Further to your comments about the unexpectedly large galactocentric distance of the supernova in N5643.....
Here are two GALEX ultraviolet images showing star forming knots in the outermost regions of two galaxies. All of these far-ultraviolet-emitting knots are likely to contain OB stars that are the progenitors of core-collapse supernovae.
M83 . The distribution of knots looks like it could be connected with a gravitational interaction with another galaxy:
NGC 404 . An S0 galaxy with little or no star formation evident in the optical regime, but in the far ultraviolet, it plainly has plenty of knots of OB stars in a disk-like structure:
(the left panel is an optical image, and the right panel is FUV+NUV from the GALEX orbiting telescope)
cheers,
Robert
Last edited by madbadgalaxyman; 23-02-2013 at 09:54 AM.
So, using the GALEX M83 image as an example, it would be interesting to overlay a UV image of NGC5643 with an optical image at the same scale that shows the location of the SN. Would any OB star knots coincide. I wonder?
Its amazing how people spot these up, well done. My image was taken during a strong wind but it is visible. Compared it to the Sky X sky survey and it is new.
Now at mag 11.5, an, as best as I can tell from going through the bright supernova pages, it would appear 2013aa is in fact the brightest supernova discovery in the 26 years since 1987A! The next closest is 1980K in NGC6946 at mag 11.4
So well worth the effort to track this down visually for all those wanting to see the end of one stellar life cycle that likely starts another.
Now at mag 11.5, an, as best as I can tell from going through the bright supernova pages, it would appear 2013aa is in fact the brightest supernova discovery in the 26 years since 1987A! The next closest is 1980K in NGC6946 at mag 11.4
So well worth the effort to track this down visually for all those wanting to see the end of one stellar life cycle that likely starts another.
Now at mag 11.5, an, as best as I can tell from going through the bright supernova pages, it would appear 2013aa is in fact the brightest supernova discovery in the 26 years since 1987A!
Peter,
this might be a very luminous supernova, as the total B-band (blue) apparent magnitude of the entire host galaxy is around 10.8 and the total V-band (visual) apparent magnitude of the entire galaxy is close to 10.0
(but I wouldn't bet that these magnitude figures are very accurate)
The HyperLeda Extragalactic Database gives a "guesstimate" (based only on the velocity distance of this galaxy and an estimate of the foreground extinction) of the luminosity of this galaxy as being Blue (B-band) absolute magnitude of -21.0
so maybe this supernova is notably luminous!!
What wavelength-band is the estimate of magnitude 11.5?
The all-important required "numbers" on extinction from foreground dust and the distance of this galaxy, are likely to be a bit "rubbery" at first, but perhaps we can come up with a reasonable estimate of the luminosity of this supernova
The galaxy itself is interesting, with some rather strong asymmetry. The arm structure and dust distribution on one side of this galaxy looks particularly unusual at shorter wavelengths, e.g. in this Carnegie Atlas image (blue)
The underlying fairly-strong bar structure is fairly well shown in this near-infrared (J+H+K) image from the 2MASS:
Galaxyman's links to all the GALEX stuff is a siren song for someone chafing at lustrous skies arriving just in time for the full moon. I'd say the GALEX images will keep me off the streets for awhile, but my area is so remote there are no streets to be off of.
Now at mag 11.5, an, as best as I can tell from going through the bright supernova pages, it would appear 2013aa is in fact the brightest supernova discovery in the 26 years since 1987A! The next closest is 1980K in NGC6946 at mag 11.4
So well worth the effort to track this down visually for all those wanting to see the end of one stellar life cycle that likely starts another.
And further to this, I see on the Bright Supernova Page that Stu has discovered the 2 brightest SNe for 2013..ie The brightest SN of the year are 2013aa (Mag 11.6) followed by 2013E (Mag 14.0) in IC2532...he's on fire alright!
I observed SN 2013aa last night in the very bright galaxy NGC 5643.
It is quite far from the galaxy but as it is quite isolated from other stars is quite easily seen.
I used eyepieces from a University Optics 55mm magx 60,also 17mm Nagler 103xmag and 9mm Nagler 200xmag.
Scope used 16" truss Newtonian.
As stated elsewhere this Supernova will be easily seen in scopes from about 6" and above.
Copy the BOSS image from the thread on the discovery started by Peter Marples Here.
If you have not managed to observe a Supernova before, now is your chance.
Cheers
__________________
Managed to bag this visually tonight. Fairly low in the sky, and the moon was almost bright enough to read the finder chart by, but definitely visible in my 10" dob.
I used the AAVSO finder chart, and got magnitude 11.8 from the comparison stars. The second SN I've seen after SN 2012fr.
this might be a very luminous supernova, as the total B-band (blue) apparent magnitude of the entire host galaxy is around 10.8 and the total V-band (visual) apparent magnitude of the entire galaxy is close to 10.0
(but I wouldn't bet that these magnitude figures are very accurate)
What wavelength-band is the estimate of magnitude 11.5?
Can I assume that this supernova peaked at V (visual) apparent magnitude 11.5 ?
I seem to recall that the AAVSO variable star comparison atlas used V magnitudes for comparison stars around a variable (though I have not used these charts for years!) so I suppose that some approximation of visual magnitude, and/or the Johnson V photometric band, is a sort of de facto standard for magnitude estimation.
Another thing I clearly remember from my "very long ago" 12 months stretch of time when I was doing visual magnitude estimation (every clear night) using just the naked eye or binos together with charts, is how inaccurate some of the other observers' magnitude estimates were when compared to photometric measurements. A small number of visual observers consistently achieved an excellent accuracy of 0.2 (or even 0.1) magnitude, while a lot of others achieved an accuracy that was 3-5 times worse than this!!
My impression is that an accuracy of +/- 0.2 magnitudes is good going for visual estimates of the apparent magnitude of a stellar source, though perhaps some variable star observers can shed some more light on this.
cheers, Robert
Last edited by madbadgalaxyman; 24-02-2013 at 10:39 AM.
Can I assume that this supernova peaked at V (visual) apparent magnitude 11.5 ?
I seem to recall that the AAVSO variable star comparison atlas gave the V magnitudes of comparison stars around a variable (though I have not used these charts for years!) so I suppose this is a sort of de facto standard for magnitude estimation.
Another thing I clearly remember from my "very long ago" 12 months stretch of time when I was doing visual magnitude estimation (every clear night) using just the naked eye or binos together with charts, is how inaccurate some of the other observers' magnitude estimates were when compared to photometric measurements. A small number of visual observers consistently achieved an excellent accuracy of 0.2 (or even 0.1) magnitude, while a lot of others achieved an accuracy that was 3-5 times worse than this!!
My impression is that an accuracy of +/- 0.2 magnitudes is good going for visual estimates of the apparent magnitude of a stellar source, though perhaps some variable star observers can shed some more light on this.
cheers, Robert
Hi Robert,
Sorry for late reply.
The 11.5 comes from the site below so I assume visual. Other estimates are listed below that so definitely peaked well below mag 12.
Keep your information and thoughts coming, as usual very interesting and informative.
Thanks!
Being a visual variable star observer, I'd say your view on accuracy of +/- 0.2 mag is not far from the mark. It does depend on a lot of things. A key one is the accuracy and short gap in brightness between adjacent comparison stars. If you have a good sequence with say 0.5 mag or so intervals between comparion stars, then it's much easier to make an estimate and its generally more accurate. Also red colour long period variables can be difficult and can result in the loss of some accuracy. Also I find it much better if you are using an instrument size that doesn't show the variable star too bright or faint helps (ie estimating a 6th mag variable star in say a 16" scope can be difficult and lead to inaccuracies.
Hope this helps. By the way I visually observed SN 2013aa this morning and at Feb 23.871UT it was mag 11.3.
"Just for fun and profit", here is a hydrogen-alpha image of NGC 5643 from Ryder's and Dopita's pioneering hydrogen-alpha imaging survey of southern galaxies
(1993, ApJS, Vol. 88, page 415)
This data was reproduced at a logarithmic scale. It appears that they have already subtracted the Red Continuum from the raw H-alpha image, so this image shows H-alpha light only and excludes red starlight.
Here is the same data, but displayed at a linear scale:
The H-alpha spiral structure appears not to be particularly strong and well defined. Given that this is not at all a dwarf galaxy, the relative disorganization of its spiral structure may be telling us something about the current events occurring in this galaxy at the time the light from it started its journey to our telescopes.
Ok, I got the facts better now (thanks to David Bishop, Bright Supernova Page) so a bit of an amendment to my previous stating 2013aa was the second brightest Supernova since 1987A.
Below are the maximum brightness that all the brighter ones since 1987A reached.
2013aa appears however to be the 2nd brightest at discovery and as an AAVSO member has now measured at 11.3 even allowing a give or take for all of them 2013aa still ranks in the top 5 in the last 26 years (1987A -today infact 26 years ago - thanks Astroron for reminding me) and within a whisker of being the 2nd. Still a remarkable find, congrats Stu!
So to all you visual observers, have you seen it yet or are Astroron and Malclocke on their lonesome?
2013aa in NGC5643 max brightness around 11.3 this time
2011fe in M101 max brightness around 9.9
2011dh in M51 max brightness around 11.1
2004dj in NGC2403 max brightness around 11.2
1998bu in M96 max brightness around 11.6
1993J in M81 max brightness around 11.3
For what it's worth, and to be taken with a suitable sized pinch of salt, my back of the envelope estimate for the galaxy core to SN distance is around 16kpc. This is based on an angular separation of 196 arcseconds, z=0.003943 for the galaxy and H_0=0.71.
By the way I visually observed SN 2013aa this morning and at Feb 23.871UT it was mag 11.3.
Hi Andrew,
I'm a complete newbie to estimating variables, and I'm way off with 11.8 compared to your 11.3 for around the same time. Were you using the AAVSO chart? If so, which comp stars did you use?
Malc's z=0.003943 value for N5643, coupled with Robert's Carnegie blue and now his Ha images showing irregular disk torques got me to thinking about ancient interactivity affecting the gx. There's a faint galaxy, PGC 538542, roughly 6' SSE with a NED listed z=0.003595 (subject to important NED "See essential note" caveat) and Heliocentr.radial vel. of 1078 m/sec. No transverse velocity available, but a back-of-envelope (and part of front) calculation makes me wonder if the PGC may have grazed 5643's arm some 55+ myr ago. The locale of SN 2013aa 196 arcsec fm 5643's core (thanks again, Malc) still has me wondering how it got there. Now the thought comes it might be an ejected binary system.
I wonder if any of IIS's experienced AP hands might try some very deep field images in the B band seeking faint emissions not recorded in existing images. Then, as per Greg Bock's excl suggestion, overlay the images on the SN and see what turns up.
2013aa in NGC5643 max brightness around 11.3 this time
2011fe in M101 max brightness around 9.9
2011dh in M51 max brightness around 11.1
2004dj in NGC2403 max brightness around 11.2
1998bu in M96 max brightness around 11.6
1993J in M81 max brightness around 11.3
Yes David Bishop’s web page is one of the most fantastic supernova sites on the net I went through his site yesterday to got the above information I was so surprised that it ranked so highly.
BTW-got a great image of 2013aa the other day with good seeing and some RGB will post later still nice and bright around 11.3 as Pete says.
What a BOSS find thanks all for really interesting posts keep them coming. If only we could find the
Progenitor wouldn’t that be cool.
