (SNe Ic), 10 broad-lined SNe Ic (SNe Ic-bl) without observed gamma-ray bursts (GRBs), and 11 SNe Ic-bl with GRBs (SN-GRBs) as a function of time in order to probe their explosion conditions and progenitors. Using a number of novel methods, we analyze a total of 407 spectra, which were drawn from published spectra of individual SNe as well as from the densely time-sampled spectra of Modjaz+ (2014, J/AJ/147/99). In order to quantify the diversity of the SN spectra as a function of SN subtype, we construct average spectra of SNe Ic, SNe Ic-bl without GRBs, and SNe Ic-bl with GRBs. We find that SN 1994I is not a typical SN Ic, contrasting the general view, while the spectra of SN 1998bw/GRB 980425 are representative of mean spectra of SNe Ic-bl. We measure the ejecta absorption and width velocities using a new method described here and find that SNe Ic-bl with GRBs, on average, have quantifiably higher absorption velocities, as well as broader line widths than SNe without observed GRBs. In addition, we search for correlations between SN-GRB spectral properties and the energies of their accompanying GRBs. Finally, we show that the absence of clear He lines in optical spectra of SNe Ic-bl, and in particular of SN-GRBs, is not due to them being too smeared-out due to the high velocities present in the ejecta. This implies that the progenitor stars of SN-GRBs are probably free of the He-layer, in addition to being H-free, which puts strong constraints on the stellar evolutionary paths needed to produce such SN-GRB progenitors at the observed low metallicities.
