Orgnaizer
ASROC
Co-orgnaizer
ASIAA
Sponsors
MOST
會徽Logo
名稱Title
2020 ASROC Annual Meeting
ASIAA Auditorium

Abstract

HO Puppis: A Sub-Luminous Hot Star with IW-And Type Light Curve

[ Oral ]

Chien-De Lee (Graduate Institute of Astronomy, National Central University); Jia-Yu Ou (Graduate Institute of Astronomy, National Central University); Po-Chieh Yu (Graduate Institute of Astronomy, National Central University); Chow-Choong Ngeow (Graduate Institute of Astronomy, National Central University); Po-Chieh Huang (Graduate Institute of Astronomy, National Central University); Wing-Huen Ip (Graduate Institute of Astronomy, National Central University); Franz-Josef Hambsch (AAVSO); Hyun-il Sung (Korea Astronomy and Space Science Institute (KASI), Bohyunsan Optical Astronomy Observatory (BOAO)); Jan van Roestel (Division of Physics, Mathematics, and Astronomy, California Institute of Technology); ZTF buliders

HO Puppis (HO Pup) was considered a Be star candidate based on its γ Cassiopeiae-type light curve, but lacked spectroscopic confirmation. Using distance measured from Gaia Data Release 2 and the spectral energy distribution (SED) fit on broadband photometry, the Be star nature of HO Pup is ruled out. In contrast, the SED of HO Pup can be well fit with a hot and sub-luminous star or, possibly, a hot subdwarf. Furthermore, based on the 28,700 photometric data points collected from various time-domain surveys and dedicated intensive monitoring observations, the light curves of HO Pup closely resembles IW And-type stars (as pointed out in Kimura et al. 2020), exhibiting characteristics such as a standstill phase, outbursts and dips. The light curve of HO Pup displays various variability timescales, including outbursts cycles ranging from 23 to 61 days, variations with periods between 3.9 days and 50 minutes during the standstill phase, and a semi-regular ∼14 day period for the dip events. We have also collected time-series spectra (with various spectral resolutions), at which Balmer emission lines and other expected spectral lines for an IW And-type star were detected (even though some of these lines were also expected to be present on Be stars). We detect Bowen fluoresces near the outburst phase and that can be used to discriminate between IW And-type stars and Be stars. Finally, despite only observing for 4 nights, the polarization variation was detected, indicating that HO Pup has significant intrinsic polarization.