Infrared/optical – X-ray simultaneous observations of X-ray flares in GRB 071112C and GRB 080506

Uehara, T.; Uemura, Makoto; Kawabata, Koji S.; Fukazawa, Yasushi; Yamazaki, Ryo; Arai, Akira; Sasada, Mahito; Ohsugi, T.; Mizuno, T.; Takahashi, H.; Yamashita, Takuji; Ohno, M.; Sato, G.; Sato, Shuji; Kino, Motoki

doi:10.1051/0004-6361/201014272

Cited by 11 publications

(7 citation statements)

References 48 publications

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“…Fortunately, there is no significant color change between our R-and I-band measurements. An achromatic NIR evolution was also reported by Uehara et al (2010), and which supports our optical results and indicates achromatic evolution in the Rand I-band light curves. The peak in the R band is thus unlikely due to the passage of the synchrotron peak.…”

Section: Early Bump In Optical Light Curvesupporting

confidence: 92%

“…If we exclude the flare component, the overall XRT light curve could be well fit by a single power law with an index α x = 1.36 ± 0.02. The afterglow decayed with an index of −1.36, consistent with the analysis of Uehara et al (2010). A flare occurred around t = 500 s following the burst and approached the original maximum brightness of 4.23 μJy.…”

Section: Optical and X-ray Temporal Analysissupporting

confidence: 82%

“…Urata et al (2007) investigated the late temporal properties of 14 GRBs and found that a fraction of the events are outliers of the external shock model at normal decay phase in which neither the delayed energy injection nor time dependency of shock microphysics were considered. Uehara et al (2010) studied the NIR to X-ray spectral energy distribution of GRB 071112C and concluded that the observed NIR to X-ray SEDs is consistent with the expectation from the normal afterglow component and that the cooling break (ν c ) is between the optical and X-ray bands. In other words, spectral evolution of the observed GRB 071112C should be in the region of ν m < ν o < ν c < ν x and follow the relationships predicted by external shock models, α o − α x > −1/4 for uniform ambient median or α o − α x < 1/4 for stellar wind with a density variation ρ ∝ r −2 (Urata et al…”

Section: Different Origin Of X-ray and Optical Emissionmentioning

confidence: 62%

“…Here, we adopt the value ν c = 10 7 Hz from Uehara et al (2010). In addition, we also plot the maximum value of expected X-ray flux (the dot-dashed line in the Figure 2).…”

mentioning

confidence: 99%

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GRB 071112c: A Case Study of Different Mechanisms in X-Ray and Optical Temporal Evolution

Huang¹,

Urata²,

Tung³

et al. 2012

ApJ

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We present a study on GRB 071112C X-ray and optical light curves. In these two wavelength ranges, we have found different temporal properties. The R-band light curve showed an initial rise followed by a single power-law decay, while the X-ray light curve was described by a single power-law decay plus a flare-like feature. Our analysis shows that the observed temporal evolution cannot be described by the external shock model in which the X-ray and optical emission are produced by the same emission mechanism. No significant color changes in multi-band light curves and a reasonable value of the initial Lorentz factor (Γ 0 = 275 ± 20) in a uniform interstellar medium support the afterglow onset scenario as the correct interpretation for the early R band rise. The result suggests that the optical flux is dominated by afterglow. Our further investigations show that the X-ray flux could be created by an additional feature related to energy injection and X-ray afterglow. Different theoretical interpretations indicate the additional feature in X-ray can be explained by either late internal dissipation or local inverse-Compton scattering in the external shock.

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Section: Early Bump In Optical Light Curvesupporting

confidence: 92%

Section: Optical and X-ray Temporal Analysissupporting

confidence: 82%

Section: Different Origin Of X-ray and Optical Emissionmentioning

confidence: 62%

“…Here, we adopt the value ν c = 10 7 Hz from Uehara et al (2010). In addition, we also plot the maximum value of expected X-ray flux (the dot-dashed line in the Figure 2).…”

mentioning

confidence: 99%

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GRB 071112c: A Case Study of Different Mechanisms in X-Ray and Optical Temporal Evolution

Huang¹,

Urata²,

Tung³

et al. 2012

ApJ

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“…Most rebrightenings are only observed in the X-ray band. Some early X-ray bumps, usually called X-ray flares, have no corresponding optical features (see the statistics by Melandri et al 2008 andRykoff et al 2009, as well as Uehara et al 2010, for the individual cases of GRB 071112C and GRB 080506). In contrast, but less frequently, a rebrightening feature may be seen in the optical but not in the X-ray band (e.g.…”

Section: Introductionmentioning

confidence: 99%

Diversity of multiwavelength emission bumps in the GRB 100219A afterglow

Mao

Malesani

D’Avanzo

et al. 2012

A&A

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Context. Multi-wavelength observations of gamma-ray burst (GRB) afterglows provide important information about the activity of their central engines and their environments. In particular, the short timescale variability, such as bumps and/or rebrightening features visible in the multi-wavelength light curves, is still poorly understood. Aims. We analyze the multi-wavelength observations of the GRB 100219A afterglow at redshift 4.7. In particular, we attempt to identify the physical origin of the late achromatic flares/bumps detected in the X-ray and optical bands. Methods. We present ground-based optical photometric data and Swift X-ray observations on GRB 100219A. We analyzed the temporal behavior of the X-ray and optical light curves, as well as the X-ray spectra.Results. The early flares in the X-ray and optical light curves peak simultaneously at about 1000 s after the burst trigger, while late achromatic bumps in the X-ray and optical bands appear at about 2 × 10 4 s after the burst trigger. These are uncommon features in the afterglow phenomenology. Considering the temporal and spectral properties, we argue that both optical and X-ray emissions come from the same mechanism. The late flares/bumps may be produced by late internal shocks from long-lasting activity of the central engine. An off-axis origin for a structured jet model is also discussed to interpret the bump shapes. The early optical bump can be interpreted as the afterglow onset, while the early X-ray flare could be caused by the internal activity. GRB 100219A exploded in a dense environment as revealed by the strong attenuation of X-ray emission and the optical-to-X-ray spectral energy distribution.

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The extinction curves of star-forming regions fromz = 0.1 to 6.7 using GRB afterglow spectroscopy

Zafar

Watson

Fynbo

et al. 2011

A&A

137

197

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Studies of extinction curves provide insights into the properties of interstellar dust. Until recently, however, very few extinction curves existed outside the local group. GRB afterglows are well suited to extinction studies due to their brightness, simple power-law spectra and their occurrence in distant star forming galaxies. In this paper we present results from the SED analysis of a sample of 41 GRB afterglows, from X-ray to NIR wavelengths. The sample is based on spectra from VLT-FORS, with additional data primarily from Swift. This is the largest sample of extinction curves outside the Local Group and, to date, the only extragalactic sample of absolute extinction curves based on spectroscopy. Estimates of the distribution of restframe visual extinctions, the extinction curves, and the intrinsic spectral shapes of GRB afterglows are obtained. Their correlation with H i column density as well as total and gas-phase metal column density are examined. The line-of-sight gas-to-dust and metals-to-dust ratios are determined and examined as a function of total column density, ISM metallicity and redshift. The intrinsic SEDs of the afterglows show that approximately half the sample require a cooling break between the optical and X-ray ranges. The broken power-law SEDs show an average change in the spectral index of Δβ = 0.51 with a very small standard deviation of 0.02 (excluding the outlier GRB 080210). This is consistent with the expectations from a simple synchrotron model. Such a close convergence of values suggests that the X-ray afterglows of GRBs may be used with considerably more confidence to set the absolute flux level and intrinsic spectral indices in the optical and UV. Of the sample, 63% are well described by a featureless (SMC-type) extinction curve. Almost a quarter of our sample is consistent with no significant extinction (typically A V 0.1). The 2175 Å extinction bump is detected unequivocally in 7% of our sample (3 GRBs), which all have A V > 1.0, while one afterglow has a very unusual extinction curve with a sharp UV rise. However, we can only say that the bump is not present in about a quarter of our sample because of low extinction or lack of coverage of the 2200 Å region. All the afterglows well fit with SMC type curves have moderate or low extinction, with A V < 0.65. This suggests that the SMC extinction curve is not as nearly-universal as previously believed and that extinction curves more similar to those found in the Galaxy and the LMC may be quite prevalent. We find an anti-correlation between gas-to-dust ratio and metallicity consistent with the Local Group relation; we find, however, no correlation between the metals-to-dust ratios and the metallicities, redshift and visual extinction; we find no strong correlation of the extinction column with metallicity either. Our metals-to-dust ratios derived from the soft X-ray absorption are always larger (3-30 times) than the Local Group value, which may mean that GRB hosts may be less efficient at turning their metals into dust. Howe...

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Infrared/optical – X-ray simultaneous observations of X-ray flares in GRB 071112C and GRB 080506

Cited by 11 publications

References 48 publications

GRB 071112c: A Case Study of Different Mechanisms in X-Ray and Optical Temporal Evolution

GRB 071112c: A Case Study of Different Mechanisms in X-Ray and Optical Temporal Evolution

Diversity of multiwavelength emission bumps in the GRB 100219A afterglow

The extinction curves of star-forming regions fromz = 0.1 to 6.7 using GRB afterglow spectroscopy

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