Supernova in M101 !

Forums Variable Stars Supernova in M101 !

Viewing 20 posts - 21 through 40 (of 86 total)
  • Author
    Posts
  • #617456
    Robin Leadbeater
    Participant

    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

    #617457
    Nick James
    Participant

    That’s interesting. The latest non-detection on TNS is from ATLAS at 2023-05-18 10:17 UT when they reported > 20.5.

    #617460
    Eric Watkins
    Participant

    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

    #617461
    Nick James
    Participant

    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.

    #617462
    Paul G. Abel
    Participant

    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.

    #617465
    Paul G. Abel
    Participant

    I see we have the same magnitude estimate for tonight Nick! It does seem to be brightening quite quickly!

    #617466
    Robin Leadbeater
    Participant

    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 tomorrow

    Cheers
    Robin

    #617497
    Mr Ian David Sharp
    Participant

    Hi 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 = 11.11

    So a full magnitude brighter than 2 nights ago. Attached is the current light-curve from the BAA photometry database.

    #617507
    Dr Paul Leyland
    Participant

    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.

    #617508
    Kwong Man
    Participant

    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.
    Kwong

    #617509
    Kwong Man
    Participant

    Hi,
    What is the V filter ?
    How do you calculate its magnitude please ?

    Thanks.

    Kwong

    #617510
    Mr Ian David Sharp
    Participant

    Hi 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 = 11.02

    Cheers
    Ian.

    #617511
    Mr Ian David Sharp
    Participant

    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
    Ian

    #617512
    Mr Ian David Sharp
    Participant

    How 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:

    https://www.aavso.org/sites/default/files/publications_files/ccd_photometry_guide/CCDPhotometryGuide.pdf

    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.
    Ian

    #617513
    Dr Paul Leyland
    Participant

    As 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.

    • This reply was modified 1 year ago by Dr Paul Leyland. Reason: Fix typoh in Russ' name
    #617515
    Mr Ian David Sharp
    Participant

    It’s definitely plateaued

    Here are my mags from last night (24th May around 22:30)

    V = 11.03
    B = 11.04
    R = 10.99

    Cheers
    Ian.

    #617518
    Robin Leadbeater
    Participant

    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
    Robin

    #617521
    Robin Leadbeater
    Participant

    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.png

    Cheers
    Robin

    #617522
    Andy Wilson
    Keymaster

    Hi,
    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.

    https://app.aavso.org/vsp/chart/?star=SN%202023ixf&fov=60&maglimit=14.5&resolution=150&north=up&east=left

    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)

    #617523
    Mr Ian David Sharp
    Participant

    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.

Viewing 20 posts - 21 through 40 (of 86 total)
  • You must be logged in to reply to this topic.