Browsing by Author "Sibthorpe, B."

Now showing 1 - 7 of 7
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    An unbiased study of debris discs around A-type stars with Herschel
    (2014) Thureau, N. D.; Grebas, J. S.; Matthews, B. C.; Kennedy, G.; Phillips, N.; Haworth-Booth, Mark; Duchêne, G.; Horner, J.; Rodríguez, D. R.; Sibthorpe, B.; Wyatt, M. C.
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    DOES THE PRESENCE OF PLANETS AFFECT THE FREQUENCY AND PROPERTIES OF EXTRASOLAR KUIPER BELTS? RESULTS FROM THE HERSCHEL DEBRIS AND DUNES SURVEYS
    (2015) Moro-Martin, A.; Marshall, J. P.; Kennedy, G.; Sibthorpe, B.; Matthews, B. C.; Eiroa, C.; Wyatt, M. C.; Lestrade, J. -F.; Maldonado, J.; Rodriguez, D.; Greaves, J. S.; Montesinos, B.; Mora, A.; Booth, M.; Duchene, G.; Wilner, D.; Horner, J.
    The study of the planet-debris disk connection can shed light on the formation and evolution of planetary systems. and may help "predict" the presence of planets around stars with certain disk characteristics. In preliminary analyses of subsamples of the Herschel DEBRIS and DUNES surveys, Wyatt et al. and Marshall et al. identified a tentative correlation between debris and the presence of low-mass planets. Here we use the cleanest possible sample out of these Herschel surveys to assess the presence of such a correlation, discarding stars without known ages, with ages <1 Gyr, and with binary companions <100 AU. to rule out possible correlations due to effects other than planet presence. In our resulting subsample of 204 FGK stars, we do not find evidence that debris disks are more common or more dusty around stars harboring high-mass or low-mass planets compared to a control sample without identified planets. There is no evidence either that the characteristic dust temperature of the debris disks around planet-bearing stars is any different from that in debris disks without identified planets, nor that debris disks are more or less common (or more or less dusty) around stars harboring multiple planets compared to single-planet systems. Diverse dynamical histories may account for the lack of correlations. The data show a correlation between the presence of high-mass planets and stellar metallicity, but no correlation between the presence of low-mass planets or debris and stellar metallicity. Comparing the observed cumulative distribution of fractional luminosity to those expected from a Gaussian distribution in logarithmic scale, we find that a distribution centered on the solar system's value fits the data well, while one centered at 10 times this value can be rejected. This is of interest in the context of future terrestrial planet detection and characterization because it indicates that there are good prospects for finding a large number of debris disk systems (i.e., with evidence of harboring planetesimals, the building blocks of planets) with exozodiacal emission low enough to be appropriate targets for an ATLAST-type mission to search for biosignatures.
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    Resolved imaging of the HR 8799 debris disk with Herschel
    (2014) Matthews, B.; Kennedy, G.; Sibthorpe, B.; Haworth-Booth, Mark; Wyatt, M.; Broekhoven-Fiene, H.; Macintosh, B.; Marois, C.
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    SPATIALLY RESOLVED IMAGING OF THE TWO-COMPONENT eta Crv DEBRIS DISK WITH HERSCHEL
    (2014) Duchêne, G.; Arriaga, P.; Wyatt, M.; Kennedy, G.; Sibthorpe, B.; Lisse, C.; Holland, W.; Wisniewski, J.; Clampin, M.; Haworth-Booth, Mark
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    The AU Mic Debris Disk: far-infrared and submillimeter resolved imaging
    (2015) Matthews, B.; Kennedy, G.; Sibthorpe, B.; Holland, W.; Haworth-Booth, Mark; Kalas, P.; Macgregor, M.; Wilner, D.; Vandenbussche, B.; Olofsson, G.; Blommaert, J.; Brandeker, A.; Dent, W.; De, Vries, B.; Di, Francesco, J.; Fridlund, M.
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    The debris disc of solar analogue tau Ceti: Herschel observations and dynamical simulations of the proposed multiplanet system
    (2014) Lawler, S.; Di Francesco, J.; Kennedy, G.; Sibthorpe, B.; Haworth-Booth, Mark; Vandenbussche, B.; Matthews, B.; Holland, W.; Greaves, J.; Wilner, D.
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    Triple trouble for XZ Tau: deep imaging with the Jansky Very Large Array
    (2014) Forgan, D.; Ivison, R. J.; Sibthorpe, B.; Greaves, J. S.; Ibar, E.
    We present new observations of the XZ Tau system made at high angular resolution (55 mas) with the Karl G. Jansky Very Large Array (VLA) at a wavelength of 7 mm. Observations of XZ Tau made with the VLA in 2004 appeared to show a triple-star system, with XZ Tau A resolved into two sources, XZ Tau A and XZ Tau C. The angular separation of XZ Tau A and C (0.09 arcsec) suggested a projected orbital separation of around 13 au with a possible orbital period of around 40 yr. Our follow-up observations were obtained approximately 8 yr later, a fifth of this putative orbital period, and should therefore allow us to constrain the orbital parameters of XZ Tau C, and evaluate the possibility that a recent periastron passage of C coincided with the launch of extended optical outflows from XZ Tau A. Despite improved sensitivity and resolution, as compared with the 2004 observations, we find no evidence of XZ Tau C in our data. Components A and B are detected with a signal-to-noise ratio greater than 10; their orbital motions are consistent with previous studies of the system, although the emission from XZ Tau A appears to be weaker. Three possible interpretations are offered: either XZ Tau C is transiting XZ Tau A, which is broadly consistent with the periastron passage hypothesis, or the emission seen in 2004 was that of a transient, or XZ Tau C does not exist. A fourth interpretation, that XZ Tau C was ejected from the system, is dismissed due to the lack of angular momentum redistribution in the orbits of XZ Tau A and XZ Tau B that would result from such an event. Transients are rare but cannot be ruled out in a T Tauri system known to exhibit variable behaviour. Our observations are insufficient to distinguish between the remaining possibilities, at least not until we obtain further VLA observations at a sufficiently later time. A further non-detection would allow us to reject the transit hypothesis, and the periastron passage of XZ Tau C as agent of XZ Tau A's outflows.