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Session 59 - Pulsating/Variable Stars.
Display session, Wednesday, June 12
Great Hall,

[59.11] The MACHO Project LMC Variable Star Inventory: New R Coronae Borealis Stars

G. C. Clayton (CASA, Univ. of Colorado), D. L. Welch (McMaster), D. Kilkenny (SAAO), C. Alcock, D. Alves, D. P. Bennett, K. H. Cook, S. L. Marshall, D. Minniti (LLNL/CfPA), R. A. Allsman (ANU), A. Becker, M. R. Pratt, C. W. Stubbs (UW/CfPA), T. S. Axelrod, K. C. Freeman, B. A. Peterson, A. W. Rodgers (MSSSO), P. J. Quinn (ESO), K. Griest, J. A. Guern, M. J. Lehner (CfPA/UCSD), W. Sutherland (Oxford)

We report the discovery of several new R Coronae Borealis (RCB) star candidates in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The identification of two stars has been confirmed spectroscopically. One is a cool RCB star (T_eff\sim 5000 K) characterized by very strong Swan bands of C_2 and violet bands of CN, and weak or absent Balmer lines, G-band and ^12C^13C bands. The second star is an example of a hot RCB star of which only 3 were previously known to exist in the Galaxy and none in the LMC. Its spectrum is characterized by several C II lines in emission. Both stars have shown deep declines of \Delta V \ge 4 mag in brightness. The new stars are significantly fainter at maximum light than the three previously known LMC RCB stars. The amount of reddening toward these stars is somewhat uncertain but both seem to have the absolute luminosities, M_V, about half a magnitude fainter than the other three stars. Estimates of M_Bol find that the hot RCB star lies in the range of the other three stars while the cool RCB star is fainter. The two cool LMC RCB stars are the faintest at M_Bol. The discovery of these two new stars brings to five the number of known RCB stars in the LMC and demonstrates the utility of the MACHO photometric database for the discovery of new RCB stars.

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