Multiplicity of disc-bearing stars in Upper Scorpius and Upper Centaurus-Lupus. (2018)
Keywords :
techniques radial velocities - protoplanetary discs - binaries: spectroscopic - stars: formation - stars: pre-main-sequence
Abstract:We present observations of disc-bearing stars in Upper Scorpius (US) and Upper Centaurus-Lupus (UCL) with moderate resolution spectroscopy in order to determine the influence of multiplicity on disc persistence after ~5-20Myr. Discs were identified using infrared (IR) excess from the Wide-field Infrared Survey Explorer (WISE) survey. Our survey consists of 55 US members and 28 UCL members, using spatial and kinematic information to assign a probability of membership. Spectra are gathered from the ANU 2.3m telescope using the Wide Field Spectrograph (WiFeS) to detect radial velocity variations that indicate the presence of a companion. We identify two double-lined spectroscopic binaries, both of which have strong IR excess. We find
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We selected candidate US and UCL members using kinematic and
photometric data from UCAC4, 2MASS, USNO-B, and APASS (Monet et al.
2003AJ....125..984M, Cat. I/284; Skrutskie et al. 2006AJ....131.1163S,
Cat. VII/233; Henden et al. 2012; Zacharias et al.
2013AJ....145...44Z, Cat. I/322) using the Bayesian membership
selection method of Rizzuto et al. (2011MNRAS.416.3108R, Cat.
J/MNRAS/416/3108) and Rizzuto et al. (2015MNRAS.448.2737R, Cat.
J/MNRAS/448/2737), which uses kinematic and spatial information to
assign membership probabilities. We also used the photometry and a
15Myr pre-main sequence isochrone (Siess, Dufour & Forestini
2000A&A...358..593S) to estimate each candidate member's distance.
This selection was magnitude limited, and covered all stars in the
UCAC4 catalogue with 10<V<16, and comprised of several thousand
candidate members with membership probability greater than 25 per
cent.
To obtain spectroscopic data to determine the radial velocities of our
targets, we used the Wide Field Spectrograph (WiFeS) (Dopita et al.
2007Ap&SS.310..255D). WiFeS is an integral field spectrograph on the
Australian National University 2.3m Telescope at Siding Spring
Observatory. We use this instrument to search for RV variation
overtime for our targets. The instrument consists of a blue camera
with spectral range 329-558nm and red camera with spectral range
529-912nm.
Data for our targets were collected from 2013 June to 2017 July. Our
observations include Ne-Ar arc exposures every 15-30 min to
characterize the wavelength scale variation of the instrument over the
night due to temperature fluctuations. The WiFeS R ~7000 grating is
used to perform RV measurements. We observe RV standards with
well-characterized velocities of various spectral types.
