[Paper Review] BeppoSAX follow-up search for the X-ray afterglow of GRB970111

M. Feroci, L. A. Antonelli+18 more|arXiv (Cornell University)|Mar 3, 1998

Gamma-ray bursts and supernovae5 citations

TL;DR

This paper reports on the BeppoSAX satellite's follow-up observation of GRB970111, 16 hours after the gamma-ray burst, searching for an X-ray afterglow. Despite detecting a faint X-ray source (1SAXJ1528.1+1937) near the burst position, it is inconsistent with the interplanetary network (IPN) localization, and the X-ray flux is significantly lower than expected for such a bright gamma-ray burst, indicating no clear correlation between peak gamma-ray flux and afterglow intensity.

ABSTRACT

The BeppoSAX satellite has recently opened a new way towards the solution of the long standing gamma-ray bursts' (GRBs) enigma, providing accurate coordinates few hours after the event thus allowing for multiwavelength follow-up observational campaigns. The BeppoSAX Narrow Field Instruments observed the region of sky containing GRB970111 16 hours after the burst. In contrast to other GRBs observed by BeppoSAX no bright afterglow was unambiguously observed. A faint source (1SAXJ1528.1+1937) is detected in a position consistent with the BeppoSAX Wide Field Camera position, but unconsistent with the IPN annulus. Whether 1SAXJ1528.1+1937 is associated with GRB970111 or not, the X-ray intensity of the afterglow is significantly lower than expected, based on the properties of the other BeppoSAX GRB afterglows. Given that GRB970111 is one of the brightest GRBs observed, this implies that there is no obvious relation between the GRB gamma-ray peak flux and the intensity of the X-ray afterglow.

Motivation & Objective

• To search for the X-ray afterglow of GRB970111 using BeppoSAX's Narrow Field Instruments after a 16-hour delay.
• To determine whether the detected X-ray source is associated with the gamma-ray burst based on positional consistency.
• To assess the X-ray afterglow flux in relation to the burst's high gamma-ray peak flux.
• To investigate the relationship between gamma-ray brightness and X-ray afterglow luminosity in long-duration GRBs.

Proposed method

• BeppoSAX Narrow Field Instruments observed the sky region of GRB970111 16 hours after the burst trigger.
• X-ray source detection was performed using the satellite's X-ray imaging and spectroscopy capabilities.
• Positional comparison was made between the detected X-ray source and the BeppoSAX Wide Field Camera (WFC) position and the Interplanetary Network (IPN) annulus.
• The X-ray flux of the candidate source was measured and compared to the expected afterglow flux based on other BeppoSAX GRBs.
• Statistical analysis was used to assess the significance of the detected source and its consistency with the GRB position.
• The luminosity of the afterglow was inferred from the measured flux and distance estimates.

Experimental results

Research questions

• RQ1 Is there a detectable X-ray afterglow associated with GRB970111 in BeppoSAX observations 16 hours post-burst?
• RQ2 Does the position of the detected X-ray source match the BeppoSAX WFC position and the IPN localization?
• RQ3 How does the X-ray flux of GRB970111 compare to the flux expected from other BeppoSAX GRBs with similar gamma-ray peak flux?
• RQ4 Is there a correlation between the gamma-ray peak flux and the X-ray afterglow luminosity in long-duration GRBs?

Key findings

• A faint X-ray source, 1SAXJ1528.1+1937, was detected at a position consistent with the BeppoSAX Wide Field Camera position.
• The X-ray source position is inconsistent with the Interplanetary Network (IPN) annulus, reducing confidence in its association with GRB970111.
• The X-ray afterglow flux is significantly lower than expected based on the luminosity of other BeppoSAX GRB afterglows.
• GRB970111 is one of the brightest GRBs observed, yet its X-ray afterglow is faint, indicating no clear correlation between gamma-ray peak flux and afterglow intensity.
• The lack of a bright afterglow challenges the assumption that high gamma-ray flux implies high afterglow luminosity.