Weak optical activity in HDE245770/A0535+26 system
ATel #6969; F. Giovannelli (INAF-Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy), C. Rossi (Dpt of Physics, La Sapienza University, Roma, Italy), I. Bruni (INAF-Osservatorio Astronomico di Bologna, Stazione Astronomica di Loiano, Italy), G. S. Bisnovatyi-Kogan (IKI- Space Research Institute, Moscow, Russia), J. Salas Procas (Agrupación Astronómica de Huesca, Spain)
on 20 Jan 2015; 20:26 UT
Credential Certification: Corinne Rossi (corinne.rossi@uniroma1.it)
Subjects: Optical, Binary, Neutron Star
Optical photometry of HDE 245770 around the periastron passage of the neutron star A0535+26 (JD 2457043) following the ephemeris of Giovannelli et al.: 2013, A&A, 560, A1G [JD_opt-out = JD_0(2444944) +- n(111.0 +- 0.4) days]. This passage is just 109 orbital periods after the 811205-E. The results of photometry show a weak enhancement in the optical luminosity in V band of about 0.01 mag around the periastron passage. This is an indication that the X-ray pulsar is close to experience an X-ray outburst after about 8 days from the periastron passage, with an expected intensity of about 5-20 mCrab. X-ray measurements are strongly required.