Protoplanetary disk evolution and stellar parameters of T Tauri binaries in Chamaeleon I

Abstract

Aims. This study aims to determine the impact of stellar binary companions on the lifetime and evolution of circumstellar disks in the Chamaeleon I (Cha I) star-forming region by measuring the frequency and strength of accretion and circumstellar dust signatures around the individual components of T Tauri binary stars. Methods. We used high-angular resolution adaptive optics JHK s L -band photometry and 1.5-2.5 μm spectroscopy of 19 visual binary and 7 triple stars in Cha I -including one newly discovered tertiary component -with separations between ∼25 and ∼1000 AU. The data allowed us to infer stellar component masses and ages and, from the detection of near-infrared excess emission and the strength of Brackett-γ emission, the presence of ongoing accretion and hot circumstellar dust of the individual stellar components of each binary. Results. Of all the stellar components in close binaries with separations of 25-100 AU, 10 +15 −5 % show signs of accretion. This is less than half of the accretor fraction found in wider binaries, which itself appears significantly reduced (∼44%) compared with previous measurements of single stars in Cha I. Hot dust was found around 50 +30 −15 % of the target components, a value that is indistinguishable from that of Cha I single stars. Only the closest binaries (<25 AU) were inferred to have a significantly reduced fraction ( 25%) of components that harbor hot dust. Accretors were exclusively found in binary systems with unequal component masses M secondary /M primary < 0.8, implying that the detected accelerated disk dispersal is a function of mass-ratio. This agrees with the finding that only one accreting secondary star was found, which is also the weakest accretor in the sample. Conclusions. The results imply that disk dispersal is more accelerated the stronger the dynamical disk truncation, i.e., the smaller the inferred radius of the disk. Nonetheless, the overall measured mass accretion rates appear to be independent of the cluster environment or the existence of stellar companions at any separation 25 AU, because they agree well with observations from our previous binary study in the Orion Nebula cluster and with studies of single stars in these and other star-forming regions.

X-Shooter study of accretion in Chamaeleon I

“…The A V = 3.4 mag derived here is smaller than the A V > 4 mag reported by Daemgen et al (2013), while the L determined here is the same as that reported by Daemgen et al (2013) for component B. It is thus possible that in the VIS and UVB arm the spectrum of component B dominates, as Daemgen et al (2013) reported that component A has A V = 10.5 mag and it is as bright as component B in the near-infrared. The latter has only A V = 4.3 mag, according to Daemgen et al (2013), thus at optical wavelengths component B is significantly brighter than component A.…”

“…The stellar parameters (SpT, A V , L ) for all the targets discussed here have previously been derived by several studies (e.g., Luhman 2007;Spezzi et al 2008;Daemgen et al 2013;Frasca et al 2015, cf. Tables A.1-A.2).…”

“…It is thus possible that in the VIS and UVB arm the spectrum of component B dominates, as Daemgen et al (2013) reported that component A has A V = 10.5 mag and it is as bright as component B in the near-infrared. The latter has only A V = 4.3 mag, according to Daemgen et al (2013), thus at optical wavelengths component B is significantly brighter than component A.…”

“…It is reported to be a close binary (0.28 separation) of two objects with the same SpT (M0.5, Daemgen et al 2013). Therefore, both objects have probably been included in the slit and are not resolved.…”

Evolution of the T Tauri star population in the Lupus association

“…Recently, Daemgen et al (2013) have investigated the impact of binary companions on the evolution of circumstellar disks and concluded that they evolve faster in binary systems. In this context, we decided to remove the binaries (and multiple systems) from our sample to inspect this point.…”