NGC 3239 (Arp 263) and Supernova 2012A

Last Sunday, Jimi Lowrey, Jim Chandler and I took a look at NGC 3239. I had completely forgotten about SN 2012, discovered early last month, but picked it in the observation --

48" (2/19/12): NGC 3239 = Arp 263 is a large, disrupted Irregular dominated by numerous HII regions and a fascinating sight at 488x. A mag 10 star is superimposed on the SW side of the galaxy with the patchy, highly irregular surface brightness glow of the galaxy extending mainly north and east of the star.

Most prominent is a very bright, round knot of ~15" diameter on the SE side of the galaxy, which is catalogued as VV 95B in NED and in Hodge-Kennicutt's 1983 "An Atlas of HII Regions in 125 Galaxies" as #6 and #10. A faint star or knot is attached on the north side. A "star" recorded just off the west side of this knot turns out to be supernova SN 2012A, discovered on 7 Jan 2012, still currently around 14th magnitude. Very faint haze extends SE of the knot, but a "tail" structure was not seen.

Along the north side of the galaxy (elongated east-west) are several additional knots. About 30" due north of VV 95B is HK[83] #3 and #4. This close pair of knots appeared as a faint, small, irregular glow, ~6" diameter. Patchy haze is just west, but with no condensed spots. Further west, and 40" due north of the mag 10 star, is a moderately bright, small, round knot, ~10" diameter that has several HK[83] entries (#28/29/31/34). To the west of this knot, the glow of the galaxy ends near HK[83] #57/58, a faint low surface brightness knot that is elongated N-S.

Adam Block's image of the galaxy and supernova is at http://skycenter.arizona.edu/gallery/Galaxies/ngc3239

GREAT SCOTT! (Dr Watson's favorite line I believe)

Not only do I have no observing note for this unusual Arp 263 but also I have not seen that wonderful 'Y formation' group to it's north as well as the stragglers just east. A group of 8 (or 9 if you count 3239 as perhaps a left over from a colision since trails seem apparent from DSS). This is a MUST see group and object. Thanks for the tip Steve.
Marko

Hey, Marko, glad to see you participating here. I observed some of the nearby galaxies (as well as Arp 263) with my 18" Starmaster on March 28, 2009 from DeepSky Ranch. I didn't log who was there that evening, but I'm guessing you might have been in attendance! Here are my notes on some of the nearby CGCG's ---

CGCG 094-039 = MCG +03-27-023 = PGC 30564
10 25 00.9 +17 17 32
Size 0.55'x0.45'; PA = 66d
Faint, small, slightly elongated, 20"x15". Located 8.5' N of N3239 with several nearby faint companions.

CGCG 094-040 = MCG +03-27-024 = PGC 30563
10 25 04.6 +17 13 52
Size 0.9'x0.5'; PA = 46d
Very faint, very small, round, low surface brightness, 18" diameter. Located 4.8' N of N3239 in a group of small galaxies.

CGCG 094-043 = MCG +03-27-026 = PGC 30573 = PGC 30577
10 25 11.5 +17 15 20
Size 0.8'x0.7'; PA = 95d
Faint, very small, round, 20" diameter, very small bright core, fainter halo. Located 6.3' NNE of N3239 and surrounded by several other faint galaxies.

CGCG 094-042 = MCG +03-27-027 = PGC 30585
10 25 17.7 +17 08 21
V = 13.9; Size 1.0'x0.7'; Surf Br = 13.3
Very faint, very small, round, 20" diameter. Located 2.9' SE of N3239.

UGC 5639 = MCG +03-27-029 = CGCG 094-045 = PGC 30595
10 25 26.0 +17 15 42
V = 13.9; Size 1.2'x0.8'; Surf Br = 13.7; PA = 138d
Very faint, fairly small, slightly elongated NW-SE, 25"x20", low surface brightness. Located 8' NE of N3239 in a group with CGCG 94-43 3.4' W, CGCG 94-39 6' WNW and CGCG 94-40 5.4' SW.

CGCG 094-046 = MCG +03-27-030 = PGC 30606
10 25 36.8 +17 04 51
Size 1.0'x0.9'; PA = 170d
Very faint, very small, slightly elongated, 24"x18". Located 8.5' SE of N3239 in a group.

Steve

Looked it up. It was a killer night but we had to wait for clouds to clear by 10. Here is my intro to my OR
Willow Springs DSR Sat 28Mar2009 Observations 10pm to 4am 21.5 to 21.73 Mag/ArcSec2
Observers: KevinR, Steve Gottlieb, Mark Wagner, Richard N, Greg LaFlamme, Mark Johnston

That was the night I worked the Ngc3158 group (a big-time fav of mine). I spent a lot of time in Hydra1 cluster and assorted virgo and leo galaxies. Really a great night with the whole 'gang' present and accounted.

Hi there,

I had a chance to observe Arp 263 (NGC 3239) with my 18" on Saturday night from my favorite dark sky location at Xyliatos, Cyprus (altitude approximately 2,500ft but surrounded by higher mountains). Conditions were far from perfect but with acceptable transparency on the northern half of the sky, the southern half been affected by some Saharan dust being brought in by the jetstream. Seeing though was bad, with stars balooning to more than 2 arcseconds... Anyway, I managed to observe Arp 263 as it was in the clearer half of the sky. I was amazed at the amount of detail this galaxy possesed. There was quite a bit of nebulosity especially N and E of the embedded star, creating several brighter knots. There was a darker marking right to the east of the star, with a a patch of nebulosity connecting the two brightest knots, the eastern knot harboring a stellar-like brightening - possibly SN2012A? The northern part of the galaxy seemed to have less brightness variations, and I was not able to observe the "soft fading of the glow into the background" as described by B. Wilson in The Arp Observing Guide of Kanipe and Webb. I also recorded a faint nebulosity extension from the embedded star to the SE, giving a bird-like image of the galaxy (it reminded me of a pelican - see attached sketch)...