Nova Cas 2021

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  • #584155
    Mike Harlow
    Participant

    Hi Hugh,

    Thanks for the info, that’s very useful.

    And I must say your animations of the changing spectrum are fascinating to watch.  Really excellent work and thanks for sharing them on your members page.

    Mike.

    #584160
    Daryl Dobbs
    Participant

    Clouds interfered last night but first glimpse I’ve had of it for a week through my opticron 15×70’s, difficult to estimate the magnitude due to clouds but I estimate around 7.8. Seems to have brightened quite a bit since a week ago 

    #584186
    Robin Leadbeater
    Participant

     The steady rise has turned into a rapid  brightening to mag 6 currently

    #584187
    Mike Harlow
    Participant

    Luckily I was out last night (7th) taking another spectrum of the nova but with slightly better resolution.  As soon as I found the field in the finderscope it was obvious the nova had brightened significantly. The spectrum now shows very well defined P-Cygni features on most of the emission lines.

    Astronomer’s telegram ATel14614 gives a nice update on the nova’s evolution. 

    #584189
    Hugh Allen
    Participant

    Hi Mike,

    i hope you don’t mind. I had a go at processing your spectrum image in BASS:

    I calibrated it using the emission line wavelengths from one of my own Alpy spectra. And I made a response correction using the reference star BD +60 2540 that you highlighted in your image. I used the Pickles reference for an A5III star because there is no reference for an A5II. I think the calibration and response correction came out pretty well:

    Anyway, it was a bit of fun and I think it shows the quality of your spectrum down in the green-blue end. I think the red end was maybe saturated in your image which could explain the fat, squat appearance of the Halpha emission

    Cheers

    Hugh

    #584190
    Mike Harlow
    Participant

    Hi Hugh,

    Wow…that’s a really nice spectrum!  I’m impressed that you got such a nice result from the .jpg without even seeing the .fts file. Anyway, it does show one thing…I need to get to grips with some spectroscopy software to produce some more useful results.

    You’re right that the red end is saturated as it’s difficult to get the exposure right to show both ends correctly exposed, especially for red objects. 

    Some background on the prism.  It was instrument no. 179 in the BAA instrument collection and I took it out on loan in 2012.  Thanks to Bob Marriott for organising the loan and even delivering it in person!  I purchased it from the BAA a few years back when the instrument collection was finally sold off.  Apparently it has been used by some famous names in the past including Mike Hendrie and David Sinden.  But most notably it was used in the 1980s and 1990s by Maurice Gavin for much of his pioneering work on spectroscopy with film and CCDs.  This work was published in the BAA Journal in 1996:  ‘Stellar spectroscopy with CCDs-some preliminary results’.  J. Br. Astron. Assoc. 106(1) 1996, p11-15.

    It may be old technology but as you’ve shown it can still produce useful spectra. And given it’s history I feel I should keep using it as long as I can.

    Thanks for taking the time to analyse my spectrum…I must make more effort!

    Mike.

    #584192
    Steve Brown
    Participant

    I last viewed the nova in mid-April so I’m keen to get out to see it after the increase in brightness. Hopefully tonight will stay clear! This shot is from 12 April.

    #584194
    Andrew Robertson
    Participant

    I made a visual estimate this morning at 00:25 hrs UT using 7×50 bins and put it at mag 5.4

    Andrew

    #584195
    Jeremy Shears
    Participant

    I’ve seen a naked eye observation of the nova, reported on the VSnet list. Filipp Romanov observing from Nakhodka, Russia (nr Vladivostok, 42degN) had it at 5.1 vis last night (2021 05 10.75). “It was easily seen next to the star 4 Cas against the background of the Milky Way”, Romanov notes.

    This is the first NE obs report I’ve seen. It will be interesting to hear if a BAA member gets to see it with their NE, although its position is quite challenge, along with bright skies.

    #584197
    Mike Harlow
    Participant

    An image from 23:30UT last night (10th)…nova at centre of 25 x 25 arc minute frame, north up. It may seem like overkill to image a mag 5.3 nova with a 30cm telescope (!) but I’ll be able to follow it as it fades back to mag 18,19 or less with the same set-up.  Should make a nice sequence…maybe even an animation…!?

    I did look but couldn’t see it naked-eye. But it was very nice through binoculars and the 4 inch F/5 finderscope on the main telescope. 

    Mike.

    #584199
    Hugh Allen
    Participant

    Amazingly there was a hole in the weather here in Somerset last night. The nova was incredibly bright! I had to drop the camera exposure from 300 to 90sec to avoid over exposing the H alpha emission. It is now putting on a complex display of emission lines with beautiful P Cygni profiles. The H Balmer series is still prominent whilst helium emission lines have now disappeared to be replaced by a forest of singly ionised iron emission lines some of which I’ve marked. Also very striking is the pair of singly ionised calcium emission lines down in the violet, their associated blue-shifted absorption reminiscent of the solar spectrum. A wonderful spectrum!

    #584201
    Mike Harlow
    Participant

    Ideal conditions last night to try for a higher res. spectrum; no wind and low humidity.  The result is on my members page and shows some nice detail at the blue end of the spectrum.

    Mike.

    #584203
    Jeremy Shears
    Participant

    Here’s a plot from the BAA Variable Star Section database. Looks like it is past the peak, BUT this type of nova might have a second (or third) peak. Keep watching!

    #584204
    Steve Brown
    Participant

    I managed to get to the same site on the moors and get a shot of the brighter nova. Unfortunately, it was very windy so my capture was not as good as the previous one. You can see how much brighter it is though! 

    #584212
    Jeremy Shears
    Participant

    Kato-san posted the following on VSnet overnight:

    V1405 Cas rapid fading

       Several observers have noted rapid fading.

       Itoh-san’s data:

    May 14  V=6.11, B-V=+0.57
    May 15  V=6.95, B=V=+0.27

     This fading is apparently not caused by dust formation.”

    #584216
    Jeremy Shears
    Participant

    Latest plot from VSS database

    #584279
    Mike Harlow
    Participant

    I’m still taking spectra of the nova whenever possible and the latest one from last night seems to suggest that the helium lines are coming back.  Can anyone confirm this?  I’m no expert on novae but I can’t remember seeing one like this before.  Can anyone explain what it’s doing and has this sort of behaviour been seen before? And it appears to be creeping up in magnitude again!

    Thanks,

    Mike.

    #584281
    Hugh Allen
    Participant

    Yes Mike, the HeI emission has returned amongst a few other significant changes in this wonderful nova. I’ve captured a dozen spectra since Mar 22, here’s an offset relative flux plot of a few of them showing the disappearnce and then return of the HeI emission:

    I’ve also been monitoring the expansion velocity. Until May 24 it was showing a perhaps expected gradual decline, but then briefly increased in my spectrum of May 24 around the time the nova began to brighten again. My latest spectrum from last night May 30 suggests the decline in expansion velocity has resumed accompanied by a strengthening again of the P Cygni profiles:

    The spectrum is dominated by the overwhelming relative brightness of the H alpha emission line. Here is the spectrum from May 24:

    A truly remarkable object and great fun to follow in a spectroscope!

    Cheers

    Hugh

    #584282
    Mike Harlow
    Participant

    Thanks Hugh, that’s a really interesting summary of recent changes…I’m glad I was seeing something real!  It will be fascinating to see what it does next…

    Mike.

    #584284
    Jeremy Shears
    Participant

    The BAA VSS light curve indicates the nova has been gradually brightening again over the last few days. 

    May 31.208  7.24 TG (Gary Poyner)

    May 31.995  7.1 vis (Paul Abel)

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