TY - JOUR
T1 - The shallow-decay phase in both optical and x-ray afterglows of Swift GRB 090529A
T2 - Energy injection into a wind-type medium?
AU - Xin, L.P.
AU - Pozanenko, A.
AU - Kann, D.A.
AU - Gorosabel, J.
AU - Xu, Dong
AU - Leloudas, Georgios
AU - Ugarte Postigo, Antonio de
AU - Wei, J.Y.
AU - Andreev, M.
AU - Qin, S.F.
AU - Ibrahimov, M.
AU - Fynbo, Johan Peter Uldall
AU - Qiu, Y.L-
PY - 2012/5/1
Y1 - 2012/5/1
N2 - The energy injection model is the usual choice for interpreting the shallow-decay phase in Swift gamma-ray burst (GRB) X-ray afterglows. However, very few GRBs have simultaneous signatures of energy injection in their optical and X-ray afterglows. Here, we report on the optical observations of GRB 090529A from 2000s to ~106s after the burst, in which an achromatic decay is seen at both wavelengths. The optical light curve shows a decay from 0.37 to 0.99, with a break at ~105 s. In the same time interval, the decay indices of the X-ray light curve changed from 0.04 to 1.2. Comparing these values with the closure relations, the segment after 3 × 104s is consistent with the prediction of the forward shock in an interstellar medium without any energy injection. The shallow-decay phase between 2000 and 3 × 104s could be a result of the external shock in a wind-type medium with an energy injection under the condition of νo < νc < νx. However, the constraint of the spectral region is not consistent with the multiband observations. For this shallow-decay phase, other models are also possible, such as energy injection with evolving microphysical parameters, a jet viewed off-axis, etc.
AB - The energy injection model is the usual choice for interpreting the shallow-decay phase in Swift gamma-ray burst (GRB) X-ray afterglows. However, very few GRBs have simultaneous signatures of energy injection in their optical and X-ray afterglows. Here, we report on the optical observations of GRB 090529A from 2000s to ~106s after the burst, in which an achromatic decay is seen at both wavelengths. The optical light curve shows a decay from 0.37 to 0.99, with a break at ~105 s. In the same time interval, the decay indices of the X-ray light curve changed from 0.04 to 1.2. Comparing these values with the closure relations, the segment after 3 × 104s is consistent with the prediction of the forward shock in an interstellar medium without any energy injection. The shallow-decay phase between 2000 and 3 × 104s could be a result of the external shock in a wind-type medium with an energy injection under the condition of νo < νc < νx. However, the constraint of the spectral region is not consistent with the multiband observations. For this shallow-decay phase, other models are also possible, such as energy injection with evolving microphysical parameters, a jet viewed off-axis, etc.
U2 - 10.1111/j.1365-2966.2012.20681.x
DO - 10.1111/j.1365-2966.2012.20681.x
M3 - Journal article
SN - 0035-8711
VL - 422
SP - 2044
EP - 2050
JO - Royal Astronomical Society. Monthly Notices
JF - Royal Astronomical Society. Monthly Notices
IS - 3
ER -