Introducing the Zwicky Transient Facility and the Be star variability program: a progress report at the National Central University

Abstract

The Zwicky Transient Facility (ZTF) is a modern-day wide-field optical survey to systematically explore the transient and variable sky. The ZTF utilizes the 48-inch Samuel Oschin Schmidt Telescope located at the Palomar Observatory. This telescope is equipped with a mosaic CCD camera that provides a field of view of 47 squared degrees. The allocated observing time of ZTF can be divided into partnership time (40%), public time (40%) and Caltech time (20%). The public time contains two surveys: a 3-day cadence for the Northern Sky Survey and a 1-day cadence for the Galactic Plane Survey. Astronomical communities in South East Asian countries are encouraged to explore the public ZTF data once it is released in March 2019. Taiwan’s National Central University (NCU) is one of the partnered institutions, and a major ZTF-related project carried out at NCU is the ZTF Be stars variability (ZTF-BeV) program. The main goal of our program is to study the variability of Be stars in the range of ∼13.5 to ∼20.5 magnitudes.

The ZTF Source Classification Project – II. Periodicity and variability processing metrics

“…While these surveys can be used to follow-up objects of interest, here, we are primarily interested in "untargeted" searches, i.e., searches without a priori knowledge about objects, for variable and periodic objects. These searches enable identification of populations of objects, such as cataclysmic variables (Szkody et al 2020), Be stars (Ngeow et al 2019), Cepheids and RR Lyrae, useful for studying the processes and properties of galaxy formation (Saha 1984(Saha , 1985Catelan 2009) and measuring the expansion rate of the Universe (Freedman et al 2001). In addition, they are also sensitive to rare objects, such as short-period white dwarf binaries (Burdge et al 2019a,b;Coughlin et al 2020), large-amplitude, radial-mode hot subdwarf pulsators (Kupfer et al 2019), and ultracompact hot subdwarf binaries (Kupfer et al 2020).…”

HO Puppis: Not a Be Star, but a Newly Confirmed IW And-type Star

“…In recent years, we have studied the evolutionary effect on the formation of Be stars in open clusters (Yu et al 2015(Yu et al , 2016(Yu et al , 2018 using the Palomar Transient Factory (Law et al 2009) and the intermediate Palomar Transient Factory (iPTF; Kulkarni 2013). The Zwicky Transient Facility (ZTF; Bellm et al 2019;Graham et al 2019;Masci et al 2019) came after iPTF, and its improved data can extend our investigation on the variability of Be stars (Ngeow et al 2019), especially for the Be stars and Be-star candidates at the faint end (m > 13 mag), which were largely excluded from previous works (e.g., in Labadie- Bartz et al 2017). Together with accompanying time-series spectroscopic data, we have a new opportunity to explore the fundamental time-domain nature of Be stars.…”