We report that the fast declining transient reported in Astronote 2023-178 by Swain et al., was discovered and first reported to the Transient Name Server by our ATLAS team. ATLAS discovered AT2023lcr (ATLAS23msn/ZTF23aaoohpy) on MJD 60113.405 (2023-06-18 09:43:47 UTC) at m_c = 19.3 +/- 0.1 (see TNS Astronomical Transient Report No. 180429). The last non-detection through forced photometry was on MJD = 60111.403 (2023-06-16 09:40:14 UTC), measuring a 5σ limit of m_c > 20.5.
AT2023lcr is offset by 5.0 arcsec South, 2.6 arcsec East from a possible host galaxy SDSS J163137.24+262203.3, a r=20.3 source with a photoz = 0.35 +/- 0.1. A finder is attached. If the transient were associated, it would be approximately 29 kpc offset from the SDSS galaxy.
The fast-fading and red nature of AT2023lcr was first noticed by Swain et al., (GCN #34022), and the fast nature was later confirmed by Gompertz et al., (GCN #34023). Our ATLAS measurements are summarised in the table below within the context of the Swain et al. and Gompertz et al. data. The object should be known as its discovery name, AT2023lcr, and the discovery provenance noted.
| MJD | Survey | Filter | Mag | MagErr |
|---|---|---|---|---|
| 60111.403 | ATLAS | c | >20.5 | |
| 60112.993 | GOTO | L | >20.3 | |
| 60113.061 | GOTO | L | 18.8 | 0.1 |
| 60113.275 | ZTF | g | 19.7 | 0.1 |
| 60113.337 | ZTF | r | 19.4 | 0.1 |
| 60113.405 | ATLAS | c | 19.3 | 0.1 |
| 60114.279 | ZTF | g | 20.7 | 0.3 |
| 60114.341 | ZTF | r | 20.4 | 0.2 |
Note that the ATLAS filter c is a g+r composite. To reasonable approximation c = (g+r)/2
| 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 | 2023lcr [ATLAS23msn] | 16:31:37.405 | +26:21:58.35 | 16:31:37.416 | +26:21:58.31 | SN Ic-BL | 1.027 |
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