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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
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). 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:
FileName Lrecl Records Explanations
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
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
Bytes Format Units Label Explanations
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
Note (1): Individual notes: *: This source also displays short-term variability (Wallace et al., 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
Byte-by-byte Description of file: table5a.dat
Bytes Format Units Label Explanations
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)
Byte-by-byte Description of file: table5b.dat
Bytes Format Units Label Explanations
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)
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
Byte-by-byte Description of file: survey.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table6.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table7.dat
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table8.dat
Bytes Format Units Label Explanations
1- 9 A9 --- 3EGJ 3EG source designation ("J" omitted) 11- 13 F3.1 --- I Average statistical index of variability, I=mu/26.9
Acknowledgements: Diego Torres References: Romero et al., Paper I, 1999A&A...348..868R
(End) Patricia Bauer [CDS] 16-Feb-2001
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