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Alert Notice 593: VV Cep eclipse monitoring requested

Edit: The information given in this alert notice has been updated to correct eclipse depth values. Please see AAVSO Alert Notice 594

August 16, 2017: The AAVSO is requesting monitoring of the eclipse of the very bright Algol-type eclipsing binary variable VV Cep, predicted to have begun in June 2017 and to conclude in November 2019.

VV Cep consists of a M2Iabe primary star and a B0/2Ve secondary star, with mass transfer occurring from the M supergiant to the Be star. Its eclipse period is 20.53 years (7498 days), making it one of the longest-period eclipsing binaries known. Its last eclipse occurred in 1996-1999.

Multicolor photometry (V and Rc filters preferred) is requested beginning now and continuing for at least one month after the eclipse is over (late 2019). A few observations per night are requested during the eclipse, and then nightly snapshots for a month after the eclipse is over. Visual observations are welcome.

The timing and length of VV Cep eclipses has varied in the past, with eclipses as short as 650 days and as long as 1000 days. The ephemeris for the 2017-2019 eclipse given here is from VSX. It was calculated by Sebastián Otero, who took a period change into account in his calculations, a change not included in ephemerides that predict the eclipse to begin in August.

Epoch (JD)    Start                Midpoint           End
2458356        01 Jun 2017    25 Aug 2018    18 Nov 2019

The range of VV Cep is given in VSX as 4.88 - 5.40 V. Observations in the AAVSO International Database show that, out of eclipse, VV Cep varies between 4.91 V and 5.2-5.3 V. In V, the eclipse may be slightly under a magnitude in depth.

Dr. Ernst Pollmann (Active Spectroscopy in Astronomy) has compiled a project page (http://astrospectroscopy.de/projects.html) containing links to several campaigns on VV Cep to observe various aspects of the eclipse. On that page, scroll down to find No. 9 VV Cep.

Coordinates (2000):   R.A. 21 56 39.14   Dec. +63 37 32.0

Charts: An annotated AAVSO 'a' scale chart with recommended comparison stars for the eclipse of VV Cep is linked to here. Please use the stars indicated by the arrows (43: B=4.630 V=4.29 Rc=4.001; 55: B=7.040  V=5.52  Rc=4.281). If these stars are not within the field of view, please use the stars labeled C1 and C2. This modified AAVSO chart is from the VV Cep brightness campaign being coordinated by Frank Walter of the BAV (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V.). The AAVSO has chosen to use these comparison stars for compatibility with the BAV campaign.

Submit observations: Please submit observations to the AAVSO International Database using the name VV CEP.  Be sure to report the comparison stars used.

This campaign is being followed on the Campaigns and Observation Reports Forum at https://www.aavso.org/vv-cep-observing-campaign.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

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