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Revealing the characteristics of the dark GRB 150309A: Dust extinguished or high-z?⋆
Astronomy & Astrophysics ( IF 6.5 ) Pub Date : 2024-03-04 , DOI: 10.1051/0004-6361/202346042
A. J. Castro-Tirado , R. Gupta , S. B. Pandey , A. Nicuesa Guelbenzu , S. Eikenberry , K. Ackley , A. Gerarts , A. F. Valeev , S. Jeong , I. H. Park , S. R. Oates , B.-B. Zhang , R. Sánchez-Ramírez , A. Martín-Carrillo , J. C. Tello , M. Jelínek , Y.-D. Hu , R. Cunniffe , V. V. Sokolov , S. Guziy , P. Ferrero , M. D. Caballero-García , A. K. Ror , A. Aryan , M. A. Castro Tirado , E. Fernández-García , M. Gritsevich , I. Olivares , I. Pérez-García , J. M. Castro Cerón , J. Cepa

Context. Dark gamma-ray bursts (GRBs) constitute a significant fraction of the GRB population. In this paper, we present a multi-wavelength analysis (both prompt emission and afterglow) of an intense (3.98 × 10−5 erg cm−2 using Fermi-Gamma-Ray Burst Monitor) two-episodic GRB 150309A observed early on until ∼114 days post burst. Despite the strong gamma-ray emission, no optical afterglow was detected for this burst. However, we discovered near-infrared (NIR) afterglow (KS-band), ∼5.2 h post burst, with the CIRCE instrument mounted at the 10.4 m Gran Telescopio Canarias (hereafter, GTC).Aims. We aim to examine the characteristics of GRB 150309A as a dark burst and to constrain other properties using multi-wavelength observations.Methods. We used Fermi observations of GRB 150309A to understand the prompt emission mechanisms and jet composition. We performed early optical observations using the BOOTES robotic telescope and late-time afterglow observations using the GTC. A potential faint host galaxy was also detected in the optical wavelength using the GTC. We modelled the potential host galaxy of GRB 150309A in order to explore the environment of the burst.Results. The time-resolved spectral analysis of Fermi data indicates a hybrid jet composition consisting of a matter-dominated fireball and magnetic-dominated Poynting flux. The GTC observations of the afterglow revealed that the counterpart of GRB 150309A was very red, with H − KS > 2.1 mag (95% confidence). The red counterpart was not discovered in any bluer filters of Swift UVOT/BOOTES, which would be indicative of a high redshift origin. Therefore we discarded this possibility based on multiple arguments, such as spectral analysis of the X-ray afterglow constrain z < 4.15 and a moderate redshift value obtained using the spectral energy distribution (SED) modelling of the potential galaxy. The broadband (X-ray to NIR bands) afterglow SED implies a very dusty host galaxy with a deeply embedded GRB (suggesting AV ≳ 35 mag).Conclusions. The environment of GRB 150309A demands a high extinction towards the line of sight. Demanding dust obscuration is the most probable origin of optical darkness as well as the very red afterglow of GRB 150309A. This result establishes GRB 150309A as the most extinguished GRB known to date.

中文翻译:

揭示暗GRB 150309A的特征:尘埃熄灭还是高z?⋆

语境。暗伽马射线暴 (GRB) 构成了 GRB 群体的很大一部分。在本文中,我们对早期观测到的强烈(3.98 × 10 -5 erg cm -2使用费米伽马射线爆发监视器)两幕式 GRB 150309A 进行了多波长分析(包括瞬时发射和余辉),直到 ∼爆发后 114 天。尽管伽马射线发射很强,但这次爆发没有检测到光学余辉。然而,我们在爆发后约 5.2 小时发现了近红外 (NIR) 余辉(K S波段),CIRCE 仪器安装在 10.4 m Gran Telescopio Canarias(以下简称 GTC)上。目标。我们的目标是检查 GRB 150309A 作为暗爆发的特征,并使用多波长观测来限制其他属性。方法。我们利用GRB 150309A 的费米观测来了解瞬发发射机制和喷流成分。我们使用 BOOTES 机器人望远镜进行了早期光学观测,并使用 GTC 进行了后期余辉观测。使用 GTC 还在光学波长中检测到了一个潜在的微弱宿主星系。我们对 GRB 150309A 的潜在宿主星系进行了建模,以探索爆发的环境。结果。费米数据的时间分辨光谱分析表明,混合喷流成分由物质主导的火球和磁主导的坡印廷通量组成。GTC 对余辉的观测表明,GRB 150309A 的对应物非常红,H  −  K S  > 2.1 mag(95% 置信度)。在Swift UVOT/BOOTES的任何蓝色滤光片中都没有发现红色对应物,这表明存在高红移起源。因此,我们基于多种论点放弃了这种可能性,例如 X 射线余辉约束z  < 4.15 的光谱分析以及使用潜在星系的光谱能量分布 (SED) 建模获得的适度红移值。宽带(X 射线到近红外波段)余辉 SED 暗示着一个布满尘埃的主星系,其中有一个深深嵌入的伽马射线暴(表明A V  ≳ 35 星等)。结论。GRB 150309A 的环境要求对视线具有高度消光。要求严格的尘埃遮蔽是光学黑暗以及 GRB 150309A 非常红色的余辉最可能的来源。这一结果使GRB 150309A成为迄今为止已知最熄灭的GRB。
更新日期:2024-03-04
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