A Global Photoionization Response to Prompt Emission and Outliers: Different Origin of Long Gamma-ray Bursts?

Abstract

By using the line ratio C IVλ1549/C IIλ1335 as a tracer of ionization ratio of the interstellar medium (ISM) illuminated by a long gamma-ray burst (LGRB), we identify a global photoionization response of the ionization ratio to the photon luminosity of the prompt emission assessed by either L iso /E peak or L iso /E 2 peak . The ionization ratio increases with both L iso /E peak and L iso /E 2 peak for a majority of the LGRBs in our sample, although there are a few outliers. The identified dependence of C IV/C II on L iso /E 2 peak suggests that the scatter of the widely accepted Amati relation is related with the ionization ratio in ISM. The outliers tend to have relatively high C IV/C II values as well as relatively high C IVλ1549/Si IVλ1403 ratios, which suggests an existence of Wolf-Rayet stars in the environment of these LGRBs. We finally argue that the outliers and the LGRBs following the identified C IV/C II−L iso /E peak (L iso /E 2 peak ) correlation might come from different progenitors with different local environments.

A pilot study of catching high-z GRBs and exploring circumburst environment in the forthcoming SVOM era

“…The best-fitted relationship is overplotted in Figure 3. Compared to our previous study in Wang et al (2018), the current enlarged sample results in a much shallow dependence because of the deviation at the large L iso /E 2 peak end, although the intrinsic scatter ǫ is almost not changed.…”

“…Figure 3 shows updated dependence of CIV/CII line ratio on both L iso /E 2 peak (right panel) and L iso /E peak (middle panel) by combining the current XS-GRB sample and the sample previously used in Wang et al (2018). The line ratio is also plotted against L iso in the left panel in the same figure.…”

“…Rapid follow-up in spectroscopy of GRBs is in fact quite important in (1) discovery of high-z GRBs through a redshift measurement; (2) exploring structure and evolution of early universe through a study of reionization and cosmic star formation history; and (3) examining the properties of the progenitors from the response of the circumburst gas to the central engine. In this paper, we perform a pilot study on the spectroscopic follow-up in the SVOM era by focusing on the following two aspects: (1) the capability of rapid identification of optical candidates of high-z GRB; and (2) an updated global photoionization response of circumburst gas to GRB prompt emission (Wang et al 2018) that is believed to be intensively addressed by the SVOM mission.…”

Spectroscopy of the Type Ic Supernova SN 2017iuk Associated with Low-redshift GRB 171205A

“…Study of the SNe associated with LGRBs is important for exploring the nature of death of massive stars. Even though it is widely accepted that LGRBs originate from core-collapse of young massive stars (e.g., Woosley & Bloom 2006;Hjorth & Bloom 2012;Wang et al 2018 and references therein), the compact objects formed in the core-collapse are still under hot debate. They could be either a stellar-mass blackhole (e.g., Woosley 1993;MacFadyen & Woosley 1999) or a magentar (i.e.…”