J/A+A/615/A117 55 Cnc geocoronal emission lines template (Bourrier+, 2018)
High-energy environment of super-Earth 55 Cnc e.
I: Far-UV chromospheric variability as a possible tracer of planet-induced
coronal rain
Bourrier V., Ehrenreich D., Lecavelier des Etangs A., Louden T.,
Wheatley P.J., Wyttenbach A., Vidal-Madjar A., Lavie B., Pepe F., Udry S.
<Astron. Astrophys. 615, A117 (2018)>
=2018A&A...615A.117B 2018A&A...615A.117B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Exoplanets ; Spectroscopy
Keywords: methods: data analysis - techniques: spectroscopic -
planets and satellites: individual: 55 Cnc e - stars: chromospheres -
ultraviolet: stars
Abstract:
The high-energy X-ray to ultraviolet (XUV) irradiation of close-in
planets by their host star influences their evolution and might be
responsible for the existence of a population of ultra-short period
planets eroded to their bare core. In orbit around a bright, nearby
G-type star, the super-Earth 55 Cnc e offers the possibility to
address these issues through transit observations at UV wavelengths.
We used the Hubble Space Telescope to observe the transit in the
far-ultraviolet (FUV) over three epochs in April 2016, January 2017,
and February 2017. Together, these observations cover nearly half of
the orbital trajectory in between the two quadratures, and reveal
significant short- and long-term variability in 55 Cnc chromospheric
emission lines. In the last two epochs, we detected a larger flux in
the CIII, SiIII, and SiIV lines after the planet passed the
approaching quadrature, followed by a flux decrease in the SiIV
doublet. In the second epoch these variations are contemporaneous with
flux decreases in the SiII and CII doublet. All epochs show flux
decreases in the NV doublet as well, albeit at different orbital
phases. These flux decreases are consistent with absorption from
optically thin clouds of gas, are mostly localized at low and
redshifted radial velocities in the star rest frame, and occur
preferentially before and during the planet transit. These three
points make it unlikely that the variations are purely stellar in
origin, yet we show that the occulting material is also unlikely to
originate from the planet. We thus tentatively propose that the motion
of 55 Cnc e at the fringes of the stellar corona leads to the
formation of a cool coronal rain. The inhomogeneity and temporal
evolution of the stellar corona would be responsible for the
differences between the three visits. Additional variations are
detected in the CII doublet in the first epoch and in the OI triplet
in all epochs with a different behavior that points toward intrinsic
stellar variability. Further observations at FUV wavelengths are
required to disentangle definitively between star-planet interactions
in the 55 Cnc system and the activity of the star.
Description:
We provide four tables that contain observational templates for four
geocoronal emission lines (one table per line, indicated in the file
name). We caution that the lines are not centered on their rest
wavelengths and have an arbitrary flux scaling. The user must fit the
position and amplitude of the templates according to their
observations, as these properties are specific to a given observation
with the HST.
The templates can be seen in the paper in the following figures:
atoi1305.dat: OI line (rest wavelength 1304.8576 A) in Fig. 4
atoi1306.dat: OI line (rest wavelength 1306.0286 A) in Fig. 4
atoi1302.dat: OI line (rest wavelength 1302.1685 A) in Fig. 5
athi1216.dat: HI line (rest wavelength 1215.6702 A) in Fig. 6
Objects:
------------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------------
08 52 35.81 +28 19 51.0 55 CnC = * rho01 Cnc
------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
atoi1305.dat 51 273 OI line (rest wavelength 1304.8576Å) in Fig. 4
atoi1306.dat 51 272 OI line (rest wavelength 1306.0286Å) in Fig. 4
atoi1302.dat 51 271 OI line (rest wavelength 1302.1685Å) in Fig. 5
athi1216.dat 51 272 HI line (rest wavelength 1215.6702Å) in Fig. 6
--------------------------------------------------------------------------------
See also:
J/A+A/533/A114 : Transit of super-Earth 55 Cnc e (Demory+, 2011)
J/A+A/539/A28 : New transit photometry for super-Earth 55 Cnc e (Gillon+, 2012
J/A+A/545/A97 : 0.8-6µm calibrated spectrum of 55 Cnc (Crossfield, 2012)
J/ApJ/778/132 : C and O abundances in 55 Cnc (Teske+, 2013)
J/ApJ/792/L31 : 55 Cnc HARPS & HARPS-N radial velocities (Lopez-Morales+ 2014)
Byte-by-byte Description of file: at*.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.6 0.1nm lambda Wavelength, in angstroms
15- 31 E17.10 10-2W/m2/nm Flux Flux of a given geocoronal emission line,
in erg/cm2/Å/s
36- 51 E16.10 10-2W/m2/nm e_Flux Flux associated error, in erg/cm2/Å/s
--------------------------------------------------------------------------------
Acknowledgements:
Vincent Bourrier, Vincent.Bourrier(at)unige.ch
(End) Patricia Vannier [CDS] 26-Mar-2018