Astrosat CZT Imager Observations of GRB 151006a: Timing, Spectroscopy, and Polarization Study

Rao, A. R.; Chand, Vikas; Hingar, M. K.; Iyyani, Shabnam; Khanna, Rakesh; Kutty, A. P. K.; Malkar, J. P.; Paul, Debdutta; Bhalerao, V.; Bhattacharya, Dipankar; Dewangan, G. C.; Pawar, Pramod; Vibhute, A.; Chattopadhyay, Tanmoy; Mithun, N. P. S.; Vadawale, S.; Vagshette, N. D.; Basak, Rupal; Pradeep, P. I.; Samuel, Essy; Sreekumar, S.; Vinod, P.; Navalgund, K. H.; Pandiyan, R.; Sarma, K. S.; Seetha, S.; Subbarao, Kamesh

doi:10.3847/1538-4357/833/1/86

Cited by 48 publications

(40 citation statements)

References 40 publications

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“…12) has provided hints of a polarization signal being measured for a gamma ray burst (GRB) of fluence less than 2  10 -5 ergs cm -2 . Detection of brighter GRBs is expected to provide a much more significant polarization signal that will help to clearly distinguish between various models of GRB prompt emission mechanism 13 . The CZTI has sensitivity matching that of the Fermi GBM and therefore can detect possible hard X-ray emission associated with gravitational wave events.…”

Section: Scientific Objectives and Some Results From Individual Telesmentioning

confidence: 99%

Multi-Colour Hues of the Universe Observed with AstroSat

Singh

Bhattacharya

2017

Current Science

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India's space astronomy observatory AstroSat was launched on 28 September 2015, carrying instruments to observe cosmic sources over a large spectral band, from optical/UV to hard X-rays. The mission, with all its payloads, has been operating successfully since its launch. After an initial period of performance verification and calibration, the satellite is now in full science operation. This article gives a brief introduction about the capabilities of the mission and presents some of the early science results.

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Section: Scientific Objectives and Some Results From Individual Telesmentioning

confidence: 99%

Multi-Colour Hues of the Universe Observed with AstroSat

Singh

Bhattacharya

2017

Current Science

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“…In the current analysis we have included the XRT data only until ∼ 600 s, i.e the part with WT mode observation and nearly coincident with the observed BAT emission. 2 GRB 151006A was also the first GRB detected by the Astrosat CZTI, on it's first day of operation Rao et al 2016). Both CZTI and Veto detector light curves also show a single FRED like pulse in both the energy ranges 50-200 keV and 100 -500 keV, see Figure 2 in Rao et al (2016).…”

Section: Observations and Data Analysismentioning

confidence: 99%

Surprise in simplicity: an unusual spectral evolution of a single pulse GRB 151006A

Basak

Iyyani

Chand

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a detailed analysis of GRB 151006A, the first GRB detected by Astrosat CZT Imager (CZTI). We study the long term spectral evolution by exploiting the capabilities of Fermi and Swift satellites at different phases, which is complemented by the polarization measurement with the CZTI. While the light curve of the GRB in different energy bands show a simple pulse profile, the spectrum shows an unusual evolution. The first phase exhibits a hard-to-soft (HTS) evolution until ∼ 16 − 20 s, followed by a sudden increase in the spectral peak reaching a few MeV. Such a dramatic change in the spectral evolution in case of a single pulse burst is reported for the first time. This is captured by all models we used namely, Band function, Blackbody+Band and two blackbodies+power law. Interestingly, the Fermi Large Area Telescope (LAT) also detects its first photon (> 100 MeV) during this time. This new injection of energy may be associated with either the beginning of afterglow phase, or a second hard pulse of the prompt emission itself which, however, is not seen in the otherwise smooth pulse profile. By constructing Bayesian blocks and studying the hardness evolution we find a good evidence for a second hard pulse. The Swift data at late epochs (> T 90 of the GRB) also shows a significant spectral evolution consistent with the early second phase. The CZTI data (100-350 keV), though having low significance (1σ), show high values of polarization in the two epochs (77% to 94%), in agreement with our interpretation.

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“…47 The Astrosat mission, launched in September 2015, has a cadmium zinc telluride (CZT) imager 48 with the capability to make time resolved polarisation measurements for 5-6 GRBs per year. 49 Off-axis angle (degrees) The left panel of Figure 4 shows the expected sensitivity of e-ASTROGAM for the detection of GRBs in the 0.2-2 MeV energy range, as a function of the off-axis angle θ off−axis . Here, the GRB emission spectrum has been approximated by a typical Band function 50 with α = −1.1, β = −2.3, and E peak = 0.3 MeV.…”

Section: +31mentioning

confidence: 99%

e-ASTROGAM mission: a major step forward for gamma-ray polarimetry

2017

J. Astron. Telesc. Instrum. Syst

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Abstract. e-ASTROGAM is a gamma-ray space mission proposed for the fifth Medium-size mission (M5) of the European Space Agency. It is dedicated to the study of the non-thermal Universe in the photon energy range from ∼0.15 MeV to 3 GeV with unprecedented sensitivity, angular and energy resolution, together with a groundbreaking capability for gamma-ray polarimetric measurements over its entire bandwidth. We discuss here the main polarization results expected at low energies, between 150 keV and 5 MeV, using Compton interactions in the e-ASTROGAM instrument, from observations of active galactic nuclei, gamma-ray bursts, microquasars, and the Crab pulsar and nebula. The anticipated performance of the proposed observatory for polarimetry is illustrated by simulations of the polarization signals expected from various sources. We show that polarimetric analyses with e-ASTROGAM should provide definitive insight into the geometry, magnetization and content of the high-energy plasmas found in the emitting sources, as well as on the processes of radiation of these plasmas.

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Astrosat CZT Imager Observations of GRB 151006a: Timing, Spectroscopy, and Polarization Study

Cited by 48 publications

References 40 publications

Multi-Colour Hues of the Universe Observed with AstroSat

Multi-Colour Hues of the Universe Observed with AstroSat

Surprise in simplicity: an unusual spectral evolution of a single pulse GRB 151006A

e-ASTROGAM mission: a major step forward for gamma-ray polarimetry

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