Bright Supernova in NGC 7793

[ngcles]

Hi All,

I've just learned from Brian Skiff on the AMASTRO mailing list that a supernova has been discovered in the nearby galaxy NGC 7793.

NGC 7793 is a member of the Sculptor or South Polar group of galaxies -- one of the nearest groups to the Local Group. NGC 7793 is an SA(s)d type galaxy and is estimated to be about 12 mly distant.

The position of the new object is RA 23 57 47.5 Dec -32 33 24 (J2000), which according to Brian, is 26 arc-seconds east and 138 arc-seconds north of the host galaxy's nucleus. This is probably within the outer (visible) halo of the galaxy.

At present it is estimated at mag +12.6. The type of event is not known at this stage or whether it will brighten further.

Pity that part of the sky is virtually in conjunction with the Sun! Pre-dawn might be the best bet to see it at this stage.

Best,

Les D
Contributing Editor
AS&T

[Ric]

Thanks for the posting Les, that will be one to have a go at imaging wise.

Cheers

[Karlsson]

thanks for the heads-up, Les...

[Jen]

:eyepop: sounds cool but what sort of scope would u need to see this?
:astron:

[astroron]

Hi Jen, an 8" scope will see a 12.6 mag supernova, you will need a photo of the galaxy and a clear dark sky plus if possible a photo of the galaxy with the supernova in it to find it.
Of cause the bigger the scope the better.
This site has normally has images of supernova but one has not been published for this supernova. http://www.rochesterastronomy.org/SNIMAGES/
Have a look anyway it will give you an idea what these things look like.:thumbsup:
Ron

[Jen]

:hi:Astro thanks for the lovely advice dam i wish i had an 8" :whistle: ive just got a 150mm skywatcher newtonian reflector for now :rolleyes: but it wont be the last scope i buy hehe :thumbsup:

[astroron]

ive just got a 150mm skywatcher newtonian reflector for now but it wont be the last scope i buy hehe
Jen we all have to start somewhere:)I started with a 60mm Refractor, now I use a 40cm Reflector:eyepop:
Ron

[Jen]

:eyepop:u lucky thing ;)

[Rob_K]

Any more news on this one Les? I can't seem to hunt down any information on it - nothing in Google searches, or in AAVSO or Yahoo variable star forums. Thanks!

Cheers -

[astroron]

Hi Ken, my names not Les;) but the only info I could find is in the bright Supernova page website, see post 6, there is only a report ,no photo or type:shrug:
:thumbsup:
Ron

[ngcles]

Hi Ron & All,

I learned of it from the AMASTRO mailing list but it wasn't until yesterday I got the CBET circular which is reproduced:

Electronic Telegram No. 1315
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://www.cfa.harvard.edu/iau/cbat.html


SUPERNOVA 2008bk IN NGC 7793
L. A. G. Monard, Pretoria, South Africa, reports his discovery of an
apparent supernova (mag about 12.6 +/- 0.2) on images taken on Mar. 25.141 and
26.148 UT at the Bronberg Observatory. The new object is located at R.A. =
23h57m47s.5 +/- 0s.2, Decl. = -32o33'24" +/- 2" (equinox 2000.0), which is
26" east and 138" north of the nucleus of the Scd-type galaxy NGC 7793.
Nothing is visible at this position on an image of the Digitized Sky Survey
(limiting red mag 20.5) or on images taken by Monard on Jan. 2.742 (limiting
red mag 17.5) and earlier.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2008 CBAT
2008 March 26 (CBET 1315) Daniel W. E. Green

* * *


Jen, seems though you live under the dark skies of Swan Hill, your 6" might just be enough. The galaxy is a pretty bright one -- easily within reach an 6" but the supernova will be pretty faint though.

Have a go, you never know!

Les D
Contributing Ediitor
AS&T

[Rob_K]

Thanks Les!

Cheers -

[astroron]

Les,Thats where I get my info also from here. http://www.rochesterastronomy.org/SNIMAGES/
No updates at present.
Ron

[ngcles]

Hi All,

I've just this minute recieved a CBET circular update on this supernova which includes the possible iidentification of a progenitor star from previous deep images of the galaxy.

This indicates this potential progenitor was a Red Supergiant and the event is likely therefore to be a Type II. Still not certain of this as there is no spectra yet.

The reproduced circular (below) also gives magnitude estimates of the new object.

Anyone had a go at tracking it down yet?

* * *

Electronic Telegram No. 1319
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://www.cfa.harvard.edu/iau/cbat.html


SUPERNOVA 2008bk IN NGC 7793
W. Li, University of California, Berkeley (UCB); S. D. Van Dyk, Spitzer
Science Center, California Institute of Technology; A. V. Filippenko and R. J.
Foley, UCB; G. Pignata, M. Hamuy, and J. Moza, Universidad de Chile; and D.
Reichart, K. Ivarsen, A. Crain, D. Foster, M. Nysewander, and A. LaCluyze,
University of North Carolina at Chapel Hill, report that they have analyzed
the discovery images of SN 2008bk that were taken by Monard (cf. CBET 1315)
and also images taken with the 0.41-m "PROMPT 2" telescope at Cerro Tololo on
Mar. 28.41 UT. Using half a dozen stars for an astrometric solution, they
derive the following precise position for 2008bk: R.A. = 23h57m50s.42,
Decl. = -32d33'21".5 (equinox 2000.0), which is 9".2 east and 126".4 north of
the nucleus of NGC 7793.
Li et al. have further applied their astrometric solution to deep
archival ground-based images taken with the Very Large Telescopes (VLT).
Within the uncertainty of the solution (0".2 error radius), they identified a
single point source on an I-band image taken on 2001 Sept. 16 UT, which Li
et al. propose as the possible progenitor for SN 2008bk. The source is not
detected in the B- and V-band images, so it is a red source [likely a red
supergiant (RSG) star]. The possible progenitor of 2008bk also resides in
a cluster of bright blue and red supergiant stars. Based on the environment
of SN 2008bk and its possible progenitor identification, Li et al. postulate
that 2008bk is a core collapse (likely a type-II) event. Further analysis on
the astrometry and photometry of the progenitor star is on-going. A finder
chart for the possible progenitor can be found at the following website URL:
http://astro.berkeley.edu/~weidong/sn2008bk.vlt-prog.gif

G. Pignata, J. Maza, M. Hamuy, R. Antezana, L. Gonzalez, P. Gonzalez, P.
Lopez, S. Silva, and G. Folatelli, Universidad de Chile; and D. Reichart, K.
Ivarsen, A. Crain, D. Foster, M. Nysewander, and A. LaCluyze, University of
North Carolina at Chapel Hill, on the behalf CHASE project, report that
images taken with the "PROMPT2" and "PROMPT4" telescopes yield the following
magnitudes (+/- 0.05) for 2008bk: Mar. 28.41 UT, B = 12.78, V = 13.05
(indicating B-V = -0.27); Mar. 29.40, B = 12.79, V = 13.02. The calibration
star is listed in the Tycho-2 catalogue (at R.A. = 23h57m53s.03, Decl. =
-32o32'42".9; B = 12.499, V = 12.476).


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.

(C) Copyright 2008 CBAT
2008 March 30 (CBET 1319) Daniel W. E. Green


* * *

Best,

Les D
Contributing Editor
AS&T

[Jen]

Jen, seems though you live under the dark skies of Swan Hill, your 6" might just be enough. The galaxy is a pretty bright one -- easily within reach an 6" but the supernova will be pretty faint though.

Have a go, you never know!

Ok cool thanks :thumbsup: where is it near i will see if i can find it, i dont understand all the RA and degree stuff that goes on around here :ashamed: but im a quick learner and willing to learn i just need to be shown i think :D:screwy:

[glenc]

I independently "discovered" this SN this morning. I looked at NGC 7793 and noticed two stars next to it. I knew that was unusual so I looked at Desktop Universe and saw the second star was not there. Then I looked at CBAT and found it had already been seen.
Back in the 1980s (7/8/83) I was looking at M77 and noticed a comet next to it. I thought I had discovered something but it turned out to be Comet Temple 2. Maybe the third time will be lucky.
The attached image from SkyMap Pro shows the galaxy without the SN. The star inside the green curve is mag 12.48, the SN is about 1' from it and the same magnitude.

[glenc]

Jen at 5am NGC 253 is due east and NGC 7793 is 70 degrees above the horizon. Here is a map from SkyMapPro and here is an image of the galaxy. http://www.ngcic.org/dss/n/7/n7793.jpg
This shows the SN. http://www.rochesterastronomy.org/sn2008/n7793s3.jpg

[renormalised]

Thanks for the head's up, Les. Might take a look at it soon.

[Jen]

Thank you Glenc i will go check it out cheers :thumbsup:
:astron:

[astroron]

With a bit of luck and the weather stays fine I will attempt to observe this S/N after 01:30 when it will be about 30degs above my horizon:astron:
Image included S/N marked
Ron

[glenc]

Ron you will have no trouble seeing it, even in moonlight.

[astroron]

Glen My nabour has planted lots of grevillia type bushes and they are about 3.5mt tall so I will have to wait till NGC clears the bushes before I can observe it.
It's a little bit windy here so at least there will be no DEW
Thanks Glen .
Ron

[Gargoyle_Steve]

Good luck Ron, hope you do get to observe this.
Don't like my chances here though - too many sodium vapour streetlights I suspect.

[astroron]

weather nice and clear here.
Weather station clogged up my computer so have disconected it
Going observing now.
Ron

[astroron]

Just came in for a coffee.
Supernova in NGC7793 easely seen even with the Moon about 25 degs above the horizon.
Even though the galaxy was just barely seen the SN was quite plainly seen with 13mm Nagler.
Ron

[Rob_K]

Managed to image 2008bk last night, barely, LOL! The exercise was really just to get something to show! I was shooting at 200mm in the Canon 400D, way beyond the capabilities of my shaky hand-guiding, but necessary if I was to register anything (tight split with a Milky Way star). 2 x 2.5 min subs, wide open, LOL! :rolleyes:

I just find it fascinating - what impact must this have had on the surrounding areas of NGC7793, when to us it looks for all the world like a faint MW star, and the other stars of 7793 are but a billionth part of a tiny grey fog...

Cheers -

[MrB]

Nice work Rob!

[Ric]

A very nice capture Rob, well done.

Cheers