Modelling the KIC8462852 light curves: compatibility of the dips and secular dimming with an exocomet interpretation

Abstract This paper shows how the dips and secular dimming in the KIC8462852 light curve can originate in circumstellar material distributed around a single elliptical orbit (e.g. exocomets). The expected thermal emission and wavelength dependent dimming is derived for different orbital parameters a...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2018-02, Vol.473 (4), p.5286-5307
Main Authors: Wyatt, M. C., van Lieshout, R., Kennedy, G. M., Boyajian, T. S.
Format: Article
Language:English
Subjects:
Brightening
Clumps
Comets
Dimming
Dust
Elliptical orbits
Extrasolar
Light curve
Luminosity
Optical properties
Radiation
Size distribution
Stellar radiation
Thermal emission
Transit
Wavelengths
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Summary:Abstract This paper shows how the dips and secular dimming in the KIC8462852 light curve can originate in circumstellar material distributed around a single elliptical orbit (e.g. exocomets). The expected thermal emission and wavelength dependent dimming is derived for different orbital parameters and geometries, including dust that is optically thick to stellar radiation, and for a size distribution of dust with realistic optical properties. We first consider dust distributed evenly around the orbit, then show how to derive its uneven distribution from the optical light curve and to predict light curves at different wavelengths. The fractional luminosity of an even distribution is approximately the level of dimming times stellar radius divided by distance from the star at transit. Non-detection of dust thermal emission for KIC8462852 thus provides a lower limit on the transit distance to complement the 0.6 au upper limit imposed by 0.4 d dips. Unless the dust distribution is optically thick, the putative 16 per cent century-long secular dimming must have disappeared before the WISE 12 μm measurement in 2010, and subsequent 4.5 μm observations require transits at >0.05 au. However, self-absorption of thermal emission removes these constraints for opaque dust distributions. The passage of dust clumps through pericentre is predicted to cause infrared brightening lasting tens of days and dimming during transit, such that total flux received decreases at wavelengths
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stx2713