Alert Notice 747: V627 Peg photometry and spectroscopy requested

Note: Please continue observations of V627 Peg until further notice.  -  Elizabeth O. Waagen, December 6, 2021

July 20, 2021

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns and Observation Reports:
- Cataclysmic Variables:
- Spectroscopy:

Please subscribe to these threads if you are participating in the campaign so you can be updated by the astronomer and by HQ. Join in the discussion or ask questions there!

Dr. Christian Knigge (University of Southampton) has requested AAVSO observers' assistance in obtaining photometry and spectroscopy of the WZ Sge-type cataclysmic variable V627 Peg, which is in outburst. He writes:

“We're currently trying to get a multi-wavelength campaign spanning radio, optical, UV and X-ray observations off the ground. We're particularly excited by the fact that this is such a nearby object, which means that there is a good chance we'll be able to monitor all of these wavebands carefully, including even radio! That means we may be able to link up different features across the bands -- e.g. we know the radio tends to flare (probably due to a jet turning on and off), and we'd love to know whether this goes hand in hand with other things, e.g. the development of superhumps, or color evolution in the optical, or X-ray emission.

“[We encourage] observers to get on this system as soon as possible and to get as good a coverage of it as possible. Since it's so bright, high-cadence, multi-band imaging should be possible for at least some of the observers, and that would be fantastic. (High cadence meaning, really, as fast as you can go, without being dominated by overheads due to readout. Time-scales of the order of seconds would be great, for example.) Multi-band would be good because we're particularly interested in colour evolution.”

V and B filters have highest priority, in that order. Unfiltered observations reduced to a V zeropoint (CV) and DSLR observations are also welcome. Visual observations are welcome to supplement the light curve. V627 Peg has a V range of 8.8 - 16.3; observations reported to the AAVSO International Database indicate that as of 2021 July 20.0399 UT it was 9.85 V +/- 0.037 (M. Larsson, Malmoe, Sweden). AAVSO observations show previous outbursts occurred in 2010 and 2014.

Spectroscopy is also requested - “this would be a perfect target to flex those [spectroscopy] muscles. At peak, it'll be about 9th mag, so bright enough to yield good spectra with even relatively modest-sized scopes. It would be ideal to monitor the system into the decline spectroscopically -- we expect to see an evolution there from absorption-line dominated to emission-line dominated, and -- here again -- we'd love to know whether/how that transition connects to other transitions at other wavelengths.

“If it's possible to get decent S/N in, say, 5 - 10 minutes, then probably something like a few hour runs at highish resolution would be great, because then we can see if there is something one can do in terms of a radial velocity study. (It would be great if wavelength calibrations could be done, e.g. via a lamp or by observing an RV standard.) If that's too much, even just low-resolution spectra at whatever cadence -- even if it's just one or a few per night -- would be great for checking when and how the spectrum changes from absorption to emission. For high resolution, the focus would probably want to be on the Hbeta, He II 4686 region or possibly Halpha.”

Please continue to observe V627 Peg for at least 30 days after it has returned to minimum. Updates about the subsequent duration of the campaign, and any revisions to observing instructions, will be posted in the AAVSO forum threads given above - please subscribe to those threads to stay informed.

The AAVSO Sequence Team notes that there is a V=15.1 star 2.5” to the NW of V627 Peg, and that V627 Peg itself is a fast moving object heading away from the optical companion toward the northeast. Be careful to identify V627 Peg correctly as it fades.

Coordinates (2000.0): R.A. 21 38 06.63   Decl. +26 19 56.0 (from VSX page for V627 Peg)

Charts: Charts with comparison stars for V627 Peg may be created using the AAVSO Variable Star Plotter (VSP). As noted above, please be aware of the V=15.1 star 2.5” NW of the variable.

Submit observations: Please submit observations using the name V627 PEG to the AAVSO International Database or the AAVSO Spectroscopy Database as appropriate (see below for links).

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material provided by Christian Knigge.


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