A MAGELLAN MIKE AND SPITZER MIPS STUDY OF 1.5–1.0 M☉ STARS IN SCORPIUS-CENTAURUS

We obtained Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) 24 μm and 70 μm observations of 182 nearby, Hipparcos F- and G-type common proper motion single and binary systems in the nearest OB association, Scorpius-Centaurus. We also obtained Magellan/MIKE R ~ 50,000 visual spectra at 3500-10500 A for 181 candidate ScoCen stars in single and binary systems. Combining our MIPS observations with those of other ScoCen stars in the literature, we estimate 24 μm F+G-type disk fractions of 9/27 (33% ± 11%), 21/67 (31% ± 7%), and 25/71 (35% ± 7%) for Upper Scorpius (~10 Myr), Upper Centaurus Lupus (~15 Myr), and Lower Centaurus Crux (~17 Myr), respectively. We confirm previous IRAS and MIPS excess detections and present new discoveries of 41 protoplanetary and debris disk systems, with fractional infrared luminosities ranging from L IR/L * = 10–5 to 10–2 and grain temperatures ranging from T gr = 40-300 K. We searched for an increase in 24 μm excess at an age of 15-20 Myr, consistent with the onset of debris production predicted by coagulation N-body simulations of outer planetary systems. We found such an increase around 1.5 M ☉ stars but discovered a decrease in the 24 μm excess around 1.0 M ☉ stars. We additionally discovered that the 24 μm excess around 1.0 M ☉ stars is larger than predicted by self-stirred models. Finally, we found a weak anti-correlation between fractional infrared luminosity (L IR/L *) and chromospheric activity (R'HK), that may be the result of differences in stellar properties, such as mass, luminosity, and/or winds.

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