First ALMA Light Curve Constrains Refreshed Reverse Shocks and Jet Magnetization in GRB 161219B

Laskar, T.; Alexander, K. D.; Berger, E.; Guidorzi, C.; Margutti, R.; Fong, W.; Kilpatrick, C. D.; Milne, Peter; Drout, M. R.; Mundell, C. G.; Kobayashi, S.; Lunnan, R.; Duran, R. Barniol; Menten, K. M.; Ioka, Kunihito; Williams, Peter K. G.

doi:10.3847/1538-4357/aacbcc

Cited by 42 publications

(45 citation statements)

References 194 publications

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“…The relative magnetization of R B ≈ 0.6 observed in this event is similar to R B ≈ 1 for GRB 161219B (Laskar et al 2018c) and R B ≈ 0.6 for GRB 140304A (Laskar et al 2018b). On the other hand, these values are all smaller than 1 R B 5 for GRB 130427A (Laskar et al 2013), R B ≈ 8 for GRB 160509A (Laskar et al 2016), R B ∼ 1-100 for GRB 160509A (Alexander et al 2017), and R B ≈ 1-100 derived for GRBs with optical flashes (Gomboc et al 2008(Gomboc et al , 2009Japelj et al 2014).…”

Section: Ejecta Magnetizationsupporting

confidence: 77%

“…This scenario requires a distribution of Lorentz factors in the jet, which has indeed been inferred in other events (Laskar et al 2015;Laskar et al 2018b,c), and remains feasible here. We note that a similar discrepancy was present in the only other ALMA light curve of a GRB available at this date, that of GRB 161219B (Laskar et al 2018c). In that case, the model under-predicts the data at ≈ 3 days, corresponding to a similar RS-FS transition.…”

Section: Intermediate Millimeter Excesssupporting

confidence: 64%

“…We now use the MCMC results to derive the initial Lorentz factor of the jet. The jet's initial Lorentz factor can be determined from joint RS and FS observations by solving the following equations self-consistently (Zhang et al 2003;Laskar et al 2018c) at the deceleration time,…”

Section: Determination Of Ejecta Initial Lorentz Factormentioning

confidence: 99%

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A Reverse Shock in GRB 181201A

Laskar

Eerten

Schady

et al. 2019

ApJ

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We present comprehensive multiwavelength radio to X-ray observations of GRB 181201A spanning from ≈ 150 s to ≈ 163 days after the burst, comprising the first joint ALMA-VLA-GMRT observations of a gamma-ray burst (GRB) afterglow. The radio and mm-band data reveal a distinct signature at ≈ 3.9 days, which we interpret as reverse shock (RS) emission. Our observations present the first time that a single radio-frequency spectral energy distribution can be decomposed directly into RS and forward shock (FS) components. We perform detailed modeling of the full multiwavelength data set, using Markov Chain Monte Carlo sampling to construct the joint posterior density function of the underlying physical parameters describing the RS and FS synchrotron emission. We uncover and account for all degeneracies in the model parameters. The joint RS-FS modeling reveals a weakly magnetized (σ ≈ 3 × 10 −3 ), mildly relativistic RS, from which we derive an initial bulk Lorentz factor of Γ 0 ≈ 103 for the GRB jet. Our results support the hypothesis that low-density environments are conducive to the observability of RS emission. We compare our observations to other events with strong RS detections, and find a likely observational bias selecting for longer lasting, non-relativistic reverse shocks. We present and begin to address new challenges in modeling posed by the present generation of comprehensive, multi-frequency data sets.

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Section: Ejecta Magnetizationsupporting

confidence: 77%

Section: Intermediate Millimeter Excesssupporting

confidence: 64%

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A Reverse Shock in GRB 181201A

Laskar

Eerten

Schady

et al. 2019

ApJ

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“…Furthermore, light emitted in this wavelength range is not affected by dust obscuration, enabling us to penetrate the densest regions of the galaxies. In the last years, new powerful millimetre and submillimetre observations, such as those performed by ALMA or NOEMA, are allowing us to study in detail GRBs and their galaxies using photometric (Wang et al 2012;Hatsukade et al 2014;Sánchez-Ramírez et al 2017;Laskar et al 2018), spectroscopic (Michałowski et al 2016;de Ugarte Postigo et al 2018;Hatsukade et al 2019) and polarimetric (Laskar et al 2019) techniques. GRB 190114C, localised (Gropp et al 2019) by the Neil Gehrels Swift Observatory (Swift hereafter; Gehrels et al 2004), is the first GRB with confirmed very-high energy (VHE) emission (up to one TeV), and is thus a milestone in high-energy as-Article number, page 1 of 11 arXiv:1911.07876v1 [astro-ph.HE] 18 Nov 2019 A&A proofs: manuscript no.…”

Section: Introductionmentioning

confidence: 99%

GRB 190114C in the nuclear region of an interacting galaxy

Postigo

Thöne

Martín

et al. 2020

A&A

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Context. GRB 190114C is the first GRB for which the detection of very-high energy emission up to the TeV range has been reported. It is still unclear whether environmental properties might have contributed to the production of these very high-energy photons, or if it is solely related to the released GRB emission. Aims. The relatively low redshift of the GRB (z = 0.425) allows us to study the host galaxy of this event in detail, and to potentially identify idiosyncrasies that could point to progenitor characteristics or environmental properties responsible for such a unique event.Methods. We use ultraviolet, optical, infrared and submillimetre imaging and spectroscopy obtained with HST, VLT and ALMA to obtain an extensive dataset on which the analysis of the host galaxy is based. Results. The host system is composed of a close pair of interacting galaxies (∆v=50 km s −1 ), both of which are well-detected by ALMA in CO(3-2). The GRB occurred within the nuclear region (∼170 pc from the centre) of the less massive but more starforming galaxy of the pair. The host is more massive (log(M/M )=9.3) than average GRB hosts at that redshift and the location of the GRB is rather unique. The enhanced star-formation rate was probably triggered by tidal interactions between the two galaxies. Our ALMA observations indicate that both host galaxy and companion have a high molecular gas fraction, as has been observed before in interacting galaxy pairs. Conclusions. The location of the GRB within the core of an interacting galaxy with an extinguished line-of-sight is indicative of a denser environment than typically observed for GRBs and could have been crucial for the generation of the very-high-energy photons that were observed.

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“…It's became clear to develope the global network of fully robotic telescopes, to have 24h of night time in both hemispheras (ROTSE [11], MASTER [12], TAROT [13], BOOTES [14]). In parallel, the development of the world's largest fully autonomous robotic optical telescopes such as the 2-m Liverpool Telescope [15] and the identical 2-m Faulkes Telescopes [16,17] that can respond to GRB discoveries within minutes of the alert notification provided new insights into the nature of the early afterglow [18][19][20][21][22], the physics of reverse shocks [23][24][25][26][27]; and the importance of ordered magnetic fields in the relativistic ejecta [28][29][30][31]. The rapid evolution of the blast-wave emission and the complexity of early time light curves within the first few minutes to hours of the GRB drove the development of autonomous software systems for immediate response to the GRB trigger combined with rapid, automatic identification, classification and selection of subsequent followup observations [32,33].…”

Section: Noname Manuscript Nomentioning

confidence: 99%

A robotic pipeline for fast GRB followup with the Las Cumbrés observatory network

et al. 2019

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In the era of multi-messenger astronomy the exploration of the early emission from transients is key for understanding the encoded physics. At the same time, current generation networks of fully-robotic telescopes provide new opportunities in terms of fast followup and sky coverage. This work describes our pipeline designed for robotic optical followup of gamma-ray bursts with the Las Cumbrés Observatory network. We designed a Python code to promptly submit observation requests to the Las Cumbrés Observatory network within 3 minutes of the receipt of the socket notice. Via Telegram the pipeline keeps the users informed, allowing them to take control upon request. Our group was able to track the early phases of the evolution of the optical output from gamma-ray bursts with a fully-robotic procedure and here we report the case of GRB180720B as an example. The developed pipeline represent a key ingredient for any reliable and rapid (minutes timescale) robotic telescope system. While successfully utilized and adapted for LCO, it can also be adapted to any other robotic facilities.

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First ALMA Light Curve Constrains Refreshed Reverse Shocks and Jet Magnetization in GRB 161219B

Cited by 42 publications

References 194 publications

A Reverse Shock in GRB 181201A

A Reverse Shock in GRB 181201A

GRB 190114C in the nuclear region of an interacting galaxy

A robotic pipeline for fast GRB followup with the Las Cumbrés observatory network

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