Confirmation of Monoperiodicity Above 20 Seconds for Two Blue Large-Amplitude Pulsators

Abstract

Blue Large-Amplitude Pulsators (BLAPs) are a new class of pulsating variable star. They are located close to the hot subdwarf branch in the Hertzsprung-Russell diagram and have spectral classes of late O or early B. Stellar evolution models indicate that these stars are likely radially pulsating, driven by iron group opacity in their interiors. A number of variable stars with a similar driving mechanism exist near the hot subdwarf branch with multi-periodic oscillations caused by either pressure (p) or gravity (g) modes. No multi-periodic signals were detected in the OGLE discovery light curves since it would be difficult to detect short period signals associated with higher-order p modes with the OGLE cadence. Using the RISE instrument on the Liverpool Telescope, we produced high cadence light curves of two BLAPs, OGLE-BLAP-009 ($m_{\mathrm{v}}=15.65$ mag) and OGLE-BLAP-014 ($m_{\mathrm{v}}=16.79$ mag) using a $720$ nm longpass filter. Frequency analysis of these light curves identify a primary oscillation with a period of $31.935\pm 0.0098$ mins and an amplitude from a Fourier series fit of $0.236$ mag for BLAP-009. The analysis of BLAP-014 identifies a period of $33.625\pm 0.0214$ mins and an amplitude of $0.225$ mag. Analysis of the residual light curves reveals no additional short period variability down to an amplitude of $15.20\pm 0.26$ mmag for BLAP-009 and $58.60\pm 3.44$ mmag for BLAP-014 for minimum periods of $20$ s and $60$ s respectively. These results further confirm that the BLAPs are monoperiodic.

10 pages, 9 figures, 4 tables, accepted to MNRAS

References in corpus (9)

• The Zwicky Transient Facility: System Overview, Performance, and First Results
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• Astrophysics Source Code Library
• The Zwicky Transient Facility: Science Objectives
• The Zwicky Transient Facility: Surveys and Scheduler
• Blue large-amplitude pulsators as a new class of variable stars
• Fe-bump instability: the excitation of pulsations in subdwarf B and other low-mass stars
• A new class of pulsating hot subdwarfs
• Pulsation in faint blue stars

Cited by in corpus (3)

• Shell helium-burning hot subdwarf B stars as candidates for blue large-amplitude pulsators
• Identifying Blue Large Amplitude Pulsators from Gaia DR2 & ZTF DR3
• HD 133729: A blue large-amplitude pulsator in orbit around a main-sequence B-type star