Mr.
Galaxy's Supernovae
Mr.
Galaxy's Supernovae
Early in April, 1995 I found my third supernova, SN1995J, and wanted to share the experience with my fellow amateurs. I enjoy hearing stories about other people's adventures and I hope you will enjoy this account.
The last time I looked at '95J, while attending the RTMC's CCD shoot-out over the Memorial Day weekend, it was still holding steady at about magnitude 16.5. Last year's SN1994I in M51 plummeted out of sight shortly after myself and fellow OCA member, Doug Millar, co-discovered it early in April, 1994 with Tim Puckett and Jerry Armstrong of Atlanta, GA and Richard Berry who now lives in Oregon. My co-discovery of SN1991T in the Virgo cluster galaxy, NGC 4527, involved even more people spread over the entire globe. That supernova put on a nice show for a long time and was viewed by many people at the 1991 RTMC. Each story detailing the discovery of a supernova or similar object is unique and should be told so that people can vicariously participate in the adventure. It also provides incentive for someone who may have read the story to repeat the effort in their own way and write their own story.
To begin the story, the weather in Southern California had been horrible for too long and I was in need of a "photon fix". Almost all of the star parties since October 1994 had been clouded out and the only time the sky seemed to clear was around full moon, not optimum deep-sky observing time! Around the end of March, we had a spell of good weather and I decided to head out to the Orange County Astronomer's (OCA's) Anza Observatory Thursday night to get in an extra night of observing. The Saturday of that weekend was going to be busy because of a Star Party/Messier Marathon. Thursday and Friday nights were both good nights of observing; fellow OCA member, Jim Leonard (whose own CCD camera was out for repairs) and I were able to take about 50 CCD images on each of the two nights. Saturday night was spent entertaining the several dozen people who showed up at the site for the Marathon. We had the 22-inch trained on various objects as people took breaks from their hunting to see the sights through the club telescope. After midnight Jim and I attached the CCD camera onto the big scope and imaged various galaxies around the sky. Sunday came and everybody left except for myself. The weather looked promising and I decided one more night wouldn't hurt. I always visually examine the objects I image with the CCD camera for anything obvious through the previewing eyepiece. I also take a quick look at the images as they appear on the monitor while I am observing. Still, I spent all day Sunday examining and compressing images to make room on our computer's constantly overloaded hard-drive for the next night's catch. No SN suspects were seen in the previous three days' images even after double-checking. Sunday night's images had a dearth of suspects although I took another 50 or so images.
Monday came and the weather still looked great. I called my wife, Arlene, and before I could utter a word she wistfully said, "You're staying another night, aren't you?"
I sheepishly said, "Yes, I have to take advantage of the weather!".
She replied, "Well, you better find something."
Monday's promise of good weather remained intact through the night and I imaged away until dawn even though I knew I had to pack and drive back home and drag myself through school the next day. Monday was the most exciting of the nights in this run because I had a couple SN suspects that took a little investigation to eliminate early in the evening. Much later that night I was imaging galaxies from Thompson and Bryan's Supernova Search Charts and decided to try NGC 4236, which is a nice obliquely oriented spiral located in the far northern skies of Draco, the dragon. I saw nothing suspicious in that galaxy and then looked at the Uranometria 2000 star charts to see what else was of interest in the area. There was a scattered grouping of 13th and 14th magnitude galaxies about 5 degrees south of NGC 4236 that I thought would be nice to add to the OCA's image library. In that area was a close pair of galaxies consisting of NGC 4512 and 4521 that would fit in the 15 arcminute field of view of the CCD camera. It was getting late (about 4:15am), the pre-dawn light was creeping up and I needed to get packing. One of the strategies I use when supernova hunting is to search for pairs or groups because I can get more galaxies for less effort; it increases the probability of finding something. As luck would have it, both galaxies had stars (or SN suspects in my optimistic view of the world) superimposed on them or very close by. Neither one had a reference image to compare with. I took another image of the pair about 15 minutes later as the dawn light was beginning to intrude more and more. I saw no motion among any of the "stars" near the galaxies in the two images I examined. They really were fixed "stars" and not asteroids as far as I could tell. There should have been some detectable motion in that amount of time, which I could determine by electronically blinking the two images together. The stellar points were not "hot pixels" or cosmic rays either because they were repeatable. I had just enough time to shoot a few more short exposures of some globular clusters that were nicely situated for observing and then closed up the observatory to drive an hour and a half to school.
While at school I sent an email inquiry to good friend, Harold Corwin, at JPL to check out the three stars I considered to be suspected SNe, giving him the approximate magnitude and location with respect to the two parent galaxies' nuclei. I left school without getting a reply and when I arrived home I made a more thorough check of the photographic and CCD atlases of images I have there. One of my references contained an image of NGC 4521 showing a star superimposed on it where I saw the one suspect. I was severely disappointed; if there was ever a good SN candidate, that was it. As for the other galaxy, NGC 4512, the two stars near it were field stars as far as I could tell, but I still could not find any reference image of that galaxy to prove it. After much hesitation, I decided to phone another good friend, Jean Mueller, at Palomar Mountain to see if she could help out. Jean said she would check them in a little while and to call her back later. When I phoned her again she said that the one star to the SW of N4512 belonged there, but the other star to the NE was not on the Palomar Sky Survey charts! I had a good candidate for a supernova!
The next step was to contact Dan Green at the Central Bureau for Astronomical Telegrams (CBAT) in Cambridge, MA to notify him of the new magnitude 16.5 stellar object in NGC 4512 approximately 30" (arcseconds) East and 30" North of its nucleus. He then sent out a notification to the astronomical community about the apparent supernova to ask for further observations and confirming spectra. No SN is "officially" recognized unless it has had its spectrum analyzed. In the meantime, Harold emailed me and said that he, too, did not see any star where my suspect was and that he would send a message to CBAT to bolster my observation. About two days after my report to the IAU, astronomer Alex Filippenko's group at UC Berkeley, using a spectrograph on the 4-m (120-inch) Shane telescope at Mount Hamilton outside of San Jose, CA, finally got some clear weather and confirmed the suspect to be a genuine Type II SN about 2 months past maximum brightness. Now the new star could be officially designated SN1995J (or Wayne's supernova as it rapidly became known at the RTMC!) since it was the 10th SN of the year. The "J" had nothing to do with my last name, though that was a nice touch. I still find it hard to believe that '95J had to wait that long for someone to find it. Another SN hunting friend, David Lane from Canada, said that he had been interested in N4521 because of the superimposed star I mentioned earlier and that images he had taken of that galaxy missed my supernova by only an arcminute or two! In a later conversation with Alex, he said that this star is a good example of a Type IIP (for plateau) SN, which means that after it has peaked, the supernova may fade a little but then will maintain its brightness for awhile (in this case about 2 months), then gradually plummet into oblivion. SN1995J has been a fun, although faint, object to monitor.
The moral of this story is that there may be many people looking for novae, supernovae, comets or asteroids, but there are about 41,000 square degrees on the sky and nearly half a million reasonable galaxies to search. No one person or group of people can possibly monitor all the sky or all those objects at any one time. There is always room for someone else to help out in this never-ending search. I encourage everyone to keep looking up and be aware of the changes in our seemingly changeless skies, there is more happening than you could ever imagine.
Clear skies, Wayne (aka Mr. Galaxy)