AAVSO: American Association of Variable Star Observers

Proposal #122

Proposer (1573) David Cowall (cowall@comcast.net) obscode: CWD
Assigned To(3663) Dirk Terrell
Date SubmittedNov. 6, 2019

Continued period analysis of BW Vul using both AAVSOnet and Lowell Observatory data completed in 2017 is underway. Pending final edits from my co-author Brian Skiff (Lowell), we are prepared to submit our manuscript to JAAVSO. Historically, this star has exhibited >20 year times of constant period of ~5 hours with abrupt period increases. A predicted period increase around 2004 did not occur. Analysis of our combined data suggests that the period has paradoxically decreased by about 10% beginning in about 2009. Further data are needed to confirm, and the Lowell Observatory has made the decision to continue observations.
I therefore propose an additional 2 years of monitoring BW Vul using the BSMs. I request rapid cadence time series of 3-6 hours using B and V band filters as telescope time permits. (Previous experience has shown that exposure times in both B and V bands worked best when they were the same which comports with this hot star radiating most of its energy in the UV.) This proposed project should generate sufficient max/min timings along with the Lowell data to clarify if this period decrease is real.
Thank you for your consideration.
David Cowall (cwd)

Target RA (H.HH) Dec (D.DD) Magnitude Telescope Observation Frequency Expiration Date Proprietary Term
BW Vul 20.906219 28.52200 6.44–6.68 No


(3663) Dirk Terrell — Nov. 13, 2019, 3:14 p.m.

W Vul's magnitude range falls nicely in the sweet spot for BSM systems. Cowall and Dick Sabo are the only ones who have contributed BV photometry to the AAVSO for this target. I don't see any technical problem with continuing the monitoring for Cowall. As the period is about 5 hours, time series are required, which do impact the available BSM time. Because the period is changing, you cannot concentrate the time series in, say, the early fall when it is in opposition. The time series need to be spaced throughout the observing season. I'd recommend one time series every couple of weeks, as doing so would lessen the impact on the northern BSMs. As you reach the end of the observing season, using two BSMs to get the required 5hrs would be nice, but I don't think we can coordinate that effort easily.

(3663) Dirk Terrell — Nov. 13, 2019, 3:14 p.m.

Above quote is from Arne.

(1573) David Cowall — Dec. 19, 2019, 9:41 a.m.


Comments on this proposal are closed.