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I 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
That’s interesting. The latest non-detection on TNS is from ATLAS at 2023-05-18 10:17 UT when they reported > 20.5.
Robin,
that is certainly encouraging for those of us contemplating SN hunting. M101 is a bright object regularly observed and that eluded discovery for almost 24 hrs. I’m close to having a 20″ Newt set up specifically for SN hunting. The biggest problem I will encounter I think will be a good, quick, and reliable automated method of checking images for suspects. If there any software writers interested in either a blink or image subtraction method or both I’d be interested in corresponding.
Eric
It’s now (2023-05-21 22h UT) around 11.3 so still brightening quickly. The total integrated magnitude of M101 is around 8.0 so this one object is currently 5% of the brightness of the entire galaxy.
I have it! Couldn’t see much of M101 except for a faint core. Anyhow SN 2023ixf was quite easy to see tonight and I used an AAVSO chart to make a magnitude estimate. My estimate was 117+4 giving an estimated visual magnitude Mv= 11.3. A slight orange colour present I thought.
I see we have the same magnitude estimate for tonight Nick! It does seem to be brightening quite quickly!
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
RobinHi all,
Here are my magnitudes from 23:00 UTC (center) last night. Averaged from 10 measurements with each filter using 120s exposures:
V = 11.09
B = 11.06
R = 11.11So a full magnitude brighter than 2 nights ago. Attached is the current light-curve from the BAA photometry database.
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From ATel 16050:
We searched the HST archival data for the progenitor of SN 2023ixf. A clear
source can be seen at the SN position (https://antares.noirlab.edu/loci/ANT2023l4lgj6bhp4rt)
in the F814W image from the HST program 9490 (PI: Kuntz), which was observed
on UT 2002-11-16. The source is, however, not visible in the bluer bands
(F435W and F555W). We measure a preliminary F814W magnitude of 24.39+/-0.08
for the source. Considering it as the candidate progenitor of SN 2023ixf
and using a distance modulus of 29.05 for M101 (Shappee and Stanek, 2011,
ApJ, 733), we obtain an approximate absolute magnitude (no extinction correction)
of -4.66, which is in line with a supergiant progenitor.Hi,
What is the V filter I read on earlier?
I want to do photometry on this. Do you need a really high focal length telescope e.g. C11 or can you do it with smaller lower focal length refractors?
Can you use a h-alpha filter 7nm bandwidth and do useful photometry ? as I am in a light pollution area.Thanks.
KwongHi all,
Very fractionally brighter again last night but looks to be flattening off. These from 22:30 UTC last night:
V = 11.04
B = 11.00
R = 11.02Cheers
Ian.What is the V filter I read on earlier?
I want to do photometry on this. Do you need a really high focal length telescope e.g. C11 or can you do it with smaller lower focal length refractors?
Can you use a h-alpha filter 7nm bandwidth and do useful photometry ? as I am in a light pollution area.You can use smaller telescopes – I regularly use a 100mm refractor to measure stars down to 13th magnitude.
The V filter is a Johnson/Cousins V Filter. These are standard photometric filters. You can still work unfiltered or use a colour R, G or B filter as long as you specify which was used.
I don’t believe you would have much success with a narrowband filter.
Hope that helps
IanHow do you calculate its magnitude please ?
This is not an easy question to answer! I would recommend reading the AAVSO photometry guide which is kept well up to date:
As to the choice of software, I can personally recommend the Tycho Tracker software. The Pro version is well worth the $50 for the licence and is very easy to get going with. There are plenty of YouTube videos to get you started. Many will say to use AstroImageJ (which is free) but I think this is hard to get going with. I also use the amazing (and underrated) AstroArt8 software which is easily scriptable.
https://www.tycho-tracker.com/
Hope that helps.
IanAs to the choice of software, I can personally recommend the Tycho Tracker software.
I am a great fan of Russ Laher’s APT (Aperture Photometry Tool) and use it for my VS work. There is a good overview at https://en.wikipedia.org/wiki/Aperture_Photometry_Tool which includes a link to the official site. The software is free and runs on all common operating systems.
It’s definitely plateaued
Here are my mags from last night (24th May around 22:30)
V = 11.03
B = 11.04
R = 10.99Cheers
Ian.Attachments:
Hi 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:
The 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,
How do you calculate its magnitude please ?Hi Kwong,
A variety of software packages can do photometry, including some image processing packages such as MaxIm DL. If the software you are already using doesn’t have the ability to calculate magnitudes, then I would opt for a free package that is easy to use, unless you are sure you will get into photometry of variable stars, exoplanets or asteroids.
There is a list of some software packages at the top of this page on submitting to the BAA Photometry database.
https://britastro.org/vssdb/notes_submissions.php
I’ve not tried them all, but MuniPack might be the easiest to get started with.
The trick is you have to measure the magnitude of the target star (the supernova) as well as several comparison stars. The comparison stars need to be carefully chosen, to avoid variable stars and to ensure they themselves have a robust magnitude. The AAVSO chart plotter is the perfect place for this.
The other key point. The supernova and none of the comparison stars must be over exposed as that would cause the calculation to go wrong. A good rule of thumb is for the peak counts in any pixel of those stars should be at most 2/3rds the full well capacity of your camera.
Good luck with your observations.
Andy (BAA Variable Star Section Database Secretary)
That’s useful. The continuum in my spectrum from last night does indeed match an A0v star which by definition has B=V=R
Thanks for the info Robin, most interesting. I’ve attached my graph again – updated with last night’s points. It seems that the R and B are slowly swapping dominance! Also note the very slight dimming.
Ian.
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