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Alert Notice 495 on PSN J09554214+6940260

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We just issued AAVSO Alert Notice 495 on the bright (11th mag V) Type-Ia supernova in M82 = PSN J09554214+6940260. This Alert Notice gives particulars and announces an observing campaign. Visual and photometric observations are strongly requested.

(Check your inbox for the email version if the webpage is not yet available.)

Many thanks and good observing  -  Elizabeth Waagen, AAVSO HQ

 

PSN J09554214+6940260 = SN 2014J
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According to Electronic Telegram No. 3792 from the Central Bureau for Astronomical Telegrams,  PSN J09554214+6940260 has been given the name SN 2014J.

Mike Simonsen
AAVSO

Does SN2014J show fast variations?
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No one has ever looked at any supernova with long time series of fast photometry, so we do not know whether any supernova actually does or does not display fast variations (i.e., dips or flares).  Well, certainly, *theory* would be surprised to find fast variations because the expanding shell is so large, and large objects 'cannot' change their brightness on a fast time scale.  (So, a shell one light-day in size should not vary faster than one day or so.  There are exceptions to this rule, perhaps most likely in this case if some small bright spot appears somewhere on the surface of the shell before cooling and fading fast.)   This theory argument also applies to nova when in the optically-thick shell phase, so no one expected that novae around their peak in eruption should show fast variations, and so no one looked.  But the first time that anyone looked at a nova with a lot of fast time-series photometry (for the U Sco eruption in 2010), we found hour-long flares.  This surprise to 'theory' still has not been explained.  No one knows whether supernovae can also show similar flares (or maybe dips).  Theory is all fine, but let us see what reality is.


Fast variations in supernovae cannot be too large in amplitude or too frequent, otherwise any of many groups would have previously picked them out (say, as scatter about some light curve template) even with their one-or-twice a night light curves.  So we are looking for moderate or small amplitude (say, <0.25 mag or so) variations.  This forces us to get time series where the individual images have a statistical uncertainty of 0.01 mag or better (S/N ratio of >100 or so).  The not-high-frequency of the phenomena means that we have to accumulate a long time series to have a hope for catching the events.  Professional scopes cannot allocate so much time to such a program, and certainly, no allocation committee would grant time for such an 'impossible' possibility.  This means that AAVSOers are uniquely and perfectly set up to test out whether supernovae have fast variations, because we can devote many whole nights to sitting on one target.  If the flares/dips are uncommon, then we have the responsibility of providing convincing evidence that any claimed event is real.  For example, we can imagine all sorts of artifacts that could be interpreted as a dip or a flare, like time-variable seeing where the amount of light entering the photometry aperture from the surrounding M82 galaxy changes as the seeing changes and might be thought to be a change in the supernova.  For uncommon events, the best way to convince people is to have two completely independent observers simultaneously report the same flare or dip.  This means that we need multiple people following SN2014J at any given time, so any flare or dip can be proven by mutual confirmation.  So again, the many AAVSOers are perfect because we can marshall many observers round the clock.

 

I don't know what we'll find, but then no one has ever looked in this way at a supernova before.  Finding a fast flare or dip would be big news, partly because it is so startling and a challenge to theory, but also because it might represent an new phenomenon not realized before.  But before we declare a new phenomenon, we have to have strong proof, and that means multiple simultaneous observations with high photometric accuracy for which we can rule out possible artifacts.

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