2007A&A...469L..13M

Query : 2007A&A...469L..13M

2007A&A...469L..13M - Astronomy and Astrophysics, volume 469, L13-16 (2007/7-1)

REM observations of GRB 060418 and GRB 060607A: the onset of the afterglow and the initial fireball. Lorentz factor determination.

MOLINARI E., VERGANI S.D., MALESANI D., COVINO S., D'AVANZO P., CHINCARINI G., ZERBI F.M., ANTONELLI L.A., CONCONI P., TESTA V., TOSTI G., VITALI F., D'ALESSIO F., MALASPINA G., NICASTRO L., PALAZZI E., GUETTA D., CAMPANA S., GOLDONI P., MASETTI N., MEURS E.J.A., MONFARDINI A., NORCI L., PIAN E., PIRANOMONTE S., RIZZUTO D., STEFANON M., STELLA L., TAGLIAFERRI G., WARD P.A., IHLE G., GONZALEZ L., PIZARRO A., SINCLAIRE P. and VALENZUELA J.

Abstract (from CDS):

Gamma-ray burst (GRB) emission is believed to originate in highly relativistic fireballs. Currently, only lower limits were securely set to the initial fireball Lorentz factor Γ0. We aim to provide a direct measure of Γ0. The early-time afterglow light curve carries information about Γ0, which determines the time of the afterglow peak. We have obtained early observations of the near-infrared afterglows of GRB060418 and GRB060607A with the REM robotic telescope. For both events, the afterglow peak could be clearly singled out, allowing a firm determination of the fireball Lorentz of Γ0∼400, fully confirming the highly relativistic nature of GRB fireballs. The deceleration radius was inferred to be Rdec≃1017cm. This is much larger than the internal shocks radius (believed to power the prompt emission), thus providing further evidence for a different origin of the prompt and afterglow stages of the GRB.

Abstract Copyright: ∼

Journal keyword(s): gamma rays: bursts - relativity

Simbad objects: 14

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Number of rows : 14
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 GRB 041219 gB 00 24 27.7 +62 50 34           ~ 225 1
2 GRB 021004 gB 00 26 54.68 +18 55 41.6           ~ 547 0
3 GRB 050904 gB 00 54 50.794 +14 05 09.42           ~ 469 0
4 GRB 060210 gB 03 50 57.370 +27 01 34.40   20.27       ~ 253 0
5 GRB 060124 gB 05 08 25.900 +69 44 26.98   18.91 17.35     ~ 264 0
6 SN 2002lt SN* 08 08 59.858 +06 43 37.52           SNIc: 352 1
7 GRB 030418 gB 10 54 33.69 -07 01 40.8           ~ 68 0
8 GRB 060206 gB 13 31 43.420 +35 03 03.60   19.99 17.09     ~ 313 0
9 GRB 050801 gB 13 36 35.000 -21 55 41.00 15.03 15.82 15.46     ~ 156 0
10 GRB 050730 gB 14 08 17.090 -03 46 18.90   20.32 17.68     ~ 313 0
11 GRB 990123 gB 15 25 29 +44 45.0     8.95     ~ 989 1
12 GRB 060418 gB 15 45 42.600 -03 38 20.00 15.73 16.19 14.98     ~ 360 0
13 GRB 060607 gB 21 58 50.400 -22 29 46.70 18.49 16.67 15.09     ~ 295 0
14 GRB 050820A gB 22 29 38.110 +19 33 37.10 18.33 19.00 18.47     ~ 386 0

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