Photometry of V725 TauP needed immediately
AAVSO Alert Notice 562November 15, 2016
Photometry of V725 TauP needed immediately
Dr. Franco Giovannelli (Istituto di Astrofisica e Planetologia
Spaziali di Roma) has requested AAVSO assistance in monitoring
V725 Tau, the Be star in the high-mass X-ray transient
A0535+26/HDE245770, in order to plan for the X-ray outburst that
follows 8 days after the optical brightening that occurs at
periastron passage.
Periastron passage will occur on 16 November 2016, so coverage is
needed beginning immediately and continuing for at least 15 days
after periastron, until December 2.
BVRI photometry - V is most important - is requested. V725 Tau has
a range of V=8.88-9.47; visual and V observations in the AAVSO
International Database show it between about 8.6 and 9.2 since
late 2011, about 8.6-8.9 as of May 2016.
Dr. Giovannelli writes: "The cadence is at least one
photometric point each night, maybe averaged with several images
(or photoelectric points if photon counting photometers are used).
However, if it is possible to get more points (2-3 in the same
night) it is of course better. We are searching for variations of
order 0.02-0.05 magnitudes. Sometimes these variations can reach
about 0.2 mag depending on the state of the O9.7 IIIe star."
Coordinates (2000.0): R.A. 05 38 54.57 Dec. +26 18 56.8
Charts with a comparison star sequence for V725 Tau may be created
using the AAVSO Variable Star Plotter (VSP, https://www.aavso.org/vsp).
Please submit observations to the AAVSO International Database
using the name V725 TAU.
This campaign is being followed on the AAVSO Observing Campaigns
webpage (https://www.aavso.org/observing-campaigns). A thread has
been created on the Campaigns and Observation Reports forum at
(https://www.aavso.org/content/v725-tau-observing-campaign).
This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.
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