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A Spitzer Study of Debris Disks in the Young Nearby Cluster NGC 2232: Icy Planets Are Common around ~1.5-3 M☉ Stars

Currie, Thayne and Plavchan, Peter and Kenyon, Scott J. (2008) A Spitzer Study of Debris Disks in the Young Nearby Cluster NGC 2232: Icy Planets Are Common around ~1.5-3 M☉ Stars. Astrophysical Journal, 688 (1). pp. 597-615. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:CURapj08

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Abstract

We describe Spitzer IRAC and MIPS observations of the nearby 25 Myr old open cluster NGC 2232. Combining these data with ROSAT All-Sky Survey observations, proper motions, and optical photometry/spectroscopy, we construct a list of highly probable cluster members. We identify one A-type star, HD 45435, that has definite excess emission at 4.5-24 μm indicative of debris from terrestrial planet formation. We also identify 2-4 late-type stars with possible 8 μm excesses and 8 early-type stars with definite 24 μm excesses. Constraints on the dust luminosity and temperature suggest that the detected excesses are produced by debris disks. From our sample of B and A stars, stellar rotation appears to be correlated with 24 μm excess, a result that would be expected if massive primordial disks evolve into massive debris disks. To explore the evolution of the frequency and magnitude of debris around A-type stars, we combine our results with data for other young clusters. The frequency of debris disks around A-type stars appears to increase from ~25% at 5 Myr to ~50%-60% at 20-25 Myr. Older A-type stars have smaller debris disk frequencies: ~20% at 50-100 Myr. For these ages, the typical level of debris emission increases from 5 to 20 Myr and then declines. Because 24 μm dust emission probes icy planet formation around A-type stars, our results suggest that the frequency of icy planet formation is ηi ≳ 0.5-0.6. Thus, most A-type stars (≈1.5-3 M☉) produce icy planets.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1086/591842DOIArticle
ORCID:
AuthorORCID
Currie, Thayne0000-0002-7405-3119
Plavchan, Peter0000-0002-8864-1667
Kenyon, Scott J.0000-0003-0214-609X
Additional Information:© 2008. The American Astronomical Society. Received 2008 May 7; accepted 2008 July 10; published 2008 November 20. Print publication: Issue 1 (2008 November 20). We thank the anonymous referee for a thorough review and helpful suggestions that improved the quality of this paper. We also thank Nancy Remage Evans for advice on ROSAT archival data and Jesus Hernández for use of the SPTCLASS spectral-typing code. Finally, we thank Ken Rines for taking a spectrum of ID 18012 on short notice. This work is supported by Spitzer GO grant 1320379, NASA Astrophysics Theory grant NAG5-13278, and NASA grant NNG06GH25G. This paper makes use of the WEBDA open cluster database.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NASAGO 1320379
NASANAG5-13278
NASANNG06GH25G
Subject Keywords:circumstellar matter; open clusters and associations: individual (NGC 2232); planetary systems: formation; planetary systems: protoplanetary disks; stars: pre-main-sequence
Issue or Number:1
Record Number:CaltechAUTHORS:CURapj08
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:CURapj08
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13264
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:05 Feb 2009 20:20
Last Modified:09 Mar 2020 13:18

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