title: Decay of the GRB 990123 optical afterglow: implications for the fireball model
abstract: Broad-band (ultraviolet to near-infrared) observations of the intense gamma ray burst GRB 990123 started approximately 8.5 hours after the event and continued until 18 February 1999. When combined with other data, in particular from the Robotic Telescope and Transient Source Experiment (ROTSE) and the Hubble Space Telescope (HST), evidence emerges for a smoothly declining light curve, suggesting some color dependence that could be related to a cooling break passing the ultraviolet-optical band at about 1 day after the high-energy event. The steeper decline rate seen after 1.5 to 2 days may be evidence for a collimated jet pointing toward the observer.
authors: Instituto de Astrofisica de Andalucia, IAA-CSIC, Granada, Spain. Instituto de Astrofisica de Canarias, La Laguna, Tenerife, Spain. Astronomical Observatory, University of Copenhagen, Copenhagen, Denmark. Nordic Optical Telescope, La Palma, T.
authors: A J
authors: AJ
authors: Castro-Tirado
authors: M R
authors: MR
authors: Zapatero-Osorio
authors: N
authors: N
authors: Caon
authors: L M
authors: LM
authors: Cairos
authors: J
authors: J
authors: Hjorth
authors: H
authors: H
authors: Pedersen
authors: M I
authors: MI
authors: Andersen
authors: J
authors: J
authors: Gorosabel
authors: C
authors: C
authors: Bartolini
authors: A
authors: A
authors: Guarnieri
authors: A
authors: A
authors: Piccioni
authors: F
authors: F
authors: Frontera
authors: N
authors: N
authors: Masetti
authors: E
authors: E
authors: Palazzi
authors: E
authors: E
authors: Pian
authors: J
authors: J
authors: Greiner
authors: R
authors: R
authors: Hudec
authors: R
authors: R
authors: Sagar
authors: A K
authors: AK
authors: Pandey
authors: V
authors: V
authors: Mohan
authors: R K
authors: RK
authors: Yadav
authors: Nilakshi
authors: C
authors: C
authors: Bjornsson
authors: P
authors: P
authors: Jakobsson
authors: I
authors: I
authors: Burud
authors: F
authors: F
authors: Courbin
authors: G
authors: G
authors: Valentini
authors: A
authors: A
authors: Piersimoni
authors: J
authors: J
authors: Aceituno
authors: L M
authors: LM
authors: Montoya
authors: S
authors: S
authors: Pedraz
authors: R
authors: R
authors: Gredel
authors: C F
authors: CF
authors: Claver
authors: T A
authors: TA
authors: Rector
authors: J E
authors: JE
authors: Rhoads
authors: F
authors: F
authors: Walter
authors: J
authors: J
authors: Ott
authors: H
authors: H
authors: Hippelein
authors: V
authors: V
authors: Sàsnchez-Bèjar
authors: C
authors: C
authors: Gutiérrez
authors: J
authors: J
authors: Wei
authors: A
authors: A
authors: Zhou
authors: S
authors: S
authors: Guziy
authors: A
authors: A
authors: Shlyapnikov
authors: J
authors: J
authors: Heise
authors: E
authors: E
authors: Costa
authors: M
authors: M
authors: Feroci
authors: L
authors: L
authors: Piro