77 replies to this topic

[yuzameh]

hot off the epress

 

https://www.astronom...org/?read=16046

 

given the B-V I'd say at that time that the supereddington pseudophotosphere was the same colour as an early F star, so it's temperature is likely about the same.

 

A_V is apparently miniscule towards this galaxy (from NED), but there is the chance of local interstellar absorption for the SN and the error range is +/- 0.1 so it could sneak into spectral type A colours which'd give about 10,000 K.  If I'm doing it right!  V-R is the same as B-V which surprised me a little given some of the spectra showing such a strong Halpha peak I've seen.

 

The dates and values should help given those feeling the need to evaluate their own estimates some reference point, and let them know if they need to swap out any comparison stars.

[Jamey L Jenkins]

Image from last evening of 2023 IXF in M101. This is a single negative image of my photometric workup determining a magnitude of 11.323V, specifically 2023 May 22 @ 2:36UT. The inset is a stack of several of my images just to illustrate how the supernova may appear through a larger telescope. Acquired with a William Optics 102mm f/7 ED refractor, V-filter, and Atik 314L+ mono camera.

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[dhkaiser]

Nice work Jamey.  What software did you use for the differential photometry?

[robin_astro]

hot off the epress

 

https://www.astronom...org/?read=16046

 

given the B-V I'd say at that time that the supereddington pseudophotosphere was the same colour as an early F star, so it's temperature is likely about the same.

 

 

B-V is -0.2  there which would make it an ~B3 star with a temperature around 17000K which is similar to the Planck curve fit to my spectrum taken around the same time

https://britastro.or...81642b90b339b4b

 

Robin

[yuzameh]

B-V is -0.2  there which would make it an ~B3 star with a temperature around 17000K which is similar to the Planck curve fit to my spectrum taken around the same time

https://britastro.or...81642b90b339b4b

 

Robin

thank's twice, misread the data in the prior atel.

 

a later atel quoting other photometry does the sums for us arithmetically challenged like me

 

https://www.astronom...org/?read=16047

[robin_astro]

 

I think I saw this SN being classed as SN IIb on S&T (well, n is next to b on the keyboard).  This is very strange given that apparently a lack of hydrogen lines to speak of, especially Halpha, is a major diagnostic of IIb.  Unless I misread it.

 

 

The spectrum has to have Hydrogen to be classed as any type  II (By definition type II is showing Hydrogen and type I is Hydrogen absent) and there is indeed Hydrogen in the spectrum of this supernova (along with He,C,N in the early spectrum in this case) TNS has a nice tool to identify lines in the spectrum and here are the Hydrogen Balmer lines in my spectrum

 

[yuzameh]

apparently they (IIb) do have weak Halpha emission lines that disappear after a while and emulate Ib afterwards.

 

Taxonomy based on spectra can lead to a bit of confusion on mechanism categorisation for some of the less common types, or rather mixing of object natures, with Ib and Ic being core collapse objects and Ia being deflagration ones.  It almost sounds like Ib and IIb are nearer to each other than another type of SN (eg than SN IIn and SN IIb).

 

Found some 1998S lightcurve and spectra data

 

https://www.research...ernova_SN_1998S

[SeymoreStars]

Would it be useful to capture B, V and R data now - UTC 02:47 May 24th?

 

Steve H

Edited by SeymoreStars, 23 May 2023 - 09:52 PM.

[yuzameh]

Would it be useful to capture B, V and R data now - UTC 02:47 May 24th?

 

Steve H

Every little bit helps, and of course it would be useful for your own interest.

[yuzameh]

Two new ATELs

 

https://www.astronom...org/?read=16049

 

You're supposed to be able to calculate extinction, A_V (absorption in the visual, well, johnson V) using NH, or column density. (number of H atoms).  This doesn't add up here though as you divide the measure they give derived from the xray slope taking fluxes at differing wavelengths (well, xrays are usually passbanded in electron Volts), take the column density number and divide by a number, which is quoted with different emprically determined values which average out at around 2 x 10^21 per cm^2 .  But here they quote 2 x 10^23 per cm^2 which would give A_V of 100 which is ridiculous, so either the xrays are behind the optical stuff or I've got something wrong.  We've already seen it demonstrated that I can't add up (or subtract), so probably the latter.  I've got it to work in the past though, so maybe I've forgotten something.

 

The other ATEL

 

https://www.astronom...org/?read=16050

 

stikes me a bit suspect as when I use a well known list of absolute magnitudes and colours and spectral types synthesised by a bloke called Pickles -4.7 fits bright giants, not supergiants, most of which are about absolulte magnitude -6.5 or brighter.  I checked the image they quote in the Hubble Legacy Archive (I couldn't get their link to display anything) and found the object they mention.  The interface there had built in DAOPHOT and SEXTRACTOR and both those independently gave a magnitude of nearly 25, not far off the one they quote.

 

However, Pickles quotes bolometric absolute magnitude.  However, even ditching the bolometric correction values (which he also gives) doesn't get anything below -6 or so.  On the other hand the HST passband being used is centred on 815 nanometres, which if anything is nearer Cousins I  than optical.  Fortunately again 'Pickles gives V-Ic, but even then it doesn't quite fit.

 

That is, unless you make it a red supergiant.  Then BCv and and V-Ic versus Abs Mag_bol just about fits -4.7 ish.  Again, if I've done my arithmetic correctly...

 

The ATEL does note that they couldn't find it on HST images in blue passbands, and extinction seems to be minimal.

 

There are quite a few other candidates within a fraction of an arcsecond of this candidate though in the image.  The WIS-TNS astrometry, to full quoted precision, does however fit very, very close to this object.

 

An interesting thing I noticed is the small somewhat circular HII region this lies just off of.  I had noticed in some of the deeper images people have been taking that the supernova did seem to have a little pimple on one side, which may well be this object.  I'll have to stare at the blinked images a bit harder.

 

Just woolgathering really whilst waiting to see if the thing has got nearer mag 10 yet.

[robin_astro]

 

 

Taxonomy based on spectra can lead to a bit of confusion on mechanism categorisation for some of the less common types, or rather mixing of object natures, with Ib and Ic being core collapse objects and Ia being deflagration ones.  It almost sounds like Ib and IIb are nearer to each other than another type of SN (eg than SN IIn and SN IIb).

 

 

Yes indeed as so often happens where the taxonomy precedes understanding (particularly seen in evolutionary biology for example where genetics shows the true picture) Another astronomical example of course is the reordering of spectral classes OBAFGKM in temperature rather than Balmer line strength.

[SeymoreStars]

I captured SN 2023ixf last night. 210 - 60 second images. With Johnson Cousins R-V-B filters. Here's the images combined and cropped into pretty picture version. I will submit the individual images to AAVSO, it will be my first submission.

 

Steve H

 

 

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[yuzameh]

I've seen one or two quoted mags from the 24th that suggests that B-V and V-Rc are now around 0.

 

That'd mean it's slowly cooling, if the measures are valid, and the pseudophotosphere, the part of the expanding front that's optically bright, would now be around the temperature of an A0 star.  That makes sense for an expanding wavefront, volume increases, so surface area is increasing, so same amount of luminosity (power output) spread over a larger area.

 

Note it seems that some SN IIn can still have short little blips of brightening if it hits any circumstellar materials on its way outwards.  Also, the fade should be gentle, at least at first.  However it looks like SN IIn are quite variable in their nature, and according to some potentially having more than one type of progenitor, and circumstellar material varies greatly from star to star both in amount and distribution relative to the line of sight, and of course the stars haven't read the books, so nothing is certain except uncertainty.  In other words, there's things it should do, whether it does or not is something else.

[robin_astro]

I've seen one or two quoted mags from the 24th that suggests that B-V and V-Rc are now around 0.

 

That'd mean it's slowly cooling, if the measures are valid, and the pseudophotosphere, the part of the expanding front that's optically bright, would now be around the temperature of an A0 star.  That makes sense for an expanding wavefront, volume increases, so surface area is increasing, so same amount of luminosity (power output) spread over a larger area.

 

 

Yes my spectra confirm this. Here is a rather messy plot comparing my spectra 3 days apart. It shows a few interesting changes

 

 

 

1. The emission features have reduced 

 

2. The broad base of the Balmer  lines (H alpha beta) have narrowed preferentially on the blue edge indicating a reduced velocity of the ejecta we see (actually it is not a slowing down appreciably, we just see deeper as the fireball becomes more transparent)

 

3. The temperature has reduced, the best fit Planck curve is now 14000K rather than 18000 K

 

4. the continuum now roughly matches than of an A0V star which by definition has a colour (B-V) =0, confirming the recent photometry

(Note 14000K is not the effective temperature Teff that you see quoted in books for A0V stars eg Vega. See this Wikipedia for the explanation (Stars are not black bodies)

https://en.wikipedia..._comparison.png

 

Cheers

Robin

[robin_astro]

Although very weak at the moment, the H alpha line in last night's spectrum is developing a broad P Cygni profile more typical of type II supernovae.

 

 

The test for the n subtype will be if a narrow component persists rather than just being a transient phenomenon in the flash ionisation spectrum. This would likely need higher resolution than this though

[robin_astro]

An animation showing the evolution of the spectrum over the past week. 

 

 

Robin

Edited by robin_astro, 28 May 2023 - 08:15 AM.

[yuzameh]

An animation showing the evolution of the spectrum over the past week. 

 

SN2023ixf_animation_20230521-0527.gif

 

Robin

That's absolutely lovely, not only is it marvellously illustrative, but it looks good too!

 

It's a bit smooth, though (the animation).  Is there some interpolation between actual images?  That is, if it was just the images would the animation look more stepped.

 

Not a complaint, just interested.

[robin_astro]

That's absolutely lovely, not only is it marvellously illustrative, but it looks good too!

 

It's a bit smooth, though (the animation).  Is there some interpolation between actual images?  That is, if it was just the images would the animation look more stepped.

 

Not a complaint, just interested.

It is made up of nightly measurements taken at roughly the same time and interpolated in 0.1day steps, 100ms/step using ISIS software to make a nice movie so not strictly scientific but the changes are slow so probably close to what actually happened in between. The individual spectra are in the BAA database

 

Cheers

Robin

Edited by robin_astro, 28 May 2023 - 06:50 PM.

[mwr]

The similarity of the spectrum recorded by the SPRAT (SPectrograph for the Rapid Acquisition of Transients) of the Liverpool Telescope (https://telescope.li...nst/Inst/SPRAT/) to an early spectrum of SN 1998S is really striking:

 

Folie1.JPG

 

The deconvolution of the H alpha and H beta emission lines of SN 2023ixf fits well the observed line profiles:

 

Folie2.JPG

 

Taking into account the resolution of approximately R=350 (18Å) of the SPRAT (instrumental line broadening) one can calculate a velocity value of approx. 2850 km/s for the broad line profile and a velocity of <640 km/s for the unresolved narrow line profile. The deconvoluted profiles are well comparable the profile of the H alpha line of SN 1998 S (top left profile):

 

Folie3.JPG

 

The publication on SN 1998S could be used as a road map for what to expect from SN 2023ixf in the future:

 

The latest spectrum recorded by Forrest Sims now clearly shows a broad P Cygni-like profile:

 

https://britastro.or...ment=&plot=Plot

 

The deconvoluted H alpha profile is again well comparable the  profile of the H alpha line of SN 1998 S (top left; 2nd and 3rd profile):

 

 

The additional, narrower P Cygni-like absorption that is visible in the highly resolved spectrum of SN 1998S is probably not resolved in Forrest Sim's LISA spectrum. 

 

How can the H alpha line profile interpreted? Fassia et al. give some explanations for the distinct lines:

 

Early broad emission line:

"We recall that the early-time broad component had a FWHM >=4000 km/s, was present as early as day 3, and had faded significantly by days 12–14. While lines of this width in SNe are usually associated with the ejecta, the absence of any corresponding P Cygni absorption is a robust indicator that these lines are driven by the high-energy radiation of the shock resulting from the interaction of the ejecta with dense circumstellar material in the immediate vicinity of the supernova."

 

Early narrow emission line:

"We attribute the early, narrow, usually unresolved, lines to recombination and heating following ionization of the slowly moving outer circumstellar material  (OCSM) by the UV/X-ray flash at shock break-out. These lines were present in the earliest spectra (day 3.3) as the narrow (FWHM <= 500 km/s) components of the emission lines. By days 12–14, the narrow H and He I lines began to take on the form of P Cygni profiles [....]"

 

Late, broader absorption line:

"We turn now to the broader (350 km/s) shallower absorption component seen in the H and He I lines. We recall that this feature deepened between days 17.4 and 36.3. [....] Thus a possible explanation for the broader absorption is that it occurred in a component of the OCSM produced when the progenitor was going through a blue supergiant (BSG) phase."

 

Apparently SN 2023ixf is indeed a beautiful type IIn SN. Unfortunately out of reach for my low budget equipment. I suffer agony.

[yuzameh]

It is made up of nightly measurements taken at roughly the same time and interpolated in 0.1day steps, 100ms/step using ISIS software to make a nice movie so not strictly scientific but the changes are slow so probably close to what actually happened in between. The individual spectra are in the BAA database

 

Cheers

Robin

Thanks.  That's an interesting bit of software to be able to do that.

 

Surprisingly little in the way of announcements from the so called multimessenger people across the board.  Likely it's neither not far enough or not close enough for them to be excited.  No doubt swift is following it (I saw a notice to the fact somewhere), and there are sum null radio results (uGMRT and VLA) and one null neutrino report (IceCube) but unless dedicated papers appear in about a year it seems on the surface not to be causing much excitement among the professionals, at least not enough to excite media reports and press releases.

 

I keep worrying that by the time T CrB blows up again that all the multimessenger stuff will only get to it after it has declined rapidly.  I know RS Oph gleaned very little professional interest in its recent outburst compared to the past.  And this despite all the new transient and fast response setups coming online of late.  The follow up aspect seems to be the weak link, relying on community interest to ask for ToEs by the looks, instead of being on automatic lists.

[robin_astro]

 

Surprisingly little in the way of announcements from the so called multimessenger people across the board.  Likely it's neither not far enough or not close enough for them to be excited. 

Oh I suspect there will be plenty going on behind the scenes. This excellent piece in the radio program "Science in Action" on the BBC World Service

https://www.bbc.co.u...s/play/w3ct4sc9

is a good listen and gives a flavour of what the professionals are following up.

 

At least one researcher interviewed there who has been waiting for just such event sounds pretty excited !

Edited by robin_astro, 29 May 2023 - 11:30 AM.

[robin_astro]

The latest spectrum recorded by Forrest Sims now clearly shows a broad P Cygni-like profile:

 

https://britastro.or...ment=&plot=Plot

 

The deconvoluted H alpha profile is again well comparable the  profile of the H alpha line of SN 1998 S (top left; 2nd and 3rd profile):

 

SN.jpg

 

The additional, narrower P Cygni-like absorption that is visible in the highly resolved spectrum of SN 1998S is probably not resolved in Forrest Sim's LISA spectrum. 

 

 

Over the past couple of nights I have been looking at this region at higher resolution (R~2000) with my LHIRES.  (about 5 hours total exposure) The H alpha P Cygni feature is weak but shows a clear narrow emission line (FWHM ~200km/s at the galaxy rest wavelength). This is a region with  HII emission sources though so there may be contamination from these.

 

 

Cheers

Robin

[mwr]

This is a region with  HII emission sources though so there may be contamination from these.

 

 

A great spectrum (the first ProAm high resolution spectrum of SN 2023ixf) and an important finding. I've seen your recent spectrum in the BAA database that clearly shows this potential HII region contamination:

 

https://britastro.or...2&download=View

https://britastro.or...image&plot=Plot

 

Chapeau !

[robin_astro]

I've seen your recent spectrum in the BAA database that clearly shows this potential HII region contamination:

 

https://britastro.or...2&download=View

https://britastro.or...image&plot=Plot

 

 

I've looked at the cross section of the spectrum at the H alpha location.

 

 

That particular HII region right next to the spectrum (actually ~7 arcsec from it) does appear to be separated from the supernova in the spectrum. but the problem is we don't know what is directly underneath/on top at the location of  the supernova image.  A high resolution (at an arcsec or two) H alpha image pre explosion might tell us. Does anyone know where I might find one ?

[pvdv]

It is quite close to NGC 5461 - lots of papers about it. Probably images as well.
From my previous non HA images (and many on astrobin) the whole area is quite reddish.