[Paper Review] Amplitude variations of the CoRoT Be star 102719279

J. Gutiérrez–Soto, T. Semaan+4 more|arXiv (Cornell University)|Oct 10, 2010

Stellar, planetary, and galactic studies1 references3 citations

TL;DR

This study analyzes amplitude variations in the CoRoT Be star 102719279 using high-precision photometry from two CoRoT runs, revealing that the two dominant pulsation frequencies (1.143 and 2.324 c d⁻¹) reach maximum amplitude just before observed outbursts or flux fadings. The synchronized amplitude maxima of these non-radial pulsation modes precede mass ejection events, supporting a link between pulsational activity and disk formation in Be stars.

ABSTRACT

The Be star 102719279 is an interesting target observed with CoRoT during two runs, giving us the possibility to study the stability of the detected frequencies and to search for any correlation with outburts, as it was recently found in the Be star HD 49330 (Huat et al. 2009). The light curve of the star 102719279 shows fadings, multiperiodicity, stable and transient frequencies, etc. The short-term variations of the light curve are probably produced by non-radial pulsations together with some material that is ejected from the star, which produces the transient frequency. It is should be noted that the two main frequencies are synchronized and have the maximum amplitude just before the outburst.

Motivation & Objective

• To investigate the correlation between amplitude variations of non-radial pulsations and outbursts in the Be star 102719279.
• To determine whether the timing of outbursts is linked to the phase or amplitude of pulsation modes.
• To assess the stability and evolution of pulsation frequencies across two CoRoT observation runs (IR and LRA1).
• To explore the role of non-radial pulsations in triggering mass ejection events that form the circumstellar disk.

Proposed method

• Performed standard Fourier analysis on CoRoT light curves from two observation runs (IR: 57 days, LRA1: 131 days) to detect significant frequencies.
• Applied Morlet wavelet analysis with 1 μHz frequency resolution (≈2.5-day time resolution) to track time-varying amplitudes of key frequencies.
• Used synthetic spectral fitting (GIRFIT) with SYNSPEC and ATLAS9 models to derive stellar parameters: T_eff = 20000 ± 1500 K, log g = 3.5 ± 0.2 dex, V sin i = 270 ± 20 km s⁻¹.
• Identified transient frequencies and compared their amplitudes with flux fadings, interpreted as obscuration by ejected material.
• Cross-referenced photometric results with low- and medium-resolution spectroscopy (CAFOS, VLT-FLAMES) to confirm stellar and circumstellar features.
• Compared findings with previous studies on HD 49330 to test consistency of the pulsation-outburst correlation.

Experimental results

Research questions

• RQ1 Do the amplitudes of the dominant pulsation frequencies in 102719279 vary over time, and if so, how do these variations correlate with observed outbursts?
• RQ2 Is there a temporal relationship between the maximum amplitude of non-radial pulsation modes and the onset of flux fadings (interpreted as mass ejections)?
• RQ3 Are the detected frequencies stable between the two CoRoT observation runs, or do they show significant evolution?
• RQ4 Can the observed transient frequencies (e.g., 0.988 c d⁻¹) be linked to material in the circumstellar disk during outbursts?
• RQ5 Do the pulsation modes in 102719279 exhibit synchronized behavior that precedes outburst events, as seen in HD 49330?

Key findings

• The two main pulsation frequencies, 1.143 c d⁻¹ and 2.324 c d⁻¹, reach their maximum amplitudes just before flux fadings in both the IR and LRA1 datasets.
• The amplitude maxima of these two frequencies are synchronized and occur immediately prior to the onset of outbursts, supporting a causal link between pulsations and mass ejection.
• A transient frequency at 0.988 c d⁻¹ is detected only in the IR dataset and reaches maximum amplitude just after the main frequencies, coinciding with the start of flux decrease.
• The wavelet analysis reveals significant amplitude modulation of the main frequencies over time, with multiple modes appearing and disappearing across the two observation runs.
• The LRA1 dataset shows higher frequency resolution and no exact harmonic relationships between dominant frequencies, suggesting complex, non-linear pulsation behavior.
• The observed amplitude variations and outbursts are consistent with a model where non-radial pulsations drive material ejection, forming the circumstellar disk.