Fast spectrophotometry of WD1145+017
Published version
Peer-reviewed
Repository URI
Repository DOI
Type
Change log
Authors
Abstract
WD1145+017 is currently the only white dwarf known to exhibit periodic transits of planetary debris as well as absorption lines from circumstellar gas. We present the first simultaneous fast optical spectrophotometry and broad-band photometry of the system, obtained with the Gran Telescopio Canarias (GTC) and the Liverpool Telescope, respectively. The observations spanned 5.5 h, somewhat longer than the 4.5-h orbital period of the debris. Dividing the GTC spectrophotometry into five wavelength bands reveals no significant colour differences, confirming grey transits in the optical.We argue that absorption by an optically thick structure is a plausible alternative explanation for the achromatic nature of the transits that can allow the presence of small-sized (~μm) particles. The longest (87 min) and deepest (50 per cent attenuation) transit recorded in our data exhibits a complex structure around minimum light that can be well modelled by multiple overlapping dust clouds. The strongest circumstellar absorption line, Fe II λ5169, significantly weakens during this transit, with its equivalent width reducing from a mean out-of-transit value of 2 to 1Å in-transit, supporting spatial correlation between the circumstellar gas and dust. Finally, we made use of the Gaia Data Release 2 and archival photometry to determine the white dwarf parameters. Adopting a helium-dominated atmosphere containing traces of hydrogen and metals, and a reddening E(B - V) = 0.01 we find Teff = 15 020 ± 520 K, log g = 8.07 ± 0.07, corresponding to MWD = 0.63 ± 0.05M⊙ and a cooling age of 224 ± 30 Myr.
Description
Keywords
Journal Title
Conference Name
Journal ISSN
1365-2966
Volume Title
Publisher
Publisher DOI
Sponsorship
Science and Technology Facilities Council (ST/J003344/2)
Science and Technology Facilities Council (ST/K003453/1)
Science and Technology Facilities Council (ST/R000476/1)