J/A+A/633/A110 K band spectrum of beta Pictoris b (GRAVITY+, 2020)
Peering into the formation history of beta Pictoris b with VLTI/GRAVITY
long-baseline interferometry.
GRAVITY Collaboration, Nowak M., Lacour S., Molliere P., Wang J.,
Charnay B., van Dishoeck E.F., Abuter R., Amorim A., Berger J.P., Beust H.,
Bonnefoy M., Bonnet H., Brandner W., Buron A., Cantalloube F., Collin C.,
Chapron F., Clenet Y., Coude du Foresto V., de Zeeuw P.T., Dembet R.,
Dexter J., Duvert G., Eckart A., Eisenhauer F., Forster Schreiber N.M.,
Fedou P., Garcia Lopez R., Gao F., Gendron E., Genzel R., Gillessen S.,
Haussmann F., Henning T., Hippler S., Hubert Z., Jocou L., Kervella P.,
Lagrange A.-M., Lapeyrere V., Le Bouquin J.-B., Lena P., Maire A.-L.,
Ott T., Paumard T., Paladini C., Perraut K., Perrin G., Pueyo L., Pfuhl O.,
Rabien S., Rau C., Rodriguez-Coira G., Rousset G., Scheithauer S.,
Shangguan J., Straub O., Straubmeier C., Sturm E., Tacconi L.J.,
Vincent F., Widmann F., Wieprecht E., Wiezorrek E., Woillez J., Yazici S.,
Ziegler D.
<Astron. Astrophys. 633, A110 (2020)>
=2020A&A...633A.110G 2020A&A...633A.110G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Spectra, infrared
Keywords: planets and satellites: formation -
planets and satellites: atmospheres - techniques: interferometric -
stars: individual: beta Pictoris
Abstract:
Beta Pictoris is arguably one of the most studied stellar systems
outside of our own. Some 30 years of observations have revealed a
highly-structured circumstellar disk, with rings, belts, and a giant
planet: beta Pictoris b. However very little is known about how this
system came into being. Our objective is to estimate the C/O ratio in
the atmosphere of β Pictoris b and obtain an estimate of the
dynamical mass of the planet, as well as to refine its orbital
parameters using high-precision astrometry. We used the GRAVITY
instrument with the four 8.2m telescopes of the Very Large Telescope
Interferometer to obtain K-band spectro-interferometric data on β
Pic b. We extracted a medium resolution (R=500) K-band spectrum of the
planet and a high- precision astrometric position. We estimated the
planetary C/O ratio using two different approaches (forward modeling
and free retrieval) from two different codes (ExoREM and
petitRADTRANS, respectively). Finally, we used a simplified model of
two formation scenarios (gravitational collapse and core-accretion) to
determine which can best explain the measured C/O ratio. Our new
astrometry disfavors a circular orbit for beta Pic b
(e=0.15+0.05-0.04). Combined with previous results and with
Hipparcos/GAIA measurements, this astrometry points to a planet mass
of M=12.7±2.2M{Jup}. This value is compatible with the mass
derived with the free-retrieval code petitRADTRANS using spectral data
only. The forward modeling and free-retrieval approches yield very
similar results regarding the atmosphere of beta Pic b. In particular,
the C/O ratios derived with the two codes are identical (0.43±0.05
vs $0.43+0.04-0.03). We argue that if the stellar C/O in beta Pic
is Solar, then this combination of a very high mass and a low C/O
ratio for the planet suggests a formation through core-accretion, with
strong planetesimal enrichment.
Description:
The data consist of an absolute flux-calibrated spectrum of the giant
planet beta Pic b in K band (1.97 to 2.49 microns).
The data reduction procedure (see paper) gives the contrast spectrum
(planet/star), which is then calibrated using a model spectrum of the
star. The non-calibrated contrast spectrum is also given.
List of HDUs contained in the FITS file:
NAME DIMENSION DESCRIPTION
--------------------------------------------------------------------------
PRIMARY 1D Absolute flux-calibrated spectrum (W/m2/um)
WAVELENGTH 1D The wavelength coordinates of the pixels (um)
COV 2D Covariance matrix of the flux-calibrated spectrum
Pixel [n, m], or equivalently [m, n] gives the
covariance between pixel n and pixel m of the
spectrum, in W2/m4/um2
CONTRAST 1D Contrast spectrum (planet/star)
CONTRAST_COV 2D Same as COV for the contrast spectrum
--------------------------------------------------------------------------
Data obtained with VLTI/GRAVITY on September, 22, 2018.
Objects:
-------------------------------------------------
RA (2000) DE Designation(s)
-------------------------------------------------
05 47 17.09 -51 03 59.4 beta Pic = HR 2020
-------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 79 1 Information on fits files
fits/* . 1 Fits files
spectrum.dat 33 237 beta Pic GRAVITY spectrum
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See also:
J/A+A/542/A18 : β Pic Harps radial velocity data (Lagrange+, 2012)
J/A+A/607/A25 : beta Pic HARPS spectrum (Vidal-Madjar+, 2017)
J/A+A/627/A28 : beta Pic BRITE, bRing, SMEI light curves (Zwintz+, 2019)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Right Ascension (J2000)
4- 5 I2 min RAm Right Ascension (J2000)
7- 11 F5.2 s RAs Right Ascension (J2000)
12 A1 --- DE- Declination sign (J2000)
13- 14 I2 deg DEd Declination (J2000)
16- 17 I2 arcmin DEm Declination (J2000)
19- 23 F5.2 arcsec DEs Declination (J2000)
25- 34 A10 "date" Obs.date Observation date
36 I1 --- Ext [6] Number of extensions in fits file
38- 40 I3 Kibyte size Size of FITS file
42- 53 A12 --- FileName Name of FITS file, in subdirectory fits
55- 79 A25 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Byte-by-byte Description of file: spectrum.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
4- 17 A14 um lambda Wavelength
20- 33 F14.12 10-15W/m2/um Flux K-band flux
--------------------------------------------------------------------------------
Acknowledgements:
Mathias Nowak, mathias.nowak(at)obspm.fr
(End) Mathias Nowak [LESIA, Meudon], Patricia Vannier [CDS] 13-Dec-2019