Constraints on Relativistic Jets from the Fast X-Ray Transient 210423 Using Prompt Radio Follow-up Observations

Dina Ibrahimzade; R. Margutti; J. S. Bright; P. Blanchard; K. Paterson; D. Lin; H. Sears; A. Polzin; I. Andreoni; G. Schroeder; K. D. Alexander; E. Berger; D. L. Coppejans; A. Hajela; J. Irwin; T. Laskar; B. D. Metzger; J. C. Rastinejad; L. Rhodes

doi:10.3847/1538-4357/ad9397

The Astrophysical Journal (Jan 2025)

Constraints on Relativistic Jets from the Fast X-Ray Transient 210423 Using Prompt Radio Follow-up Observations

Dina Ibrahimzade,
R. Margutti,
J. S. Bright,
P. Blanchard,
K. Paterson,
D. Lin,
H. Sears,
A. Polzin,
I. Andreoni,
G. Schroeder,
K. D. Alexander,
E. Berger,
D. L. Coppejans,
A. Hajela,
J. Irwin,
T. Laskar,
B. D. Metzger,
J. C. Rastinejad,
L. Rhodes

Affiliations

Dina Ibrahimzade: ORCiD; Department of Astronomy, University of California , Berkeley, CA 94720-3411, USA ; [email protected]
R. Margutti: ORCiD; Department of Astronomy, University of California , Berkeley, CA 94720-3411, USA ; [email protected]; Department of Physics, University of California , 366 Physics North MC 7300, Berkeley, CA 94720, USA
J. S. Bright: ORCiD; Department of Astronomy, University of California , Berkeley, CA 94720-3411, USA ; [email protected]; Astrophysics, Department of Physics, University of Oxford , Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
P. Blanchard: ORCiD; Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , Evanston, IL 60202, USA; Department of Physics and Astronomy, Northwestern University , Evanston, IL 60208, USA
K. Paterson: ORCiD; Max-Planck-Institut für Astronomie , Königstuhl 17, 69117 Heidelberg, Germany
D. Lin: ORCiD; Department of Physics, Northeastern University , Boston, MA 02115-5000, USA
H. Sears: ORCiD; Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , Evanston, IL 60202, USA; Department of Physics and Astronomy, Northwestern University , Evanston, IL 60208, USA
A. Polzin: ORCiD; Department of Astronomy and Astrophysics, The University of Chicago , Chicago, IL 60637, USA
I. Andreoni: ORCiD; Joint Space-Science Institute, University of Maryland , College Park, MD 20742, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Astrophysics Science Division, NASA Goddard Space Flight Center , Mail Code 661, Greenbelt, MD 20771, USA
G. Schroeder: ORCiD; Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , Evanston, IL 60202, USA; Department of Physics and Astronomy, Northwestern University , Evanston, IL 60208, USA
K. D. Alexander: ORCiD; Department of Astronomy/Steward Observatory , 933 North Cherry Avenue, Rm. N204, Tucson, AZ 85721-0065, USA
E. Berger: ORCiD; Center for Astrophysics—Harvard & Smithsonian , 60 Garden Street, Cambridge, MA 02138-1516, USA
D. L. Coppejans: ORCiD; Department of Physics, University of Warwick , Gibbet Hill Road, Coventry CV4 7AL, UK
A. Hajela: ORCiD; DARK, Niels Bohr Institute, University of Copenhagen , Jagtvej 128, 2200 Copenhagen, Denmark
J. Irwin: ORCiD; Department of Physics & Astronomy, University of Alabama , Tuscaloosa, AL 35487-0324, USA
T. Laskar: ORCiD; Department of Physics & Astronomy, University of Utah , Salt Lake City, UT 84112, USA
B. D. Metzger: ORCiD; Department of Physics, Columbia University , New York, NY 10027, USA; Center for Computational Astrophysics, Flatiron Institute , 162 5th Avenue, New York, NY 10010, USA
J. C. Rastinejad: ORCiD; Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , Evanston, IL 60202, USA; Department of Physics and Astronomy, Northwestern University , Evanston, IL 60208, USA
L. Rhodes: ORCiD; Astrophysics, Department of Physics, University of Oxford , Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK

DOI: https://doi.org/10.3847/1538-4357/ad9397
Journal volume & issue: Vol. 980, no. 1
p. 92

Abstract

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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.

X-ray transient sources

Published in The Astrophysical Journal

ISSN: 1538-4357 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/0004-637X

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