Searching for northern roap stars: the UBC-OAN photometric survey

• Main Author: Chagnon, François
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/8021

Because they pulsate in multiple high-overtone p-modes, rapidly oscillating Ap stars (roAp) represent a very powerful tool to apply the techniques of asteroseismology, which can lead to the global properties and internal structure of stars. The majority of roAp stars are in the Southern Hemisphere, beyond the reach of northern observatories like CFHT and DAO, which have superb coude spectrographs that can help reveal additional modes and clues to the pulsation dynamics. To try to correct this imbalance, we began a systematic search for roAp stars in the Northern Hemisphere. The UBC-OAN roAp star Survey was conducted with the 84-cm and 1.5-m telescopes at the Observatorio Astronomico Nacional (OAN) in Mexico, equipped with a single-channel photoelectric photometer and a Johnson B filter. During 28 nights in July/August 1997 and 16 nights in May/June 1998, we monitored about 50 cool A-Fp stars with time resolution of less than a minute. The reduced data were Fourier analysed to search for periodic signals and we were generally sensitive to amplitudes as small as 0.3 millimagnitude in the period range of 4-15 min. We have made one detection, HD 10088, which shows two periods near 9.3 and 10.6 min, and amplitudes of about 1.6 and 1.3 mmag respectively, at the 99% confidence level. A tentative candidate, HD 3883, with period near 9.2 min and amplitude around 1.35 mmag is highlighted for further study. We also observed the known roAp star 10 Aql (HD 176232) and detected its main pulsation at a period near 11.5 min, the largest amplitude yet observed for this star. Finally, we independently confirm the newly discovered roAp star HD 122970 (Handler & Paunzen 1998) and combine our data with those of a global campaign (Handler et al. 1998) to infer some of the characteristics of this star.