<i>Herschel</i>PACS and SPIRE observations of TW Hydrae association brown dwarf disks

Riaz, B.; Gizis, John E.

doi:10.1051/0004-6361/201219524

Cited by 7 publications

(13 citation statements)

References 37 publications

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“…There are some differences between our estimates of f d /f * and those in the literature, but not by enough to change our disc classifications. For the 12 objects with W 1−W 4 > 1.0, in all but two cases there is broad agreement and agreement on the nature of the disc: for ǫ Cha 17 and 2M J1207 (targets H and L) we find primordial discs whereas in the literature these were reported as transitional and debris discs, respectively (Manoj et al 2011 andGizis 2012). Four of the seven objects with W 1 − W 4 < 1.0, but significant W 4 excess have been reported in previous work as either confirmed debris discs or debris disc candidates, which is in broad agreement with our classification scheme.…”

Section: Comparison With the Literaturesupporting

confidence: 59%

“…Target L, 2MASSJ12073346-3932539 -Literature searches for any additional evidence for a disc revealed that this target was the brown dwarf 2M1207, which is host to the giant exoplanet candidate 2M1207b (Mamajek 2005;Barman et al 2011). Riaz & Gizis (2012) suggest that 2M1207 has a transition disc with an inner disc evacuation due to grain growth/dust settling, however our measurement of f d /f * > 1.0 clearly indicates a primordial disc. Target M, 2MASSJ08173943−8243298 -This target is reported as a likely new member of the BPMG in Malo et al (2014b).…”

Section: Acknowledgementsmentioning

confidence: 76%

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A WISE-based search for debris discs amongst M dwarfs in nearby, young, moving groups

Binks¹,

Jeffries²

2017

Monthly Notices of the Royal Astronomical Society

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We present a search for debris discs amongst M-dwarf members of nearby, young (5-150 Myr) moving groups (MGs) using infrared (IR) photometry, primarily from the Wide Infrared Survey Explorer (W ISE). A catalogue of 100 MG M-dwarfs that have suitable W ISE data is compiled and 19 of these are found to have significant IR excess emission at 22 µm. Our search is likely to be complete for discs where the ratio of flux from the disc to flux from the star f d /f * > 10 −3 . The spectral energy distributions are supplemented with 2MASS photometry and data at longer wavelengths and fitted with simple disc models to characterise the IR excesses. There is a bimodal distribution -twelve targets have W 1 − W 4 > 3, corresponding to f d /f * > 0.02 and are likely to be gas-rich, primordial discs. The remaining seven targets have W 1 − W 4 < 1 (f d /f * 10 −3 ) and include three objects with previously known or suspected debris discs and four new debris disc candidates that are all members of the Beta Pic MG. All of the IR excesses are identified in stars that are likely members of MGs with age < 30 Myr. The detected debris disc frequency falls from 13 ± 5 per cent to < 7 per cent (at 95 per cent confidence) for objects younger or older than 30 Myr respectively. This provides evidence for the evolution of debris discs on this timescale and does not support models where the maximum of debris disc emission occurs much later in lower-mass stars.

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Section: Comparison With the Literaturesupporting

confidence: 59%

Section: Acknowledgementsmentioning

confidence: 76%

A WISE-based search for debris discs amongst M dwarfs in nearby, young, moving groups

Binks¹,

Jeffries²

2017

Monthly Notices of the Royal Astronomical Society

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“…An attempt by Riaz & Gizis (2012) to detect brown dwarf disks with Herschel in the TW Hydrae association (∼10 Myr) has not been successful. Based on the derived upper limits at far-IR wavelengths and radiative transfer modelling, they estimate that the TW Hydrae brown dwarf disks have a lower mass than younger counterparts.…”

Section: Comparison To Other Disk Studiesmentioning

confidence: 99%

Herschelsurvey of brown dwarf disks inρOphiuchi

Oliveira

Ábrahám

Márton

et al. 2013

A&A

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Context. Young brown dwarfs are known to possess circumstellar disks, a characteristic that is fundamental to the understanding of their formation process, and raises the possibility that these objects harbour planets. Aims. We want to characterise the far-IR emission of disks around the young brown dwarf population of the ρ Ophiuchi cluster in LDN 1688. Methods. Recent observations of the ρ Ophiuchi cluster with the Herschel Space Observatory allow us to probe the spectral energy distribution (SED) of the brown dwarf population in the far-IR, where the disk emission peaks. We performed aperture photometry at 70, 100, and 160 µm, and constructed SEDs for all previously known brown dwarfs detected. These were complemented with ancillary photometry at shorter wavelengths. We compared the observed SEDs to a grid of synthetic disks produced with the radiative transfer code MCFOST, and used the relative figure of merit estimated from the Bayesian inference of each disk parameter to analyse the structural properties. Results. We detected 12 Class II brown dwarfs with Herschel, which corresponds to one-third of all currently known brown dwarf members of ρ Ophiuchi. We did not detect any of the known Class III brown dwarfs. Comparison to models reveals that the disks are best described by an inner radius between 0.01 and 0.07 AU, and a flared disk geometry with a flaring index between 1.05 and 1.2. Furthermore, we can exclude values of the disk scale-height lower than 10 AU (measured at a fiducial radius of 100 AU). We combined the Herschel data with recent ALMA observations of the brown dwarf GY92 204 (ISO−Oph 102), and by comparing its SED to the same grid of disk models, we derived an inner disk radius of 0.035 AU, a scale height of 15 AU with a flaring index of β ∼ 1.15, an exponent for dust settling of −1.5, and a disk mass of 0.001 M . This corresponds to a disk-to-central object mass ratio of ∼1%. Conclusions. The structural parameters constrained by the extended SED coverage (inner radius and flaring index) show a narrow distribution for the young brown dwarfs detected in ρ Ophiuchi, suggesting that these objects share the same disk evolution and, perhaps, formation.

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“…1 shows the 17 objects that qualify. Spectral class indices (α = d log λF λ /d log λ) are calculated following the procedure in Riaz & Gizis (2012) and all objects with W 1 − W 4 > 1.0 are either class II or III (see Table 1). …”

Section: Identifying and Characterising Disk Excessmentioning

confidence: 99%

The Debris Disk Fraction for M-dwarfs in Nearby Young Moving Groups

Binks

2015

Proc. IAU

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Abstract.I present the first substantial work to measure the fraction of debris disks for M-dwarfs in nearby moving groups (MGs). Utilising the AllW ISE IR catalog, 17 out of 151 MG members are found with an IR photometric excess indicative of disk structure. The M-dwarf debris disk fraction is 6 per cent in MGs younger than 40 Myr, and none are found in the groups older than 40 Myr. Simulations show, however, that debris disks around M-dwarfs are not present above a W ISE W 1 − W 4 colour of ∼ 2.5, making calculating the absolute disk fractions difficult. The debris disk dissipation timescale appears to be faster than for higher-mass stars, and mechanisms such as enhanced stellar wind drag and/or photoevaporation could account for the more rapid decline of disks observed amongst M-dwarfs.

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HerschelPACS and SPIRE observations of TW Hydrae association brown dwarf disks

Cited by 7 publications

References 37 publications

A WISE-based search for debris discs amongst M dwarfs in nearby, young, moving groups

A WISE-based search for debris discs amongst M dwarfs in nearby, young, moving groups

Herschelsurvey of brown dwarf disks inρOphiuchi

The Debris Disk Fraction for M-dwarfs in Nearby Young Moving Groups

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