J/AJ/163/67 5-55000Å spectrum of TOI 560 (Zhang+, 2022)
Escaping Helium from TOI 560.01, a Young Mini-Neptune.
Zhang M., Knutson H.A., Wang L., Dai F., Barragan O.
<Astron. J., 163, 67 (2022)>
=2022AJ....163...67Z 2022AJ....163...67Z
ADC_Keywords: Stars, K-type; Exoplanets; Spectra, ultraviolet; Spectra, optical;
Spectra, infrared; X-ray sources
Keywords: Exoplanet atmospheres ; Exoplanet astronomy ; Exoplanets ;
Exoplanet evolution ; Mini-Neptunes
Abstract:
We report helium absorption from the escaping atmosphere of TOI560.01
(HD73583b), an R=2.8R⊕, P=6.4day mini-Neptune orbiting a young
(∼600Myr) K-dwarf. Using Keck/NIRSPEC, we detect a signal with an
average depth of 0.68%±0.08% in the line core. The absorption
signal repeats during a partial transit obtained a month later, but is
marginally stronger and bluer, perhaps reflecting changes in the
stellar wind environment. Ingress occurs on time, and egress occurs
within 12 minutes of the white light egress, although absorption rises
more gradually than it declines. This suggests that the outflow is
slightly asymmetric and confined to regions close to the planet. The
absorption signal also exhibits a slight 4km/s redshift rather than
the expected blueshift; this might be explained if the planet has a
modest orbital eccentricity, although the radial velocity data
disfavors such an explanation. We use XMM-Newton observations to
reconstruct the high-energy stellar spectrum and model the planet's
outflow with 1D and 3D hydrodynamic simulations. We find that our
models generally overpredict the measured magnitude of the absorption
during transit, the size of the blueshift, or both. Increasing the
metallicity to 100x solar suppresses the signal, but the dependence of
the predicted signal strength on metallicity is non-monotonic.
Decreasing the assumed stellar EUV flux by a factor of three likewise
suppresses the signal substantially.
Description:
We used Keck/NIRSPEC to observe a full transit of TOI560.01 on 2021
March 18 (UTC) and a partial transit on April 19, 2021 UTC (40% of
T14). All observations were obtained in Y band using the
high-resolution mode with the 12x0.432" slit, resulting in a spectral
resolution of 25000.
On April 21, XMM-Newton measured the star's X-ray and MUV spectrum,
which are crucial for modeling photoevaporative mass loss and
predicting the metastable helium population. We observed the system
for a total of 13ks as part of XMM prop.ID088287 (PI: Michael Zhang).
We configured the EPIC cameras to observe with the medium filter and
small window, giving us 97% observing efficiency on the two MOS CCDs
and 71% efficiency on the one pn CCD. We configured the Optical
Monitor to observe the star in the UVM2 filter (231±48nm) for
7.2ks and the UVW2 filter (212±50nm) for 4.4ks.
Objects:
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RA (2000) DE Designation(s)
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08 38 45.26 -13 15 24.1 TOI560 = HD 73583
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig10.dat 16 6569 Fiducial stellar spectrum
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See also:
I/196 : Hipparcos Input Catalogue, Version 2 (Turon+ 1993)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/MNRAS/441/2361 : Stellar magnetism, age and rotation (Vidotto+, 2014)
J/A+A/576/A21 : The PLUTO CLOUDY Interface (TPCI) (Salz+, 2015)
J/A+A/586/A75 : Simulations of hot gas planets atmospheres (Salz+, 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/A+A/601/A10 : A grid of MARCS model atmospheres for S stars (Van Eck+, 2017)
J/AJ/156/264 : California-Kepler Survey VII Planet radius gap (Fulton+, 2018)
J/AJ/155/48 : California-Kepler Survey. V. Masses and radii (Weiss+, 2018)
Byte-by-byte Description of file: fig10.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- 16 F8.5 cW/m2/nm Flux [0/28.1] 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], 06-May-2022