Context. Interferometry can provide spatially resolved observations of massive star binary systems and their colliding winds, which thus far have been studied mostly with spatially unresolved ...observations. Aims. We present the first AMBER/VLTI observations, taken at orbital phase 0.32, of the Wolf-Rayet and O (WR+O) star binary system \gamma arrow up Velorum and use the interferometric observables to constrain its properties. Methods. The AMBER/VLTI instrument was used with the telescopes UT2, UT3, and UT4 on baselines ranging from 46 m to 85 m. It delivered spectrally dispersed visibilities, as well as differential and closure phases, with a resolution R =1500 in the spectral band 1.95-2.17 \mum. We interpret these data in the context of a binary system with unresolved components, neglecting in a first approximation the wind-wind collision zone flux contribution. Results. Using WR- and O-star synthetic spectra, we show that the AMBER/VLTI observables result primarily from the contribution of the individual components of the WR+O binary system. We discuss several interpretations of the residuals, and speculate on the detection of an additional continuum component, originating from the free-free emission associated with the wind-wind collision zone (WWCZ), and contributing at most to the observed K-band flux at the 5% level. Based on the accurate spectroscopic orbit and the Hipparcos distance, the expected absolute separation and position angle at the time of observations were 5.1\pm0.9 mas and 66\pm15 degree , respectively. However, using theoretical estimates for the spatial extent of both continuum and line emission from each component, we infer a separation of 3.62 super(+0.11) sub(-0.30) mas and a position angle of 73 \degr, compatible with the expected one. Our analysis thus implies that the binary system lies at a distance of 368 super(+38) sub(-13) pc, in agreement with recent spectrophotometric estimates, but significantly larger than the Hipparcos value of 258 super(+41) sub(-31) pc.
The young stellar object MWC 297 is an embedded B1.5Ve star exhibiting strong hydrogen emission lines and a strong near-infrared continuum excess. This object has been observed with the VLT ...interferometer equipped with the AMBER instrument during its first commissioning run. VLTI/AMBER is currently the only near infrared interferometer which can observe spectrally dispersed visibilities. MWC 297 has been spatially resolved in the continuum with a visibility of $0.50^{+0.08}_{-0.10}$ as well as in the Brgamma emission line where the visibility decrease to a lower value of $0.33\pm0.06$. This change in the visibility with the wavelength can be interpreted by the presence of an optically thick disk responsible for the visibility in the continuum and of a stellar wind traced by the Brgamma emission line and whose apparent size is 40% larger. We validate this interpretation by building a model of the stellar environment that combines a geometrically thin, optically thick accretion disk model consisting of gas and dust, and a latitude-dependent stellar wind outflowing above the disk surface. The continuum emission and visibilities obtained from this model are fully consistent with the interferometric AMBER data. They agree also with existing optical, near-infrared spectra and other broad-band near-infrared interferometric visibilities. We also reproduce the shape of the visibilities in the Brgamma line as well as the profile of this line obtained at an higher spectral resolution with the VLT/ISAAC spectrograph, and those of the Halpha and Hbeta lines. The disk and wind models yield a consistent inclination of the system of approximately 20 degrees. A picture emerges in which MWC 297 is surrounded by an equatorial flat disk that is possibly still accreting and an outflowing wind which has a much higher velocity in the polar region than at the equator. The VLTI/AMBER unique capability to measure spectral visibilities therefore allows us for the first time to compare the apparent geometry of a wind with the disk structure in a young stellar system.
CubeSats are tiny satellites with increasing capabilities. They have been used for more than a decade by universities to train students on space technologies, in a hands-on project aiming at ...building, launching and operating a real satellite. Still today, one shortcoming of CubeSats is their poor ability to transmit large amounts of data to the ground. A possible way to overcome this limitation relies on optical communications. Universite Cote d'Azur is studying the feasibility of a student's CubeSat whose main goal is to transmit data with an optical link to the ground at the moderate rate of 1 kb/s (or better). In this paper, we will present the current state of the project and its future developments.
Microlensing detections of cool planets are important for the construction of an unbiased sample to estimate the frequency of planets beyond the snow line, which is where giant planets are thought to ...form according to the core accretion theory of planet formation. In this paper, we report the discovery of a giant planet detected from the analysis of the light curve of a high-magnification microlensing event MOA-2010-BLG-477. The measured planet-star mass ratio is \(q=(2.181\pm0.004)\times 10^{-3}\) and the projected separation is \(s=1.1228\pm0.0006\) in units of the Einstein radius. The angular Einstein radius is unusually large \(\theta_{\rm E}=1.38\pm 0.11\) mas. Combining this measurement with constraints on the "microlens parallax" and the lens flux, we can only limit the host mass to the range \(0.13<M/M_\odot<1.0\). In this particular case, the strong degeneracy between microlensing parallax and planet orbital motion prevents us from measuring more accurate host and planet masses. However, we find that adding Bayesian priors from two effects (Galactic model and Keplerian orbit) each independently favors the upper end of this mass range, yielding star and planet masses of \(M_*=0.67^{+0.33}_{-0.13}\ M_\odot\) and \(m_p=1.5^{+0.8}_{-0.3}\ M_{\rm JUP}\) at a distance of \(D=2.3\pm0.6\) kpc, and with a semi-major axis of \(a=2^{+3}_{-1}\) AU. Finally, we show that the lens mass can be determined from future high-resolution near-IR adaptive optics observations independently from two effects, photometric and astrometric.
In this work, we present the first AMBER observations, of the Wolf-Rayet and
O (WR+O) star binary system y2 Velorum. The AMBER instrument was used with the
telescopes UT2, UT3, and UT4 on baselines ...ranging from 46m to 85m. It delivered
spectrally dispersed visibilities, as well as differential and closure phases,
with a resolution R = 1500 in the spectral band 1.95-2.17 micron. We interpret
these data in the context of a binary system with unresolved components,
neglecting in a first approximation the wind-wind collision zone flux
contribution. We show that the AMBER observables result primarily from the
contribution of the individual components of the WR+O binary system. We discuss
several interpretations of the residuals, and speculate on the detection of an
additional continuum component, originating from the free-free emission
associated with the wind-wind collision zone (WWCZ), and contributing at most
to the observed K-band flux at the 5% level. The expected absolute separation
and position angle at the time of observations were 5.1±0.9mas and
66±15° respectively. However, we infer a separation of
3.62+0.11-0.30 mas and a position angle of 73+9-11°. Our analysis thus
implies that the binary system lies at a distance of 368+38-13 pc, in agreement
with recent spectrophotometric estimates, but significantly larger than the
Hipparcos value of 258+41-31 pc.
AMBER: a near infrared focal instrument for the VLTI Petrov, Romain G.; Malbet, Fabien; Richichi, Andrea ...
Comptes rendus de l'Académie des sciences. Série IV, Physique, astrophysique,
2001, 2001-1-00, Volume:
2, Issue:
1
Journal Article
Open access
AMBER is the General User near-infrared focal instrument of the Very Large Telescope interferometer. Its specifications are based on three key programs on Young Stellar Objects, Active Galactic ...Nuclei central regions, masses and spectra of hot Extra Solar Planets. It has an imaging capacity because it combines up to three beams and very high accuracy measurement are expected from the spatial filtering of beams by single mode fibers and the comparison of measurements made simultaneously in different spectral channels.
AMBER est l'instruments focal proche infra rouge du mode interférométrique du Très Grand Télescope Européen. Les spécifications de cet instrument généraliste ont été définies pour trois programmes clefs sur les systèmes stellaires en formation, les régions centrales des noyaux actifs de galaxies et les masses et les spectres de planètes extra solaires géantes chaudes. Il combine trois faisceaux, ce qui lui donne une capacité de reconstruction d'images, et est optimisé pour la précision des mesures grâce à un filtrage spatial des faisceaux par des fibres optiques mono mode et à une combinaison des informations obtenues simultanément à différentes longueurs d'onde.
In this work, we present the first AMBER observations, of the Wolf-Rayet and O (WR+O) star binary system y2 Velorum. The AMBER instrument was used with the telescopes UT2, UT3, and UT4 on baselines ...ranging from 46m to 85m. It delivered spectrally dispersed visibilities, as well as differential and closure phases, with a resolution R = 1500 in the spectral band 1.95-2.17 micron. We interpret these data in the context of a binary system with unresolved components, neglecting in a first approximation the wind-wind collision zone flux contribution. We show that the AMBER observables result primarily from the contribution of the individual components of the WR+O binary system. We discuss several interpretations of the residuals, and speculate on the detection of an additional continuum component, originating from the free-free emission associated with the wind-wind collision zone (WWCZ), and contributing at most to the observed K-band flux at the 5% level. The expected absolute separation and position angle at the time of observations were 5.1±0.9mas and 66±15° respectively. However, we infer a separation of 3.62+0.11-0.30 mas and a position angle of 73+9-11°. Our analysis thus implies that the binary system lies at a distance of 368+38-13 pc, in agreement with recent spectrophotometric estimates, but significantly larger than the Hipparcos value of 258+41-31 pc.
Aims. The Antarctica Search for Transiting Extrasolar Planets (ASTEP), an automatized 400 mm telescope located at Concordia station in Antarctica, monitored β Pictoris continuously to detect any ...variability linked to the transit of the Hill sphere of its planet β Pictoris b. The long observation sequence, from March to September 2017, combined with the quality and high level duty cycle of our data, enables us to detect and analyse the δ Scuti pulsations of the star. Methods. Time series photometric data were obtained using aperture photometry by telescope defocussing. The 66 418 data points were analysed using the software package Period04. We only selected frequencies with amplitudes that exceed four times the local noise level in the amplitude spectrum. Results. We detect 31 δ Scuti pulsation frequencies, 28 of which are new detections. All the frequencies detected are in the interval 34.76−75.68 d-1. We also find that β Pictoris exhibits at least one pulsation mode that varies in amplitude over our monitoring duration of seven months.
Aims.
Photometric monitoring of
β
Pic in 1981 showed anomalous fluctuations of up to 4% over several days, consistent with foreground material transiting the stellar disk. The subsequent discovery of ...the gas giant planet
β
Pic b and the predicted transit of its Hill sphere to within a 0.1 au projected separation of the planet provided an opportunity to search for the transit of a circumplanetary disk (CPD) in this 21 ± 4 Myr-old planetary system. We aim to detect, or put an upper limit on, the density and nature of the material in the circumplanetary environment of the planet via the continuous photometric monitoring of the Hill sphere transit that occurred in 2017 and 2018.
Methods.
Continuous broadband photometric monitoring of
β
Pic requires ground-based observatories at multiple longitudes to provide redundancy and to provide triggers for rapid spectroscopic follow-up. These include the dedicated
β
Pic monitoring bRing observatories in Sutherland and Siding Springs, the ASTEP400 telescope at Concordia, and the space observatories BRITE and the
Hubble
Space Telescope (HST). We search the combined light curves for evidence of short-period transient events caused by rings as well as for longer-term photometric variability due to diffuse circumplanetary material.
Results.
We find no photometric event that matches with the event seen in November 1981, and there is no systematic photometric dimming of the star as a function of the Hill sphere radius.
Conclusions.
We conclude that the 1981 event was not caused by the transit of a CPD around
β
Pic b. The upper limit on the long-term variability of
β
Pic places an upper limit of 1.8 × 10
22
g of dust within the Hill sphere (comparable to the ~100 km radius asteroid 16 Psyche). Circumplanetary material is either condensed into a disk that does not transit
β
Pic, condensed into a disk with moons that has an obliquity that does not intersect with the path of
β
Pic behind the Hill sphere, or is below our detection threshold. This is the first time that a dedicated international campaign has mapped the Hill sphere transit of an extrasolar gas giant planet at 10 au.
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