Volume 545, September 2012
|Number of page(s)||4|
|Section||Planets and planetary systems|
|Published online||12 September 2012|
ACME stellar spectra
I. Absolutely calibrated, mostly empirical flux densities of 55 Cancri and its transiting planet 55 Cancri e⋆
Max-Planck Institüt für Astronomie, Königstuhl 17,
2 Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA
Received: 15 June 2012
Accepted: 24 July 2012
The ACME Spectra project provides absolutely calibrated, mostly empirical spectra of exoplanet host stars for use in analysis of the stars and their planets. Spectra are obtained from ground-based telescopes and are tied directly to calibrated ground- and space-based photometry. The spectra remain only “mostly” empirical because of telluric absorption, but interpolation of stellar models over the gaps in wavelength coverage provides continuous stellar spectra. Among other uses, the spectra are suitable for precisely converting observed secondary eclipses (occultations) into absolute flux units with minimal recourse to models. In this paper, I introduce ACME’s methods and present a calibrated spectrum of the nearby, super-Earth hosting star 55 Cancri that spans the range from 0.81–5.05 μm. This spectrum is well-suited for interpreting near- and thermal-infrared eclipse observations. With this spectrum I show that the brightness temperature of the small, low-mass transiting planet 55 Cnc e is 1950-190+260 K at 4.5 μm (cooler than previously reported), which corresponds to a planetary flux of 0.44-0.08+0.12 mJy. This result suggests the planet has some combination of a nonzero albedo, a moderately efficient redistribution of absorbed stellar irradiation, and/or an optically thick atmosphere, but more precise eclipse measurements are required to distinguish between these scenarii.
Key words: methods: observational / techniques: spectroscopic / techniques: high angular resolution / infrared: stars / planets and satellites: atmospheres / stars: individual: 55 Cnc
The calibrated spectrum of the planet-hosting star 55 Cancri is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/A97
© ESO, 2012
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