Pulsational analysis of V 588 Mon and V 589 Mon observed with the MOST and CoRoT satellites

The Astrophysical Journal (Impact Factor: 6.28). 01/2011; 729(1). DOI: 10.1088/0004-637X/729/1/20
Source: arXiv

ABSTRACT The two pulsating pre-main sequence (PMS) stars V 588 Mon and V 589 Mon were
observed by CoRoT for 23.4 days in March 2008 during the Short Run SRa01 and in
2004 and 2006 by MOST for a total of ~70 days. We present their photometric
variability up to 1000 $\mu$ Hz and down to residual amplitude noise levels of
23 and 10 ppm of the CoRoT data for V 588 Mon and V 589 Mon, respectively. The
CoRoT imagette data as well as the two MOST data sets allowed for detailed
frequency analyses using Period04 and SigSpec. We confirm all previously
identified frequencies, improve the known pulsation spectra to a total of 21
frequencies for V 588 Mon and 37 for V 589 Mon and compare them to our PMS
model predictions. No model oscillation spectrum with l = 0, 1, 2, and 3
p-modes matches all the observed frequencies. When rotation is included we find
that the rotationally split modes of the slower rotating star, V 589 Mon, are
addressable via perturbative methods while for the more rapidly rotating star,
V 588 Mon, they are not and, consequently, will require more sophisticated
modeling. The high precision of the CoRoT data allowed us to investigate the
large density of frequencies found in the region from 0 to 300 $\mu$Hz. The
presence of granulation appears to be a more attractive explanation than the
excitation of high-degree modes. Granulation was modeled with a superposition
of white noise, a sum of Lorentzian-like functions and a Gaussian. Our analysis
clearly illustrates the need for a more sophisticated granulation model.


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