ZTF Observations of the Disk Formation and Dissipation Process in the Eruptive Be Stars HO Puppis

Chien-De Lee^1*, Chow-Choong Ngeow¹, Po-Chieh Yu¹, Jia-Yu Ou¹, on behalf of the ZTF Collaboration²

¹Graduate Institution of Astronomy, National Central University, Taoyuan, Taiwan
²Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, USA

* Presenter:Chien-De Lee, email:cdlee@astro.ncu.edu.tw

The hot circumstellar gas in the line-emitting region of Be stars were mainly supplied by the eruptive stellar activity like matter outburst, known as decretion disk. During the outburst events, because of the obscuration along the line of sight from popped up materials, such Be stars will display dips or fading on their light curves, together with the spectroscopic brightening in Balmer lines. However, a well-covered spectroscopic follow up observations was rarely achieved, because most of the fading events last more than hundreds days. In this work, we report the finding of fading events for HO Pup, a Be star known as Gamma Cassiopeia type variable, based on a few months commissioning data from the Zwicky Transient Facility (ZTF). The g and r band light curves from ZTF clearly displayed the fading events up to 2.5 magnitudes. We supplemented the ZTF data with light curve data from ASAS-SN survey, the combined light curves clearly display eruptive variability in the past 4 years. Together with the proposed spectroscopic observations, we may witnessing the entire disk decretion process including formation and dissipation for HO Pup.

Keywords: Astrophysics, Stars: emission-line, emission-line, Be, Stars: general, Be – Stars: individual (HO puppies)