Orphan optical flare as SOSS emission afterglow, localization in time

Липунов, В. М.; Корнилов, В. Г.; Zhirkov, K.; Tyurina, N.; Gorbovskoy, E.; Vlasenko, D.; Simakov, S. G.; Topolev, V.; Francile, C.; Подеста, Р.; Подеста, Ф.; Svinkin, D.; Буднев, Н.; Гресс, О. А.; Balanutsa, P.; Kuznetsov, A.; Chasovnikov, A.; Serra-Ricart, M.; Габович, А.; Minkina, E.; Antipov, G.; Свертилов, С. И.; Tlatov, A.; Senik, V.; Tselik, Yu.; Kechin, Ya.; Yurkov, V.

doi:10.1093/mnras/stac1906

Cited by 5 publications

(11 citation statements)

References 65 publications

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“…The obtained parameters are as . Comparing our results with those obtained by Lipunov et al (2022), it is evident that our inferred burst time is earlier than theirs and meanwhile the peak time is somewhat later. The fitted rising power-law index, r ∼ 3, is consistent with the rising index expected for the early afterglow light curves in a uniform medium (Panaitescu & Vestrand 2008).…”

Section: Fitting the Burst Time Of At2021lfasupporting

confidence: 69%

“…This allowed them to estimate the burst time as T 0 = 2021 May 3, 06:57:36 (all dates and times provided in this article are in Coordinated Universal Time, UTC). In contrast, Lipunov et al (2022) employed the SOSS model to match the light curve of AT2021lfa and derived a burst time: T trig = 2021 May 4, 01:33. A discrepancy of 0.77 day is evident in the burst times obtained through these two approaches, which would significantly impact the subsequent analysis of light curve fitting for AT2021lfa.…”

Section: Fitting the Burst Time Of At2021lfamentioning

confidence: 99%

“…However, the absence of corresponding prompt emissions suggests that it may be a potential candidate for an "orphan afterglow." Lipunov et al (2022) employed the smooth optical self-similar emission (SOSS) model for GRBs to model the optical light curve of AT2021lfa. The fitting results revealed an initial Lorentz factor of Γ 0 = 20 ± 10.…”

Section: Introductionmentioning

confidence: 99%

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Optical Transient Source AT2021lfa: A Possible “Dirty Fireball”

Ye,

Wei,

Zhu

et al. 2024

Res. Astron. Astrophys.

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AT2021lfa, also known as ZTF21aayokph, was detected by the Zwicky Transient Facility on May 4, 2021, at 05:34:48 UTC. Follow-up observations were conducted using a range of ground-based optical telescopes, as well as Swift/XRT and VLA instruments. AT2021lfa is classified as an ``orphan afterglow'' candidate due to its rapid flux decline and its reddened color ($g-r = 0.17 \pm 0.14$ mag). For optical transient source without prompt gamma-ray detection, one key point is to determine its burst time. Here we measure the burst time through fitting the initial bump feature of AT2021lfa and obtain its burst time as May 3, 2021, at 22:09:50 UTC. Using \texttt{Afterglowpy}, we model the multi-band afterglow of AT2021lfa and find that the standard model cannot reproduce the late radio observations well. Considering that the microphysical parameters $\epsilon_e$, $\epsilon_B$ (the energy fraction given to electrons and magnetic field), and $\xi_N$ (the fraction of accelerated electrons) may vary with time, we then model the afterglow of AT2021lfa taking into account the temporal evolution of the physical parameters $\epsilon_e$, $\epsilon_B$, and $\xi_N$ and find in this case the multi-wavelength observations can be reproduced well. The initial Lorentz factor of AT2021lfa can be estimated from the peak time of the early afterglow, which yields a value of about 18, suggesting that AT2021lfa should be classified as a ``dirty fireball''. From the upper limit for the prompt emission energy of AT2021lfa, we obtain the radiation efficiency is less than 0.02\%, which is much smaller than that of ordinary gamma-ray bursts. It is also interesting that the fitted values of jet angle and viewing angle are very large, $\theta_c \sim$ 0.66 rad, $\theta_v \sim$ 0.53 rad, which may lead to the low Lorentz factor and radiation efficiency. When compared with GRB afterglow samples, it is evident that the onset bump timescale of AT2021lfa satisfies the empirical relationships observed in GRB samples. Additionally, the luminosity of AT2021lfa falls within the range of observations for GRB samples. Additionally, the luminosity of AT2021lfa falls within the range of observations for GRB samples; however, approximately 1 day after the burst, its luminosity exceeds that of the majority of GRB samples.

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Section: Fitting the Burst Time Of At2021lfasupporting

confidence: 69%

Section: Fitting the Burst Time Of At2021lfamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optical Transient Source AT2021lfa: A Possible “Dirty Fireball”

Ye,

Wei,

Zhu

et al. 2024

Res. Astron. Astrophys.

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“…This identification was subsequently confirmed via observations from a number of additional observatories, including [9][10][11][78][79][80]. We acquired two further epochs of observations with ULTRACAM on the following nights with 10 × 20s exposures in the Super SDSS u, g and i, bands.…”

Section: Ntt -Afterglow Discoverymentioning

confidence: 86%

“…Visual inspection of the images compared to those obtained with the Legacy Survey [7] revealed a new source coincident with the Swift X-ray source, and we identified it as the optical afterglow of GRB 230307A [8]. This identification was subsequently confirmed via imaging by several additional observatories [9][10][11]. The location was also serendipitously imaged by the Transiting Exoplanet Survey Satellite (TESS) from 3 days before to 3 days after the GRB [12].…”

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confidence: 85%

JWST detection of heavy neutron capture elements in a compact object merger

Levan,

Gompertz,

Salafia

et al. 2023

Preprint

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The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs), sources of high-frequency gravitational waves and likely production sites for heavy element nucleosynthesis via rapid neutron capture (the r-process). These heavy elements include some of great geophysical, biological and cultural importance, such as thorium, iodine, and gold. Here we present observations of the exceptionally bright gamma-ray burst GRB230307A. We show that GRB 230307A belongs to the class of long-duration gamma-ray bursts associated with compact object mergers, and contains a kilonova similar to AT2017gfo, associated with the gravitational-wave merger GW170817. We obtained James Webb Space Telescope mid-infrared (mid-IR) imaging and spectroscopy 29 & 61 days after the burst. The spectroscopy shows an emission line at 2.1 microns which we interpret as tellurium (atomic mass A=130), and a very red source, emitting most of its light in the mid-IR due to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy element nucleosynthesis across the Universe.

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Possible origin of AT2021any: A failed gamma-ray burst from a structured jet

Xu,

Huang,

Geng

2023

A&A

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Afterglows not associated with any gamma-ray bursts (GRBs) are called orphan afterglows. The detection of such afterglows is an important goal in many sky survey programs. Recently, a promising orphan afterglow candidate, AT2021any, was found by the Zwicky Transient Facility. In this work, we performed multi-wavelength fittings of AT2021any with two different outflow models, namely, the top-hat jet model and the structured Gaussian jet model. Although both models can fit the observed light curves well, we found that the structured Gaussian jet model presents a better result and is thus preferred by observations. In this framework, the best-fit Lorentz factor is about 68, which indicates that AT2021any should be a failed GRB. The half-opening angle of the jet and the viewing angle were found to be 0.1 and 0.02, respectively, which means that the jet is essentially observed on-axis. We inferred the trigger time of the GRB to be about 1000 s before the first detection of the orphan afterglow, and we derived an upper limit of 21.5% for the radiative efficiency, which is typical for GRBs.

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Orphan optical flare as SOSS emission afterglow, localization in time

Cited by 5 publications

References 65 publications

Optical Transient Source AT2021lfa: A Possible “Dirty Fireball”

Optical Transient Source AT2021lfa: A Possible “Dirty Fireball”

JWST detection of heavy neutron capture elements in a compact object merger

Possible origin of AT2021any: A failed gamma-ray burst from a structured jet

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