J/AJ/163/68 Fiducial stellar spectrum of HD 63433 (Zhang+, 2022)
Detection of Ongoing Mass Loss from HD 63433c, a Young Mini-Neptune.
Zhang M., Knutson H.A., Wang L., Dai F., dos Santos L.A., Fossati L.,
Henry G.W., Ehrenreich D., Alibert Y., Hoyer S., Wilson T.G., Bonfanti A.
<Astron. J., 163, 68 (2022)>
=2022AJ....163...68Z 2022AJ....163...68Z
ADC_Keywords: Exoplanets; Stars, G-type; X-ray sources; Spectra, ultraviolet;
Spectra, optical; Spectra, infrared
Keywords: Exoplanet atmospheres ; Exoplanet atmospheric composition ;
Exoplanet systems ; Exoplanets ; Mini Neptunes ; Exoplanet
evolution ; Extrasolar rocky planets ; Exosphere
Abstract:
We detect Lyα absorption from the escaping atmosphere of
HD63433c, a R=2.67R⊕, P=20.5day mini-Neptune orbiting a young
(440Myr) solar analog in the Ursa Major Moving Group. Using Hubble
Space Telescope (HST)/Space Telescope Imaging Spectrograph, we measure
a transit depth of 11.1±1.5% in the blue wing and 8±3% in the
red. This signal is unlikely to be due to stellar variability, but
should be confirmed by an upcoming second transit observation with
HST. We do not detect Lyα absorption from the inner planet, a
smaller R=2.15R⊕ mini-Neptune on a 7.1day orbit. We use
Keck/NIRSPEC to place an upper limit of 0.5% on helium absorption for
both planets. We measure the host star's X-ray spectrum and
mid-ultraviolet flux with XMM-Newton, and model the outflow from both
planets using a 3D hydrodynamic code. This model provides a reasonable
match to the light curve in the blue wing of the Lyα line and
the helium nondetection for planet c, although it does not explain the
tentative red wing absorption or reproduce the excess absorption
spectrum in detail. Its predictions of strong Lyα and helium
absorption from b are ruled out by the observations. This model
predicts a much shorter mass-loss timescale for planet b, suggesting
that b and c are fundamentally different: while the latter still
retains its hydrogen/helium envelope, the former has likely lost its
primordial atmosphere.
Description:
With Space Telescope Imaging Spectrograph on the Hubble Space
Telescope (HST/STIS), we obtained two nine-orbit transit observations
of the Lyα line with the Multi-Anode Microchannel Array detector
(program 16319, PI:Michael Zhang). All orbits except the first contain
2523s of science exposure time in TIME-TAG mode using the G140M grism
with a central wavelength of 1222Å and a slit width of 52x0.1".
Our NIRSPEC/Keck data (program C261) were taken on 2020 December 30
(transit of planet c) and 2021 January 7 (transit of planet b). All
observations were in the Y band in the high-resolution mode. On
December 30, the transit was in progress when our observations
started. We collected 3.4hr of in-transit observations and 5hr of
posttransit baseline. On January 7, the transit started toward the end
of our observations. We collected 5.4hr of pretransit and 2.6hr of
in-transit observations. On both nights, we used the 12x0.432" slit,
giving the spectrograph a resolution of 25000.
On 2021 March 26 XMM-Newton observed the star for 6ks (XMM prop. ID
088287, PI: Michael Zhang). XMM-Newton has three European Photon
Imaging Camera (EPIC) detectors with different technologies (two
metal-oxide-silicon (MOS), one pn), two Reflection Grating
Spectrometers, and an Optical Monitor, all of which observe the target
simultaneously. We configured the Optical Monitor to observe the star
in the UVM2 filter (231±48nm) for 2.7ks and the UVW2 filter
(212{/-}50nm) for 2.9ks.
Objects:
---------------------------------------------------------
RA (2000) DE Designation(s) (Period)
---------------------------------------------------------
07 49 55.06 +27 21 47.5 HD63433c = HD 63433c (P=20.5d)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig11.dat 15 6569 Fiducial stellar spectrum
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See also:
J/AJ/129/1669 : BV photometry of HD37824, HD181809, & HD217188 (Fekel+, 2005)
J/A+A/480/611 : XMM-Newton slew survey catalogue, XMMSL1 (Saxton+, 2008)
J/ApJS/211/9 : Variability in UV line emission of F-M stars (Loyd+, 2014)
J/MNRAS/441/2361 : Stellar magnetism, age and rotation (Vidotto+, 2014)
J/ApJ/806/183 : Planet radii of Kepler Object of Interest (Wolfgang+, 2015)
J/A+A/588/A103 : Second ROSAT all-sky survey source catalog (Boller+, 2016)
J/ApJ/825/19 : Mass-radius relationship planets with Rp<4 (Wolfgang+, 2016)
J/ApJ/834/17 : Mass & radius of planets, moons, low mass stars (Chen+, 2017)
J/AJ/154/109 : California-Kepler Survey. III. Planet radii (Fulton+, 2017)
J/AJ/154/5 : Transit timing variations 145 Kepler planets (Hadden+, 2017)
J/AJ/156/264 : California-Kepler Survey VII Planet radius gap (Fulton+, 2018)
Byte-by-byte Description of file: fig11.dat
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Bytes Format Units Label Explanations
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1- 7 F7.1 0.1nm Wave [5/54990] Wavelength; Angstroms
9- 15 F7.3 cW/m2/nm Flux [0.001/172] Flux at 1AU; erg/s/cm2/Angstroms
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 30-May-2022