CoRoT 223992193: A new, low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk

Abstract

We present the discovery of CoRoT 223992193, a double-lined, detached eclipsing binary, comprising two pre-main sequence M dwarfs, discovered by the CoRoT space mission during a 23-day observation of the 3 Myr old NGC 2264 star-forming region. Using multi-epoch optical and near-IR follow-up spectroscopy with FLAMES on the Very Large Telescope and ISIS on the William Herschel Telescope we obtain a full orbital solution and derive the fundamental parameters of both stars by modelling the light curve and radial velocity data. The orbit is circular and has a period of 3.8745745 ± 0.0000014 days. The masses and radii of the two stars are 0.67 ± 0.01 and 0.495 ± 0.007 M and 1.30 ± 0.04 and 1.11 +0.04 −0.05 R , respectively. This system is a useful test of evolutionary models of young low-mass stars, as it lies in a region of parameter space where observational constraints are scarce; comparison with these models indicates an apparent age of ∼3.5-6 Myr. The systemic velocity is within 1σ of the cluster value which, along with the presence of lithium absorption, strongly indicates cluster membership. The CoRoT light curve also contains large-amplitude, rapidly evolving out-of-eclipse variations, which are difficult to explain using starspots alone. The system's spectral energy distribution reveals a mid-infrared excess, which we model as thermal emission from a small amount of dust located in the inner cavity of a circumbinary disk. In turn, this opens up the possibility that some of the out-of-eclipse variability could be due to occultations of the central stars by material located at the inner edge or in the central cavity of the circumbinary disk.

Csi 2264: Characterizing Young Stars in NGC 2264 With Short-Duration Periodic Flux Dips in Their Light Curves

“…The Sung et al (1997) distance is in good agreement with a recent VLBI distance for a maser source in the cluster (d = 738 +57 −50 pc; Kamezaki et al 2014) and with a recent analysis of data for a newly identified NGC 2264 pre-main sequence EB (d = 756 ± 96 pc; Gillen et al 2014). …”

“…Figure 2 shows two eclipsing binary (EB) light curves from the 2008 NGC 2264 campaign. Figure 2(a) is the light curve for Mon-256, a dM-dM binary member of NGC 2264 (Gillen et al 2014) that is a borderline CTTS (broad and structured Hα profile; modest IR excess); this is the only EB in NGC 2264 with an IR excess presumably due to circumstellar Cody et al (2014) and the Appendix for the sources of the spectral type and Hα equivalent width (EW) data. Here we use the convention that negative values are in emission, which is opposite to the convention in Cody et al (2014).…”

New Low-mass Eclipsing Binary Systems in Praesepe Discovered by K2

“…The GP model utilizes the george package 7 (Ambikasaran et al 2014) and is used to model the out-of-eclipse (OOE) photometric data. A detailed description of GP regression is beyond the scope of this paper but the interested reader is referred to Roberts et al (2012) for a gentle introduction, Rasmussen & Williams (2006) for a more detailed entry, Aigrain et al (2012) for application to stellar light curves, and Gillen et al (2014) for application to EB light curves and cross-correlation functions.…”

Dynamic Young Stars and their Disks: A Temporal View of NGC 2264 with Spitzer and CoRoT*

“…Also displaying fading behavior but in a strictly periodic manner are the eclipsing binaries of NGC 2264. The most intriguing of these exhibits aperiodic out-of-eclipse variability indicative of a circumbinary disk ( [10]). While the dippers and eclipsing binaries display fading, the opposite behavior appears in stars that we refer to as "bursters"-objects with frequent episodes of rapidly increasing flux.…”