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This table contains the complete list of all 233 Fermi-AT20G matches.
A list of 216 target fields were observed with the VLA. The instantaneous bandwidth was split into two parts, with one half centered at 5.0 GHz (4.5 - 5.5 GHz) and the other centered at 7.3 GHz (6.8 - 7.8 GHz). The observations were made on 2012 October 26 and 2012 November 3. See section 2.1 of the reference paper for more details. These data are included in this HEASARC table.
During the first campaign with the ATCA from 2012 September 19-20, the authors observed 411 2FGL unassociated sources in a Declination range of -90 degrees to +10 degrees at 5.5 and 9 GHz. The details of this observing campaign and results have been reported by Petrov et al. (2013, MNRAS, 432, 1294: available at the HEASARC as the AT2FGLUS table). The authors detected a total of 424 point sources. In a second ATCA campaign on 2013 September 25-28, the authors re-observed sources that were detected at 5 GHz, but were not detected at 9 GHz. See section 2.2 of the reference paper for more details. These data are included in this HEASARC table.
Follow-up observations of 149 targets selected from the VLA and ATCA surveys above -30 degrees Declination were conducted with the VLBA between 2013 Feb-Aug (VCS7 project; 4.128 - 4.608 and 7.392 - 7.872 GHz simultaneously) and in 2013 Jun-Dec (campaign S5272; 7.392 - 7.872 GHz only). See section 2.3 of the reference paper for more details. These data are NOT included in this HEASARC table.
For sources with Declination below -30 degrees, the authors added 21 objects to the on-going LCS campaign being conducted using the LBA (Petrov et al. 2011, MNRAS, 414, 2528) in 2013 Mar-2013 Jun at 8.200 - 8.520 GHz. See section 2.4 of the reference paper for more details. These data are NOT included in this HEASARC table.
This catalog contains the flares and sources detected by running FAVA over the first 7.4 years of Fermi mission, from Modified Julian Date (MJD) 54682 (2008-08-04) to 57391 (2016-01-04). The analysis has been run in weekly time bins and in two independent energy bands, 100-800 MeV and 0.8-300 GeV. The detection threshold applied to the catalog flares is equivalent to 6 sigma (pre trials).
The sources in the 2FAV are identified as clusters of flares. Their position and the corresponding error are derived from a weighted average of the best localized flares in the cluster. Likely gamma-ray counterparts, based on positional coincidence, are provided for the sources.
Compared to the 2FGL catalog, the 3FGL catalog incorporates twice as much data as well as a number of analysis improvements, including improved calibrations at the event reconstruction level, an updated model for Galactic diffuse gamma-ray emission, a refined procedure for source detection, and improved methods for associating LAT sources with potential counterparts at other wavelengths.
Sources were detected and characterized in the 100 MeV to 300 GeV range. Source detection was based on a threshold likelihood Test Statistic of 25, corresponding to a significance of just over 4 sigma.
This catalog includes source location regions, defined in terms of elliptical fits to the 95% confidence regions and spectral fits with three different spectral forms; power-law for most sources, log-parabola for significantly curved sources, and power-law with exponential cutoff for known gamma-ray pulsars. It also includes flux measurements in 5 bands for each source. The Fermi LAT Team has evaluated the populations of gamma-ray sources that are represented in the catalog using a protocol defined before launch. Individual LAT-detected sources have been provided identifications or plausible associations with sources in other astronomical catalogs. Care was taken to characterize the sensitivity of the results to the model of interstellar diffuse gamma-ray emission used to model the bright foreground, and a number of sources at low Galactic latitudes and toward bright local interstellar clouds are flagged as having positions that are strongly dependent on the model or as potentially entirely due to incorrectly modeled structure in the Galactic diffuse emission.
This catalog has been superseded by the Fermi LAT 8-Year Point Source Catalog, also known as 4FGL. Please refer to that if you want the latest version.
This table lists all of the triggers observed by a subset of the 14 GBM detectors (12 NaI and 2 BGO) which have been classified as gamma-ray bursts (GRBs). Note that there are two Browse catalogs resulting from GBM triggers. All GBM triggers are entered in the Fermi GBM Trigger Catalog, while only those triggers classified as bursts are entered in the Burst Catalog. Thus, a burst will be found in both the Trigger and Burst Catalogs. The Burst Catalog analysis requires human intervention; therefore, GRBs will be entered in the Trigger Catalog before the Burst Catalog. The latency requirements are 1 day for triggers and 3 days for bursts. There are four fewer bursts in the online catalog than in the Gruber et al. 2014 paper. The four missing events (081007224, 091013989, 091022752, and 091208623) have not been classified with certainty as GRBs and are not included in the general GRB catalog. This classification may be revised at a later stage.
The GBM consists of an array of 12 sodium iodide (NaI) detectors which cover the lower end of the energy range up to 1 MeV. The GBM triggers off of the rates in the NaI detectors, with some Terrestrial Gamma-ray Flash (TGF)-specific algorithms using the bismuth germanate (BGO) detectors, sensitive to higher energies, up to 40 MeV. The NaI detectors are placed around the Fermi spacecraft with different orientations to provide the required sensitivity and FOV. The cosine-like angular response of the thin NaI detectors is used to localize burst sources by comparing rates from detectors with different viewing angles. The two BGO detectors are placed on opposite sides of the spacecraft so that all sky positions are visible to at least one BGO detector.
The signals from all 14 GBM detectors are collected by a central Data Processing Unit (DPU). This unit digitizes and time-tags the detectors' pulse height signals, packages the resulting data into several different types for transmission to the ground (via the Fermi spacecraft), and performs various data processing tasks such as autonomous burst triggering.
The GRB science products are transmitted to the FSSC in two types of files. The first file, called the "bcat" file, provides basic burst parameters such as duration, peak flux and fluence, calculated from 8-channel data using a spectral model which has a power-law in energy that falls exponentially above an energy EPeak, known as the Comptonized model. The crude 8-channel binning and the simple spectral model allow data fits in batch mode over numerous time bins in an efficient and robust fashion, including intervals with little or no flux, yielding both values for the burst duration, and deconvolved lightcurves for the detectors included in the fit. The bcat file includes two extensions. The first, containing detailed information about energy channels and detectors used in the calculations, is detector-specific, and includes the time history of the deconvolved flux over the time intervals of the burst. The second shows the evolution of the spectral parameters obtained in a joint fit of the included detectors for the model used, usually the Comptonized model described above. The bcat files and their time-varying quantities contained in these two extensions are available at the HEASARC FTP site. Quantities derived from these batch fits are given in the bcat primary header and presented in the Browse table, as described below. The main purpose of the analysis contained in the bcat file is to produce a measure of the duration of the burst after deconvolving the instrument response. The duration quantities are:
* 't50' - the time taken to accumulate 50% of the burst fluence starting at the 25% fluence level. * 't90' - the time taken to accumulate 90% of the burst fluence starting at the 5% fluence level.By-products of this analysis include fluxes on various timescales and fluences, both obtained using the simple Comptonized model described above. These quantities are detailed in the Browse table using the following prefixes:
* 'flux' - the peak flux over 3 different timescales obtained in the batch mode fit used to calculate t50/t90. * 'fluence' - the total fluence accumulated in the t50/t90 calculation.The fluxes and fluences derived from the 8-channel data for these bcat files should be considered less reliable than those in the spectral analysis files described below.
Analysis methods used in obtaining these quantities are detailed in the first GBM GRB Catalog (Paciesas et al. 2011). Updates of bcat files will be sent (with new version numbers) as these parameters are refined. This "bcat" file is produced for triggers that are classified as GRBs (with exceptions as described below), and supplements the initial data in the trigger or "tcat" file that is produced for all triggers.
The second type of file (the spectrum or "scat" file) provides parameter values and goodness-of-fit measures for different types of spectral fits and models. These fits are performed using 128-channel data, either CSPEC or, for short bursts, TTE data. The type and model are coded into the file name. There are currently two spectrum categories:
* Peak flux ('pflx') - a single spectrum over the time range of the peak flux of the burst * Fluence ('flnc') - a single spectrum over the entire burst duration selected by the duty scientist.Like the bcat files, the scat files have two extensions. The first extension gives detector-specific information, including photon fluxes and fluences for each detector, which are provided for each energy channel. The second extension provides derived quantities such as flux, fluence and model parameters for the joint fit of all included detectors. The scat files and their energy-resolved quantities contained in these two extensions are available in the Fermi data archive at the HEASARC. Quantities derived from these spectral fits are available in the Browse table, as described below and in Goldstein et al. (2011).
The spectra are fit with a number of models, with the signal-to-noise ratio of the spectrum often determining whether a more complex model is statistically favored. The current set is:
* Power law ('plaw'), * Comptonized (exponentially attenuated power law; 'comp') * Band ('band') * Smoothly broken power law ('sbpl')
Warnings
The bcat and scat files result from two completely independent analyses, and consequently, it is possible that the same quantities might show differences. Indeed,
1) the fluxes and fluences in the "scat" files should be considered more reliable than those in the "bcat" files, with the official fluxes and fluences being those yielded by the statistically favored model ("Best_Fitting_Model" in the Browse table) and with the full energy resolution of the instrument;
2) in both the bcat and scat analyses, the set of detectors used for the fits ("Scat_Detector_Mask" in the Browse table) may not be the same as the set of detectors that triggered GBM ("Bcat_Detector_Mask" in the Browse table);
3) background definitions are different for the bcat and scat analysis (see References below).
Finally, for weak events, it is not always possible to perform duration or spectral analyses, and some bursts occur too close in time to South Atlantic Anomaly entries or exits by Fermi with resultant data truncations that prevent background determinations for the duration analysis. There is not an exact one-to-one correspondence between those events for which the duration analysis fails and those which are too weak to have a useful spectral characterization. This means that in the HEASARC Browse table there are a handful of GRBs which have duration parameters but not spectral fit parameters, and vice versa. In these cases, blank entries in the table indicate missing values where an analysis was not possible. Values of 0.0 for the uncertainties on spectral parameters indicate those parameters have been fixed in the fit from which other parameters or quantities in the table were derived. Missing values for model fit parameters indicate that the fit failed to converge for this model. This is true mostly for the more complicated models (SBPL or BAND) when the fits fail to converge for weaker bursts. Bad spectral fits can often result in unphysical flux and fluence values with undefined errors. We include these bad fits but leave the error fields blank when they contain undefined values. The selection criteria used in the first catalog (Goldstein et al. 2011) for the determination of the best-fit spectral model are different from those in the second catalog (Gruber et al. 2014). The results using the two methods on the sample included in Goldstein et al. (2011) are compared in Gruber et al. (2014). The old catalog files can be retrieved using the HEASARC ftp archive tree, under "previous" directories. The values returned by Browse always come from the "current" directories. The chi-squared statistic was not used in the 2nd catalog, either for parameter optimization or model comparison. The chi-squared values are missing for a few GRBs. This is believed to be because of a known software issue and should not be considered indicative of a bad fit.
The variable "scatalog" included in the Browse tables and in the FITS files indicates which catalog a file belongs to, with 2 being the current catalog, and 1 (or absent) the first catalog (preliminary values may appear with value 0).
The daily data products consist of GBM data that are produced continuously regardless of whether a burst occurred. Thus these products are the count rates from all detectors, the monitoring of the detector calibrations (e.g., the position of the 511 keV line), and the spacecraft position and orientation.
Some days may also have event lists known as time-tagged event (TTE) files associated with them. These TTE files have the same format as those produced for bursts. Due to the large data volume associated with TTE files, only certain portions of the day considered of scientific interest to the instrument team will have TTE data.
The underlying Level 0 data arrive continuously with each Ku band downlink. However, the GBM Instrument Operations Center (GIOC) will form FITS files of the resulting Level 1 data covering an entire calendar day (UTC); these daily files are then sent to the FSSC. Consequently, the data latency is about one day: the first bit from the beginning of a calendar day may arrive a few hours after the day began while the last bit will be processed and added to the data product file a few hours after the day ended. These data products may be sent to the FSSC file by file as they are produced, not necessarily in one package for a given day.
Note that the data may include events from slightly before and slightly after the day official boundaries, which will be reflected in the start and stop times in the table. Consequently, some events may be listed in files for two consecutive days (e.g., at the end of one and the beginning of the next).
Due to the continuous nature of GBM processing, new data files may arrive after the day has been included in Browse and reprocessed version may also arrive at any time. The reprocessed data will have the version number incremented (see file name conventions below). Browse will automatically download the latest versions of the data files.
The GBM consists of an array of 12 sodium iodide (NaI) detectors which cover the lower end of the energy range up to 1 MeV. The GBM triggers off of the rates in the NaI detectors, with some Terrestrial Gamma-ray Flash (TGF)-specific algorithms using the bismuth germanate (BGO) detectors, sensitive to higher energies, up to 40 MeV. The NaI detectors are placed around the Fermi spacecraft with different orientations to provide the required sensitivity and FOV. The cosine-like angular response of the thin NaI detectors is used to localize burst sources by comparing rates from detectors with different viewing angles. The two BGO detectors are placed on opposite sides of the spacecraft so that all sky positions are visible to at least one BGO detector.
The signals from all 14 GBM detectors are collected by a central Data Processing Unit (DPU). This unit digitizes and time-tags the detectors' pulse height signals, packages the resulting data into several different types for transmission to the ground (via the Fermi spacecraft), and performs various data processing tasks such as autonomous burst triggering.
The tabulated fluxes are derived at the LAT Instrument Science Operations center in a 'quick look' analysis to produce results quickly to facilitate follow-up multi-wavelength observations of flaring sources. The table of released fluxes will be updated as analysis and calibrations improve.
These early flux estimates do not include systematic uncertainties and do not have an absolute flux calibration. Use of these data as absolute flux measurements for constraining models or for comparison to other data is strongly discouraged at this time. In addition to overall normalization uncertainties, source fluxes may have variations of up to 10% due to currently-uncorrected dependencies of the gamma-ray detection efficiency on variations of the particle background in orbit. Please note that these results are produced using preliminary instrument response functions and calibrations. The quality and stability of these results will improve when updated calibrations become available over the coming months.
Looking beyond the gamma-ray features of blazars, interesting information can be obtained from a multiwavelength study of the sources and particularly from X-ray and radio flux. In this study the authors tested the possibility to use those two parameters to improve the performance of the network. They did not consider any optical spectroscopy data because, when considering uncertain sources, optical spectra are very often not available or not sufficiently descriptive of the nature of the source.
The gamma-ray flux was obtained by adding five time-integrated fluxes in five bands (0.1-0.3, 0.3-1, 1-3, 3-10, 10-100 GeV) from the 3FGL Catalog (Acero et al. 2015ApJS..218...23A, CDS Cat. J/ApJS/218/23). Radio and X-ray data were obtained from the Fermi LAT 4-Year AGN Catalog 3LAC (Ackermann et al. 2015ApJ...810...14A, CDS Cat. J/ApJ/810/14). Radio fluxes used were measured at frequencies of 1.4 and 0.8 GHz; the X-ray fluxes were measured in the 0.1-2.4keV range.
The complete list of 567 classified BCUs is presented in this table in which sources are ordered by increasing likelihood of a source being a BL Lac.
The time interval analyzed here is from the beginning of Fermi LAT science operations on 2008 August 4 (MET 239557447) to 2011 August 1 (MET 333849586), covering very nearly 3 years. In this work, the authors analyze gamma rays with energies in the range 10-500 GeV. To limit the contamination from gamma rays produced by cosmic-ray interactions in the upper atmosphere, gamma rays with zenith angles greater than 105 degrees were excluded. To further reduce the residual gamma rays from the upper atmosphere only data for time periods when the spacecraft rocking angle was less than 52 degrees were considered. See Section 2 of the reference paper for further explanations.
The standard LLE selection applied to the downloaded events is the following:
(FswGamState==0 && TkrNumTracks>0 && (GltEngine==6 || GltEngine==7) && EvtEnergyCorr > 0) && (FT1ZenithTheta<90.0) && (FT1Theta<=90.0) && (((cos(FT1Dec*0.0174533)*(FT1Ra - (RA)))2 + (FT1Dec - (DEC))2) < PSF(EvtEnergyCorr, Theta)
where
* FswGamState is the status of the Flight Sofware Gamma filter. We require that the event is a gamma-ray (FswGamState==0). * TkrNumTracks is the number of tracks in the tracker. We require that there is at least one track. This requires the event to have a reconstructed direction. * GltEngine is the status of the Global LAT Trigger. We require that GltEngine equals 6 or 7, which corresponds to taking all the events that trigger in the tracker TKR but did not have a region of interest (ROI) associated (GltEngine 7) or all the events that pass the CalHI (at least 1 GeV in one crystal). * EvtEnergyCorr is the best estimation of the reconstructed energy, especially at low energy. * Theta is the reconstructed source direction (Theta) with respect the LAT boresight. * PSF(EvtEnergyCorr, Theta) represents the functional form of the containment radius of the Point Spread Function (PSF) of the LAT.
The exact cut used to select the events is saved in the keyword LLECUT in the primary header of each LLE file. If the GBM catalog position of the burst is updated (due to a refined localization from LAT or Swift or from subsequent on ground analysis), the LLE data are automatically updated and new versions of the LLE files are produced. In some cases, LLE data are manually generated (using a better localization which may or may not have been used in the GBM Trigger Catalog). For each updated position, the version of the corresponding LLE files increases by one.
There are six FITS files provided for each entry: the LLE event file, the time-binned spectrum (CSPEC) file, the CSPEC response (RSP) file, and the extracted burst spectrum (the PHA-I file) for the entire duration of the burst, an LLE event file with same time cut as the RSP and PHA-I files, and a LAT pointing and livetime history file.
There are six FITS files provided for each entry: the LLE event file (gll_lle_bnNNNNNNNNN_vMM.fit), the time-binned spectrum (CSPEC) file (gll_cspec_bnNNNNNNNNN_vMM.pha), the CSPEC response (RSP) file (gll_cspec _bnNNNNNNNNN_vMM.rsp), and the extracted burst spectrum (the PHA-I file) for the entire duration of the burst (gll_pha_bnNNNNNNNNN_vMM.fit), an LLE event file with same time cut as the RSP and PHA-I files (gll_selected_bnNNNNNNNNN_vMM.fit), and a LAT pointing and livetime history file (gll_pt_bnNNNNNNNNN_vMM.fit).
The LLE event file format is similar to the LAT photon file format with some exceptions. Because the LLE data are tightly connected to a particular object (position and time), the FITS keyword OBJECT has been added to the file. Generally, OBJECT will correspond to the entry of the GBM Trigger Catalog used to generate LLE data and corresponds to the "name" column in the FERMILLE table (and in the GBM Trigger Catalog table). For similar reasons, the position of the object used to select LLE file is written in the header of each extension of each LLE file. PROC_VER corresponds to the iteration of the analysis of LLE data. PASS_VER corresponds to the iteration for the reconstruction and the general event classification (Pass6, Pass7, etc.). VERSION corresponds to the version of the LLE product for this particular event. The update of a location of a GRB will increase the number of VERSION in the file, but will leave the PASS_VER and PROC_VER unchanged.
The CSPEC file is obtained from directly binning the TTE files. It provides a series of spectra, accumulated every second, from -1000 to 1000 seconds around the burst. Each spectrum is binned in 50 energy channels, ranging typically from 10 MeV to 100 GeV. The format of the CSPEC file is tailored to satisfy rmfit standards, and it is not directly usable in XSPEC.
The CSPEC Response file (the RSP file) is the detector response matrix calculated from Monte Carlo simulation, and it corresponds to a single response matrix for each Gamma-Ray Burst or Solar Flare.
The PHA-I file contains the count spectrum. The PHA-I file is created from the same time interval used to compute the response matrix.
The selected events file is identical to the LLE event file with an additional time selection applied to match the cut used to compute response matrix and PHA-I files.
The LAT pointing and livetime history file is identical to the standard LAT file but with entries every second (instead of every 30 seconds). It spans 4600 seconds before and 4600 after the trigger time.
For each week, the FSSC provides two FITS files: an all-sky file of photons containing positions, energies, etc. and a spacecraft pointing history file. The underscore separated fields in the file names indicate the file type (photon or spacecraft), the Fermi mission week (e.g., w009 = week 9), the processing version (which will change with each major reprocessing of LAT data), and a version number for the file itself. Note that currently the data may include events from slightly after the official week boundaries, which will be reflected in the start and stop times in the table. Any "run" of LAT data the FSSC receives that starts in a given week is put into the weekly file for that week and not broken up.
Note additional selections must be applied to the weekly files prior to use in a data analysis. See LAT Data Selection Recommendations and Caveats About Analyzing LAT Data for more information.
For queries based on position, energy, and exact times, use the FSSC's LAT data server.
The authors have assembled the largest and most complete catalog of HSP blazars to date, which includes 1691 sources. A number of population properties, such as infrared colors, synchrotron peak, redshift distributions, and gamma-ray spectral properties, have been used to characterize the sample and maximize completeness. The authors also derived the radio log N - log S distribution. This catalog has already been used to provide seeds to discover new very high energy objects within Fermi-LAT data and to look for the counterparts of neutrino and ultra-high energy cosmic ray sources, showing its potential for the identification of promising high-energy gamma-ray sources and multi-messenger targets.
This table comprises the 2WHSP catalog, a multi-frequency catalog of HSP. It contains 1691 sources, 288 of which are newly identified HSPs, 540 are previously known HSPs, 814 are HSP candidates, 45 are HSP blazars taken from the 2FHL catalog, and 4 from TeVCat (http://tevcat.uchicago.edu).