Finding proto-spectroscopic binaries

Abstract

The formation of spectroscopic binaries (SB) may be a natural byproduct of star formation. The early dynamical evolution of multiple stellar systems after the initial fragmentation of molecular clouds leaves characteristic imprints on the properties of young, multiple stars. The discovery and the characterization of the youngest SB will allow us to infer the mechanisms and timescales involved in their formation. Our work aims to find spectroscopic companions around young stellar objects (YSO). We present a near-IR high-resolution (R ∼ 60 000) multi-epoch radial velocity survey of seven YSO in the star-forming region (SFR) ρ Ophiuchus. The radial velocities of each source were derived using a two-dimensional cross-correlation function, using the zero-point established by the Earth's atmosphere as reference. More than 14 spectral lines in the CO Δν = (0−2) bandhead window were used in the cross-correlation against LTE atmospheric models to compute the final results. We found that the spectra of the protostars in our sample agree well with the predicted stellar photospheric profiles, indicating that the radial velocities derived are indeed of stellar nature. Three of the targets analyzed exhibit large radial velocity variations during the three observation epochs. These objects -pending further confirmation and orbital characteristics -may become the first evidence for proto-spectroscopic binaries, and will provide important constraints on their formation. Our preliminary binary fraction (BF) of ∼71% (when merging our results with those of previous studies) is in line with the notion that multiplicity is very high at young ages and therefore a byproduct of star formation.

A Radial Velocity Survey of Embedded Sources in the Rho Ophiuchi Cluster

“…WL17. The radial velocities we derive from spectra obtained in 2001 and 2012 are in good agreement but not consistent with the values reported by Viana Almeida et al (2012). High spatial resolution ALMA images reveal a transition disk in a disk/envelope system, suggesting that planets can form at an early embedded stage (Sheehan & Eisner 2017).…”

Evidence of a substellar companion around a very young T Tauri star

“…Laboratory wavelength zero-points of each telluric spectral line were collected from the HITRAN database (Rothman & Gordon 2009). The RVs in this study were derived using the Figueira et al (2010c) pipeline and its adapted version to young stars developed by Viana Almeida et al (2012). Both versions of the pipeline are based on a two-dimensional (2D) cross-correlation function (CCF) inspired by TODCOR (Mazeh & Zucker 1992).…”

Stellar Multiplicity

“…Based on 2 or 3 measurements per systems (Viana Almeida et al 2012) or com-paring a protostar radial velocity to that of gas in its parent cloud (Covey et al 2006), small-scaled surveys suggest that some systems tighter than a few AU have already formed by the Class I phase, but their interpretation remains ambiguous.…”