Galaxy Zoo Talk

Artifact? / Supernova imposter / outburst from a cool hypergiant star

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    DECaLS DR2

    enter image description here


    enter image description here


  • Budgieye by Budgieye moderator

    Good spotting. You mean, is it a supernova?

    Well there are three listed in NED. I'll have to match coordinated to see if it is

    SN 2012P 14h59m59.1s +01d53m24s SN

    SN 2004dg 14h59m58.9s +01d53m26s SN

    iPTF13bvn 15h00m00.1s +01d52m53s SN

    Supernovae of #NGC 5806 #NGC5806

    enter image description here

    Doesn't seem to be a recorded supernova


  • Budgieye by Budgieye moderator

    Could it be an asteroid? Maybe an overlap of two asteroids on two days.

    enter image description here

    enter image description here

    Hmm, all the exposures are on different days.

    The green image is the b exposure

    The yellow image is one of the z (red) exposures (red superimposed on green makes yellow)

    Exposure 425098, g band, 72.0 sec exposure time, seeing 1.19 arcsec, file decam/CP20150326/c4d_150327_073352_ooi_g_v1.fits.fz

    Exposure 347289, r band, 65.0 sec exposure time, seeing 1.13 arcsec, file decam/CP20140810_r_v2/c4d_140813_000101_ooi_r_v2.fits.fz

    Exposure 425097, r band, 64.0 sec exposure time, seeing 1.51 arcsec, file decam/CP20150326/c4d_150327_073222_ooi_r_v1.fits.fz

    Exposure 192973, z band, 100.0 sec exposure time, seeing 1.05 arcsec, file decam/NonDECaLS/CP20130330/c4d_130401_085440_ooi_z_v1.fits.fz

    Exposure 193743, z band, 100.0 sec exposure time, seeing 0.94 arcsec, file decam/NonDECaLS/CP20130330/c4d_130403_090532_ooi_z_v1.fits.fz

    Exposure 346943, z band, 116.0 sec exposure time, seeing 1.11 arcsec, file decam/CP20140810_z_v2/c4d_140811_235635_ooi_z_v2.fits.fz

    Images are different size, maybe two different asteroids on different days.

    14 08 13 00:01:01 green image taken. All red images taken on other days.


  • Ghost_Sheep_SWR by Ghost_Sheep_SWR in response to Budgieye's comment.

    I've seen so much interesting things that turned out to be artifacts it just seems the right first question now 😃

    But anyway didn't expect supernova, it' colors are of and not bright enough. And it's visible in DECaLS, so +/- 2015 would not be in the records now?

    Asteroid overlap could be possible, z band on 14-08-11and r band on 14-08-13 could be possible overlap. Would make it apparent slow-moving, and the yellow is slightly displaced from the green. Conventional direction prograde.


  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    • checked the Small Body Database for every band and time ( including the one z band exposure you ommitted 😃 ) but turned up nothing at all. So if it's an asteroid it's unidentified, which is very unlikely with this magnitude.

    • checked all the NED objects, unfortunately its not a photometric object

    • there does seems to be an object in SDSS, and further searching in ADS and SDSS DR12 turns up the very likely candidate SN Hunt 248, which is an Supernova 'imposter'!! 8) This strange thing is right on the coordinate spot, and somewhat supernova-like.

    Simbad object

    SN Hunt 248 paper

    Explainatory page

    Well that certainly took some time and effort, but well worth it. Unbelievable what strange things keep coming up



  • Budgieye by Budgieye moderator

    How absolutely fascinating! Great research 😃 I'll put it in the index. I'll improve the title of this discussion too.

    Index for Galaxy Zoo Talk : our Milky Way Galaxy and its stars SN Hunt 248&submit=submit

    enter image description here Outburst from a cool hypergiant star.

    Exposure 425098, g band, 72.0 sec exposure time, seeing 1.19 arcsec, file decam/CP20150326/c4d_150327_073352_ooi_g_v1.fits.fz had not star image

    The outburst associated with SN Hunt 248 was observed in May to June
    2014 and it occurred in two stages. Between May 21and June 3, the
    source brightened slowly. On June 4, it began to brighten rapidly,
    reaching a peak on June 16. The source then plateaued for ~10 days at
    peak brightness before fading away.

    Peak brightness June 15

    Four Reds taken, must be the 140811. August 11, 2014 that registered an image.

    Two Greens taken, must be the 2014 08 13 August 13 2014 that registered an image. Funny that the green image is bigger than the red (looks yellow) image. I would expect the green to be smaller.

    Blue taken 150327 March 27 2015 when the star had faded away.


  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    That's great!

    Good thing the star and its process was already found and described in several papers.

    And off to find more crazy stuff 😃