Once in a blue moon: detection of “bluing” during debris transits in the white dwarf WD 1145+017

0478704 - ASÚ 2018 RIV GB eng J - Journal Article
Hallakoun, N. - Xu, S. - Maoz, D. - Marsh, T. R. - Ivanov, V.D. - Dhillon, V. S. - Boursot, P. - Parsons, S. G. - Kerry, P. - Sharma, S. - Su, K. - Rengaswamy, S. - Pravec, Petr - Kušnirák, Peter - Kučáková, H. - Armstrong, J. D. - Arnold, C. - Gerard, N. - Vanzi, L.
Once in a blue moon: detection of “bluing” during debris transits in the white dwarf WD 1145+017.
Monthly Notices of the Royal Astronomical Society. Roč. 469, č. 3 (2017), s. 3213-3224. ISSN 0035-8711. E-ISSN 1365-2966
Institutional support: RVO:67985815
Keywords : planetary-atmospheres * scattering * white dwarfs
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 5.194, year: 2017

We present the first detection of a change in colour of WD 1145+017 during transits, using simultaneous multiband fast-photometry ULTRACAM measurements over the u'g'r'i' bands. The observations reveal what appears to be bluing during transits. Transits are deeper in the redder bands, with a u' r' colour difference of up to similar to-0.05 mag. We explore various possible explanations for the bluing, including limb darkening or peculiar dust properties. 'Spectral' photometry obtained by integrating over bandpasses in the spectroscopic data in and out of transit, compared to the photometric data, shows that the observed colour difference is most likely the result of reduced circumstellar absorption in the spectrum during transits. This indicates that the transiting objects and the gas share the same line of sight and that the gas covers the white dwarf only partially, as would be expected if the gas, the transiting debris and the dust emitting the infrared excess are part of the same general disc structure (although possibly at different radii). In addition, we present the results of a week-long monitoring campaign of the system using a global network of telescopes.
Permanent Link: http://hdl.handle.net/11104/0274773