Outburst of the WZ Sge star V627 Peg

Forums Variable Stars Outburst of the WZ Sge star V627 Peg

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    David Boyd

    The WZ Sge star V627 Peg has been reported in outburst by Maeda Yutaka (Japan) confirmed in observations by the ASAS-SN Sky Patrol and ZTF.

    Christian Knigge (Southampton U) is putting together a multi-wavelength campaign to study the outburst. Amateur data will be welcome.

    Last night (15th July) I observed the star at V magnitude 10.48 and rising. The following spectrum was recorded with a LISA spectroscope on a C11 scope.


    Gary Poyner

    I recorded it at 10.51CV on a SLOOH image on Jly 16.158 UT.

    There is a close 151 star a couple of arc seconds away, so my measure was of a blended object.  Very difficult at minimum visually to get a good measure.


    Jeremy Shears

    Christian Knigge (U of Southampton) notes:

    “I just wanted to flag up that we’re
    currently still trying to follow the outburst of V627 Peg — one of the
    closest WZ Sge stars that erupts only every 5 years (at best) and has
    just recently gone off. I’m involved in a campaign to get X-ray,
    ultraviolet and radio coverage of the outburst, alongside, of course,

    The thing is really bright in outburst — V ~ 8-10 or so — so it’s
    great for high-cadence photometry or even spectroscopy, for anybody who
    has a spectrograph. For our campaign, any long sequences would be
    useful. Ideally we’d have long runs covering the full outburst in 2
    filters, say B and V.

    In terms of spectra, time-resolved spectroscopy would be awesome — I’m
    particularly interested in the transition from a pure absorption line
    spectrum near plateau to a pure emission line spectrum in quiescence.
    Where and how fast does this happen, and does it correlate with other
    things happening at other wavelengths.

    Christian “

    David Boyd

    Recent V-band data on the AAVSO website show strong modulation close to the orbital period of 0.05408978(5) d reported by John Thorstensen.

    Peranso PDM analysis of 3 night’s data.

    Spectra calibrated in absolute flux follow the changing brightness of the star with the Balmer lines evolving from initally pure absorption to now having emission cores.


    Robin Leadbeater

    Christian Knigge also suggested following the  He II / H beta region at higher resolution looking for RV variations. Here is 4 hour time series at 10 minutes cadence from last night with the LHIRES at R~2000 . Not sure there is much to see above the noise though (SNR in a 10 min exposure is ~50)

    The average 

    and  the individual spectra (rectified)

    Robin Leadbeater

    The intensity of the emission component of the Balmer lines and of the He II emission which have gradually been increasing has significantly reduced tonight. Is this expected behaviour or signs of a further outburst ?



    David Boyd

    I confirm what Robin reported above that the emission cores of the Balmer lines have progressively disappeared over the past 4 days. The spectral profile and flux of the star are now very similar to what they were on 15th July shortly after the outburst was detected.


    Robin Leadbeater

    After a brief plateau of a few days the brightness  started dropping rapidly last night and the emission in the core of the Balmer absorption lines has increased.


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