J/A+A/370/468 Variability of gamma-ray sources (Torres+, 2001)
A variability analysis of low-latitude unidentified gamma-ray sources
Torres D.F., Romero G.E., Combi J.A., Benaglia P., Andernach H., Punsly B.
<Astron. Astrophys. 370, 468 (2001)>
=2001A&A...370..468T 2001A&A...370..468T
ADC_Keywords: Gamma rays ; Radio sources
Keywords: gamma-rays: observations - gamma-rays: theory -
ISM: supernova remnants - black holes physics
Abstract:
We present a study of 40 low-latitude unidentified 3EG gamma-ray
sources which were found to be not positionally coincident with any
known class of potential gamma-ray emitters in the Galaxy (Romero et
al., 1999A&A...348..868R 1999A&A...348..868R). We have performed a variability analysis
which reveals that many of these 40 sources are variable. These
sources have, in addition, a steep mean value of the gamma-ray
spectral index, <Γ≥2.41±0.2, which, combined with the high
level of variability, seems to rule out a pulsar origin. The
positional coincidences with uncatalogued candidates to supernova
remnants were also studied. Only 7 sources in the sample are spatially
coincident with these candidates, a result that is shown to be
consistent with the expected level of pure chance association. A
complementary search for weak radio counterparts was also conducted
and the results are presented as an extensive table containing all
significant point-like radio sources within the 40 EGRET fields. We
argue that in order to produce the high variability, steep gamma-ray
spectra, and absence of strong radio counterparts observed in some of
the gamma-ray sources of our sample, a new class of objects should be
postulated, and we analyze a viable candidate.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 63 40 Unidentified 3EG sources without known possible
galactic counterparts
table1.tex 74 117 LaTeX version of table1
table5.txt 110 2783 Original table5
table5a.dat 36 40 Gamma-source positions
table5b.dat 218 1883 Possible radio-counterparts for each 3EG source.
survey.dat 118 116 Survey references
table6.dat 28 101 SNRs candidates
table7.dat 75 67 Statistical variability of AGNs.
table8.dat 32 75 Variability index I for all low latitude
unidentified sources
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See also:
J/ApJS/123/79 : Third EGRET catalog (3EG) (Hartman+, 1999)
J/A+AS/131/11 : Radio sources related to gamma-ray emission (Reich+ 1998)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- 3EGJ 3EG source designation ("J" omitted)
10 A1 --- n_3EGJ [+*] Note on 3EG source (1)
12- 17 F6.2 deg GLON Galactic longitude
19- 24 F6.2 deg GLAT Galactic latitude
26- 29 F4.2 deg e_Pos Error in the position (2)
31- 34 F4.2 --- SI Spectral index, Γ
(N(E) ∝ E-Γ)
36- 39 F4.2 --- e_SI rms uncertainty on SI
41- 44 F4.1 10-8cm-2/s Fgamma γ-ray flux
46- 49 F4.1 10-8cm-2/s sigma Standard deviation of the flux measurements
51- 52 I2 --- Nvp Number of viewing periods
54- 58 F5.1 % mu Fluctuation index, µ=100σ/<Fgamma>
60- 63 F4.2 --- I Average statistical index of variability,
I=µ/26.9
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Note (1): Individual notes:
*: This source also displays short-term variability
(Wallace et al., 2000ApJ...540..184W 2000ApJ...540..184W)
+: Source which was suggested as possible AGN by Hartman et al.
(1999, Cat. J/ApJS/123/79)
Note (2): Error in the position, assumed to be represented by the 95%
confidence contours given by the 3EG catalog
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Byte-by-byte Description of file: table5a.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [3EGJ]
5- 13 A9 --- 3EGJ Gamma-ray 3EG source designation ("J" omitted)
17- 18 I2 h RAh Right ascension (J2000.0)
20- 21 I2 min RAm Right ascension (J2000.0)
23- 26 F4.1 s RAs Right ascension (J2000.0)
28 A1 --- DE- Declination sign (J2000.0)
29- 30 I2 deg DEd Declination (J2000.0)
32- 33 I2 arcmin DEm Declination (J2000.0)
35- 36 I2 arcsec DEs Declination (J2000.0)
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Byte-by-byte Description of file: table5b.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [3EGJ]
5- 13 A9 --- 3EGJ Gamma-ray 3EG source name ("J" omitted)
15- 17 A3 --- Seq Sequential number (or letter) for group of
radio source around gamma-ray source
19- 23 A5 --- Survey Radio survey used (ref. in surveys.dat file)
25- 41 A17 --- RSource Radio source name
42- 43 I2 h RAh ? Right ascension (J2000)
45- 46 I2 min RAm ? Right ascension (J2000)
48- 52 F5.2 s RAs ? Right ascension (J2000)
55- 60 F6.3 s e_RAs ? rms uncertainty on right ascension
61 A1 --- n_RAs [?n] Note (1)
63 A1 --- DE- Declination sign (J2000)
64- 65 I2 deg DEd ? Declination (J2000)
67- 68 I2 arcmin DEm ? Declination (J2000)
70- 74 F5.2 arcsec DEs [0,60]? Declination (J2000)
76- 83 F8.2 arcsec e_DEs ? rms uncertainty on declination
84 A1 --- n_DEs [?n] Note (1)
88- 94 F7.1 MHz Freq ? Observed frequency
95 A1 --- u_Freq [?n] Note (1)
96 A1 --- l_Flux Limit flag on Flux
97-106 F10.6 Jy Flux ? Flux at the observed frequency
107 A1 --- n_Flux [pn] Note (1)
110-116 F7.5 Jy e_Flux ? rms uncertainty on Flux
117 A1 --- neFlux [?np] Note (1)
119-148 A30 ---- Com Comments (2)
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Note (1): Notes:
?: unknown
n: not analysed
p: peak flux
Note (2): Abbreviations:
B: blend of several sources
EX: extended source
IS: inverted spectrum
FS: flat spectrum
GLC: gravitational lens. candidate
P: indicates an unresolved source (size limit for NVSS typically
<20", but more for other surveys).
Otherwise the DEconvolved size and position angles are given.
PN: planetary nebula
SI: spectral index
SP: possibly spurious source
SS: steep spectrum
V: variable
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Byte-by-byte Description of file: survey.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Survey Survey designation
6- 7 I2 --- n_Survey ? Part of the survey
9- 27 A19 --- BibCode BibCode
29- 53 A25 --- Aut Author's names
55-118 A64 --- Com Comments
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 deg GLON Galactic longitude
7- 11 F5.1 deg GLAT Galactic latitude
13- 18 F6.1 arcmin Theta Diameter of the extended source
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- 3EGJ 3EG source designation ("J" omitted)
12- 19 A8 --- AGN AGN Name
23- 27 F5.1 deg GLON Galactic longitude
31- 35 F5.1 deg GLAT Galactic latitude
39- 42 F4.2 --- SI ? Spectral index, Γ
(N(E) ∝ E-Γ)
46- 50 F5.2 10-8cm-2/s Fgamma γ-ray flux
53- 57 F5.1 10-8cm-2/s e_Fgamma rms uncertainty on Fgamma
61- 62 I2 --- Nvp Number of viewing periods
65- 69 F5.1 % mu Fluctuation index,
µ=100σ/<Fgamma>
72- 75 F4.1 --- I Average statistical index of variability,
I=mu/26.9
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- 3EGJ 3EG source designation ("J" omitted)
11- 13 F3.1 --- I Average statistical index of variability,
I=mu/26.9
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Acknowledgements: Diego Torres
References:
Romero et al., Paper I, 1999A&A...348..868R 1999A&A...348..868R
(End) Patricia Bauer [CDS] 16-Feb-2001