Detection and localization of FRB 20220912A with DSA-110

ATel #15693; Vikram Ravi on behalf of the DSA-110 team
on 18 Oct 2022; 20:01 UT
Credential Certification: Liam Connor (liam.dean.connor@gmail.com)

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We report the detection and interferometric localization of FRB 20220912A with the Deep Synoptic Array (DSA-110). A single burst was detected at 2022-10-18 05:20:48.395 UTC (arrival time at 1530 MHz) with a detection S/N of 12.2 and a detected dispersion measure (DM) of 228.3 pc/cm^3. The burst arrival time and DM were produced by the real-time detection pipeline and will be subject to offline optimization. A preliminary inspection of the data suggests complex structure in the dedispersed dynamic spectrum, and the data are consistent with the reported DM of FRB 20220912A (ATEL #15679, ATEL #15691).

The DSA-110 is a radio interferometer purpose-built for fast radio burst (FRB) detection and localization. The array is located at Caltech's Owens Valley Radio Observatory (OVRO) in California, USA. The array is currently comprised of 48x4.65-m dishes evenly spaced on the east-west arm of a Tee, which continuously search coherently beamformed data for FRBs in a band between 1280-1530MHz. If an event is detected, raw voltage data from 15x4.65-m "outrigger" antennas are dumped to allow for interferometric localization.

DSA-110 is a transit instrument with an approximately 10 sqdeg field-of-view. The dishes were pointed at the declination of FRB 20220912A after (ATEL #15679). The burst was detected in 55 min of exposure over the 21-min transit of the source. At boresight, the search SEFD is approximately 140 Jy.

Our best-fit preliminary localization for FRB 20220912A is

23h09h05.49s +48d42m25.6s (J2000)

The reported localization is derived from voltage data preserved at the 48 core antennas on the east-west arm and the 15 outrigger antennas, and ultimately calibrated with reference to several tens of >50mJy compact sources from the NRAO VLA Sky Survey (Condon et al., 1998, AJ, 115, 1693). The synthesized beam size was 29"x14" at a position angle of 85 degrees, and the image S/N was 16. We verified the absolute astrometric calibration by imaging the VLBI calibrators J2258+4937 (separated by 2 degrees from FRB 20220912A) and J2325+4806 (separated by 2.8 degrees from FRB 20220912A), and recovered their positions at offsets of 0.7" and 0.4" respectively. Pending a formal analysis of our localization uncertainty, we consider the approximate 90% confidence localization ellipse to have semi-axes of 2" in RA and 1" in DEC, at a PA of 90 degrees.

The DSA-110 position is in agreement with the 90% uncertainty region reported by CHIME/FRB. There is a faint uncataloged object within the DSA-110 localization region in archival PanSTARRS g-band data. Further follow-up is ongoing and encouraged to assess this object and other galaxies near the DSA-110 localization region (ATEL #15679).

The DSA-110 is supported by the National Science Foundation Mid-Scale Innovations Program in Astronomical Sciences (MSIP) under grant AST-1836018. Data on the DSA-110 detection of FRB 20220912A will be made available below. Note the RA and Dec in the png are from the preliminary detection and not the localization analysis.

FRB20220912A_DSA110