Correction to AAVSO Alert Notice 593

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Correction to AAVSO Alert Notice 593

文章 PTS » 週五 18 8月, 2017 08:43

Correction to AAVSO Alert Notice 593
In AAVSO Alert Notice 593 we announced a campaign on the very long period VV Cep M2Iabe+B0/2Ve binary. The amplitude of the eclipse was wrongly given as slightly under a magnitude in the V band when it is actually around 0.1 mag. This means that the VV Cep eclipse is largely undetectable visually, and is not a good candidate for visual observations. CCD and DSLR photometry, however, are still encouraged.

The eclipse depth is large only in the U band (1.8 mag.) and decreases rapidly as we go to longer wavelengths: 0.45 in B and 0.1 in V. The eclipse becomes invisible in Rc and Ic where only the flux from the supergiant is present. High precision multicolor photometry (V and/or B filters preferred) every clear night is requested beginning now and continuing for at least one month after the eclipse is over (late 2019). The eclipse will be difficult to detect even in V due to the superposition of the red supergiant pulsations (P ~145 d.). The range of VV Cep is given in VSX as 4.88 - 5.40 V, the range of the supergiant pulsations.

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 and is based on the research by Leedjärv et al. (1999) (http://adsabs.harvard.edu/abs/1999A&A...349..511L) who interpreted the eclipse timing from 1997-1998 as a result of a period change, 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

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 and Sebastian Otero.


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