An X-ray upper limit towards CHIME J1634+44 in a radio-active state, from Chandra follow-up
ATel #17474; Mason Ng (McGill University; Trottier Space Institute at McGill University) for the CHIME/FRB/Pulsar Collaborations
on 4 Nov 2025; 15:06 UT
Credential Certification: Mason Ng (masonng@mit.edu)
Subjects: Radio, X-ray, Transient
Referred to by ATel #: 17478
CHIME J1634+44 is a long-period radio transient that has recently entered another radio-active bursting phase (ATels #17434, #17440).
We observed J1634+44 with the ACIS-S instrument aboard Chandra via a DDT observation for approximately 10 ks, between 2025/10/28 20:18 and 2025/10/28 23:44 (TT). We present results from a preliminary analysis at this point, and will report detailed analysis in a forthcoming publication.
We do not detect a significant source at (or near) the known source coordinates at the 3σ level using CIAO/wavdetect. Thus, we derived a preliminary 3σ upper limit on the 0.5-7.0 keV unabsorbed flux of 2.8 × 10-15 erg/s/cm2 using the aprates, aplimits, and modelflux tools in CIAO. This assumes a fiducial power law spectrum with NH = 0.075 × 1022 cm-2 (Dong et al., 2025, ApJ, 988L, 29) and Γ = 1.7. At a distance of d = 3 kpc, this corresponds to an upper limit on the 0.5-7 keV luminosity of 3.1 × 1030 erg/s.
We thank the Chandra team for promptly scheduling this observation.
