Discovery of FRB 20250316A, a bright fast radio burst in the direction of the nearby galaxy NGC 4141

ATel #17081; Mason Ng (McGill University) on behalf of the CHIME/FRB Collaboration
on 17 Mar 2025; 00:00 UT
Credential Certification: Mason Ng (masonng@mit.edu)

Tweet

The CHIME/FRB Collaboration reports a bright (S/N > 5000) fast radio burst (FRB) in the direction of the nearby galaxy NGC 4141. FRB 20250316A (VOEvent #439373176) was detected on 2025 March 16 at 08:33:50.842 (± 0.008) UTC (real-time pipeline; topocentric at 400 MHz) with a nominal real-time pipeline dispersion measure (DM) of 161.3 ± 0.4 pc/cc. Using the raw-voltage data (baseband data), we determine the best-fit localization (Michilli et al. 2021) to be (J2000) R.A. = 182.476 deg., DEC. = +58.8494 deg., (Gal_l = 132.9154 deg., Gal_b = +57.4666 deg.) and the structure-maximizing DM to be 161.81 ± 0.03 pc/cc. Unfortunately, an uncertainty on this position using the raw-voltage data is not currently possible, due to missing system temperature information. We caution that without system temperature information, we are unable to correct for the thermal expansion of the metal structure of the telescope, and thus there may be localization errors of up to a few arcminutes in the N-S direction (Michilli et al. 2021).

Using the baseband position and a representative ~1 arcminute radius error circle, the source appears to be associated with the galaxy NGC 4141 with a PATH probability (Aggarwal et al. 2021) of 94.8%. NGC 4141 is an SBc galaxy at a Tully-Fisher distance of 37-44 Mpc (Sorce et al. 2014; Tully et al. 2016) and with a star formation rate of ~0.6 M_⊙/year (Kewley et al. 2005). Two relatively recent core-collapse supernovae have been detected in NGC 4141: SN 2008X (Boles 2008; Madison et al. 2008) and SN 2009E (Boles 2009; Pastorello et al. 2011).

The peak flux density of FRB 20250316A as determined using the baseband data is 1.6 ± 0.1 kJy with a fluence of 1.7 ± 0.2 kJy ms. At a distance of 40 Mpc and assuming isotropy with a bandwidth of 400 MHz, this corresponds to a luminosity of ~10⁴² erg/s and an emitted energy of ~10³⁹ erg, given a burst width of 0.7 ms (see method of Fonseca et al. 2023).

A ToO request was sent to Swift, which is on target as of 21:07 UTC on 2025 March 16. We have requested follow-up observations with the Onsala 25-m telescope, as well as with NICER. We encourage additional multiwavelength follow-up.

At the distance of NGC 4141, the estimated foreground DM due to the intergalactic medium is ~5 pc/cc. The expected foreground DM contribution from the Milky Way disk in this direction is ~20-30 pc/cc (Cordes & Lazio 2002; Yao et al. 2016). For an assumed upper limit on the Milky Way halo contribution of <50 pc/cc (Cook et al. 2023), the DM contribution of the host galaxy and FRB local environment is then ~75-135 pc/cc.

Sub-arcsecond VLBI localization of the source using the CHIME/Outriggers is currently in progress and will be reported in a follow-up ATel as soon as possible.

http://storage.googleapis.com/chimefrb-dev.appspot.com/FRB20250316A/FRB20250316A_basebandwaterfall.png