NOAO >   Observing Info >   Approved Programs >   2012A-0195

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Proposal Information for 2012A-0195


PI: Peter Allen, University of Pennsylvania, prallen137@gmail.com
Address: Physics Department, 209 South 33rd Street, Philadelphia, PA 19104, USA

CoI: Laird Close, University of Arizona

Title: A Multi-Epoch Survey for Faint, Close, Low-Mass Tertiaries to Nearby Spectroscopic Binaries: Follow-up Confirmation

Abstract: We propose to use NGS AO Altair/NIRI imaging to carry out follow-up observations of candidate common proper motion (CPM) companions discovered by our previous Gemini Altair/NIRI programs during 2009A to 2010B. Recent star formation simulations and observations have demonstrated that main sequence spectroscopic binaries (SB) have an enhanced wide (>30 AU) companion rate compared to single stars. This rate has been found to be from 60% to nearly 100% depending on the period of the SB. We took advantage of this high tertiary companion rate to look for ultracool companions with separations from a few AU (>0\farcs1) to a few hundred AU (<20\arcsec). Six new candidates from our two epoch observations likely comprise one M dwarf, two L dwarfs, a L/T transition dwarf, a T dwarf, and a T_eff < 500 K brown dwarf with signs of CH4 absorption. A seventh candidate was just confirmed as a physical L dwarf companion. Here we ask for JHK_s imaging, which will determine if the candidates show colors consistent with the predicted type of companion and will provide indisputable confirmation of the previously measured CPM. These CPM companions are the highlight discoveries of our previous 55 hours of search programs. The photometric and spectroscopic characterization of these interesting objects will significantly inform our, to date, poor understanding of low-mass companions to SB systems. The fact that our one follow-up observation discovered a real L dwarf companion means that likely all 6 objects are real companions. We just need the NIR colors to be sure that they are very red, hence real, ultracool companions.


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