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Wikipedia's article on SN 2023ixf begins:

SN 2023ixf is a type II (core collapse) supernova located in the Pinwheel Galaxy (M101). It was first observed on May 19, 2023 by Koichi Itagaki and immediately classified as a type II supernova. Initial magnitude at discovery was 14.9. After discovery, the Zwicky Transient Facility project found a precovery image of the supernova at magnitude 15.87 two days before discovery. The supernova is about 21 million light-years from Earth and is expected to have left behind either a neutron star or black hole based on current stellar evolution models.

Wikipedia's Type II supernova discusses several classes (e.g. -L, -P, n, b) and these don't all share a single "universal" light curve

I've never (knowingly) seen a supernova and still don't have a telescope of my own. However there are several I know about. I'm curious how bright this SN will get and how quickly it will dim. To that end, I'd like to ask:

Question: Has the new type II supernova SN 2023ixf's subtype been determined yet, and is a tentative light curve possible? Is it still getting brighter?


From Sky & Telescope's A supergiant star exploded as a supernova in the prominent galaxy M101 in Ursa Major. It’s now bright enough to see in a 4.5-inch telescope!

The new supernova SN 2023ixf, pictured here on May 21st, shines close to a prominent HII region, NGC 5461, in an outer spiral arm of the bright galaxy M101. (Eliot Herman) from https://skyandtelescope.org/astronomy-news/bright-supernova-blazes-in-m101-the-pinwheel-galaxy/

The new supernova SN 2023ixf, pictured here on May 21st, shines close to a prominent HII region, NGC 5461, in an outer spiral arm of the bright galaxy M101. Discovered on May 19th at magnitude 14.9, it has already brightened to magnitude 11. The object is located 227.7″ east and 134.1″ south of the galaxy's center at R.A. 14h 03m 38.6″ and Dec. +54° 18′ 42″. M101 lies approximately 21 million light-years away, making this one of the closest supernovae visible in recent years. (Eliot Herman)

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The TL;DR is that in the optical, it rose in brightness over about a week and is currently in a plateau. It might stay that way for a few months or it might buck the trend and begin to dim -- we don't know.

While we're still in the early stages of monitoring this supernova and things are very much in flux, a preprint did hit arXiv within the last day or two that tentatively addressed some of these questions (Jacobson-Galan et al. 2023). UV/optical data indicate that:

  • SN2023ixf increased in brightness across the bands with rise times of 5-8 days and has held constant since then, indicating potential Type II-P-like behavior. However, the spectra indicate that the supernova has not yet reached the hydrogen recombination phase we'd expect to associate with a plateau.
  • The supernova is interacting heavily with the circumstellar medium (CSM) and shows Type IIn profiles lasting on the order of a week. This is consistent with what we see from CSM-interacting supernova whose progenitors experienced reasonably significant mass-loss rates in the few years before the explosion.

So right now, it's holding steady. If it behaves like a Type II-P supernova, SN2023ixf may remain at roughly constant brightness for a few months until the hydrogen recombination wave finishes propagating. If it is indeed a Type IIn supernova, things could be more complicated (see e.g. Nyholm et al. 2020). Some IIn subtypes show plateaus while others decline quickly; some show bumps in brightness which may be due to regions of increased CSM density, and others don't. We won't know how SN2023ixf will evolve in time until . . . well, until it evolves in time.

Again, all of this is quite tentative. I'm sure other groups will be weighing in as observations continue. Lots of us are watching this thing very carefully. (Parenthetically, at least one ATel from a week and a half ago (Sutaria et al. 2023) compared different observing runs favorably to Type II-L and Type IIn examples, although that was based on extremely limited spectral data -- and not light curves.)

For folks interested, here are the light curves from Jacobson-Galan et al.:

Light curves from Jacobson-Galan et al. 2023. The plot shows light curves from ultraviolet and optical observations of SN2023ixf compared with a few previously-known supernovae. SN2023ixf's curves rise on timescales fo 5-8 days across all bands, and mostly remain roughly constant.

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  • $\begingroup$ This is great, thanks! My take-home message for the moment will be to take steps (walk, not run) to locate a telescope and keep an eye on the weather (cwb.gov.tw/eng) and try to have a look-see in the next few weeks. $\endgroup$
    – uhoh
    Jun 10, 2023 at 5:16
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    $\begingroup$ I'm glad it was helpful. I might recommend jogging instead of walking just in case it does suddenly start dimming, but I doubt it's in the category of within-the-next-24-hours urgency. $\endgroup$
    – HDE 226868
    Jun 10, 2023 at 13:03

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