Dust discs around intermediate mass and Sun-like stars in the 16 Myr old NGC 1960 open cluster

TL;DR

This study analyzes infrared data from the 16 Myr old NGC 1960 cluster, revealing debris discs around intermediate-mass stars and setting limits on excess emission around Sun-like stars, informing planet formation timelines.

Contribution

First comprehensive infrared analysis of NGC 1960 showing debris disc prevalence around different stellar types at a key planet formation epoch.

Findings

>30% of B-F5 stars have 24um excess emission.

>23% of F6-K9 stars have 24um excess emission.

No confirmed near-infrared excess around Sun-like stars.

Abstract

We present an analysis of Spitzer IRAC (3.6--8um) and MIPS (24um) imaging of members of the 16(+10/-5)Myr old open cluster NGC 1960 (M36). Models of terrestrial planet formation indicate that rocky planets are likely to achieve their final masses at around 10-30Myr, and thus this cluster is at an interesting epoch for planet formation. We find 21 B-F5 type stars and 14 F6-K9 type stars which have 24um excess emission, and thus determine that >30% of B-F5 type stars and >23% of F6-K9 type stars in this cluster have 24um excess emission. These excess frequencies are similar to those observed in other clusters of similar age. Three early type stars have excesses at near-infrared wavelengths. Analysis of their SEDs confirms that these are true debris discs and not remnant primordial or transitional discs. None of the 61 sun-like stars have confirmed near-infrared excess, and we can place a limit on the frequency of 8um excess emission around sun-like stars of <7%. All of the detected excesses are consistent with emission from debris discs and are not primordial.