J/A+A/640/L12 CS Cha B spectrum (Haffert+, 2020)
CS Cha B: a disk-obscured M-type star mimicking a polarized planetary companion.
Haffert S.Y., van Holstein, R.G., Ginski C., Brinchmann J., Snellen I.A.G.,
Milli J., Stolker T., Keller C.U., Girard J.
<Astron. Astrophys. 640, L12 (2020)>
=2020A&A...640L..12H 2020A&A...640L..12H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Spectra, optical ; Spectra, infrared
Keywords: planets and satellites: individual: CS Cha B - stars: low-mass -
accretion, accretion disks - stars: winds, outflows -
techniques: imaging spectroscopy
Abstract:
Direct imaging provides a steady flow of newly discovered giant
planets and brown dwarf companions. These multi-object systems can
provide information about the formation of low-mass companions in wide
orbits and/or speculate about possible migration scenarios. The
accurate classification of the companions is crucial for testing
formation pathways.
In this work we characterize further the recently discovered candidate
for a planetary-mass companion CS Cha b and determine if it is still
accreting.
MUSE is a 4-laser-adaptive-optics-assisted medium-resolution
integral-field spectrograph in the optical part of the spectrum. We
observed the CS Cha system to obtain the first spectrum of CS Cha b.
The companion is characterized by modelling both the spectrum from
6300Å, to 9300Å, and the photometry using archival data from the
visible to the near-infrared.
We find evidence of accretion and outflow signatures in Hα and OI
emission. The atmospheric models with the highest likelihood indicate
an effective temperature of 3450±50K with a logg of 3.6±0.5dex.
Based on evolutionary models, we find that the majority of the object
is obscured. We determine the mass of the faint companion with several
methods to be between 0.07 Msun and 0.71M☉ with an accretion rate
of dM/dt=4x10-11±0.4x10-11M☉/yr.
Our results show that CS Cha B is most likely a mid M-type star that
is obscured by a highly inclined disk, which has led to its previous
classification by broadband NIR photometry as a planetary-mass
companion. This shows that it is important and necessary to observe
over a broad spectral range to constrain the nature of faint
companions.
Description:
The extracted MUSE spectrum of CS Cha B.
Objects:
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RA (2000) DE Designation(s)
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11 02 24.88 -77 33 35.7 CS Cha = V* CS Cha
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 24 3466 The spectrum of CS Cha B
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 F10.5 0.1nm lambda The wavelength of each bin
14- 24 F11.5 10-16W/m2/nm Flux The flux density at each wave bin
(in 10-20erg/s/cm2/Å)
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Acknowledgements:
Sebastiaan Haffert, shaffert(at)email.arizona.edu
(End) Sebastiaan Haffert [Univ. of Arizona], Patricia Vannier [CDS] 15-Jul-2020