Optical spectrum of the host galaxy of ultra-bright fast radio burst source FRB 20250316A
ATel #17091; Liam Connor (CfA), Wasundara Athukoralalage (CfA), Allyson Bieryla (CfA), Mei Lin (Harvard University), Gage Miller (Harvard University), Dalila Oliva (Harvard University), James Patton (Harvard University)
on 20 Mar 2025; 05:39 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Liam Connor (liam.dean.connor@gmail.com)
Subjects: Radio, Optical, Transient
An optical spectrum was obtained for NGC 4141, a candidate host galaxy of FRB 20250316A (Atel #17081) using the FAST spectrograph on the 1.5 m Tillinghast Telescope. The 3 arcsecond slit was oriented to align with the reported VLBI localization from the CHIME/FRB Outrigger commissioning data (Atel #17086). The slit was placed at RA=182.4365 Dec=+58.8552, and 9.5 degrees east of north. These observations were carried out by undergraduate students during an observing trip to FLWO for the Astronomy 100 class at Harvard College.
Total on-source exposure time was 1800s. The 2D spectrum of the host galaxy exhibits strong H\alpha and H\beta, as well as Oxygen lines with multiple knots of star formation along the slit in the spiral arm. The fitted redshift was 0.0067. Given the considerable local dispersion measure (DMhost ~ 75-135 pc/cc), FRB 20250316A may be coincident with this H\alpha emission.
We thank the observatory staff for their assistance with these observations.
optical spectrum
