# The exceptionally extended flaring activity in the X-ray afterglow of GRB 050730 observed with Swift and XMM-Newton

## TL;DR

This paper analyzes the X-ray afterglow of GRB 050730, revealing extended flaring activity with detailed spectral and temporal properties, suggesting internal or refreshed shocks as possible origins, and providing insights into high-redshift GRB behavior.

## Contribution

It presents a comprehensive spectral and temporal analysis of the flaring activity in GRB 050730's X-ray afterglow, highlighting the nature and origin of the flares at high redshift.

## Key findings

- Seven re-brightening events observed over two orders of magnitude in time.
- The afterglow decay follows a double broken power-law with specific break times.
- Most flares' durations relative to peak time are about 0.6-0.7, consistent with internal or refreshed shocks.

## Abstract

We present the results of a detailed spectral and temporal analysis of Swift and XMM-Newton observations of the high redshift (z=3.969) GRB 050730. The X-ray afterglow of GRB 050730 was found to decline with time with superimposed intense flaring activity that extended over more than two orders of magnitude in time. Seven distinct re-brightening events starting from 236 s up to 41.2 ks after the burst were observed. The underlying decay of the afterglow was well described by a double broken power-law model with breaks at t_1= 237 +/- 20 s and t_2 = 10.1 (-2.2) (+4.6) ks. The temporal decay slopes before, between and after these breaks were alpha_1 = 2.1 +/- 0.3, alpha_2 = 0.44 (-0.08) (+0.14) and alpha_3 = 2.40 (+0.07) (-0.09), respectively. The spectrum of the X-ray afterglow was well described by a photoelectrically absorbed power-law with an absorbing column density N_H=(1.28 +/- 0.26) 10^22 cm^-2 in the host galaxy. Strong X-ray spectral evolution during the flaring activity was present. In the majority of the flares (6/7) the ratio Delta_t/t_p between the duration of the event and the time when the flare peaks was nearly constant and about 0.6-0.7. We showed that the observed spectral and temporal properties of the first three flares are consistent with being due both to high-latitude emission, as expected if the flares were produced by late internal shocks, or to refreshed shocks, i.e. late time energy injections into the main afterglow shock by slow moving shells ejected from the central engine during the prompt phase. The event fully satisfies the E_p-E_iso Amati relation while is not consistent with the E_p-E_jet Ghirlanda relation.