IC4901 supernova discovered by Greg Bock

[gregbradley]

I read the post by Greg Bock about discovering this supernova so I thought I would image it last night. It looked a bit small in the image using the Proline 16803 so I used the Microline 8300.

Apart from the usual dramas when you change over gear I got a couple of hours of it.

Luminance turned out best, rgb not so great yet. It would need quite a few hours.

Here is the luminance.

The Supernova is the bright star near the core. I don't know how to put those little marking lines in the image to highlight it.

7 x 10 minutes 2x2 luminance -35C CDK17/ML8300

http://www.pbase.com/image/139036871

Its quite a pretty galaxy and worth imaging in colour with lots of hours.
There must be lots of these "obscure" not imaged often galaxies in the southern hemipshere. I'd love a list of these.

Greg.

[madbadgalaxyman]

Yes, Pavo and Indus and Telescopium are full of 12th to 13th Blue magnitude galaxies for which the best available images are only Digitized Sky Survey images!
Many of these galaxies are in the IC catalog, and a few of them are brightish non-NGC/IC objects with ESO designations.
This region of sky is very poorly known.....many of the IC galaxies have had no detailed study by professional astronomers!

I had better not promise to make an observing list of these galaxies, as I am notorious for "never getting A Round Tuit"

[iceman]

Nicely done, Greg!

[iceman]

This SN discovery by Greg Bock is such a great story, your image is timely and relevant. It's now IOTW (http://www.iceinspace.com.au).

PS: I rotated your image 180deg and put the markers on to identify the SN. I hope you don't mind.

PPS: Use the "Line Tool".

[gregbradley]

Wow, thanks Mike.

I'll check out the line tool.

Greg.

[Terry B]

Very good Greg.
I prefer the less imaged stuff and I agree it would make a good project for longer exposures.

[gregbradley]

If its clear tonight I think I'll add to it. Its actually quite a pretty galaxy.

I am not sure if Comet Garradd is still viewable in the southern hemisphere but it seems
to be quite pretty also at the moment with 2 tails in a V shape.

Greg.

[Greg Bock]

HI guys
thanks Greg for the image of IC4901 with SN2011gv for this post, I have had a very busy (domestic) weekend, so I haven't kept up with the threads and posts about SN 2011gv myself. It looks great.
I took a bunch of images of it myself on Saturday night between clouds for the purpose of measuring its brightness. I'll try to post the result as soon as I can but the conditions weren't very good here.

[Greg Bock]

HI Mike S,
as usual, there is also a back-story to this discovery which involves lots of good luck for change. I haven't detailed it yet, but suffice to say that I almost deleted the discovery image of IC4901 on the night of imaging due to software issues, but I took a moment instead to look at it more closely before I did delete it, and needless to say, almost fell off my chair when I spotted the new interloper.

Thanks for publishing Greg Bradley's image of it for IOTW too.

[strongmanmike]

Hey Greg B, there looks like there might be a very faint outer section of spiral arms that would be good to try and reveal too :thumbsup:

Mike

[multiweb]

Good catch and a nice galaxy too. :thumbsup:

[atalas]

Congrats Greg & Greg!

[gregbradley]

Yes its quite a pretty galaxy. Its interesting how many of these galaxies there are in that close southern circle around Eta C and in and also there are lots of galaxies around NGC253.



Glad to help Greg.



Cheers. It's really Greg Bock not so much me. I just suffered through the hardware issues of changing over a camera. I know what you mean Greg about nearly deleting the image. I almost didn't take the shot because the Microline needed another adapter to work and then the focuser nearly got stuck - you get the idea!



Cheers Louie.

[mozzie]

great find greg......
been looking at it for the past hour and am pretty shore i can see it visually although withsome averted vision,quiet faint but a nice challenge..

[Ross G]

Hi Greg,

What an amazing capture.

A great IOTW.

Congratulations Greg Bock on your incredible discovery.

Thanks.

Ross.

[mozzie]

stayed with the galaxy till around 10pm was able to see galaxy easily and there was many stars to see..as other posts above was looking towards the centre and was able to see faint stars and am shore one of them was the s/n..
thanks for the thread enjoyed the hunt last night...

[gregbradley]

Greg Bock worked hard to discover this one.



Cheers Ross. Its really Greg Bock's hard work I was only trying to back him up as I had some clear skies that night.



I'd like to see it visually. It is really quite bright. Obviously you need a library of images of galaxies to detect these as to me it looked
like a foreground Milky Way star and I would not have suspected it unless it were a galaxy I was familiar with. So those years of hard work Greg Bock has put in imaging galaxies to form a reference library for comparison really paying off now.

Greg.

[Greg Bock]

The weather here has really been a problem since discovery, almost no opportunity to image it.

Thanks for the reports guys. If you are looking visually for it, try printing one of the images from Greg Bradley or myself as a finder chart. (or use a red screen over your laptop display)

Bob Evans reported to me that he couldn't see it in his 12" scope the night after discovery, so it will be interesting to hear of any other visual sightings.

In the meantime, I am waiting for clear skies....please!!!!

[rogerg]

Nice pic! and another discovery for BOSS! congrats! I had no idea, I have been consumed by work and not following IIS. Wish I could take a shot of it, but it's just been cloud cloud cloud here.

[Greg Bock]

OK guys,
so, here is the back-story summary. As you can see, it was a very lucky find for me because:
1. The galaxy is only high enough above the trees and house for about 1 hour per night between rising and setting
2. We had lot of broken cloud that night, so many of my images were cloud affected,
3. I wasn’t using my normal camera as it is in the US being repaired
4. I wasn’t running my normal search program. Instead, I was running a test program in an effort to try to isolate an on-going software problem that I have had for months that is stopping me from using it more effectively,
5. The supernova was in the third image of about 50 for the night of which only the first 15 were OK, the others were no good due to my software problem and I deleted them
6. Just before deleting the remaining 15, I glanced through them as a quick check to see if anything was obvious, and the bright object near IC4901 caught my eye
7. After I checked for asteroids and any previous discovery announcements for the new object, I texted BOSS members, and Peter was only just able to take a confirming image of it 20 degrees above the horizon. It set too low for him not long after he obtained that image.
8. After the discovery, it has been mostly cloudy, so if I didn’t find it on the night, I was probably never going to find it.

So, talk about “count your lucky stars!”..whew….

[Greg Bock]

Thanks Roger, same here, it's just cloud, cloud, and even more cloud!!

[madbadgalaxyman]

Hi Greg and other "SN fanatics",

According to the posts in the Visual Observing forum, we did have one definite & strong visual detection of the SN by the noticeably "eagle-eyed" Paddy..... at a dark sky site, using his 16 inch.

Ron (astroron) was able to see the SN, on and off, with his 16 inch...... but the visibility of the object was strongly dependent on the large variations in the size of the stellar seeing disk.
Ron, in the visual observing forum, estimated that the SN may have a visual magnitude of 14.8 or fainter, which is in accord with my theoretical calculations in the Science forum.

These two blokes are skilled visual observers of vast experience, yet they did not find the SN to be an easy object.

There is an extant magnitude estimate of 14.1, by Joseph Brimacombe at the www.rochesterastronomy.org/snimages (http://www.rochesterastronomy.org/snimages) supernovae site, but in my and Ron's view, this appears to be an infrared magnitude, and an infrared magnitude relates in no meaningful way to the visual magnitude and visual appearance of this object.
Brimacombe seems to have been using infrared magnitudes for his comparison stars, which is a very odd thing to do.....is there any way you can check on this, Greg?

cheers, robert

[PeterM]

Yup Robert, I think this is at the limit, rather hoped it would brighten a bit. So then how privileged are Paddy and Ron to be perhaps the only persons on Earth to have visually observed this. Its been a while since I visually looked at a SN and it's great to see dedication in the visual community in view of the onslaught of imagers, congrats guys!

PeterM

[madbadgalaxyman]

Agreed, Pete, that the SN is not exactly burning out the retinas of our visual observers.
But, keep persisting with your observations, folks!
If the light curve is typical of other type II-P supernovae, the visual brightness should stay almost the same for a long time.

[Greg Bock]

Looks like the weather isn't going our way, so rather than wait for more clear skies, I have posted my first attempt at a long exposure image of SN2011gv anyway. This was taken with cloud drifting in and out of the field several times.
It was taken on 20 October, 3 days after discovery.

Details are:
Camera: ST10XEi, Binned 1 x1, 32 x 30 second subs, no filters.
Scope: Meade 14" LX200R with Optec F7 focal Reducer at 2450mm FL, on Losmandy G11.

Comments/critique welcome.

[gregbradley]

It seems to be slowly clearing around here so maybe I will be able to image it again tonight with some luck. If I do I'll do exactly the same exposures so it will be easier to compare if it remains as bright as last time.

Greg Bradley.

[Terry B]

Greg
You need some photometry filters ;);)

[gregbradley]

What filters are they Terry?

I managed one image tonight and it seems as bright as it was last Friday. Very subjective measure but for what its worth.

Greg.

[Terry B]

Greg
I was meaning BVRI filters. Just a V filter which is a green filter is pretty useful. You take an image of the SN and surrounding stars that has a maximum value that is in the linear range of your CCD. For an antiblooming CCD that is usually about 50% of the max ADU of the camera.
Then using the known magnitude of one of the field stars you can measure the magnitude of the CCD. These mags can come from various sources.
Even using a green filter that you already have you can demonstrate the changing magnitude of the SN as long as you measure the same comparison star.

[gregbradley]

Thanks Terry.

Greg.

[Terry B]

Dear Greg
I took your image posted earlier and inverted it. I have marked a star that has a photometry measurement from the Loneos catalogue. It was the only easily obtained comparison star I found. It is V= 11.74 and B= 12.42
It is a bit bright compared to the SN but gives the idea.

[jjjnettie]

Amazing stuff!
Congratulations Greg on IOTW and
congratulations Greg on your discovery!!

[gregbradley]

Thanks Terry.



Cheers JJ. I hope IISAC was fun, not too much rain?

Greg.

[kinetic]

Here is my result from tonight with the 12" Newt.
Focus and seeing terrible. A very poor comparison.
Your image is incredible Greg, and congrats Greg Bock on the
discovery . IOTW...awesome!

Steve

[Greg Bock]

Thanks jjj and Steve
with the benefit of hindsight, I should have spent the last few days at Lostock, clouds seem to be getting worse here, and preventing me from getting a nice colour pic of the galaxy.

To all thinking of imaging it, give it a go, its relatively bright, and being a type IIP, it should have a nice leisurely drop off in brightness over the next few months.

[gregbradley]

Cheers Steve. Its been cloudy pretty much ever since.



Greg I'd love a bit of a writeup about what type of star does this, how big is it, how much energy is there in these explosions and over what area of space does this extend. It looks brighter than the galaxy itself and would appear to be very dangerous to be anywhere near it. Radiation alone from an event like this must be dangerous to life.

Greg.

[madbadgalaxyman]

Greg,

I could estimate the luminosity (absolute brightness) of this SN without too much trouble, but first I need some good estimates of its apparent magnitude.

In my opinion, The SN looks brighter than the central bulge component of this galaxy, but it is likely to be well fainter than the total light of the galaxy itself, which also includes a vast region of very faint spiral arms.

The average type II-P supernova comes in at around a Blue (B-band) luminosity of about 600 million times that of our own Sun, but individual II-P supernovae differ greatly in luminosity (by a factor of up to 6 or more)

Best Regards,
Robert

[kinetic]

from tonight, slightly better seeing.
Sorry about the hijack Greg.

Steve

[gregbradley]

Good one Steve.

I managed a short image last night before clouds spoiled the party and it still seems about the same brightness.

Greg.

[Leonardo70]

Congratulations Greg...i hope this is not to late ...
Great job.

Leo

[kinetic]

I finally got a decent night of seeing tonight Greg.
I'm pretty happy with this one.
The seeing allowed me to upsample, process, apply a bit more sharpening
and then downscale 0.75x to a good viewing size.
Seeing is king at this FL
Apologies for the moon gradient and dust bunnies though :)

Steve

[gregbradley]

Good one Steve.
Its still amazingly bright. It must be close to the brightness of the entire galaxy. What a phenomenol concept. I suppose we are looking at a massive star that is throwing up in months what normal stars would over huge periods of time.

Greg.

[DavidTrap]

I managed to setup the scope last night (actually first light for my VC200L) and did some imaging on the SN in IC4901.

Here are my offerings - a stack of 5 x 10min subs through an 8 inch scope beside a quarter moon looking south towards Brisbane. I have run a DBE on these in PixInsight which revealed just how many dust bunnies I have on my CCD - look closely at the thumbnail of the inverted image below :help: . My next post will be to Exfso about a light box!

The reference star that Terry indicated in a previous post had blown out completely in these 10min images, however, I had a one 5 min sub taken at Bin 1 in which that star was ~90% saturated. While this is pushing the friendship of linearity with an ABG chip, I followed a tutorial for Maxim DL Photometry and calculated a magnitude of the SN at ~15.2. (This was taken through a luminance filter) I'd be interested to know how this compares to measurements taken by those who actually know what they're doing!

As for the VC200L - very impressed with the field flatness - the results from CCD inspector were <10% curvature and this was with collimation done on the bench only as I didn't have time to fiddle with a star test. This yields a small round star without elongation visible in the OAG prism of the QSI. I am sure this helps the guide software track an accurate centroid. The guiding graph was almost flat.

Cheers
DT

[Terry B]

Dear all
I took a few images of this last night after the clouds had disappeared also using a VC200L
I took images of 120 sec binned 2x2 with my ST10XME through BVRI filters.
Using the loneos star I mentioned before as the comp star I measured mags of
B= 14.8
V= 14.54 (error range 0.045)
R= 14.21
I= 13.92
The attached image is of 3 x V images averaged.
All of these mags include the flux of the galaxy in the measurement annulus of the star. To make a more accurate estimate I would need to subtract an image of just the galaxy without the SN but this would have to wait until the SN is gone as I don't have an image of the galaxy without the SN.

[Greg Bock]

Hi guys
its great to see some images coming back now, wish I had the honour too, but the only clear night when I had any chance without clouds was last night, but the wind blew everything around and the seeing was terrible...
When will we get a break here in SE Qld ( or SE Cloudland)??

[gregbradley]

Just think of all the supernovas you may have missed over the years due to clouds. By the time you imaged them they may have faded!

Greg

[DavidTrap]

Thanks for posting the numbers Terry - I'm happy to be at least in the ball-park. I was experiencing the same problem with the annulus of the aperture overlapping the galaxy - was wondering what you did about that This photometry stuff seems quite clever - something to fiddle with in due course.

DT

[Terry B]

I used a 5 pixel (radius) central annulus with about 30 and 40 pixel outer annulus. (the actual numbers are a home). This isolated the rest of the galaxy. The comp star was Ok with the same settings.
These settings will vary depending on the sampling size ie arcsec/ pixel and the seeing on the night.

[DavidTrap]

The FMHW of the comp star was ~4, so I set the aperture in Maxim to 8 (the tutorial I read said 1.5-2x the FMHW).

How valid is it to subtract a galaxy from a previous night - I would guess that variations in seeing could affect magnitude, or do you "scale" the amount of subtraction in some way using the known value of the comparison star?

DT