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Note that alternatively if you use ISIS (Or Demetra) software with the calibration module it can find the wavelength calibration lines for you and do the calibration automatically
Hi John,
Is it this one ? (By a different Andy)
https://britastro.org/2017/guide-to-processing-spectra-using-the-bass-software
It is linked from the Spectroscopy resources page of the equipment and Techniques section here
https://britastro.org/section_information_/equipment-and-techniques-section-overview/spectroscopy
which used to be given in a sticky post at the head of this section of the forum but seems to have become unstuck !Cheers
RobinLars – I have sent you a PM
Off topic but how did you do that? I don’t see a PM facility on the new website (something I miss)
Thanks
RobinA continuation of the animation of the spectrum. Part 2 covers 2023-05-27 to 2023-06-13 and shows the transition from an almost featureless spectrum to one showing more typical broad P Cygni Balmer lines
https://britastro.org/observations/observation.php?id=20230614_144855_b767104d96087a30Cheers
RobinThe spectrum is now showing increasing features more typical of type II supernovae (Broad P Cygni Balmer lines)
Here is an example match in SNID to SN1980K 9 days past maximumCheers
RobinHere is a low resolution spectrum for the night 3/4 June. The continuum continues to cool and now matches a black body temperature of 9000K or an F0v star ((B-V) = 0.29.) The features are still weak with a very broad H alpha component with some structure evident at higher resolution. The higher Balmer lines are increasing in absorption blue shifted by ~8000 km/s
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Attached is an example from the presentation of type Ia and type IIP spectra around or after maximum light.
Incidentally Koichi Itagaki also discovered both of these supernovae
Since type II supernovae are hydrogen-rich and type I are hydrogen-poor, would shooting through a hydrogen alpha filter be a quick-and-dirty way to distinguish them without spectroscopy?
Hydrogen present (in type II) or absent (in type Ia,b,c) in the spectrum would be a better description. The problem is other events also pretend to be type II supernovae like novae, dwarf novae, luminous blue variable supernova impostors etc. You need the detail of a spectrum to be sure of what you are looking at. The spectrum of supernovae also vary with time and with type II, H alpha emission does not really dominate the spectrum for a lot of it and when it does it is often a combination of emission and absorption (a P Cygni shape line). When typically measured a few days after discovery the type II spectrum can be almost devoid of features. This one was discovered early so did show some H alpha emission early on but even then the dominant feature was that is was very blue and currently it looks almost like an A type star but without hydrogen absorption lines, just a very small P Cygni H alpha line. See here the evolution of the spectrum over the first week.
https://britastro.org/observations/observation.php?id=20230528_140227_583fe05370c08912For a more general overview of using spectroscopy to classify supernovae I did a talk about it here
https://britastro.org/videos/using-low-resolution-spectroscopy-to-confirm-supernova-discoveries-2
In essence it is done by matching the spectrum to templates of various types of supernovae taken at different times
Attached is an example from the presentation of type Ia and type IIP spectra around or after maximum light. I think it would not be straightforward to distinguish them from just H alpha and broad band imagesCheers
RobinAttachments:
Just listened to an excellent episode of BBC World Service “Science in Action” almost entirely dedicated to SN 2023ixf
https://www.bbc.co.uk/sounds/play/w3ct4sc9
Astronomers, both amateur and professional talking enthusiastically about the discovery and what we know so far with lots of good science and even a live observing session on the radio!The evolving spectrum over the past week
https://britastro.org/observations/observation.php?id=20230528_140227_583fe05370c08912So B mag peaked in just 5 days from the explosion on the 18th. That’s pretty fast I think, even for a type II
It seems that the R and B are slowly swapping dominance!
Yes my spectrum from last night shows it cooling further to a black body temperature of ~12000K and a fit to an A3v star continuum with a B-V = +0.1
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Very interesting thread.
Could I make useful spectra of the SN with my StarAnalyzer 100?
Yes it is certainly reachable with a Star Analyser for example
https://britastro.org/observations/observation.php?id=20230523_183229_5116a1a27f78a1ea
https://britastro.org/observations/observation.php?id=20230523_194606_cc526483f5e34422but the features seen earlier have greatly reduced and at the moment even with higher resolutions it is not showing very much except a slowly cooling blue continuum. Here is the evolution with my ALPY600
https://britastro.org/specdb/data_graph.php?obs_id=13786%2C13783%2C13778%2C13774&multi=yes&legend_pos=neCheers
RobinThe continuum in my spectrum from last night does indeed match an A0v star which by definition has B=V=R
And in case anyone is wondering why a black body curve of ~15000K matches an A0V star visible spectrum when the effective temperature Teff you see in text books is 9500K this Wikipedia graphic explains it nicely
https://en.wikipedia.org/wiki/Color_temperature#/media/File:A0V-blackbody_SPD_comparison.pngCheers
RobinHi Ian,
That’s useful. The continuum in my spectrum from last night does indeed match an A0v star which by definition has B=V=R
Cheers
RobinAttachments:
Finally got a spectrum tonight in poor conditions with high cloud.
https://britastro.org/specdb/data_graph.php?obs_id=13774
I see there is an earlier one from the previous night there as well by Woody Simms. The features are similar but mine has a hotter continuum, also hotter than the confirming spectrum in TNS so I better double check my flux calibration tomorrowCheers
RobinI have been encouraging imagers on “cloudy nights” and “stargazers lounge” to check the times on their M101 images (M101 is certainly a very popular target!) The earliest detection so far is 20230518 21:15 UT, 20 hours pre discovery and it is very clear in that image so probably detectable some time earlier.
Robin
The earliest pre discovery detection I have seen now pushes back the time of explosion to at least 2023-05-18 T 21:55 (from an image posted on the Cloudy Nights forum)
ZTF report a 10 hours pre-discovery detection at mag 15.9 (g) 2023-05-19 07:45:07 and a negative (fainter than 21.3) 2023-5-16 19:35:38.00
https://www.wis-tns.org/astronotes/astronote/2023-120
so any deep image between those dates could be interestingUnfortunately I am clouded out just a few miles from clear skies 🙁
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