OPTICAL HYDROGEN ABSORPTION CONSISTENT WITH A THIN BOW SHOCK LEADING THE HOT JUPITER HD 189733B

P. Wilson Cauley, Seth Redfield, Adam G. Jensen, Travis Barman, Michael Endl, William D. Cochran

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric Hα detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 Rp. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a planetary bow shock. If the bow shock is mediated by a planetary magnetosphere, the large standoff distance derived from the model suggests a large planetary magnetic field strength of Beq = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in planetary evolution and the potential development of life on planets in the habitable zone.

Original languageEnglish (US)
Article number13
JournalAstrophysical Journal
Volume810
Issue number1
DOIs
StatePublished - Sep 1 2015

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bows
transit
Jupiter (planet)
Jupiter
shock
hydrogen
extrasolar planets
planet
planetary evolution
planets
field strength
magnetic field
planetary magnetic fields
planetary magnetospheres
transition element
spectral resolution
magnetosphere
line shape
astrophysics
geometry

Keywords

  • line: profiles
  • magnetic fields
  • planet-star interactions

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

OPTICAL HYDROGEN ABSORPTION CONSISTENT WITH A THIN BOW SHOCK LEADING THE HOT JUPITER HD 189733B. / Cauley, P. Wilson; Redfield, Seth; Jensen, Adam G.; Barman, Travis; Endl, Michael; Cochran, William D.

In: Astrophysical Journal, Vol. 810, No. 1, 13, 01.09.2015.

Research output: Contribution to journalArticle

Cauley, P. Wilson ; Redfield, Seth ; Jensen, Adam G. ; Barman, Travis ; Endl, Michael ; Cochran, William D. / OPTICAL HYDROGEN ABSORPTION CONSISTENT WITH A THIN BOW SHOCK LEADING THE HOT JUPITER HD 189733B. In: Astrophysical Journal. 2015 ; Vol. 810, No. 1.
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