13 research outputs found
First light of the VLT planet finder SPHERE. I. Detection and characterization of the sub-stellar companion GJ 758 B
GJ758 B is a brown dwarf companion to a nearby (15.76 pc) solar-type,
metal-rich (M/H = +0.2 dex) main-sequence star (G9V) that was discovered with
Subaru/HiCIAO in 2009. From previous studies, it has drawn attention as being
the coldest (~600K) companion ever directly imaged around a neighboring star.
We present new high-contrast data obtained during the commissioning of the
SPHERE instrument at the VLT. The data was obtained in Y-, J-, H-, and Ks-bands
with the dual-band imaging (DBI) mode of IRDIS, providing a broad coverage of
the full near-infrared (near-IR) range at higher contrast and better spectral
sampling than previously reported. In this new set of high-quality data, we
report the re-detection of the companion, as well as the first detection of a
new candidate closer-in to the star. We use the new 8 photometric points for an
extended comparison of GJ758 B with empirical objects and 4 families of
atmospheric models. From comparison to empirical object, we estimate a T8
spectral type, but none of the comparison object can accurately represent the
observed near-IR fluxes of GJ758 B. From comparison to atmospheric models, we
attribute a Teff = 600K 100K, but we find that no atmospheric model can
adequately fit all the fluxes of GJ758 B. The photometry of the new candidate
companion is broadly consistent with L-type objects, but a second epoch with
improved photometry is necessary to clarify its status. The new astrometry of
GJ758 B shows a significant proper motion since the last epoch. We use this
result to improve the determination of the orbital characteristics using two
fitting approaches, Least-Square Monte Carlo and Markov Chain Monte Carlo.
Finally, we analyze the sensitivity of our data to additional closer-in
companions and reject the possibility of other massive brown dwarf companions
down to 4-5 AU. [abridged]Comment: 20 pages, 15 figures. Accepted for publication in A&
First light of the VLT planet finder SPHERE. II. The physical properties and the architecture of the young systems PZ Tel and HD 1160 revisited
[Abridged] Context. The young systems PZ Tel and HD 1160, hosting known
low-mass companions, were observed during the commissioning of the new planet
finder SPHERE with several imaging and spectroscopic modes. Aims. We aim to
refine the physical properties and architecture of both systems. Methods. We
use SPHERE commissioning data and REM observations, as well as literature and
unpublished data from VLT/SINFONI, VLT/NaCo, Gemini/NICI, and Keck/NIRC2.
Results. We derive new photometry and confirm the nearly daily photometric
variability of PZ Tel A. Using literature data spanning 38 yr, we show that the
star also exhibits a long-term variability trend. The 0.63-3.8 mic SED of PZ
Tel B allows us to revise its properties: spectral type M7+/-1, Teff=2700+/-100
K, log(g)<4.5 dex, log(L/L_Sun)=-2.51+/-0.10 dex, and mass 38-72 MJ. The 1-3.8
mic SED of HD 1160 B suggests a massive brown dwarf or a low-mass star with
spectral type M5.5-7.0, Teff=3000+/-100 K, [M/H]=-0.5-0.0 dex,
log(L/L_Sun)=-2.81+/-0.10 dex, and mass 39-168 MJ. We confirm the deceleration
and high eccentricity (e>0.66) of PZ Tel B. For e<0.9, the inclination,
longitude of the ascending node, and time of periastron passage are well
constrained. The system is seen close to an edge-on geometry. We reject other
brown dwarf candidates outside 0.25" for both systems, and massive giant
planets (>4 MJ) outside 0.5" for the PZ Tel system. We also show that K1-K2
color can be used with YJH low-resolution spectra to identify young L-type
companions, provided high photometric accuracy (<0.05 mag) is achieved.
Conclusions. SPHERE opens new horizons in the study of young brown dwarfs and
giant exoplanets thanks to high-contrast imaging capabilities at optical and
near-infrared wavelengths, as well as high signal-to-noise spectroscopy in the
near-infrared from low (R~30-50) to medium resolutions (R~350).Comment: 25 pages, 23 figures, accepted for publication in A&A on Oct. 13th,
2015; version including language editing. Typo on co-author name on astroph
page corrected, manuscript unchange
Post conjunction detection of Pictoris b with VLT/SPHERE
With an orbital distance comparable to that of Saturn in the solar system,
\bpic b is the closest (semi-major axis \,9\,au) exoplanet that has
been imaged to orbit a star. Thus it offers unique opportunities for detailed
studies of its orbital, physical, and atmospheric properties, and of
disk-planet interactions. With the exception of the discovery observations in
2003 with NaCo at the Very Large Telescope (VLT), all following astrometric
measurements relative to \bpic have been obtained in the southwestern part of
the orbit, which severely limits the determination of the planet's orbital
parameters. We aimed at further constraining \bpic b orbital properties using
more data, and, in particular, data taken in the northeastern part of the
orbit.
We used SPHERE at the VLT to precisely monitor the orbital motion of beta
\bpic b since first light of the instrument in 2014. We were able to monitor
the planet until November 2016, when its angular separation became too small
(125 mas, i.e., 1.6\,au) and prevented further detection. We redetected \bpic b
on the northeast side of the disk at a separation of 139\,mas and a PA of
30 in September 2018. The planetary orbit is now well constrained.
With a semi-major axis (sma) of au (1 ), it
definitely excludes previously reported possible long orbital periods, and
excludes \bpic b as the origin of photometric variations that took place in
1981. We also refine the eccentricity and inclination of the planet. From an
instrumental point of view, these data demonstrate that it is possible to
detect, if they exist, young massive Jupiters that orbit at less than 2 au from
a star that is 20 pc away.Comment: accepted by A&
OSIRIS â The scientific camera system onboard Rosetta
The Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS is the scientific camera system onboard the Rosetta spacecraft (Figure 1). The advanced high performance imaging system will be pivotal for the success of the Rosetta mission. OSIRIS will detect 67P/Churyumov-Gerasimenko from a distance of more than 106 km, characterise the comet shape and volume, its rotational state and find a suitable landing spot for Philae, the Rosetta lander. OSIRIS will observe the nucleus, its activity and surroundings down to a scale of ~2 cm pxâ1. The observations will begin well before the onset of cometary activity and will extend over months until the comet reaches perihelion. During the rendezvous episode of the Rosetta mission, OSIRIS will provide key information about the nature of cometary nuclei and reveal the physics of cometary activity that leads to the gas and dust coma.
OSIRIS comprises a high resolution Narrow Angle Camera (NAC) unit and a Wide Angle Camera (WAC) unit accompanied by three electronics boxes. The NAC is designed to obtain high resolution images of the surface of comet 7P/Churyumov-Gerasimenko through 12 discrete filters over the wavelength range 250â1000 nm at an angular resolution of 18.6 ÎŒrad pxâ1. The WAC is optimised to provide images of the near-nucleus environment in 14 discrete filters at an angular resolution of 101 ÎŒrad pxâ1. The two units use identical shutter, filter wheel, front door, and detector systems. They are operated by a common Data Processing Unit. The OSIRIS instrument has a total mass of 35 kg and is provided by institutes from six European countrie
A SPHERE survey of self-shadowed planet-forming disks
Stars and planetary system
Polarimetric imaging mode of VLT/SPHERE/IRDIS: II. Characterization and correction of instrumental polarization effects
International audienc
The Odin satellite - I. Radiometer design and test
The Sub-millimetre and Millimetre Radiometer (SMR) is the main instrument on the Swedish, Canadian, Finnish and French spacecraft Odin. It consists of a 1.1 metre diameter telescope with four tuneable heterodyne receivers covering the ranges 486-504 GHz and 541-581 GHz, and one fixed at 118.75 GHz together with backends that provide spectral resolution from 150 kHz to 1 MHz. This Letter describes the Odin radiometer, its operation and performance with the data processing and calibration described in Paper II
VizieR Online Data Catalog: HR 8799e and HR 8799d spectra (Zurlo+, 2016)
VizieR Online Data Catalog. 2015. vol. 358.The files contain the wavelength in micrometers in the first column, the flux in W/m2/mum in the second column and the corresponding error in the third. We refer to the text for more informations /Users/alice/paper_hr8799/readme.txt. Any further question can be addressed to [email protected] (2 data files)
VizieR Online Data Catalog: HR 8799e and HR 8799d spectra (Zurlo+, 2016)
VizieR Online Data Catalog. 2015. vol. 358.The files contain the wavelength in micrometers in the first column, the flux in W/m2/mum in the second column and the corresponding error in the third. We refer to the text for more informations /Users/alice/paper_hr8799/readme.txt. Any further question can be addressed to [email protected] (2 data files)