D. Vernet

RETURN OF THE KING: TIME-SERIES PHOTOMETRY OF FO AQUARII’S INITIAL RECOVERY FROM ITS UNPRECEDENTED 2016 LOW STATE

In 2016 May, the intermediate polar FO~Aqr was detected in a low state for the first time in its observational history. We report time-resolved photometry of the system during its initial recovery from this faint state. Our data, which includes high-speed photometry with cadences of just 2 sec, shows the existence of very strong periodicities at 22.5 min and 11.26 min, equivalent to the spin-orbit beat frequency and twice its value, respectively. A pulse at the spin frequency is also present but at a much lower amplitude than is normally observed in the bright state. By comparing our power spectra with theoretical models, we infer that a substantial amount of accretion was stream-fed during our observations, in contrast to the disk-fed accretion that dominates the bright state. In addition, we find that FO~Aqrs rate of recovery has been unusually slow in comparison to rates of recovery seen in other magnetic cataclysmic variables, with an

A polarimetric investigation of Jupiter: Disk-resolved imaging polarimetry and spectropolarimetry

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Spatial intensity interferometry on three bright stars

-folding time of 115

The phase-polarization curve of asteroid (3200) Phaethon†

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Optical long baseline intensity interferometry: prospects for stellar physics

days. The recovery also shows irregular variations in the median brightness of as much as 0.2~mag over a 10-day span. Finally, we show that the arrival times of the spin pulses are dependent upon the systems overall brightness.

Optical design options for hypertelescopes and prototype testing

Context. Polarimetry is a powerful remote sensing tool to characterise solar system planets and, potentially, to detect and characterise exoplanets. The linear polarisation of a planet as a function of wavelength and phase angle is sensitive to the cloud and haze particle properties in planetary atmospheres, as well as to their altitudes and optical thicknesses.Aims. We present for the first time polarimetric signals of Jupiter mapped over the entire disk, showing features such as contrasts between the belts and zones, the polar regions, and the Great Red Spot. We investigate the use of these maps for atmospheric characterisation and discuss the potential application of polarimetry to the study of the atmospheres of exoplanets. Methods. We have obtained polarimetric images of Jupiter, in the B , V , and R filters, over a phase angle range of α = 4°–10.5°. In addition, we have obtained two spectropolarimetric datasets, over the wavelength range 500–850 nm. An atmospheric model was sought for all of the datasets, which was consistent with the observed behaviour over the wavelength and phase angle range. Results. The polarimetric maps show clear latitudinal structure, with increasing polarisation towards the polar regions, in all filters. The spectropolarimetric datasets show a decrease in polarisation as a function of wavelength along with changes in the polarisation in methane absorption bands. A model fit was achieved by varying the cloud height and haze optical thickness; this can roughly produce the variation across latitude for the V and R filters, but not for the B filter data. The same model particles are also able to produce a close fit to the spectropolarimetric data. The atmosphere of Jupiter is known to be complex in structure, and data taken at intermediate phase angles (unreachable for Earth-based telescopes) seems essential for a complete characterisation of the atmospheric constituents. Because exoplanets orbit other stars, they are observable at intermediate phase angles and thus promise to be better targets for Earth-based polarimetry.

Intensity interferometry revival on the Côte d’Azur

The present articlereports on the first spatial intensity interferometry measurements on stars since the observations at Narrabri Observatory by Hanbury Brown et al. in the 1970s. Taking advantage of the progresses in recent years on photon-counting detectors and fast electronics, we were able to measure the zero-time delay intensity correlation

Rotational variation of the linear polarization of the asteroid (3200) Phaethon as evidence for inhomogeneity in its surface properties

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New polarimetric and spectroscopic evidence of anomalous enrichment in spinel-bearing calcium-aluminium-rich inclusions among L-type asteroids

between the light collected by two 1-m optical telescopes separated by 15 m. Using two marginally resolved stars (

Temporal intensity interferometry: photon bunching in three bright stars

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