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Crossing into the substellar regime in Praesepe

Chappelle, RJ, Pinfield, DJ, Steele, IA, Dobbie, RD and Magazzu, A (2005) Crossing into the substellar regime in Praesepe. Monthly Notices of the Royal Astronomical Society, 361 (4). pp. 1323-1336. ISSN 0035-8711

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We present the results of a deep optical 2.6 deg2 survey with near-infrared (NIR) follow-up measurements of the intermediate-aged Praesepe open cluster. The survey is complete to Ic= 21.3, Z= 20.5, corresponding to M∼ 0.06 M⊙ assuming a cluster age of 0.5 Gyr. Using three to five passbands to constrain cluster membership, we identify 32 new low-mass cluster members, at least four of which are likely to be substellar. We use the low-mass census to trace the region where the sequence moves away from the NEXTGEN towards the DUSTY regime at Teff= 2200 K. In doing so, we identify four unresolved binaries, yielding a substellar binary fraction (BF) of ∼30 per cent. The BFs appear to decrease below 0.1 M⊙, in contrast to the rising fractions found in the Pleiades. We also identify a paucity of late M dwarfs, thought to be due to a steepening in the mass-luminosity relation at these spectral types, and compare the properties of this gap in the sequence to those observed in younger clusters. We note an overdensity of faint sources in the region of the so-called subcluster (possibly an older smaller cluster within Praesepe), and subsequently derive the luminosity and mass functions (MFs) for the main Praesepe cluster, revealing a turnover near the substellar boundary. We conclude by presenting astrometric measurements for low-mass Praesepe candidates from the literature and rule out as a likely foreground dwarf RPr1, hitherto thought to be a substellar member.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2005 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 19 Jan 2017 09:45
Last Modified: 04 Sep 2021 12:04
DOI or ID number: 10.1111/j.1365-2966.2005.09285.x
URI: https://researchonline.ljmu.ac.uk/id/eprint/5293
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