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An optical transient was reported by the MASTER survey at 15.1 mag (unfiltered) on Nov 26.826. It was also independently discovered by Yuji Nakamura at 11.7 mag (unfiltered) on Nov 28.469.
The progenitor appears to have been mag 21.9 r, suggesting an amplitude of ~10 mags.
Latest observation by Robert Fidrich, Budakeszi, Hungary (using a remote scope at Mayhill, New Mexico) has it at 11.9V on Nov 29.089 UT.
A spectrum by Klein et al. “shows a hot blue continuum with strong Balmer lines at an apparent redshift of zero, confirming a galactic origin for AT2021afpi. It also exhibits HeI and HeII emission lines. The spectrum resembles that of V2860 Ori, a classical nova of subclass He/N (De et al. 2021). Given this, and the rapid 10 magnitude brightening, AT2021afpi is likely a young He nova”.
Further observations (photometry and spectrometry) are requested. It is unusual to find a nova in Aries!
Nova Ari 2021 (MASTER OT J030227.28+191754.5; AT2021afpi) is at RA 03 02 27.31 Dec +19 17 54.4 (J2000.0)
A chart is available here, but no comparison stars are yet indicted. No doubt this will be updated later.
An ATel by Taguchi et al. (Tokyo U) reports a low res spectrum consistent with a nova, but a UGWZ dwarf nova classification cannot be ruled out at this stage.
More observations needed!
In a further ATel a claim is made that IceCube picked up a neutrino from this object. If true, and significant doubt has been cast on the claim, it would be the first ever detection of a nova by a neutrino telescope.
https://astronomerstelegram.org/?read=15067 and 15073 for more.
Further info on this transient continues to roll in. Isogai et al. report that the spectrum of this object suggests it is a dwarf nova of the WZ Sge type. They also observed early superhump-like modulations that occur in this type of object. If confirmed this would be the WZ Sge-type dwarf nova having the largest outburst amplitude ever seen.
Observations made last night ~ Nov 29.9 by Tamas Tordai (Hungary) show beautiful ~ 0.1 mg humps, varying between ~12.4-12.5 in V (AAVSO data)
Not a hope of the cloud shifting here in Birmingham, but a SLOOH measure from last night has this new DN as…
Nov 30.833 UT 12.59C
Gary
I performed Aperture photometry in IRIS on the G channel of the source AT2021afpi Wed Dec 1 2021 18:45UT. I used the 12.2 and 13.2 comparison stars on the AAVSO chart X27438A. I got the magnitude at 12.8m
I took another quick look, dodging the showers under poor conditions, this time with the very low resolution faint object setup.
The emission lines are very narrow (which confirms it is not a classical nova) so do not show well at the lower resolution but the blue continuum is unchanged.
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