2020, Schwope, Axel D., Thinius, Bernd D.

We present time-resolved photometry of the cataclysmic variable PTF1J2224+17 obtained during four nights in October 2018 and January 2019 from Inastars observatory. The object is variable on a period of 103.82 min. Archival Catalina Real-Time Transient Survey (CRTS), Palomar Transient Factory, and Zwicky Transient Facility-data show frequent changes between high and low states. Based on its photometric properties and the cyclotron humps in the identification spectrum the object is certainly classified as an AM Herculis star (or polar) with a likely magnetic field strength of B∼65 MG. Its accretion duty cycle was estimated from 9 years of photometric monitoring to be about 35%.

2020, Wörpel, Hauke, Schwope, Axel D., Traulsen, Iris, Brown, Michael J.I.

Optical surveys, such as theMACHO project, often uncover variable stars whose classification requires follow-up observations by other instruments. We performed X-ray spectroscopy and photometry of the unusual variable starMACHO 311.37557.169 with XMM-Newton in April 2018, supplemented by archival X-ray and optical spectrographic data. The star has a bolometric X-ray luminosity of about 1 × 1032 erg s−1 cm−2 and a heavily absorbed two-temperature plasma spectrum. The shape of its light curve, its overall brightness, its X-ray spectrum, and the emission lines in its optical spectrum suggest that it is most likely a VY Scl cataclysmic variable.