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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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uncorrupted link
https://www.wis-tns.org/object/2023ixf
Here is the discovery image
https://www.wis-tns.org/system/files/comment_files/2023ixf.jpg
Robin
The 29P event was unobservable from the observatory so I set up some kit on the patio with a clear view and blue skies in the afternoon but was clouded out well before the event which was a shame as I was just inside the Eastern edge of the predicted track.
On an associated note, does anyone know if these kinds of events (not necessarily occulting the nucleus) can be used to probe cometary “atmospheres” (coma and tail) using multiband photometry or spectroscopy? This star would be too faint for high cadence spectroscopy but comets sometimes pass close to brighter stars
Thanks
RobinThere are some a nice high resolution spectra coming from from the amateur 2SPOT team using their new echelle spectrograph on their remote setup dedicated to spectroscopy in Chile.
http://www.spectro-aras.com/forum/viewtopic.php?f=36&t=3090
Here is a picture of their setup on the telescope farm showing both the original low resolution faint object spectrograph on the Newtonian and the high resolution fibre fed echelle using the RC, both on the same mount
https://i.postimg.cc/440QkQdV/RC12-Aube-1.jpgEven MIT asteroid specialists are partial to the odd NTU and have even provided a conversion factor.
https://skyandtelescope.org/astronomy-news/does-earth-have-new-quasi-moon/
Longtime asteroid specialist Richard Binzel (MIT) tells Sky & Telescope he estimates this object’s [2023 FW13] size to be about 10 to 15 meters across: “Somewhere between a boxcar and a large Winnebago.”
I see someone else has spotted this authors propensity for the use of NTU (or is this blog yours under a pseudonym)
https://boingboing.net/2023/03/16/a-nice-asteroid-69-alligators-long-passed-by-the-earth-this-week.html
At first I wondered if he might be a BAA member deliberately taunting you but looking at his linkedin CV perhaps measurements in Parthenons or WWE rings might have been more appropriate
https://il.linkedin.com/in/aaron-reich-018ab9124I see cropping the spectrum to remove the bad edges is mentioned in the ISIS tutorial ~ 2/3 the way down. I think you have just missed that step
“Tip: The response profile changes shape very rapidly near the edges and it may not accurately represent the response in these regions as the signal there is almost zero. It is a good idea to crop the useful part before smoothing the spectrum. Use the “Cut” tool for this operation. The smoothing will then be easier and the results better. Here is the smoothing result under these conditions:”
Cheers
RobinHi Jonathan,
Firstly congratulations on getting as far as you have with ISIS. Although it is very powerful, particularly for producing research grade spectra from more advanced spectrographs than the Star Analyser, it can be tough to master and most people use different software with the SA like Visual Spec, RSpec, BASS project which can be easier to use with the SA. (I tend to use mixture of VisualSpec and ISIS, mainly because that was what was around then). I think you actually are ok though with what you have done and I suspect the flat line is just because the resulting spectrum has some really high and low values at the edges outside the wavelength range where there is good data and ISIS has autoscaled to include them. If you rescale manually or crop the bad edges (using the crop tool in the profile display) hopefully you should be able to see the result.
There are also some other resources on the website here that you might find useful
https://britastro.org/section_information_/equipment-and-techniques-section-overview/spectroscopy
David Boyd’s “Scientific analysis of amateur spectra” at the top is an excellent overview of the whole subject.
Particularly for the Star Analyser, my slides for the tutorial “Low Resolution Slitless Spectroscopy” downloadable here
https://britastro.org/document_folder/baa-document-store/past-talks/spectroscopy-workshop-at-the-nlo-oct-2015
Also the document on my website here specifically tackles the subject of response correction (flux calibration)
http://www.threehillsobservatory.co.uk/astro/Relative_flux_calibration_20221222.pdfCheers
RobinThe earlier Baader filters were conventional multilayered coloured glass filters which would explain the interference rings, with I believe a dielectric coating to block IR leaks (I have an old V filter from a different supplier which has delaminated on the edge.) The RGB and latest BVRI filters from Baader (and others) are now a single thickness of dielectric coated glass
Cheers
RobinI’ve just been reading in The Darkness Manifesto by Johan Eklof about how the craze for floodlighting churches in Sweden significantly affected bat populations. (In the space of ten years half of the church roosts were lost with two species now on the red list.) Apparently turning off the lights before midnight helped to some degree
