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The Multiplicity of T Tauri Stars in the Star Forming Regions Taurus-Auriga and Ophiucus-Scorpius: A 2.2 µm Speckle Imaging Survey


Ghez, Andrea Mia (1993) The Multiplicity of T Tauri Stars in the Star Forming Regions Taurus-Auriga and Ophiucus-Scorpius: A 2.2 µm Speckle Imaging Survey. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/AD5X-DA38.


We present the results of a magnitude limited (K ≤ 8.5 mag) multiplicity survey of T Tauri stars (TTS) in two nearby star forming regions (SFR), Taurus-Auriga and Ophiuchus-Scorpius. Each of the 69 stars in the sample was observed at K(2.2 µm) with an infrared array camera on the Hale 5-m Telescope at Palomar Observatory and imaged using two-dimensional speckle interferometric techniques.

Thirty three companion stars were found, of which 15 were new detections. A subset of 64 observations was sensitive to all companion stars in the projected linear range 14 to 225 AU and the magnitude difference range 0.0 to 2.0 mag. We used this subset and region to study the multiplicity of TTS; the frequency of companion stars within this region is 34 ± 9%, independent of SFR. We discovered a distinction between the classical TTS (CTTS) and the weak-lined TTS (WTTS) based on the binary star frequency as a function of separation; the WITS dominate the binary star distribution at the closer separations and the CTTS populate the wider separations. The cross over occurred near 100 AU, the size typically quoted for a circumstellar disk. We suggest that all TTS begin as CTTS and become WTTS when accretion has ceased, and that the nearby companion stars act to shorten the accretion timescale in multiple star systems.

Integrated over all magnitude differences the binary star frequency in the projected linear separation range 14 to 225 AU for TTS (59 ± 16%) is a factor of 3.5 greater than that of the solar-type main sequence stars (17 ± 3%). Given the limited angular separation range that we are sensitive to, i.e., both the spectroscopic and wide binaries are missed, the rate at which binaries are detected suggests that most, if not all, TTS stars have companions. We propose that the observed overabundance of companions to TTS with respect to their older counterparts on the main sequence is an evolutionary effect; in this scheme triple and higher order TTS, which are observed at higher frequencies than for the solar-type main sequence stars, are disrupted by close encounters with another star or system of stars.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Astronomy; binary stars; high angular resolution imaging; T Tauri stars; young stars
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Awards:The Nobel Prize in Physics, 2020. Caltech Distinguished Alumni Award, 2012
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Neugebauer, Gerry
Group:Nobel Prize, Astronomy Department, Caltech Distinguished Alumni Award
Thesis Committee:
  • Neugebauer, Gerry (chair)
  • Frautschi, Steven C.
  • Prince, Thomas A.
  • Sargent, Anneila Isabel
  • Soifer, B. Thomas
Defense Date:29 September 1992
Non-Caltech Author Email:ghez (AT)
Additional Information:The Nobel Prize in Physics 2020 was divided, one half awarded to Roger Penrose "for the discovery that black hole formation is a robust prediction of the general theory of relativity", the other half jointly to Reinhard Genzel and Andrea Ghez "for the discovery of a supermassive compact object at the centre of our galaxy."
Funding AgencyGrant Number
Pacific Telesis FoundationUNSPECIFIED
Amelia Earhart FellowshipUNSPECIFIED
Record Number:CaltechETD:etd-10072004-143305
Persistent URL:
Related URLs:
URLURL TypeDescription Prize announcement (Physics, 2020)
Ghez, Andrea Mia0000-0003-3230-5055
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3971
Deposited By: Imported from ETD-db
Deposited On:08 Oct 2004
Last Modified:27 Jul 2021 00:12

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