Optical behavior of GRB 061121 around its X-Ray shallow decay phase

Uehara, T.; Uemura, Makoto; Arai, Akira; Yamazaki, Ryo; Kawabata, Koji S.; Ohno, M.; Fukazawa, Yasushi; Ohsugi, T.; Yoshida, Michitoshi; Sato, Shuji; Kino, Motoki

doi:10.1051/0004-6361/201015911

Cited by 5 publications

(3 citation statements)

References 45 publications

(67 reference statements)

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“…In Figure 4, we show the spectral energy distribution (SED) from optical (3.9 × 10 14 Hz) to Xray band (1.1×10 18 Hz) at t = 162-589 s. The Galactic extinction of E B−V = 0.162 (Schlegel, Finkbeiner, & Davis 1998) has been corrected for using a standard way. On the other hand, for the extinction within the host galaxy, we adopted three extinction curve models, the Milky Way (MW), the Large Magellanic Cloud (LMC), and the Small Magellanic Cloud (SMC) models, while the hydrogen column density (N ext H = 8.0 × 10 21 cm −2 ) is fixed (Uehara et al 2010(Uehara et al , 2011. Using one of these three models, we corrected the extinction in the optical bands.…”

Section: X-ray Data: Reduction and Analysismentioning

confidence: 99%

GRB 091208b: First Detection of the Optical Polarization in Early Forward Shock Emission of a Gamma-Ray Burst Afterglow

Uehara¹,

Toma²,

Kawabata³

et al. 2012

ApJ

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We report that the optical polarization in the afterglow of GRB 091208B is measured at t = 149 − 706 s after the burst trigger, and the polarization degree is P = 10.4% ± 2.5%. The optical light curve at this time shows a power-law decay with index −0.75 ± 0.02, which is interpreted as the forward shock synchrotron emission, and thus this is the first detection of the early-time optical polarization in the forward shock (rather than that in the reverse shock reported by (Steele et al. 2009)). This detection disfavors the afterglow model in which the magnetic fields in the emission region are random on the plasma skin depth scales, such as amplified by the plasma instabilities, e.g., Weibel instability. We suggest that the fields are amplified by the magnetohydrodynamic instabilities, which would be tested by future observations of the temporal changes of the polarization degrees and angles for other bursts.

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Section: X-ray Data: Reduction and Analysismentioning

confidence: 99%

GRB 091208b: First Detection of the Optical Polarization in Early Forward Shock Emission of a Gamma-Ray Burst Afterglow

Uehara¹,

Toma²,

Kawabata³

et al. 2012

ApJ

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“…et al (2009);Uehara et al (2011);Ishimura et al (2008);Halpern et al (2006b,a);Halpern & Armstrong (2006b,a);Gomboc et al (2008c).UVOT(v);Kanata(R); MITSuME(g,R,I); MDM2.4m(R); NMSU(I,R,V,B,U); UVOT(u,v,b,uvw1,uvw2,uvm2); ,I,V); HTC(R,B); MAO(R); OSN(I); LT(r',i'); INT(r',i',g'); Gemini-N(r',i',g') V,R,I); TNT(V,R); EST(V,R); MDM(V,R,I); KAIT(R); HTC(V); Kuiper(R); Loiano(R); PAIRITEL(J,H,K S ); SOAR(J,H,K S ); LBT(R); MMT(J); P60(R,i'); Gemini-N(r',i'); Keck(R,g'); SMARTS(B,V,R,I,J,H,K S ).…”

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confidence: 98%

Gamma-ray burst optical light-curve zoo: comparison with X-ray observations

Zaninoni

Bernardini

Margutti

et al. 2013

A&A

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Aims. We present a comprehensive analysis of the optical and X-ray light curves (LCs) and spectral energy distributions (SEDs) of a large sample of gamma-ray burst (GRB) afterglows to investigate the relationship between the optical and X-ray emission after the prompt phase. We consider all data available in the literature, which where obtained with different instruments. Methods. We collected the optical data from the literature and determined the shapes of the optical LCs. Then, using previously presented X-ray data, we modeled the optical/X-ray SEDs. We studied the SED parameter distributions and compared the optical and X-ray LC slopes and shapes. Results. The optical and X-ray spectra become softer as a function of time while the gas-to-dust ratios of GRBs are higher than the values calculated for the Milky Way and the Large and Small Magellanic Clouds. For 20% of the GRBs the difference between the optical and X-ray slopes is consistent with 0 or 1/4 within the uncertainties (we did it not consider the steep decay phase), while in the remaining 80% the optical and X-ray afterglows show significantly different temporal behaviors. Interestingly, we find an indication that the onset of the forward shock in the optical LCs (initial peaks or shallow phases) could be linked to the presence of the X-ray flares. Indeed, when X-ray flares are present during the steep decay, the optical LC initial peak or end plateau occurs during the steep decay; if instead the X-ray flares are absent or occur during the plateau, the optical initial peak or end plateau takes place during the X-ray plateau. Conclusions. The forward-shock model cannot explain all features of the optical (e.g. bumps, late re-brightenings) and X-ray (e.g. flares) LCs. However, the synchrotron model is a viable mechanism for GRBs at late times. In particular, we found a relationship between the presence of the X-ray flares and the shape of the optical LC that indicates a link between the prompt emission and the optical afterglow.

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“… *Taken from Evans et al (2009) and held constant in spectral fit; a optical light‐curve data from Greco et al (2005a), Kiziloglu et al (2005), Misra, Kamble & Pandey (2005a), Sharapov et al (2005), Woźniak et al (2005), Quimby et al (2006), Huang et al (2007) and Kamble, Resmi & Misra (2007); b Liang et al (2007); c Schady et al (2010); d optical light‐curve data from D’Avanzo et al (2005), Greco et al (2005b), Kahharov et al (2005), Misra, Kamble & Pandey (2005b), Rykoff et al (2005), De Pasquale et al (2006), Watson et al (2006) and Ghirlanda et al (2007); e Watson et al (2006); f Butler (2007); g optical light‐curve data from Yost et al (2007a); h optical light‐curve data, redshift and host galaxy extinction information from Ruiz‐Velasco et al (2007); i optical light‐curve data from Efimov, Rumyantsev & Pozanenko (2006), Halpern, Mirabal & Armstrong (2006), Halpern & Armstrong (2006a,b), Melandri et al (2006), Page et al (2007) and Uehara et al (2011); j Perley et al (2009). …”

Section: Sample Selection and Data Reductionmentioning

confidence: 99%

Observational constraints on the external shock prior emission hypothesis of gamma-ray bursts

Birnbaum¹,

Zhang²,

Zhang³

et al. 2012

Monthly Notices of the Royal Astronomical Society

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An intriguing hypothesis that there exists a decaying X-ray emission component before the gamma-ray burst (GRB) trigger has been suggested in order to explain the shallow decay phase of the X-ray afterglow detected in many Swift GRBs. If this 'prior emission' is from an external shock, one would expect a corresponding optical emission component during the GRB prompt emission phase. In this paper we apply the available prompt optical emission data (both detections and upper limits) to constrain such a scenario. We fit the shallow and normal decay segments of the X-ray Telescope light curves in our sample with a T -shifted single power law, and extrapolate the X-ray flux back to the time of the early optical observations. We then use the synchrotron spectrum predicted by the standard external shock model to extrapolate from the X-ray flux to the optical band, and obtain the possible range of the predicted optical flux. Finally, we compare the predictions with the observations. In the cases where later optical data are available, we also compare the shapes of the optical light curves to the predicted optical light curves from the external shock prior emission model. We find that for a good fraction of GRBs (four out of eight; up to 2006 December), the available data already impose severe constraints on the hypothesis. In particular, the expected optical flux from the external shock prior emission model is higher than what the data allow. We conclude that if the shallow-decay X-ray component were from a prior emission component, it would have to be of an internal origin with optical flux suppressed.

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Optical behavior of GRB 061121 around its X-Ray shallow decay phase

Cited by 5 publications

References 45 publications

GRB 091208b: First Detection of the Optical Polarization in Early Forward Shock Emission of a Gamma-Ray Burst Afterglow

GRB 091208b: First Detection of the Optical Polarization in Early Forward Shock Emission of a Gamma-Ray Burst Afterglow

Gamma-ray burst optical light-curve zoo: comparison with X-ray observations

Observational constraints on the external shock prior emission hypothesis of gamma-ray bursts

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