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| Main Authors: | , , , , , , , , , |
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| Format: | Preprint |
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2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2407.18311 |
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| _version_ | 1866916336971546624 |
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| author | Ricci, R. Troja, E. Yang, Y. Yadav, M. Liu, Y. Sun, H. Wu, X. Gao, H. Zhang, B. Yuan, W. |
| author_facet | Ricci, R. Troja, E. Yang, Y. Yadav, M. Liu, Y. Sun, H. Wu, X. Gao, H. Zhang, B. Yuan, W. |
| contents | The recent launch of Einstein Probe (EP) in early 2024 opened up a new window onto the transient X-ray sky, allowing for real-time discovery and follow-up of fast X-ray transients (FXRTs). Multi-wavelength observations of FXRTs and their counterparts are key to characterize the properties of their outflows and, ultimately, identify their progenitors. Here, we report our long-term radio monitoring of EP240315A, a long-lasting ($\sim 1000$ s) high redshift ($z=4.9$) FXRT associated to GRB~240315C. Our campaign, carried out with the Australian Telescope Compact Array (ATCA), followed the transient's evolution at two different frequencies (5.5 GHz and 9~GHz) for three months. In the radio lightcurves we identify an unusual steep rise at 9 GHz, possibly due to a refreshed reverse shock, and a late-time rapid decay of the radio flux, which we interpret as a jet break due to the outflow collimation. We find that the multi-wavelength counterpart of EP240315A is well described by a model of relativistic jet seen close to its axis, with jet half-opening angle $θ_j \approx 3 ^{\circ}$ and beaming-corrected total energy $E \simeq 4\times 10^{51}$~erg, typical of GRBs. These results show that a substantial fraction of FXRTs may be associated to standard GRBs and that sensitive X-ray monitors, such as Einstein Probe and the proposed HiZ-GUNDAM and Theseus missions, can successfully pinpoint their relativistic outflows up to high-redshifts. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_18311 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Long-term radio monitoring of the fast X-ray transient EP240315a: evidence for a relativistic jet Ricci, R. Troja, E. Yang, Y. Yadav, M. Liu, Y. Sun, H. Wu, X. Gao, H. Zhang, B. Yuan, W. High Energy Astrophysical Phenomena The recent launch of Einstein Probe (EP) in early 2024 opened up a new window onto the transient X-ray sky, allowing for real-time discovery and follow-up of fast X-ray transients (FXRTs). Multi-wavelength observations of FXRTs and their counterparts are key to characterize the properties of their outflows and, ultimately, identify their progenitors. Here, we report our long-term radio monitoring of EP240315A, a long-lasting ($\sim 1000$ s) high redshift ($z=4.9$) FXRT associated to GRB~240315C. Our campaign, carried out with the Australian Telescope Compact Array (ATCA), followed the transient's evolution at two different frequencies (5.5 GHz and 9~GHz) for three months. In the radio lightcurves we identify an unusual steep rise at 9 GHz, possibly due to a refreshed reverse shock, and a late-time rapid decay of the radio flux, which we interpret as a jet break due to the outflow collimation. We find that the multi-wavelength counterpart of EP240315A is well described by a model of relativistic jet seen close to its axis, with jet half-opening angle $θ_j \approx 3 ^{\circ}$ and beaming-corrected total energy $E \simeq 4\times 10^{51}$~erg, typical of GRBs. These results show that a substantial fraction of FXRTs may be associated to standard GRBs and that sensitive X-ray monitors, such as Einstein Probe and the proposed HiZ-GUNDAM and Theseus missions, can successfully pinpoint their relativistic outflows up to high-redshifts. |
| title | Long-term radio monitoring of the fast X-ray transient EP240315a: evidence for a relativistic jet |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2407.18311 |