We present high-resolution near-infrared spectropolarimetric observations using the SPIRou instrument at Canada-France-Hawaii Telescope (CFHT) during a transit of the recently detected young planet ...AU Mic b, with supporting spectroscopic data from iSHELL at NASA InfraRed Telescope Facility. We detect Zeeman signatures in the Stokes
V
profiles and measure a mean longitudinal magnetic field of ¯
B
ℓ
= 46.3 ± 0.7 G. Rotationally modulated magnetic spots likely cause long-term variations of the field with a slope of d
B
ℓ
/d
t
= −108.7 ± 7.7 G d
−1
. We apply the cross-correlation technique to measure line profiles and obtain radial velocities through CCF template matching. We find an empirical linear relationship between radial velocity and
B
ℓ
, which allows us to estimate the radial-velocity induced by stellar activity through rotational modulation of spots for the five hours of continuous monitoring of AU Mic with SPIRou. We model the corrected radial velocities for the classical Rossiter-McLaughlin effect, using MCMC to sample the posterior distribution of the model parameters. This analysis shows that the orbit of AU Mic b is prograde and aligned with the stellar rotation axis with a sky-projected spin-orbit obliquity of
λ
= 0°
−15°
+18°
. The aligned orbit of AU Mic b indicates that it formed in the protoplanetary disk that evolved into the current debris disk around AU Mic.
Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric compositions and luminosities, which are influenced by their formation mechanisms. Using the ...Gemini Planet Imager, we discovered a planet orbiting the ∼20-million-year-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water-vapor absorption. Modeling of the spectra and photometry yields a luminosity (normalized by the luminosity of the Sun) of 1.6 to 4.0 × 10–6 and an effective temperature of 600 to 750 kelvin. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold-start" core-accretion process that may have formed Jupiter.
The International Deep Planet Survey Galicher, R; Marois, C; Macintosh, B ...
Astronomy and astrophysics (Berlin),
10/2016, Letnik:
594
Journal Article
Recenzirano
Context. Radial velocity and transit methods are effective for the study of short orbital period exoplanets but they hardly probe objects at large separations for which direct imaging can be used. ...Aims. We carried out the international deep planet survey of 292 young nearby stars to search for giant exoplanets and determine their frequency. Methods. We developed a pipeline for a uniform processing of all the data that we have recorded with NIRC2/Keck II, NIRI/Gemini North, NICI/Gemini South, and NACO/VLT for 14 yr. The pipeline first applies cosmetic corrections and then reduces the speckle intensity to enhance the contrast in the images. Results. The main result of the international deep planet survey is the discovery of the HR8799 exoplanets. We also detected 59 visual multiple systems including 16 new binary stars and 2 new triple stellar systems, as well as 2279 point-like sources. We used Monte Carlo simulations and the Bayesian theorem to determine that (ProQuest: Formulae and/or non-USASCII text omitted) of stars harbor at least one giant planet between 0.5 and 14M sub(J) and between 20 and 300AU. This result is obtained assuming uniform distributions of planet masses and semi-major axes. If we consider power law distributions as measured for close-in planets instead, the derived frequency is (ProQuest: Formulae and/or non-USASCII text omitted), recalling the strong impact of assumptions on Monte Carlo output distributions. We also find no evidence that the derived frequency depends on the mass of the hosting star, whereas it does for close-in planets. Conclusions. The international deep planet survey provides a database of confirmed background sources that may be useful for other exoplanet direct imaging surveys. It also puts new constraints on the number of stars with at least one giant planet reducing by a factor of two the frequencies derived by almost all previous works.
Hot Jupiters are giant Jupiter-like exoplanets that orbit their host stars 100 times more closely than Jupiter orbits the Sun. These planets presumably form in the outer part of the primordial disk ...from which both the central star and surrounding planets are born, then migrate inwards and yet avoid falling into their host star. It is, however, unclear whether this occurs early in the lives of hot Jupiters, when they are still embedded within protoplanetary disks, or later, once multiple planets are formed and interact. Although numerous hot Jupiters have been detected around mature Sun-like stars, their existence has not yet been firmly demonstrated for young stars, whose magnetic activity is so intense that it overshadows the radial velocity signal that close-in giant planets can induce. Here we report that the radial velocities of the young star V830 Tau exhibit a sine wave of period 4.93 days and semi-amplitude 75 metres per second, detected with a false-alarm probability of less than 0.03 per cent, after filtering out the magnetic activity plaguing the spectra. We find that this signal is unrelated to the 2.741-day rotation period of V830 Tau and we attribute it to the presence of a planet of mass 0.77 times that of Jupiter, orbiting at a distance of 0.057 astronomical units from the host star. Our result demonstrates that hot Jupiters can migrate inwards in less than two million years, probably as a result of planet–disk interactions.
ABSTRACT
This paper presents an overview of SPIRou, the new-generation near-infrared spectropolarimeter/precision velocimeter recently installed on the 3.6-m Canada–France–Hawaii Telescope (CFHT). ...Starting from the two main science goals, i.e., the quest for planetary systems around nearby M dwarfs and the study of magnetized star/planet formation, we outline the instrument concept that was designed to efficiently address these forefront topics, and detail the in-lab and on-sky instrument performances measured throughout the intensive testing phase that SPIRou was submitted to before passing the final acceptance review in early 2019 and initiating science observations. With a central position among the newly started programmes, the SPIRou Legacy Survey (SLS) Large Programme was allocated 300 CFHT nights until at least mid 2022. We also briefly describe a few of the first results obtained in the various science topics that SPIRou started investigating, focusing in particular on planetary systems of nearby M dwarfs, transiting exoplanets and their atmospheres, magnetic fields of young stars, but also on alternate science goals like the atmospheres of M dwarfs and the Earth’s atmosphere. We finally conclude on the key role that SPIRou and the CFHT can play in coordination with forthcoming major facilities like the JWST, the ELTs, PLATO, and ARIEL over the decade.
Abstract
Based on optical high-resolution spectra obtained with CFHT/ESPaDOnS, we present new measurements of activity and magnetic field proxies of 442 low-mass K5–M7 dwarfs. The objects were ...analysed as potential targets to search for planetary-mass companions with the new spectropolarimeter and high-precision velocimeter, SPIRou. We have analysed their high-resolution spectra in an homogeneous way: circular polarization, chromospheric features and Zeeman broadening of the FeH infrared line. The complex relationship between these activity indicators is analysed; while no strong connection is found between the large-scale and small-scale magnetic fields, the latter relates with the non-thermal flux originating in the chromosphere. We then examine the relationship between various activity diagnostics and the optical radial-velocity (RV) jitter available in the literature, especially for planet host stars. We use this to derive for all stars an activity merit function (higher for quieter stars) with the goal of identifying the most favourable stars, where the RV jitter is low enough for planet searches. We find that the main contributors to the RV jitter are the large-scale magnetic field and the chromospheric non-thermal emission. In addition, three stars (GJ 1289, GJ 793 and GJ 251) have been followed along their rotation using the spectropolarimetric mode, and we derive their magnetic topology. These very slow rotators are good representatives of future SPIRou targets. They are compared to other stars, where the magnetic topology is also known. The poloidal component of the magnetic field is predominent in all three stars.
Context. Though only a handful of extrasolar planets have been discovered via direct-imaging, each of these discoveries had a tremendous impact on our understanding of planetary formation, stellar ...formation, and cool atmosphere physics. Aims. Since many of these newly imaged giant planets orbit massive A or even B stars, we investigate whether giant planets could be found orbiting low-mass stars at large separations. Methods. We have been conducting an adaptive optic imaging survey to search for planetary-mass companions of young M dwarfs in the solar neigbourhood, in order to probe different initial conditions of planetary formation. Results. We report here the direct-imaging discovery of 2MASS J01033563-5515561(AB)b, a 12–14 MJup companion at a projected separation of 84 AU from a pair of young late-M stars, with which it shares proper motion. We also detected a Keplerian-compatible orbital motion. Conclusions. This young L-type object at the planet/brown dwarf mass boundary is the first ever imaged around a binary system at a separation compatible with formation in a disc.
Abstract Although the study of X-ray binaries has led to major breakthroughs in high-energy astrophysics, their circumbinary environment at scales of ∼100–10,000 au has not been thoroughly ...investigated. In this paper, we undertake a novel and exploratory study by employing direct and high-contrast imaging techniques on a sample of X-ray binaries, using adaptive optics and the vortex coronagraph on Keck/NIRC2. High-contrast imaging opens up the possibility to search for exoplanets, brown dwarfs, circumbinary companion stars, and protoplanetary disks in these extreme systems. Here we present the first near-infrared high-contrast images of 13 high-mass X-ray binaries located within ∼2–3 kpc. The key results of this campaign involve the discovery of several candidate circumbinary companions ranging from substellar (brown dwarf) to stellar masses. By conducting an analysis based on Galactic population models, we discriminate sources that are likely background/foreground stars and isolate those that have a high probability (≳60%–99%) of being gravitationally bound to the X-ray binary. This paper seeks to establish a preliminary catalog for future analyses of proper motion and subsequent observations. With our preliminary results, we calculate the first estimate of the companion frequency and the multiplicity frequency for X-ray binaries: ≈0.6 and 1.8 ± 0.9, respectively, considering only the sources that are most likely bound to the X-ray binary. In addition to extending our comprehension of how brown dwarfs and stars can form and survive in such extreme systems, our study opens a new window to our understanding of the formation of X-ray binaries.
In an earlier campaign to characterize the mass of the transiting temperate super-Earth K2-18b with HARPS, a second, non-transiting planet was posited to exist in the system at ~9 days. Further ...radial velocity follow-up with the CARMENES spectrograph visible channel revealed a much weaker signal at 9 days, which also appeared to vary chromatically and temporally, leading to the conclusion that the origin of the 9-day signal was more likely related to stellar activity than to a planetary presence. Here we conduct a detailed reanalysis of all available RV time-series – including a set of 31 previously unpublished HARPS measurements – to investigate the effects of time-sampling and of simultaneous modelling of planetary plus activity signals on the existence and origin of the curious 9-day signal. We conclude that the 9-day signal is real and was initially seen to be suppressed in the CARMENES data due to a small number of anomalous measurements, although the exact cause of these anomalies remains unknown. Investigation of the signal’s evolution in time with wavelength and detailed model comparison reveals that the 9-day signal is most likely planetary in nature. Using this analysis, we reconcile the conflicting HARPS and CARMENES results and measure precise and self-consistent planet masses of mp,b = 8.63 ± 1.35 and mp,c sinic = 5.62 ± 0.84 Earth masses. This work, along with the previously published RV papers on the K2-18 planetary system, highlights the importance of understanding the time-sampling and of modelling the simultaneous planet plus stochastic activity, particularly when searching for sub-Neptune-sized planets with radial velocities.
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