- ID:
- ivo://nasa.heasarc/fermigtrig
- Title:
- Fermi GBM Trigger Catalog
- Short Name:
- FERMIGTRIG
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table lists all of the triggers observed by one or more of the 14 GBM detectors (12 NaI and 2 BGO). Note that there are two Browse catalogs resulting from GBM triggers. All GBM triggers are entered in the Trigger Catalog, but only those triggers classified as bursts are entered in the <a href="/W3Browse/fermi/fermigbrst.html">Fermi GBM Burst Catalog</a>. 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. 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 information in this table is provided by the Fermi Gamma-ray Burst Monitor Instrument Operations Center (GIOC) and the Fermi Science Support Center (FSSC). The values come from a trigger catalog entry file or a burst catalog entry file provided by the GIOC. These are FITS files which may contain additional data in extensions for bursts (see the spectrum_flag and fit_flag columns) and are available for download. This table is updated automatically within a day or so of new data files being processed and made available. This is a service provided by NASA HEASARC .
1 - 3 of 3
Number of results to display per page
Search Results
- ID:
- ivo://nasa.heasarc/fermille
- Title:
- Fermi LAT Low-Energy Events Catalog
- Short Name:
- FERMILLE
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- LAT Low-Energy events (LLE) are automatically produced for each GBM GRB in the GBM Trigger Catalog if the GBM GRB has a position within 90 degrees of the LAT boresight. LLE data are generated for a given position in the sky (RA, DEC) and for a given interval of time (T0, T1) corresponding to the GBM Burst. 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)))<sup>2</sup> + (FT1Dec - (DEC))<sup>2</sup>) < PSF(EvtEnergyCorr, Theta) where <pre> * 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 <a href="https://oraweb.slac.stanford.edu/pls/slacquery/DOCUMENTS.DetailedIndex?PROJECT=GLAST&P_DOC_ID=776972">Global LAT Trigger</a>. 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. </pre> 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. The information in this table is provided by the Fermi LAT Instrument Science Operations Center (LISOC) and the Fermi Science Support Center (FSSC). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/fermilasp
- Title:
- Fermi LAT Monitored Source List
- Short Name:
- FERMILASP
- Date:
- 10 May 2024
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Fermi LAT table of monitored sources provides daily and weekly fluxes for sources of interest as described in <a href="http://fermi.gsfc.nasa.gov/ssc/data/policy/LAT_Monitored_Sources.html">http://fermi.gsfc.nasa.gov/ssc/data/policy/LAT_Monitored_Sources.html</a>. In addition, similar information will be released for any source which flares above 2x10<sup>-6</sup> photons cm<sup>-2</sup> s<sup>-1</sup> until the flux drops below 2x10<sup>-7</sup> photons cm<sup>-2</sup> s<sup>-1</sup>. Fermi is currently in survey mode and observes the entire sky every day. However, if a source does not exceed the detection threshold, no entry will appear in this catalog. 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. <b>These early flux estimates do not include systematic uncertainties and do not</b> <b>have an absolute flux calibration</b>. 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. This database table is created by the HEASARC from FITS tables received from the Fermi Science Support Center (FSSC). The ASP FITS files are produced by the LAT Instrument Science Operations Center (LISOC) and transferred from the LISOC to the FSSC about once per week. This is a service provided by NASA HEASARC .
