Constraints on Relativistic Jets from the Fast X-Ray Transient 210423 Using Prompt Radio Follow-up Observations
Abstract Fast X-ray transients (FXTs) are a new observational class of phenomena with no clear physical origin. This is at least partially a consequence of limited multiwavelength follow-up of this class of transients in real time. Here we present deep optical ( g - and i -band) photometry with Keck, and prompt radio observations with the Very Large Array of FXT 210423 obtained at δ t ≈ 14–36 days since the X-ray trigger. We use these multiband observations, combined with publicly available data sets, to constrain the presence and physical properties of on-axis and off-axis relativistic jets such as those that can be launched by neutron star mergers and tidal disruption events, which are among the proposed theoretical scenarios of FXTs. Considering a wide range of possible redshifts z ≤ 3.5, circumstellar medium density n = 10 −6 –10 −1 cm −3 , and isotropic-equivalent jet kinetic energy E k ,iso = 10 48 –10 55 erg, we find that we can rule out wide jets with opening angle θ j = 15° viewed within 10° off-axis. For more collimated jets ( θ j = 3°) we can only rule out on-axis ( θ obs = 0°) orientations. This study highlights the constraining power of prompt multiwavelength observations of FXTs discovered in real time by current (e.g., Einstein Probe) and future facilities.
Authors
- Ava Polzin (ORCID: https://orcid.org/0000-0002-5283-933X)
- Lauren Rhodes (ORCID: https://orcid.org/0000-0003-2705-4941)
- K. D. Alexander (ORCID: https://orcid.org/0000-0002-8297-2473)
- T. Laskar (ORCID: https://orcid.org/0000-0003-1792-2338)
- Brian D. Metzger (ORCID: https://orcid.org/0000-0002-4670-7509)
- P. K. Blanchard (ORCID: https://orcid.org/0000-0003-0526-2248)
- Genevieve Schroeder (ORCID: https://orcid.org/0000-0001-9915-8147)
- Joe Bright (ORCID: https://orcid.org/0000-0002-7735-5796)
- A. Hajela (ORCID: https://orcid.org/0000-0003-2349-101X)
- D. L. Coppejans (ORCID: https://orcid.org/0000-0001-5126-6237)
- E. Berger (ORCID: https://orcid.org/0000-0002-9392-9681)
- Dacheng Lin (ORCID: https://orcid.org/0000-0001-5683-5339)
- Igor Andreoni (ORCID: https://orcid.org/0000-0002-8977-1498)
- Jimmy A. Irwin (ORCID: https://orcid.org/0000-0003-4307-8521)
- Jillian Rastinejad (ORCID: https://orcid.org/0000-0002-9267-6213)
- K. Paterson (ORCID: https://orcid.org/0000-0001-8340-3486)
- R. Margutti (ORCID: https://orcid.org/0000-0003-4768-7586)
- Huei Sears (ORCID: https://orcid.org/0000-0001-8023-4912)
- Dina Ibrahimzade
Institutions
- Ruhr University Bochum (DE)
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2025-02-01
- DOI
- https://doi.org/10.3847/1538-4357/ad9397
- Citations
- 2
- Primary Topic
- Gamma-ray bursts and supernovae
- Type
- article
- Field-Weighted Citation Impact
- 2.31
Funders
- National Science Foundation
- National Aeronautics and Space Administration
- Northwestern University
- Heising-Simons Foundation
- Nuclear Safety and Security Commission
- Science and Technology Facilities Council