14 May 2017 at 11:03 am #573749
mag 12.8. Fire up your ALPYs !
AT 2017eaw in NGC 6946 (SN:)
Patrick Wiggins, Tooele, UT, USA, reports his discovery
of a possible supernova (mag about 12.8) on an
unfiltered CCD frame taken 2017 May 14.2383 UT using a
0.35-m f/5.5 reflector near Erda, UT, USA. The new
object is located at
R.A. 20h34m44.24s, Decl. +60°11’35.9” (equinox 2000.0),
about 153” NW of the center of NGC 6946. The discovery
image was posted temporarily at URL
Wiggins notes that nothing was visible at this position
on an image taken on May 12.
AT 2017eaw: https://wis-tns.weizmann.ac.il/object/2017eaw
Posted by: Patrick Schmeer
Visit the BAA Variable Star Section web site at…
——————————————–14 May 2017 at 5:43 pm #578211Peter MeadowsParticipant
The attached image shows NGC 6946 acquired on 2017 May 14 at 11:07 UT using iTelescope T24 in California (the average of 3 x 120s exposures) and a comparison DSS image (using Aladin v9.0). The cross and red circle shows the new object (not visible in the DSS image). A larger version of the image is attached.
Astrometrica gives a magnitude of V=13.1 and position RA 20 34 44.24, Dec +60 11 36.1 (J2000) for the new object.15 May 2017 at 10:00 am #578213Andrew RobertsonParticipant
I managed a brief 5 minute visual view of it last night in my 12” F5 ultra-portable dob from Norfolk. It had been clear all evening and forecast to be clear most of the night but with a bit of cloud coming over early on. Issues were; Nautical dark commencing at 22:25 hrs, astronomical dark at 23:58 hrs and a 86% mon rising at 23:48 hrs. I decided about 23:30 hrs would be about the best time to get on it and had the scope set up by 22:30 hrs in preparation doing a few lollipops (M13, M5, M92 etc.) as a warm up. However shortly before 11pm I saw a cloud front slowly moving over from the SSW so thought I ‘d best have a look sooner. I found ngc 6939 easily enough but ngc 6946 was just detectable, a combination of it’s a low SB and a far from fully dark sky. I used the image by Wiggins (Owen Brazell had posted a link on the Webb Soc forum) to identify the star fields. I had a fully inverted view and quickly recognised that triangle of brightish stars just ‘above’ 6946. I was then looking for those two pairs of stars below 6946 but initially just noticed the brighter pair lower down. Another look at the image and I recognised the field. Had started off with a 24mm panoptic giving x62 but changed to a 13mm T6 Nagler giving x115. Going back to the eyepiece I then located the two pairs of stars. They were very faint in that relatively brightish sky but were direct vision – just! The pair with SN were slightly brighter than the other pair. I enjoyed the view for about 5 mins before the cloud came over. As I got my eye in, the SN became quite obvious. It did clear again but only just after the moon had risen.Very enjoyable,
Andrew Robertson15 May 2017 at 4:19 pm #578214
I was clouded out by the time it got dark enough/cleared the tree line so no spectrum from here. The confirming spectrum (type IIP) on TNS is fairly featureless with a blue continuum at the moment and a small hump at H alpha.
This should grow into a nice strong P Cygni line profile over the next couple of weeks though.
Robin18 May 2017 at 6:36 pm #578223
I was able to get just 10 mins on this object with the modified ALPY 200 before the clouds rolled in last night. This is a bright target for this setup though so it was enough to get a decent low resolution spectrum (R~130). Here is my spectrum overlaid on the confirming spectrum from 14th May posted on TNS.
The Supernova identification program SNID confirms from my spectrum it is a type IIP near maximum light. There have been some significant changes in the spectrum over the past 3 days which is expected.
The blue shifted absorption component of the H alpha P Cygni profile is clear now in my spectrum and can be used to estimate the explosion velocity (~11600km/s)
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