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  #21  
Old 21-10-2011, 03:44 PM
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Thanks Justin, Rob and Ric.

Yes, its been quite an exciting ride for the last day and a half. This is, of course, always the case whenever the BOSS team makes and submits a discovery, but it's been heightened for me this time because this is my first discovery contribution.

Normally when Stu or Pete have made discoveries, I am doing the confirmation images, analysis, and/or reporting, so it's good the have the shoe on the other foot for a change!!

As I said at the BOSS presentation at the Australian Imaging Conference in June this year, with all the technology that's available to us these days, it's a great time to be an amateur in this field. There are so many resources, information, communications, and support available for doing this and contributing back to the science. Very satisfying indeed.
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  #22  
Old 21-10-2011, 08:04 PM
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Congratulations Greg, what a tremendous effort to finally bag one!

Terry
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  #23  
Old 21-10-2011, 10:10 PM
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Peter asked how bright this supernova is going to get.

This is a tough question in the absence of a reliable distance measurement for IC 4901. There have been a couple of individual estimates of the distance of IC 4901 using the Tully-Fisher method, which unfortunately is no more accurate than using the redshift of a galaxy to estimate its distance. In fact, the two Tully-Fisher distance determinations are highly discrepant.

Sadly, IC 4901 has had very little study by professional astronomers: it gets just a brief mention in a handful of papers. This situation is exactly as I would expect from the poor results of my previous searches for info about various southern IC galaxies!

In the circumstances, it might be best to estimate the distance of this galaxy from its redshift, which is 2038 km/s in the Local Group reference frame (according to the NED database). Assuming a Hubble Constant of 73 km/s/Mpc one can then use this redshift to estimate that the distance is 28 Megaparsecs ( = 91 million light years) .

The other parameter that we need in order to estimate the probable peak magnitude of this supernova is its luminosity (absolute magnitude), which introduces further uncertainty. As I am unfamiliar with the literature on supernovae, my most recent information about the absolute magnitudes of Type II-P supernovae comes from the year 2002 (D. Richardson et al., (2002), AJ, 123, 745) and it is an average of the luminosities of a small number of these supernovae. Richardson et al. find a mean Blue absolute magnitude of -17 for Supernovae of type II-P, but they also find that the luminosities of the individual II-P supernovae events occupy a wide scatter between
B absolute magnitudes -16 and -18

Assuming a peak absolute B-band magnitude of -17 for this supernova, and a distance of 27.9 Megaparsecs (a distance modulus of
m-M = 32.23), and a total extinction (the internal extinction within IC 4901, plus the foreground extinction from the Milky Way) of 0.6 magnitudes, we can then use the standard equation for distance modulus and absolute magnitude to estimate a peak apparent blue (B-band) magnitude for this supernova of 15.8, which is quite faint.
If the supernova was absolute blue magnitude -18 in luminosity, it would probably end up being closer to Blue (B-band) magnitude 14.8

Given the uncertainties as to the distance of this galaxy and the luminosity of this supernova, not to mention uncertainty as to the precise amount of dust extinction, a peak apparent Blue magnitude of 14.6 to 16.3 can be considered a ballpark estimate.

cheers,
mad galaxy man

P.S. the amount of extinction from dust within the host galaxy and within our own Milky Way galaxy can make a considerable difference to the apparent magnitude of a supernova. I assumed only 0.2 mags of foreground extinction, together with a further 0.4 magnitudes of dimming of the SN's light coming from within IC 4901 itself. The foreground extinction from our own Galaxy can be calculated with reasonable accuracy, but the extinction of a supernova's light caused by the dust within its host galaxy will be unique for every observed supernova.

I can't put a figure on the distance uncertainty regarding IC 4901, but I assume that it could make at least a 0.3 magnitude difference to the observed magnitude of the supernova.

If, for instance, I assume that the SN is more luminous than the average for its type (in this example, assuming that the SN is -18 abs. magnitude), minimal dimming of the SN's light by dust (say, 0.4 blue magnitudes of all-sources extinction), and a 15 percent closer distance for the host galaxy (say 77 million light years), then the apparent B magnitude of the SN at its peak will be B = 14.3 magnitude.

Last edited by madbadgalaxyman; 22-10-2011 at 01:14 PM. Reason: correction and more info
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  #24  
Old 22-10-2011, 07:44 AM
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I imaged this one last night with my Planewave CDK17 and Microline 8300 camera. The luminance is not bad but the colour data not so good yet.

A bit of cloud came over during the green sub.

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

Greg.

Last edited by gregbradley; 24-10-2011 at 07:02 AM.
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  #25  
Old 22-10-2011, 08:46 AM
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Quote:
Originally Posted by Greg Bock View Post
Thanks for the generous thoughts above, and your ongoing . At mag 14.5, it should be in the range of moderate scopes (say 12" at least) under dark skies.

Hi Greg,

is that magnitude secure? Also, what bandpass is it in?
(B? V? R?, visual?)

cheers, Robert
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  #26  
Old 22-10-2011, 11:48 AM
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Congratulations Greg, fantastic story mate! well deserved discovery!

How exciting it must be for you guys and I like Peters little description of what it is that we are really seeing, it is well worth the itruspective thought as it must be easy to get held up in the idea that it is just another dot in a fuzzy blob.

Well done BOSS team

Mike
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  #27  
Old 22-10-2011, 01:21 PM
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how exciting it must be for you guys and i like peters little description of what it is that we are really seeing, it is well worth the itruspective thought as it must be easy to get held up in the idea that it is just another dot in a fuzzy blob.

I Absolutely agree, Mike. We should remember that the "dot in the fuzzy blob" is all that is left of the light of this fearsome and awesome supernova after that light has traveled some 90 million light years through space.

Some people coming to this thread for the first time might wonder, in fact, why all of us are making such a great fuss about this tiny dot of light seen in a distant galaxy.....the reason is that even a modest supernova explosion puts out about a billion times as much light as our own Sun!
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  #28  
Old 22-10-2011, 01:39 PM
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CBET 2868 : 20111022 : SUPERNOVA 2011gv IN IC 4901 = PSN J19542142-5842390

Congratulations Greg & the BOSS team!

Cheers -
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  #29  
Old 22-10-2011, 01:57 PM
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Hi all,
Thanks for the CBET details Rob, I'm out having coffee with Kath right now, so it's harder to reply properly from the iPhone, but I will get back to this thread later.
To all who have posted here, great posts guys, keep them coming, it's wonderful to have the opportunity to share this with such a supportive astro-community.

Greg
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  #30  
Old 22-10-2011, 09:44 PM
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Just managed to observe this SN in brief gaps between the clouds. Quite distinct in the 16" scope at 250X. Very exciting to see a star exploding 90 million light years away and 90 million years ago! Report to follow in Obs report section.
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  #31  
Old 22-10-2011, 10:55 PM
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Congrats, Paddy...you must be one of the very first people on the planet to see this object with the eye, as this SN news has not gone far beyond the confines of this thread!

We are getting a "back row seat" when viewing this celestial show....the light has travelled a bloody long way to reach your eye.......this is probably just as well, as I wouldn't want to be anywhere near this supernova.....

The galaxy itself looks low surface brightness in the images, with the only relatively bright part being near its centre in the form of a small bar that is surrounded by an indistinct ring structure.

Last edited by madbadgalaxyman; 22-10-2011 at 11:01 PM. Reason: more
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  #32  
Old 23-10-2011, 09:46 AM
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Quote:
Originally Posted by madbadgalaxyman View Post
Hi Greg,

is that magnitude secure? Also, what bandpass is it in?
(B? V? R?, visual?)

cheers, Robert
Hi Robert,
It was 14.5R measured by Colin Drescher. I know he uses Astrometrica nad several other programmes.


And Paddy, yes indeed you are the first we are aware of who had his eyeball exposed to this Supernova, congratulations!
PeterM
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  #33  
Old 23-10-2011, 11:59 AM
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Hi Robert,
It was 14.5R measured by Colin Drescher. I know he uses Astrometrica nad several other programmes.
Thanks, Pete, for the info about the type of magnitude.

If the SN was observed to have an R-band (Johnson-Morgan) apparent magnitude of 14.5, then what we need to derive for visual observers is its V-band photometric magnitude, which approximates its visual magnitude.
For instance, if the V minus R color of a type II-P Supernova is x, then its V-band magnitude equals (x + the R-band magnitude)

Hmmm.....let me now consult the literature regarding the optical colors of Type II-P supernovae.......(cogitation is now in progress!)

According to a study of type II-P supernovae by Kasen and Woosley (2009, ApJ, Vol.703, p.2205), the V-R color index of a type II-P supernova - in its plateau phase - is never more than 0.5, and often this color is only 0.3 to 0.4

In other words, if the Supernova is observed to be R magnitude 14.5, then the estimated V magnitude ("visual" magnitude) of this supernova will not be greater than 14.8 - 15
Or the V magnitude could be similar to the R magnitude (within the uncertainties).

Conclusion: if the observed R apparent magnitude of 14.5 is correct, then this "exploding critter" is quite bright, as its Visual magnitude may be only slightly fainter.
_____________________

Red Optical Colors of type II-P Supernovae:

One thing I did not realize before, because I am totally a "babe in the woods" when it comes to supernovae, is how red these type II-P supernovae actually are, in optical observations;
According to the aforementioned authors, the B-V color index of a type II-P supernova is often about 1 (or more) when the SN is in its initial (plateau) phase.
This should equate to a noticeable orange-red color in visual observations and photographs.
___________________________________ ___________

Because the observed Visual magnitudes of these type II events can be significantly brighter than the Blue magnitudes that I used in my estimates of how bright this SN is going to get (see a previous post in this thread), I will have to rework my "predicted brightness of this supernova" estimates.
_______________________

Best regards to all "SN crackers",
from the Mad Galaxy Man

I recommend Kasen and Woosley to all you SN enthusiasts, as it provides in depth analysis of type II-P light curves.

Last edited by madbadgalaxyman; 23-10-2011 at 12:03 PM. Reason: correct typos
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  #34  
Old 23-10-2011, 01:04 PM
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Congratulations Greg. So happy for you to finally have "one in the bag" after all the hard work by you and the rest of the team. Here's to many more!
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  #35  
Old 23-10-2011, 01:05 PM
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Originally Posted by gregbradley View Post
I imaged this one last night with my Planewave CDK17 and Microline 8300 camera. The luminance is not bad but the colour data not so good yet.

A bit of cloud came over during the green sub.

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

Greg.
Great shot Greg!
Be nice if the SN was marked in perhaps?
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  #36  
Old 23-10-2011, 02:27 PM
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And Paddy, yes indeed you are the first we are aware of who had his eyeball exposed to this Supernova, congratulations!
PeterM
Even more exciting! To save folk wading through my obs notes from the last couple of sessions, here are my notes on the supernova from last night. Thanks for the discovery and the heads-up - what a buzz! Hope to get a better night's viewing and make a sketch.


Supernova 2011gv in IC 4901 (GX in Pavo)

250X A viewing highlight indeed. Easy to find the galaxy as it is near a naked eye triangular asterism 1/3 of the way from Alpha Pavonis to the head of the peacock. To the preceding and slightly to the north of the faint galactic core is a tiny but distinct star. The galaxy itself is a faint glow slightly elongated roughly E-W 2 x1 , the supernova visible within the western edge of the glow of the galaxy. There is a foreground star 3 to the east of the galaxy. This observation before Id even properly dark adapted. My plan to return later in the evening is foiled by cloud
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  #37  
Old 24-10-2011, 05:36 AM
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Greg Bradley's image of the SN is a good one, and this story is so exciting and such a good news story, Greg's image is now IOTW.

I put the markets on the image and rotated it 180deg to match up with Greg Bock's image.
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  #38  
Old 24-10-2011, 07:01 AM
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Great shot Greg!
Be nice if the SN was marked in perhaps?
Marked in now. Iceman told me how it is done. I've never used the line tool before. Handy.

Image:

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

Greg
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  #39  
Old 24-10-2011, 07:21 AM
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Excellent work all round and well done Peter. What a buzz it must give you to find one of these suckers.

I was doing some asteroid photometry last night and took a 4 minute exposure through a V filter to see how it would show up. Its quite bright (though my image is v noisy). If the cloude keep away I'll take a few images over the next few day and see how its brightness tracks

Pete
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  #40  
Old 24-10-2011, 07:33 AM
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Oops - I mistyped. Congratulations to Greg for his find.

Pete
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