Fortnightly Fluctuations in the O-C Diagram of CS 1246

TL;DR

This study analyzes the long-term pulse timing variations of the pulsating star CS 1246, revealing a sinusoidal pattern possibly caused by a low-mass companion and a secular period decrease linked to stellar evolution.

Contribution

It presents the first detailed long-term O-C diagram analysis of CS 1246, identifying a potential companion and stellar evolution effects through pulsation timing.

Findings

Detected a 14.1-day sinusoidal O-C variation.

Observed a secular decrease in pulsation period Pdot = -1.9 x 10^-11.

Suggested presence of a low-mass companion orbiting the star.

Abstract

Dominated by a single, large-amplitude pulsation mode, the rapidly-pulsating hot subdwarf B star CS 1246 is a prime candidate for a long-term O-C diagram study. We collected nearly 400 hours of photometry with the PROMPT telescopes over a time span of 14 months to begin looking for secular variations in the pulse timings. Interestingly, the O-C diagram is dominated by a strong sinusoidal pattern with a period of 14.1 days and an amplitude of 10.7 light-seconds. Underneath this sine wave is a secular trend implying a decrease in the 371.7-s pulsational period of Pdot = -1.9 x 10^-11, which we attribute to the evolution of the star through the H-R diagram. The sinusoidal variation could be produced by the presence of a low-mass companion, with m sin i ~ 0.12 Msun, orbiting the subdwarf B star at a distance of 20 Rsun. An analysis of the combined light curve reveals the presence of a low-amplitude first harmonic to the main pulsation mode.