J/ApJ/887/18 Classification of X-ray counterparts of 3FGL sources (Kaur+, 2019)
Classification of new X-ray counterparts for Fermi unassociated gamma-ray
sources using the Swift X-Ray Telescope.
Kaur A., Falcone A.D., Stroh M.D., Kennea J.A., Ferrara E.C.
<Astrophys. J., 887, 18 (2019)>
=2019ApJ...887...18K 2019ApJ...887...18K
ADC_Keywords: Gamma rays; X-ray sources; Active gal. nuclei; Pulsars
Keywords: Gamma-ray sources ; Blazars ; Pulsars ; X-ray sources
Abstract:
Approximately one-third of the gamma-ray sources in the third
Fermi-LAT catalog are unidentified or unassociated with objects at
other wavelengths. Observations with the X-Ray Telescope on the Neil
Gehrels Swift Observatory (Swift-XRT) have yielded possible
counterparts in ∼30% of these source regions. The objective of this
work is to identify the nature of these possible counterparts,
utilizing their gamma-ray properties coupled with the Swift derived
X-ray properties. The majority of the known sources in the Fermi
catalogs are blazars, which constitute the bulk of the extragalactic
gamma-ray source population. The galactic population on the other hand
is dominated by pulsars. Overall, these two categories constitute the
majority of all gamma-ray objects. Blazars and pulsars occupy
different parameter space when X-ray fluxes are compared with various
gamma-ray properties. In this work, we utilize the X-ray observations
performed with the Swift-XRT for the unknown Fermi sources and compare
their X-ray and gamma-ray properties to differentiate between the two
source classes. We employ two machine-learning algorithms, decision
tree and random forest (RF) classifier, to our high signal-to-noise
ratio sample of 217 sources, each of which corresponds to Fermi
unassociated regions. The accuracy scores for both methods were found
to be 97% and 99%, respectively. The RF classifier, which is based on
the application of a multitude of decision trees, associated a
probability value (Pbzr) for each source to be a blazar. This
yielded 173 blazar candidates from this source sample, with
Pbzr≥90% for each of these sources, and 134 of these possible
blazar source associations had Pbzr≥99%. The results yielded
13 sources with Pbzr≤10%, which we deemed as reasonable candidates
for pulsars, seven of which result with Pbzr≤1%. There were
31 sources that exhibited intermediate probabilities and were termed
ambiguous due to their unclear characterization as a pulsar or a blazar.
Description:
A sample of unidentified objects from the 3FGL catalog were selected
for observations with Swift-XRT. Detailed information about the sample
selection, observations, and analysis methods can be found in
A. D. Falcone et al. (2019, in preparation).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 116 186 Classification with machine learning
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See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
VIII/81 : Sydney University Molonglo Sky Survey (SUMSS V2.1) (Mauch+ 2008)
J/ApJS/188/405 : Fermi-LAT first source catalog (1FGL) (Abdo+, 2010)
J/MNRAS/424/L64 : AGN/pulsar distinction for 2FGL sources (Mirabal+, 2012)
J/ApJS/199/31 : Fermi LAT second source catalog (2FGL) (Nolan+, 2012)
J/ApJS/206/12 : Blazars with γ-ray counterparts. I. (D'Abrusco+, 2013)
J/MNRAS/432/1294 : Fermi unassociated sources ATCA observations (Petrov+, 2013)
J/ApJS/218/23 : Fermi LAT third source catalog (3FGL) (Acero+, 2015)
J/ApJ/810/14 : Third catalog of LAT-detected AGNs (3LAC) (Ackermann+, 2015)
J/ApJ/820/8 : 3FGL sources statistical classif. (Saz Parkinson+, 2016)
J/MNRAS/462/3180 : 3FGL Blazar of Unknown Type classification (Chiaro+, 2016)
J/A+A/602/A86 : Blazar candidates among Fermi/LAT 3FGL (Lefaucheur+, 2017)
J/MNRAS/470/1291 : Classifying 3FGL with ANN (Salvetti+, 2017)
J/ApJ/854/99 : The Einstein@Home gamma-ray pulsar survey. II. (Wu+, 2018)
J/ApJS/247/33 : Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)
J/MNRAS/493/1926 : 4FGL blazar classification neural network (Kovacevic+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- SwF3 Swift name (JHHMMSS.s+DDMMSS)
18 A1 --- f_SwF3 [b-d] Flag on SwF3 (1)
20- 31 A12 --- 3FGL Fermi name (JHHMM.m+DDMM)
33- 45 A13 --- Class Object class (2)
47- 51 F5.3 --- Pbz [0/1] Random forest blazar probability
53- 58 F6.2 10-16W/m2 Fx [0.7/285] 0.1-2.4keV X-ray flux
in the units of 10-13erg/cm2/s
60- 65 F6.2 10-16W/m2 Fgam [5.3/536] 0.1-100GeV gamma-ray flux
in the units of 10-13erg/cm2/s
67- 72 A6 --- OT Object type in literature
74- 111 A38 --- r_OT Reference on OT (Author and bibcode)
113- 116 A4 --- OT2 Second object type from 4FGL
(Abdollahi+, 2020, J/ApJS/247/33)
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Note (1): Flag as follows:
b = Positionally coincident with a star, TYC 5993-3722-1.
c = Positionally coincident with a rotationally variable star, CD-46 10711
of type K1IV(e).
d = Positionally coincident with a star, HD162298 of type K4III.
Note (2): Class as follows:
blazar = 135 occurrences
likely blazar = 37 occurrences
likely pulsar = 7 occurrences
pulsar = 7 occurrences
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 06-May-2021