Is anyone else here following this event? This GRB seems to have an extremely bright optical afterglow, see the following GCN circulars :
https://gcn.gsfc.nasa.gov/gcn/gcn3/26555.gcn3 (142 s after trigger time m_OT~10.5 mag.)
(I guess "yearly" in the subject is a fat-fingered "early")
https://gcn.gsfc.nasa.gov/gcn/gcn3/26553.gcn3 (redshift z=1.148 , magnitude r = 17.13 , 10 h after trigger time)
https://gcn.gsfc.nasa.gov/gcn/gcn3/26534.gcn3 (Discovery)
plus some other circulars in between: https://gcn.gsfc.nasa.gov/gcn/gcn3_archive.html
I would have expected some ATEL activity on this ... but maybe my math is wrong and this is not so special after all??
Anyway I think people in Australia would still have a chance to get a glimpse of ths with bigger scopes, perhaps.
EDIT: Also, if you have an all-sky camera that records the southern sky, it might be worthwhile to check it for a glimpse of the GRB afterglow right after the event, This is not totally crazy, there has been at least one naked-eye-visible GRB afterglow in the past : https://en.wikipedia.org/wiki/GRB_080319B
CS
HB
Hello!
I observed optical afterglow of GRB 191221B (its brightness was about 18.1 mag) with remote telescope ~16.8 hours after the trigger. I sent GCN Circular #26565 https://gcn.gsfc.nasa.gov/gcn3/26565.gcn3 .
I am attaching a photo - the stack of two frames with a total exposure of 300 seconds (two defects are visible in the photo below the center).
It was already light in most of Australia, so I couldn't immediately get images from a remote telescope.
Best regards,
Filipp.
Cool, thanks for sharing.
Which filter is this? I tried the same in the same night with another iTelescope, but failed because of incoming thin clouds I guess.
One question, that thing that looks like a star to the South-West of the GRB afterglow...that is an artifact right? I don't see this on my images or on Aladin. I don't spot the second defect you mentioned.
Here's my cropped and contrast-enhanced result :
Thank you for your kind words. Astrodon luminance filter. I attached comparative images and noted defects on them. Defects are displaced in all images, but afterglow is visible in three in one place (in the fourth photo, the limiting magnitude was bad).
Best regards,
Filipp.
Ah, now I see the second defect, thanks!
I looked at your image. You can send your negative result (about upper limits) to GCN circulars, because this is also important for science (for example my GCN Circ. #26091 https://gcn.gsfc.nasa.gov/gcn3/26091.gcn3 - this is in agreement in other observations: https://gcn.gsfc.nasa.gov/gcn3/26092.gcn3).
After me with a remote telescope, this afterglow has been detected by A.K.H. Kong (GCN Circ. #26566 https://gcn.gsfc.nasa.gov/gcn3/26566.gcn3 - also T17), and after it you did the shooting.
Best regards,
Filipp.
Yeah, I was thinking about it, but I really don't have the tools to do forced photometry on the position of the GRB in my image (ALMA 's position must be the most accurate https://gcn.gsfc.nasa.gov/gcn/gcn3/26564.gcn3) and that's really close to the next, de-focused or blurred by clouds source.... I think the best this could do is constrain that no rebrightening happened after your and Dr. Kong's data points, which is not expected anyway, so I don't think it would add some meaningful science.
If you want to give it a try, I would be more than happy to share the full calibrated T17 images (those cropped images are a bit hard to plate solve). I could send you a download link.
Cheers
HB
I'm doing the same script right now and will experiment with difference images a bit. That won't be easy as the focus and seeing conditions will be different....
We'll see. OK, I've done this now:
So here you are: This is a (very streched) difference of two stacked images, each stack was 5 x 180 sec thru a clear filter with T17 of iTelescope Siding Spring Obs., a 43 cm telescope.
You can see that the difference in seeing causes bright halos around the brighter stars (white pixels were significantly brighter during the first exposure stack, black pixels were darker .. you get the idea),.
I can now believe that the first image stack captured real photons from the GRB afterglow (yeah!), but I still doubt this would be useful for meaningful photometry. Dr Kong's data (taken only a bit earlier) were done during clearer skies, BUT I can now hang this on my wall and claim it shows the GRB 191221b afterglow ! :-)
To show just how aweful the first night was, I attached the all-sky images that iTelescope attaches to your usage receipts for the two nights.
CS
HB
I congratulate you, optical afterglow is really visible in your image!
I think that useful photometry can be done with such an image. By the way, they sent me the same image from this all-sky camera, but on the website the second camera showed a completely clear sky.
I'm sorry, I did not understand: you can not do photometry now? Didn't you do photometry of variable stars (from your list by observer code) in some kind of software?
If you want to send a link to your images of afterglow, then you can do it. Are you registered with the GCN to send the circular?
By the way, this was the first time for me that I was able to photograph the optical afterglow of a gamma-ray burst!
Best regards,
Filipp.
Hi!
Yeah, I don't think I can do meaningful photometry on my original image (e.g. one that has an acceptable photometric error). Aperture photometry seems out of the question because of blending with other objects nearby, and I haven't tried PSF fitting photometry yet. Maybe I'll take this one to experiment with PSF fitting photometry, I know what the result should be after all from Dr Kong's photometry.
CS
HB
Ok, now I understand about photometry. I wish you good luck! I hope you can do it.
Best regards,
Filipp.
The preprint about GRB 191221B was published on September 29, 2020:
Spectropolarimetry, photometry and radio detection of the early afterglow of the gamma-ray burst GRB191221B
https://arxiv.org/abs/2009.14081