asassn-21qj rapid deep dimming RA8:15:23.4 dec-38:59:23.4

[Hamish Barker]

rapid deep dimming asassn-21qj, type unknown.

It's down to mag 16 now, (from previously steady at mag 14 or so.

That's too dim for my telescope but perhaps the Spot group Alpy in Chile is able to take a spectrum?

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[Hamish Barker]

well it went behind the sun and seems pretty wild for the last few months. Perhaps the 2Spot Alpy can reach that faint?

[Hamish Barker]

Now there is an ATEL. Nobody seems to have taken a spectrum yet.

https://www.astronomerstelegram.org/?read=15531
An Update on ASASSN-21qj: A Rapidly Fading, Sun-Like Star; Back With a Vengeance
ATel #15531; M. Rizzo Smith, D. M. Rowan (OSU), F. J. Hambsch (VVS, AAVSO, BAV, GEOS), H. Barker (Rutherford Street Observatory), K. Z. Stanek, C. S. Kochanek, T. Jayasinghe, C. Christy, T. A. Thompson (OSU), B. J. Shappee (Univ. of Hawaii), T. W.-S. Holoien (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), Subo Dong (KIAA-PKU), M. Stritzinger (Aarhus)
on 28 Jul 2022; 23:18 UT
Credential Certification: Krzysztof Stanek (stanek.32@osu.edu)

Subjects: Optical, Variables



During the ongoing All-Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014, Kochanek et al. 2017), using data from the quadruple 14-cm ``Cassius'', ``Payne-Gaposchkin'', and ``Paczynski'' telescopes, we previously identified a stellar source undergoing a deep dimming episode (ATel# 14879). The source ASASSN-21qj (Gaia DR3 source 5539970601632026752 at RA=08:15:23.2996, DEC=-38:59:23.304, d~556 pc, G=13.4 mag, BP-RP=0.8 mag) is classified as a Sun-like star in the Gaia DR3 catalog (R=1.03 R_Sun; L=1.1 L_Sun). It was first observed by ASAS-SN on UT 2012-02-09. Presently, ASASSN-21qj has more than ~3,500 epochs of data.

The previous ATel noted that the star had faded significantly from the quiescent mean magnitude of g~13.8 (V~13.4) following a period where it was Sun constrained. ASASSN-21qj is now showing dramatic g-band variability with an amplitude as large as ~2.5 mags. The latest ASAS-SN photometry shows that ASASSN-21qj was at g~14.2 before becoming Sun constrained on UT 2021-06-29. Since the star became observable again on UT 2021-08-26, it has continued to vary and has not returned to a quiescent state as of UT 2022-06-29. There were no similar episodes over the previous ~2,300 days spanned by the full ASAS-SN light curve.

BVI photometry taken from August 2021 through July 2022 shows similar variability. The amplitude of variability is larger in the B- and V- band (~2.5 mag) than the I-band (~1 mag), which could suggest the episode is related to obscuring dust.

Follow-up observations of this very unusual object are strongly encouraged once the source is not Sun constrained.

We would like to thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grants GBMF5490 and GBMF10501, and also funded in part by the Alfred P. Sloan Foundation grant G-2021-14192.

[Robin Leadbeater]

Just watched the BBC "The Sky at Night" piece on this. Great work guys !
https://www.bbc.co.uk/iplayer/episode/m ... -starlight
Unfortunately only available to watch in the UK but here are a couple of screen grabs

Cheers
Robin

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[Olivier GARDE]

we'd love to have the same astro show on French TV channels....

In any case, it was a very good collaboration between amateurs and professionals, and the responsiveness of the amateurs showed that it was important.