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The PTI Carbon Star Angular Size Survey: Effective Temperatures and Non-sphericity

van Belle, Gerard and Paladini, Claudia and Aringer, Bernhard and Hron, Josef and Ciardi, David (2013) The PTI Carbon Star Angular Size Survey: Effective Temperatures and Non-sphericity. Astrophysical Journal, 775 (1). Art. No. 45. ISSN 0004-637X.

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We report new interferometric angular diameter observations of 41 carbon stars observed with the Palomar Testbed Interferometer. Two of these stars are CH carbon stars and represent the first such measurements of this subtype. Of these, 39 have Yamashita spectral classes and are of sufficiently high quality that we can determine the dependence of effective temperature on spectral type. We find that there is a tendency for the effective temperature to increase with increasing temperature index by ~120 K per step, starting at T_(EFF) ≃ 2500 K for C3, y, although there is a large amount of scatter in this relationship. Overall, the median effective temperature of the carbon star sample is 2800 ± 270 K and the median linear radius is 360 ± 100 R_☉. We also find agreement, on average within 15 K, with the T_(EFF) determinations of Bergeat et al. and a refinement of the carbon star angular size prediction based on V & K magnitudes is presented that is good to an rms of 12%. A subsample of our stars have sufficient {u, v} coverage to permit non-spherical modeling of their photospheres, and a general tendency for detection of statistically significant departures from sphericity with increasing interferometric signal-to-noise is seen. The implications of most—and potentially all—carbon stars being non-spherical is considered in the context of surface inhomogeneities and a rotation-mass-loss connection.

Item Type:Article
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URLURL TypeDescription Paper
van Belle, Gerard0000-0002-8552-158X
Ciardi, David0000-0002-5741-3047
Additional Information:© 2013 American Astronomical Society. Received 2013 February 28; accepted 2013 July 23; published 2013 September 3. We thank the staff of the Palomar Observatory—in particular, Kevin Rykoski—for support during our observations and the PTI Collaboration for a generous allotment of time that made this research possible.We have made extensive use of the SIMBAD database and the VizieR catalog access tool, operated by the CDS in Strasbourg, France (Ochsenbein et al. 2000). This research has made use of the AFOEV database, operated at CDS, France. This research has made use of NASA’s Astrophysics Data System. Funding for the PTI was provided to the Jet Propulsion Laboratory under its TOPS (Towards Other Planetary Systems), ASEPS (Astronomical Studies of Extrasolar Planetary Systems), and Origins programs and from the JPL Director’s Discretionary Fund. Portions of this work were performed at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. G.v.B. would like to thank H. M. Dyck for the original inspiration and direction to make interferometric observations of both carbon stars and rotationally oblate stars. G.v.B. also thanks R. Canterna for generous support during the (very) early phases of this work. Helpful input for this article resulted from discussions with and feedback from Travis Barman, Kaspar von Braun, Jay Farihi, Terry Jones, Phil Massey, and Greg Sloan. Portions of this research were conducted while G.v.B. was in residence at the European Southern Observatory; funding for this research for G.v.B. has been generously provided in part by Lowell Observatory. This material is based upon work supported by the National Science Foundation under Grant No. AST-1212203 and NASA Grant NNX13AF01G. C.P., B.A., and J.H. were supported by the Projects P23006 of the Austrian Science Fund (FWF). The research leading to these results has received funding from the European Community’s Seventh Framework Programme under Grant Agreement 226604.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
JPL Director's Discretionary FundUNSPECIFIED
Lowell ObservatoryUNSPECIFIED
FWF Der WissenschaftsfondsP23006
European Research Council (ERC)226604
Subject Keywords:infrared: stars; instrumentation: high angular resolution; instrumentation: interferometers; stars: carbon; stars: distances; stars: fundamental parameters
Issue or Number:1
Record Number:CaltechAUTHORS:20131024-151526653
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Official Citation:The PTI Carbon Star Angular Size Survey: Effective Temperatures and Non-sphericity Gerard T. van Belle et al. 2013 ApJ 775 45
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42054
Deposited By: Ruth Sustaita
Deposited On:24 Oct 2013 22:44
Last Modified:27 Nov 2019 19:07

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