P Cygni

VALIDITY: 11. 5. 2011 - 31. 12. 2011
AUTHOR: Ernst Pollmann, Lubos Brat, 11. 5. 2011
 
The ASPA-working-community (Germany) has started in November 2008 together with the German association for variable stars BAV, an international observing campaign on photometry and spectroscopy at the "Bright Blue Variables" LBV star P Cygni.

High precision (< 0.05 mag) instrumental V-band photometry is requested to correlate with spectroscopic measurements of the equivalent width of the hydrogen (H-alpha) spectral line.

It is suspected that the photometric brightness and H-alpha line equivalent width might be correlated and variable on similar timescales. The purpose of the campaign is the continuation of an investigation of a professional Bulgarian astronomer named Nevjana Markova from the years 1998-2001. High precision (< 0.05 mag) instrumental V-band photometry is requested to correlate with spectroscopic measurements of the equivalent width of the hydrogen (H-alpha) spectral line. It is suspected that the photometric brightness and H-alpha line equivalent width might be correlated and variable on similar timescales.

This project may continue indefinitely; we ask that the star be added to the observing queues of as many observers as want to participate. Rapid time-series are not required; intra-day variability does occur, but large variations are expected to occur with timescales of weeks or longer.

This project is ideal for photoelectric observers, but may also be done by CCD observers able to observe bright stars. Please use at least a Johnson V filter; other filters may be used in addition to V, but V is the primary filter for this study.

Observers are also strongly encouraged to transform their data if at all possible. PEP data processed through the WebObs/PEPObs system are transformed automatically. CCD observers: please be very clear as to the comparison star used to perform differential photometry, and be careful to avoid saturating the variable.




P Cyg is a part of the AAVSO Photoelectric Photometry program, and has the following comparison and check stars:

Comp: SAO 69101 (= 22 Cyg, HD 188892)
RA: 19 55 51.762 , Dec: +38 29 12.14
V = 4.936 , B-V = -0.086

Chk: SAO 69803 (= 36 Cyg, HD 193369)
RA: 20 18 28.656 , Dec: +36 59 59.29
V = 5.573 , B-V = +0.056

Measurements should be sent to MEDUZA database and to Ernst Pollmann adress: ernst-pollmann@t-online.de.

Only instrumental Johnson V-Brightness are needed. There's no need to perform multi-color photometry.