We re-analysed the NTT+EFOSC2 spectrum of AT2019xis taken on 2019-12-28.29 UT (at phase ~70 days), and it is nearly identical to that of SN 1987A at about 70 days after explosion (see fig. 1). In addition, the I-band light curve provided by the OGLE survey, shifted by -17.2 mag, well matches that of SN1987A (fig. 2).
On the basis of the above arguments, we propose that AT2019xis is a light echo of SN1987A, hence SN light scattered towards us by a very small and compact dust cloud. This light echo is observed almost 33 years after the SN explosion.
If the dust cloud is approximately 200 pc in front of SN1987A, then the delay of 33 yrs is compatible with the light travel time and the observed angular separation. The reflecting source is compact but marginally more extended than stellar sources in the EFOSC2 V-band images (with 0.9" seeing). This implies a physical size of the reflecting area of about 0.2 pc.
The sky localization on AT2019xis is shown in fig. 3, along with that of SN1987A.
| 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 | 2019xis | 05:36:13.700 | -69:16:24.70 | Light-Echo | 0.0009 | OGLE-GAL-LMC517.02-374.217-667.894 | 05:36:13.700 | -69:16:24.70 | Light-Echo | 0.0009 | ||
| TNS | 1987A | 05:35:27.989 | -69:16:11.50 | SN IIP | 05:35:27.989 | -69:16:11.50 | SN IIP |
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