GRB 250704B: An Off-axis Short GRB with a Long-Lived Afterglow Plateau
Vishwajeet Swain, Tomás Ahumada, Sameer K. Patil, Yogesh Wagh, Varun Bhalerao, Mansi Kasliwal, Ehud Nakar, Shreya Anand, Igor Andreoni, G. C. Anupama, Anuraag Arya, Arvind Balasubramanian, Sudhanshu Barway, Malte Busmann, Jonathan Carney, Michael Coughlin, Deepak Eappachen, Daniel Gruen, Xander J. Hall, Viraj Karambelkar, Tanishk Mohan, Brendan O'Connor, Antonella Palmese, Utkarsh Pathak, D. K. Sahu, Aditya Pawan Saikia, Nikhil Sarin, Gokul Srinivasaragavan, Hitesh Tanenia
公開日: 2025/9/2
Abstract
We present a detailed multi-wavelength afterglow study of the short GRB 250704B, extensively monitored in optical and near-infrared bands. Its afterglow displays an unusually long-duration plateau followed by an achromatic break and a steep decline, deviating from canonical GRB afterglows. While long plateaus are often explained by central engine activity, we find that for GRB 250704B, an energy injection model requires unreasonable parameters. The afterglow is better explained by an off-axis power-law structured jet with a narrow core ($\theta_c \approx 0.7^{\circ}$) viewed at a modest angle ($\theta_v \approx 1.9^{\circ}$). A comparison with GRB 170817A shows that both events are consistent with the off-axis structured jet scenario, where the shape of the light curve is governed primarily by the geometry of the jet and the viewing angle rather than the energetics, microphysical parameters, or external density. Our results underscore the importance of incorporating the jet structure in GRB modeling.