Keck+LRIS spectroscopy of the apparently closest galaxy to Chandra Fast X-ray Transient XRT 210423
ATel #14641; Igor Andreoni (Caltech), Daniel Perley (LJMU), Mansi Kasliwal (Caltech), Kishalay De (Caltech), Shreya Anand (Caltech), Viraj Karambelkar (Caltech)
on 18 May 2021; 20:58 UT
Credential Certification: Igor Andreoni (igor.andreoni@gmail.com)
Subjects: Optical, Neutron Star, Transient, Magnetar
We observed the galaxy located ~4.6'' away from the Chandra fast transient XRT 210423 (Lin et al., ATel #14599), SDSS J134856.75+263946.7, with the Low Resolution Imaging Spectrometer (LRIS) at W. M. Keck Observatory. The coordinates of the galaxy are RA, DEC = 13h48m56.75s, +26d39m46.8s (SDSS DR12; Alam et al., 2015). Observations started on 2021 May 10 at 6:50 UT and the exposure time was 600s. The data were reduced using lpipe (Perley, 2019).
We identify with confidence only one emission line at 9,355AA in the spectrum of the galaxy. We interpret this feature as [O II] at z=1.5105. The line is resolved into a doublet with the correct spacing and a reasonable flux ratio. If this feature was attributed to any other strong line such as [O III], Hbeta, or Halpha, other strong lines would be present that were not observed. We therefore exclude that the observed galaxy belongs to the Abell 1795 galaxy cluster.
At z=1.5105, the projected physical separation between the transient and the host would be >200kpc, so an association between XRT 210423 and the SDSS J134856.75+263946.7 galaxy is highly improbable. If XRT 210423 belonged to the Abell 1795 cluster, the projected separation to the closest catalogued galaxy (HYPERLEDA 94646; RA=13h48m53.6s, Dec=+26d39m52s) would be of ~62kpc.
