The Astrophysical Journal, 661:944Y971, 2007 June 1 # 2007. The American Astronomical Society. All rights reserved. Printed in U.S.A. SPITZER LIMITS ON DUST EMISSION AND OPTICAL GAS ABSORPTION VARIABILITY AROUND NEARBY STARS WITH EDGE-ON CIRCUMSTELLAR DISK SIGNATURES Seth Redfield,1 Jacqueline E. Kessler-Silacci,2 and Lucas A. Cieza Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712; sredfi
[email protected] Received 2006 December 4; accepted 2007 March 2 ABSTRACT We present Spitzer infrared spectroscopic and photometric observations and McDonald Observatory Smith Tele- scope and AAT high spectral resolution optical observations of four nearby stars with variable or anomalous optical absorption, likely caused by circumstellar material. The optical observations of Ca ii and Na i cover a 2.8 yr baseline and extend the long-term monitoring of these systems by previous researchers. In addition, minisurveys of the LISM around our primary targets provide a reconstruction of the intervening LISM along the line of sight. We confirm that the anomalous absorption detected toward Oph is not due to circumstellar material, but to a small filamentary cloud <14.3 pc from the Sun. The three other primary targets, Car, HD 85905, and HR 10, show both short- and long-term variability, and little of the observed absorption can be attributed to the LISM along the line of sight. The Spitzer photometry and spectroscopy did not detect infrared excesses. For the three disk stars, we fit the maximum hypo- thetical infrared excess that is consistent with observed upper limits. We place upper limits on any possible fractional À6 infrared luminosity, LIR/L? < (2Y5) ; 10 .