- ID:
- ivo://nasa.heasarc/at20g1fgl
- Title:
- AT20G/Fermi 1FGL Source Catalog
- Short Name:
- AT20G1FGL
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The high-frequency radio sky, like the gamma-ray sky surveyed by the Fermi satellite, is dominated by flat-spectrum radio quasars and BL Lac objects at bright flux levels. To investigate the relationship between radio and gamma-ray emission in extragalactic sources, the authors have cross-matched the Australia Telescope 20-GHz survey catalog (AT20G: Murphy et al. 2010, MNRAS, 402, 2403, available as a HEASARC Browse table) with the Fermi-LAT 1-year Point Source Catalog (1FGL: Abdo et al. 2010, ApJS, 188, 405, also available as the HEASARC Browse table FERMILPSC). The 6.0 sr of sky covered by both catalogs (Declination < 0 degrees, |b| > 1.5 degrees) contains 5890 AT20G radio sources and 604 1FGL gamma-ray sources. The AT20G source positions are accurate to within ~1 arcsec and, after excluding known Galactic sources, 43% of Fermi 1FGL sources have an AT20G source within the 95% Fermi confidence ellipse. Monte Carlo tests imply that at least 95% of these matches are genuine associations. Only five gamma-ray sources (1% of the Fermi catalog) have more than one AT20G counterpart in the Fermi error box. The AT20G matches also generally support the active galactic nucleus (AGN) associations in the First LAT AGN Catalog. The authors find a trend of increasing gamma-ray flux density with 20 GHz radio flux density. The Fermi detection rate of AT20G sources is close to 100% for the brightest 20 GHz sources, decreasing to 20% at 1 Jy, and to roughly 1% at 100 mJy. Eight of the matched AT20G sources have no association listed in 1FGL and are presented here as potential gamma-ray AGNs for the first time. The authors also identify an alternative AGN counterpart to one 1FGL source. The percentage of Fermi sources with AT20G detections decreases toward the Galactic plane, suggesting that the 1FGL catalog contains at least 50 Galactic gamma-ray sources in the southern hemisphere that are yet to be identified. This table contains the complete list of all 233 Fermi-AT20G matches. This table was created by the HEASARC in August 2010 based on the electronic version of Table 4 obtained from the ApJ web site. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/fermi2favs
- Title:
- Fermi All-Sky Variability Analysis Second Catalog of Flaring Gamma-Ray Sources
- Short Name:
- FERMI2FAVS
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Fermi All-sky Variability Analysis (FAVA) is an analysis technique that searches for flaring sources in data collected by the Large Area Telescope (LAT) onboard NASA's Fermi Gamma-ray Space Telescope. It uses a photometric approach to blindly search for flares over the entire sky, and a likelihood analysis to precisely locate them and to measure their spectra. 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. This database table was first ingested by the HEASARC in July 2017 using electronic data obtained from the Fermi Science Support Center (FSSC). That data is available at <a href="http://fermi.gsfc.nasa.gov/ssc/data/access/lat/fava_catalog/">http://fermi.gsfc.nasa.gov/ssc/data/access/lat/fava_catalog/</a>. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/fer2fusrid
- Title:
- Fermi 2FGL Unassociated Gamma-Ray Sources Possible Radio Identifications
- Short Name:
- FER2FUSRID
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from an all-sky radio survey between 5- and 9-GHz of sky areas surrounding all unassociated gamma-ray objects listed in the Fermi Large Area Telescope (LAT) Second Source Catalog (2FGL). The goal of these observations is to find all new gamma-ray active galactic nucleus (AGN) associations with radio sources > 10 mJy at 8GHz. The authors observed with the Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA) the areas around unassociated sources, providing localizations of weak radio point sources found in 2FGL fields at arcminute scales. They then followed up a subset of these with the Very Long Baseline Array (VLBA) and the Long Baseline Array (LBA) in order to confirm detections of radio emission on parsec-scales. The authors quantified association probabilities based on known statistics of source counts and assuming a uniform distribution of background sources. In total, they found 865 radio sources at arcsecond scales as candidates for association and detected 95 of 170 selected for follow-up observations at milliarcsecond resolution. Based on this, they obtained firm associations for 76 previously unknown gamma-ray AGNs. Comparison of these new AGN associations with the predictions from using the Wide-field Infrared Survey Explorer (WISE) color-color diagram shows that half of the associations are missed. The authors found that in 129 out of 588 gamma-ray sources observed at arcminute scales not a single radio continuum source was detected above their sensitivity limit within the 3-sigma gamma-ray localization. These "empty" fields were found to be particularly concentrated at low Galactic latitudes. The nature of these Galactic gamma-ray emitters is not yet determined. 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 table was created by the HEASARC in May 2015 based on the union of <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/217/4/">CDS Catalog J/ApJS/217/4/</a> files table2.dat (the 148 'Category I' objects that were detected at 5.0/5.5 and/or 7.3/9.0 GHz within 2.7' of the 2FGL counterpart localization), table3.dat (the 501 'Category II' objects that were detected at 5.0/5.5 and/or 7.3/9.0 GHz between 2.7' and 6.5' of the 2FGL counterpart localization) and table4.dat (the 216 'Category III' objects that were detected outside of the 6.5 arcminutes but still within the 99% positional uncertainty of the 2FGL counterpart localization). It thus contains a total of 865 objects. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/fermigbrst
- Title:
- Fermi GBM Burst Catalog
- Short Name:
- FERMIGBRST
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- When referencing results from this online catalog, please cite <a href="https://iopscience.iop.org/article/10.3847/1538-4357/ab7a18">von Kienlin, A. et al. 2020</a>, <a href="http://iopscience.iop.org/0067-0049/211/1/12/">Gruber, D. et al. 2014</a>, <a href="http://iopscience.iop.org/0067-0049/211/1/13/">von Kienlin, A. et al. 2014</a>, and <a href="http://iopscience.iop.org/article/10.3847/0067-0049/223/2/28/">Bhat, P. et al. 2016</a>. 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 <a href="/W3Browse/fermi/fermigtrig.html">Fermi GBM Trigger Catalog</a>, 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: <pre> * '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. </pre> 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: <pre> * '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. </pre> 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: <pre> * 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. </pre> 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: <pre> * Power law ('plaw'), * Comptonized (exponentially attenuated power law; 'comp') * Band ('band') * Smoothly broken power law ('sbpl') </pre> <b>Warnings</b> 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 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 burst and spectral catalog entry FITS files provided by the GIOC to the FSSC. These FITS files may contain additional data 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 .
- ID:
- ivo://nasa.heasarc/fermigdays
- Title:
- Fermi GBM Daily Data
- Short Name:
- FERMIGDAYS
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Fermi GBM Daily Data database table contains entries for each day for which GBM data has been processed. 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. This database table was created by and is updated by the HEASARC based on information supplied by the Fermi Project. It is updated on a daily basis. The tte_flag parameter was added to the table in July 2010. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/fermigsol
- Title:
- Fermi GBM Solar Flare Catalog
- Short Name:
- FERMIGSOL
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- These data represent the Fermi GBM Solar Flare Catalog. Data in this catalog are targeted specifically at Fermi observations of high-energy solar phenomena, primarily solar flares, in order to facilitate the use of Fermi data by the international solar physics community. This table catalogs Fermi Gamma-Ray Burst Monitor (GBM) triggers associated with known solar flares. The Fermi GBM Solar Flare Catalog is supported by a Fermi Guest Investigator program and maintained at <a href="http://hesperia.gsfc.nasa.gov/fermi_solar">http://hesperia.gsfc.nasa.gov/fermi_solar</a>. Please include the following acknowledgment if you use these facilities in a paper or presentation: "We acknowledge the use of the Fermi Solar Flare Observations facility funded by the Fermi GI program (<a href="http://hesperia.gsfc.nasa.gov/fermi_solar/">http://hesperia.gsfc.nasa.gov/fermi_solar/</a>)." The information in this table is provided independently by a Fermi Guest Investigator grant. The tabulated data come from <a href="http://hesperia.gsfc.nasa.gov/fermi/gbm/qlook/fermi_gbm_flare_list.txt">http://hesperia.gsfc.nasa.gov/fermi/gbm/qlook/fermi_gbm_flare_list.txt</a>. This table is updated automatically within a day or so of a new data file being made available. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/fermigtrig
- Title:
- Fermi GBM Trigger Catalog
- Short Name:
- FERMIGTRIG
- Date:
- 07 Mar 2025
- 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 .
- ID:
- ivo://nasa.heasarc/fermilbsl
- Title:
- Fermi LAT Bright Source List
- Short Name:
- FERMILBSL
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The Fermi LAT table of bright sources is a list of bright LAT sources that have statistical significances of 10 sigma or higher, based on the first three months of survey data. The primary purpose of this list is to assist proposers for Guest Investigator Cycle 2 (due date 6 March). This list will eventually be superseded by the LAT Source Catalog, to be released about one year after launch. This database table was created by the HEASARC in February 2009 based on the electronic data obtained from the Fermi Science Support Center (FSSC) available at <a href="http://fermi.gsfc.nasa.gov/ssc/data/access/lat/bright_src_list/">http://fermi.gsfc.nasa.gov/ssc/data/access/lat/bright_src_list/</a>. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/fermilac
- Title:
- Fermi LAT Fourth AGN Catalog
- Short Name:
- FERMILAC
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This is the third update to the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT). This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 years of gamma-ray data with energies greater than 50 MeV. The spectral parameters, spectral energy distributions (SEDs), yearly light curves, and associations have been updated for all sources. The catalog contains includes 3407 AGN located at high Galactic latitudes (|b| > 10 degrees). This database table was first ingested by the HEASARC in February 2010. It was last updated (to the 4LAC-DR3 version) in June 2023 using electronic data obtained from the Fermi Science Support Center (FSSC). That data is available at <a href="https://fermi.gsfc.nasa.gov/ssc/data/access/lat/4LACDR3/">https://fermi.gsfc.nasa.gov/ssc/data/access/lat/4LACDR3/</a>. Note that this table does not contain the low-latitude sources given in a separate file there, which are not formally a part of the catalog. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/fermilblaz
- Title:
- Fermi LAT Gamma-Ray Blazar Classification Catalog
- Short Name:
- FERMILBLAZ
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This database table contains a catalog of classifications for blazar candidates of uncertain type (BCU) detected by the Fermi Large Area Telescope gamma-ray instrument. These classifications have been determined by an Artificial Neural Network machine learning method. The aim of the authors' study was to develop an optimized version of this Artificial Neural Network machine learning method for classifying these blazar candidates. The final result of this study increased the classification performance by about 80% with respect to the method previously used for the classification of uncertain blazars in Chiaro et al. (<a href="https://ui.adsabs.harvard.edu/abs/2016MNRAS.462.3180C">2016MNRAS.462.3180C</a>, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/462/3180/">CDS Cat. J/MNRAS/462/3180</a>), leaving only 15 unclassified blazars out of 573 blazar candidates of uncertain type listed in the Fermi LAT 4-Year Source Catalog. 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 <a href="/W3Browse/fermi/fermi3fgl.html">3FGL Catalog</a> (Acero et al. <a href="https://ui.adsabs.harvard.edu/abs/2015ApJS..218...23A">2015ApJS..218...23A</a>, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJS/218/23/">CDS Cat. J/ApJS/218/23</a>). Radio and X-ray data were obtained from the Fermi LAT 4-Year AGN Catalog 3LAC (Ackermann et al. <a href="https://ui.adsabs.harvard.edu/abs/2015ApJ...810...14A">2015ApJ...810...14A</a>, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/810/14/">CDS Cat. J/ApJ/810/14</a>). 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. This database table was ingested by the HEASARC in May 2023 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/490/4770">CDS Catalog J/MNRAS/490/4770</a> file table1.dat. This is a service provided by NASA HEASARC .
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