Supernova maybe

Looks like it might be in the same spot in more than one filter. Was searching for some color data to colorize HST imagery, and the transient is clearly not there in other imagery. Having a hard time getting data other than image cutout, though.

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It might just be in the green channel; makes it a lot harder to say it’s not an asteroid. Anyway I tried signing up for data access and I think my email is busted for the night. I’m trying to figure out what filters the map the legacy survey viewer uses. If anyone has that info off hand or a quick link to that information I’d be grateful. Just trying to fill in the info I have here:

Fantastic tidal trails on that galaxy. I can’t view the cutouts - I get a server error.

The DES DR1 layer uses RGB = z,r,g.

For DES, we only ingested their coadds, so don’t have individual epochs of imaging.


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Alrighty, thanks, Dustin. I’ll be sure to include Legacy Survey in the attribution line. Long attribution is long.

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Ok so the feature / object is definitely visible in r and i filter, not the others. I wanted to check for asteroids for you so I downloaded the FITS files and they are in FITS.FZ format, which usually isn’t a problem for me because I’ve used ‘‘7-zip’’ to deal with that before. Not this time unfortunately, no matter what i do. So i can’t open them in Aladin Desktop and can’t read the header for the observation dates so impossible to query JPL :confused:

Ofcourse the files are behind a lnik which you have to ‘‘right-click and save as’’, and if you don’t you get a nonsensical page filled with …letter & symbols & stuff.

But still I would like to try if this is a possible way for you to get the files; I paste the links here for the FITS files and you ‘‘right-click save link as’’. Again I doubt it will work but just have to try I guess…

PS I can’t find a supernova entry in TNS so this one might be submissable (if you can get a magnitude) :slight_smile:

Yeah, I can open those (and so can you!) with SAO DS9. Checking the date for each in the headers, I get…

Y DATE = ‘2016-10-07T04:19:22’ / When it was started (GMT)
g DATE = ‘2016-10-07T04:21:35’ / When it was started (GMT)
i DATE = ‘2016-10-07T04:23:54’ / When it was started (GMT)
r DATE = ‘2016-10-07T04:25:56’ / When it was started (GMT)
z DATE = ‘2016-10-07T04:27:54’ / When it was started (GMT)

Do these sound right? They’re all on the same night, in the same hour, minutes apart?? It gradually brightens and then disappears suddenly.
Y - not visible
g - maybe faint
i - definitely there
r - bright
z - gone?

That would mean the entire thing happened in or under 5 minutes… I don’t know if it’s something that went boom several times or just once and we just got very lucky to see it. What even explodes like that in under 5 minutes? And you can check for asteroids if you want, but given that it doesn’t move even a little bit I think it’s way out there.

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Ah ok great! I do have DS9 installed but so accustomed to Aladin’s intuitive UI…

In or under 5 minutes… Don’t think that’s possible for anything that goes boom? I thought maybe a slow asteroid but doesn’t really makes sense not present in g filter. Will check JPL later to make sure though now I’ve got the obs dates + time.

Also in two bands does that rule out artifact?

Don’t think it’s an artifact. I will say it’s dimmer than I thought it was going to be given the processing in the viewer. I have a lot of doubts about what I’m looking at.


The “DATE” header might be when the files were last processed, not when they were observed. Check for a DATE_OBS or MJD_OBS or some such. I would be surprised if all filters were observed in a row like that – and given that they are in alphabetical order (unix treating upper-case “Y” as coming before “g”), my guess is those are processing times (though that’s an odd comment if those are processing times). You could check the EXPTIMEs too – DECam should have about 30 seconds overhead, IIRC, so if they’re all 90 seconds exposures, could be.

If those are the observation times, then the different brightnesses in different bands could indicate color rather than variability…



Ok, that would make sense. Let me check again.

z MJD-OBS = 56950.35216024 / Modified Julian date at start
g MJD-OBS = 56950.35493697 / Modified Julian date at start
r MJD-OBS = 56950.35632249 / Modified Julian date at start
Y MJD-OBS = 56950.35910181 / Modified Julian date at start
i MJD-OBS = 56976.28443407 / Modified Julian date at start

z = 2014-Oct-20 08:27:06.64 (don’t see)
g = 2014-Oct-20 08:31:06.55 (maybe)
r = 2014-Oct-20 08:33:06.26 (brightest)
Y = 2014-Oct-20 08:37:06.40 (don’t see)
i = 2014-Nov-15 06:49:35.10 (faint)

Welp, alright. It still doesn’t make sense. I checked the bandpasses and DECam’s r filter overlaps with HST’s ACS/WFC F606W filter, but it’s completely invisible to HST. Whatever it is must be transient. It overlaps with a dusty region of the galaxy, so it could have been dust attenuated. MJD-OBS dates puts the timeline over a period of at least 1 month now.

Edit: links to bandpass graphs

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Here’s a handy blink animation.


So… your submitting it ? :slight_smile:

(date of HST observing btw?)

2018-07-09 23:30:05 UTC.

I tried submitting an unreported, archival supernova observation before, but it … wasn’t exactly the most enjoyable experience. The astronomical telegram guy did not seem interested at all.

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Ugh, luckily that has all changed now ever since the Transient Name Server is the official IAU site to report.

Once I found out that in the true spirit of astronomy professionals and amateurs alike are eligible for an account I’ve been filing my own transients and some for others.

Since then there has been a small but growing GZ group having a blast pointing out, discussing, researching establishing magnitude and submitting transients (possible supernovae) :slight_smile: from SDSS / DECaLS etc. till this very day.

I’m still planning on learning to use APT properly for establishing mags, but in the meantime Rick Nowell already figured it out and has been extremely helpful.

Perhaps scientific value is very low, but I really love that this is possible AT ALL : D

Getting an account usually takes a few days but after that submissions are recorded instantly.

PS only necessary to use APT for establishing magnitude if the survey doesn’t provide one ofcourse, which in most cases they do. So usually it’s nothing more than extract some preset data and voila :slight_smile: