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SN 2013cj

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SN 2013cj

This one is probably too faint for most of you out there.  But on the off chance that someone can pitch in, I want to make an appeal to observe SN 2013cj (RA:  17 04 52.95, Dec: +12 55 10.4).  I have identified eight comparison stars in the field and I'm happy to share those if you want to "roll your own" or I'm also happy to take raw images.  

Many of you might remember that in September 2013 the supernova impostor 2009ip had a bright outburst that had a spectrum fitting the classification of a Type II-n supernova. I put out a call for help on this AAVSO Forum and collaborated with Josch Hambsch, Ivan Curtis, and TG Tan to track the rise and decline of that event (see We were able to track the it better than almost any other Type-IIn light curve. This detailed tracking revealed bumps and fluctuations in the decline that are detailed in a manuscript submitted to the Astronomical Journal ( Other well-sampled Type II-n light curves are smooth without any structure of this magnitude (see Kiewe et a l. 2012 and Taddia et al. 2013).

Type-IIn supernovae are defined by the narrow Balmer emission lines their spectra. It is theorized that these narrow emission lines are produced when the shockwave from the supernovae interacts with material in the circumstellar environment around the progenitor. But there is also accumulating evidence that events with this type of spectra may not all be of the same type. Some suspect that a subset, if not all Type-IIn are actually supernova impostors, meaning that they are not terminal core-collapse explosions of massive stars but violent shell ejection events of unknown origin that may be a short evolutionary phase in the supermassive stars on their way to becoming core-collapse supernovae. The physics of supernova impostors is not understood mainly due to insufficient observational data.

I have been tracking a number of Type-IIn supernovae as part of an NSF collaborative grant ( designed to dramatically increase the sample of identified and observed supernova impostors. SN 2013cj has shown some variability of the type observed in the outburst of 2009ip which many believe was an impostor event, and NOT a terminal core-collaspe. Over the last 40 days, the V light curve of 2013cj has declined from 17.2 to 17.4 with at least one “bump” of about 0.1 magnitude over several days in that decline. Working on my own, I have not been able to observe it with enough detail to tell for certain. The accumulated SWIFT data shows some indication of these bumps also ( The number of observations for this object on VS-Net has been low and not useful for confirming what I have observed. I need more data to confirm this discovery.

If you can pitch in I would love to hear from you here or jmart5 _at_  Thanks and clear skies. 

SGEO's picture
Finder chart for SN 2013cj

Is there a finder chart available for SN 2013cj with the comparison stars highlighted?

I'd like to give it a shot tonight.




RE: Finder Chart

I think I have a new suggested function for Geir to work into VPHOT. :)

The field imaged in V two nights ago with the target and comparison stars marked is attached.  North is up.  East is left and the field altogether is approximately 20arcmin square.

Or download it here:

SN 2013cj, 28 Aug 2013 UT, V-Band, target and comparisons marked

Important Note

If you plan to try this object please note: there is a bright star (60 Her = 3rd magnitude) about 13 arc minutes southeast of the target.  This will burn a hole in your CCD during a long exposure.  I got around it by positioning the field so that 60 Her falls just off the bottom.  

NorseStars's picture
Going to give this a try as

Going to give this a try as soon as it is darker, do you have a preferred filter or sequence of filters?  I have Custom Scientific UBVRI to choose from.


RE: Filters

Hope this isn't too late.  In order of preference I'd be interested in V, B, R and Ic.  But I understand B might be futile with most rigs at this brightness so if that is the case for you, then R with good S/N would be preferable to B without good S/N.

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