WIDGET: System Performance and GRB Prompt Optical Observations

Urata, Y.; Tashiro, M.; Tamagawa, Toru; Usui, Fumihiko; Kuwahara, Makoto; Lin, Hsiu Mei; Kageyama, Shoichi; Iwakiri, W.; Sugasahara, T.; Takahara, K.; Kodaka, N.; Abe, K.; Masuno, K.; Onda, K.

doi:10.1093/pasj/63.1.137

Cited by 4 publications

(3 citation statements)

References 29 publications

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“…The recent development of networks of robotic telescopes (ROTSE-III: Akerlof et al 2003;GROCSE: Park et al 1997;TAROT: Klotz et al 2009;SkyNet: Graff et al 2014; WIDGET: Urata et al 2011;MASTER: Lipunov et al 2004; Pi of the Sky: Burd et al 2005; RAPTOR: Vestrand et al 2002;REM: Zerbi et al 2001;Watcher: Ferrero et al 2010) has allowed us to follow up the early optical emission of GRBs. Systematic studies (Liang et al 2010;Lü et al 2012;Ghirlanda et al 2012, G12 hereafter) derived the distribution of Γ 0 and its possible correlation with other observables.…”

Section: Introductionmentioning

confidence: 99%

Bulk Lorentz factors of gamma-ray bursts

Ghirlanda

Nappo

Ghisellini

et al. 2018

A&A

118

149

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Knowledge of the bulk Lorentz factor Γ 0 of gamma-ray bursts (GRBs) allows us to compute their comoving frame properties shedding light on their physics. Upon collisions with the circumburst matter, the fireball of a GRB starts to decelerate, producing a peak or a break (depending on the circumburst density profile) in the light curve of the afterglow. Considering all bursts with known redshift and with an early coverage of their emission, we find 67 GRBs (including one short event) with a peak in their optical or GeV light curves at a time t p . For another 106 GRBs we set an upper limit t UL p . The measure of t p provides the bulk Lorentz factor Γ 0 of the fireball before deceleration. We show that t p is due to the dynamics of the fireball deceleration and not to the passage of a characteristic frequency of the synchrotron spectrum across the optical band. Considering the t p of 66 long GRBs and the 85 most constraining upper limits, we estimate Γ 0 or a lower limit Γ LL 0 . Using censored data analysis methods, we reconstruct the most likely distribution of t p . All t p are larger than the time T p,γ when the prompt γ-ray emission peaks, and are much larger than the time T ph when the fireball becomes transparent, that is, t p >T p,γ >T ph . The reconstructed distribution of Γ 0 has median value ∼300 (150) for a uniform (wind) circumburst density profile. In the comoving frame, long GRBs have typical isotropic energy, luminosity, and peak energy E iso = 3(8) × 10 50 erg, L iso = 3(15) × 10 47 erg s −1 , and E peak = 1(2) keV in the homogeneous (wind) case. We confirm that the significant correlations between Γ 0 and the rest frame isotropic energy (E iso ), luminosity (L iso ) and peak energy (E p ) are not due to selection effects. When combined, they lead to the observed E p − E iso and E p − L iso correlations. Finally, assuming a typical opening angle of 5 degrees, we derive the distribution of the jet baryon loading which is centered around a few 10 −6 M .

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Section: Introductionmentioning

confidence: 99%

Bulk Lorentz factors of gamma-ray bursts

Ghirlanda

Nappo

Ghisellini

et al. 2018

A&A

118

149

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“…Rapid follow-up observations in the optical are critical to understand the physical processes of GRBs. There are quite a few small robotic telescopes, in addition to ROTSE-III, that have been built and installed around the world in order to rapidly search for GRB optical counterparts, e.g., GROCSE (Park et al 1997), TAROT (Klotz et al 2009), SkyNet 4 , WIDGET (Urata et al 2011), MASTER 5 , Pi of the Sky (Burd et al 2005), RAPTOR (Vestrand et al 2002), REM (Zerbi & Rem Team 2001), and Watcher GRBs.…”

Section: Discussionmentioning

confidence: 99%

The Optical Luminosity Function of Gamma-Ray Bursts Deduced From Rotse-Iii Observations

Cui

Wei

et al. 2014

ApJ

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We present the optical luminosity function (LF) of gamma-ray bursts (GRBs) estimated from a uniform sample of 58 GRBs from observations with the Robotic Optical Transient Search Experiment III (ROTSE-III). Our GRB sample is divided into two sub-samples: detected afterglows (18 GRBs), and those with upper limits (40 GRBs). The R band fluxes 100s after the onset of the burst for these two sub-samples are derived. The optical LFs at 100s are fitted by assuming that the co-moving GRB rate traces the star-formation rate. The detection function of ROTSE-III is taken into account during the fitting of the optical LFs by using Monte Carlo simulations. We find that the cumulative distribution of optical emission at 100s is well-described with an exponential rise and power-law decay (ERPLD), broken power-law (BPL), and Schechter LFs. A single power-law (SPL) LF, on the other hand, is ruled out with high confidence.

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“…Numbers of dedeicated follow-up instruments of GRBs and afterglows have been developed in γ-ray, X-ray (Gehrels et al 2004), optical, andnear-infrared (e.g. Steele 2001;Akerlof et al 2003;Vestrand et al 2002;Burd et al 2005;Klotz et al 2009;Ferrero et al 2010;Urata et al 2011). Afterglow observations in X-ray and optical have been adequately covered from very early phase including some fractions of γ-ray prompt phase (e.g.…”

Section: Status and Achievements Of Sub-millimeter Afterglow Follow-upsmentioning

confidence: 99%

A New Era of Submillimeter GRB Afterglow Follow-Ups with the Greenland Telescope

Urata

Huang

Asada

et al. 2015

Advances in Astronomy

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A planned rapid submillimeter (submm) Gamma Ray Burst (GRBs) follow-up observations conducted using the Greenland Telescope (GLT) is presented. The GLT is a 12-m submm telescope to be located at the top of the Greenland ice sheet, where the high-altitude and dry weather porvides excellent conditions for observations at submm wavelengths. With its combination of wavelength window and rapid responding system, the GLT will explore new insights on GRBs. Summarizing the current achievements of submm GRB follow-ups, we identify the following three scientific goals regarding GRBs: (1) systematic detection of bright submm emissions originating from reverse shock (RS) in the early afterglow phase, (2) characterization of forward shock and RS emissions by capturing their peak flux and frequencies and performing continuous monitoring, and (3) detections of GRBs as a result of the explosion of first-generation stars result of GRBs at a high redshift through systematic rapid follow ups. The light curves and spectra calculated by available theoretical models clearly show that the GLT could play a crucial role in these studies.

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WIDGET: System Performance and GRB Prompt Optical Observations

Cited by 4 publications

References 29 publications

Bulk Lorentz factors of gamma-ray bursts

Bulk Lorentz factors of gamma-ray bursts

The Optical Luminosity Function of Gamma-Ray Bursts Deduced From Rotse-Iii Observations

A New Era of Submillimeter GRB Afterglow Follow-Ups with the Greenland Telescope

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