Fast spectrophotometry of WD1145+017

Paula Izquierdo, Pablo Rodríguez-Gil, Boris T. Gänsicke, Alexander J. Mustill, Odette Toloza, Pier Emmanuel Tremblay, Mark Wyatt, Paul Chote, Siegfried Eggl, Jay Farihi, Detlev Koester, Wladimir Lyra, Christopher J. Manser, Thomas R. Marsh, Enric Pallé, Roberto Raddi, Dimitri Veras, Eva Villaver, Simon Portegies Zwart

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish (US)
Pages (from-to)703-714
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Volume481
Issue number1
DOIs
StatePublished - Nov 21 2018
Externally publishedYes

Keywords

  • Asteroids: general
  • Minor planets
  • Planet-star interactions
  • Planetary systems
  • Planets and satellites: physical evolution
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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