A Spitzer MIPS Study of 2.5-2.0 M\odot Stars in Scorpius-Centaurus

TL;DR

This study used Spitzer MIPS observations to analyze disk presence and properties around B- and A-type stars in the Scorpius-Centaurus association, revealing lower disk fractions than F- and G-types and suggesting stellar companions influence disk evolution.

Contribution

First comprehensive MIPS-based survey of 2.5-2.0 M⊙ stars in Sco-Cen, providing new disk detections and insights into stellar mass dependence of disk properties.

Findings

Disk fractions around B+A stars are ~25%, slightly lower than F+G stars.

Identified 51 new protoplanetary and debris disks with diverse infrared luminosities.

Most 24 μm excess sources also show 12 μm excess, indicating terrestrial planet formation.

Abstract

We have obtained Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) 24 {\mu}m and 70 {\mu}m observations of 215 nearby, Hipparcos B- and A-type common proper motion single and binary systems in the nearest OB association, Scorpius-Centaurus. Combining our MIPS observations with those of other ScoCen stars in the literature, we estimate 24 {\mu}m B+A-type disk fractions of 17/67 (25+6%), 36/131 (27+4%), and 23/95 (24+5%) for Upper Scorpius (\sim11 Myr), Upper Centaurus Lupus (\sim15 Myr), and Lower Centaurus Crux (\sim17 Myr), respectively, somewhat smaller disk fractions than previously obtained for F- and G-type members. We confirm previous IRAS excess detections and present new discoveries of 51 protoplanetary and debris disk systems, with fractional infrared luminosities ranging from LIR/L\ast = 1e-6 to 1e-2 and grain temperatures ranging from Tgr = 40 - 300 K. In addition, we confirm that the 24 {\mu}m and 70 {\mu}m excesses (or fractional infrared luminosities) around B+A type stars are smaller than those measured toward F+G type stars and hypothesize that the observed disk property dependence on stellar mass may be the result of a higher stellar companion fraction around B- and A-type stars at 10 - 200 AU and/or the presence of Jupiter-mass companions in the disks around F- and G- type stars. Finally, we note that the majority of the ScoCen 24 {\mu}m excess sources also possess 12 {\mu}m excess, indicating that Earth-like planets may be forming via collisions in the terrestrial planet zone at \sim10 - 100 Myr.