Following the identification of the luminous fast blue optical transient (LFBOT) AT2023fhn (Astronote #2023-93), we triggered ToO programs with the X-ray Telescope on board the Neil Gehrels Swift Observatory and the Northern Extended Millimeter Array (NOEMA).
Swift XRT observed the position of AT2023fhn for 3ks on 25 Apr 2023 (15 days after the first optical detection, t0), with an upper limit of 0.005 ct/s. At the redshift of AT2023fhn (z=0.24) this corresponds to an upper limit on the 0.3-10 keV luminosity of approximately 4 x 10^43 erg/s.
NOEMA observed the position of AT2023fhn on 22 April 2023, 12 days after t0, under good conditions. No significant emission was detected, with an RMS flux density at 100 GHz of 36 uJy. At the redshift of AT2023fhn, this corresponds to an upper limit on the 100 GHz luminosity of 2 x 10^29 erg/s/Hz.
The upper limits rule out X-ray and millimeter emission similar to some LFBOTs (AT2020xnd, AT2022tsd) but not AT2018cow itself.
| Catalog | Name | Reported RA | Reported DEC | Reported Obj-Type | Reported Redshift | Host Name | Host Redshift | Remarks | TNS RA | TNS DEC | TNS Obj-Type | TNS Redshift |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TNS | 2023fhn | 10:08:03.815 | +21:04:26.95 | 10:08:03.815 | +21:04:26.95 | |||||||
| TNS | 2020xnd | 22:20:02.030 | -02:50:25.30 | 22:20:02.030 | -02:50:25.30 | |||||||
| TNS | 2022tsd | 03:20:10.863 | +08:44:55.63 | 03:20:10.863 | +08:44:55.63 | |||||||
| TNS | 2018cow | 16:16:00.220 | +22:16:04.91 | SN Ic-BL | 0 | 16:16:00.220 | +22:16:04.91 | SN Ic-BL | 0.014 |
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