Modons on tidally synchronised extrasolar planets

We investigate modons on tidally synchronised extrasolar planets. Modons are highly dynamic, coherent flow structures composed of a pair of storms with opposite signs of vorticity. They are important because they divert flows on the large-scale; and, powered by the intense irradiation from the host star, they are planetary-scale sized and exhibit quasi-periodic life-cycles – chaotically moving around the planet, breaking and reforming many times over long durations (e.g. thousands of planet days). Additionally, modons transport and mix planetary-scale patches of hot and cold air around the planet, leading to high-amplitude and quasi-periodic signatures in the disc-averaged temperature flux. Hence, they induce variations of the “hotspot” longitude to either side of the planet’s sub-stellar point - consistent with observations at different epoch. The variability behaviour in our simulations broadly underscores the importance of accurately capturing vortex dynamics in extrasolar planet atmosphere modelling, particularly in understanding current observations.

On the role of orbital migration in the early phases of the evolution of planetary systems

<p class="western" lang="en-GB" align="justify">Past, present and forthcoming space missions (e.g. Kepler/K2, TESS, CHEOPS, JWST, PLATO, ARIEL) and ground-based observational facilities (e.g. VLT, VLTI, ALMA) were, are and will be the sources of the high quality data necessary to unveil the properties of the planetary systems. Thanks to them the recent enormous increase in number of known planets gives a unique opportunity to study the processes responsible for planet formation and evolution in more detail. The observed properties of numerous planets allow for the robust constraints to be put on planet formation models. Both ground and space-based surveys have derived distributions of fundamental planetary properties like the frequency of planets in the mass-distance and radius-distance planes, the planetary mass function, the eccentricity distribution, or the planetary mass-radius relation. Now it is possible to compare the theoretical predictions with the observed properties of the planet population as a whole. The technique used for this comparison is known as the planet population synthesis [1-4]. One of the assumptions in this method is the migration rate of the planets. At the early stages of the evolution, when planets are still embedded in a gaseous disc, the tidal interactions between the disc and planets cause the planetary orbital migration. The orbital migration may play an important role in shaping stable planetary configurations. The outcome of the simulation depends strongly on the way in which the planets migrate. An understanding of this stage of the evolution will provide insight on the most frequently formed architectures, which in turn are relevant for determining the planet habitability.</p> <p class="western" lang="en-GB" align="justify">There has been recently an important development in the understanding of the orbital migration of planets which are able to open a partial gap in the protoplanetary disc (e.g. [5], [6], and references therein). It has been shown that such planets migrate differently than it has been assumed till now [7]. This subject is now at the leading edge of the studies of the dynamical interactions that occur in newly formed planetary systems. Here, we are going to present our most recent results on the two super-Earths migrating in a gaseous protoplanetary disc.</p> <p class="western" lang="en-GB" align="justify">[1] Mordasini, C., Alibert, Y., Benz, W. (2009), Extrasolar planet population synthesis. I. Method, formation tracks, and mass-distance distribution, A&A, 501, 1139</p> <p class="western" lang="en-GB" align="justify">[2] Mordasini, C., Alibert, Y., Benz, W., Naef, D. (2009), Extrasolar planet population synthesis. II. Statisticalcomparison with observations, A&A, 501, 1139</p> <p class="western" lang="en-GB" align="justify">[3] Alibert, Y., Carron, F., Fortier, A., et al. (2013), Theoretical models of planetary system formation: mass vs. semi-major axis, A&A, 558, A109</p> <p class="western" lang="en-GB" align="justify">[4] Benz, W., Ida, S., Alibert, Y., Lin, D., & Mordasini, C. (2014), Planet Population Synthesis, Protostars and Planets VI, 691</p> <p class="western" lang="en-GB" align="justify">[5] Robert C. M. T., Crida A., Lega E., Méheut H., Morbidelli A. (2018) Toward a new paradigm for Type II migration, A&A, 617, A98</p> <p class="western" lang="en-GB" align="justify">[6] Kanagawa, K. D., Tanaka, H., & Szuszkiewicz, E, (2018), Radial migration of gap-opening planets in protoplanetary disks. I. The case of a single planet ApJ, 861, 140</p> <p class="western" lang="en-GB" align="justify">[7] Duffell, P. C., Haiman, Z., MacFadyen, A. I., D’Orazio, D. J., Farris, B. D. (2014), The Migration of  Gap-Opening Planets is not Locked to Viscous Disk Evolution , ApJL, 792, L10</p>

Dust from Colliding Asteroids Masqueraded as a Planet

New analysis of Hubble Space Telescope images suggests that Fomalhaut b, once believed to be an extrasolar planet, is, in fact, a cloud of dust that likely formed from the collision of enormous asteroids.

Frequency of Planets in Binaries

The frequency of planets in binaries is an important issue in the field of extrasolar planet studies because of its relevance in the estimation of the global planet population of our galaxy and the clues it can give to our understanding of planet formation and evolution. Multiple stars have often been excluded from exoplanet searches, especially those performed using the radial velocity technique, due to the technical challenges posed by such targets. As a consequence and despite recent efforts, our knowledge of the frequency of planets in multiple stellar systems is still rather incomplete. On the other hand, the lack of knowledge about the binarity at the time of the compilation of the target samples means that our estimate of the planet frequency around single stars could be tainted by the presence of unknown binaries, especially if these objects have a different behavior in terms of planet occurrence. In a previous work we investigated the binarity of the objects included in the Uniform Detectability sample defined by Fisher and Valenti (2005), showing how more than 20% of their targets were, in fact, not single stars. Here, we present an update of this census, made possible mainly by the information now available thanks to the second Gaia Data Release. The new binary sample includes a total of 313 systems, of which 114 were added through this work. We were also able to significantly improve the estimates of masses and orbital parameters for most of the pairs in the original list, especially those at close separations. A few new systems with white dwarf companions were also identified. The results of the new analysis are in good agreement with the findings of our previous work, confirming the lack of difference in the overall planet frequency between binaries and single stars but suggesting a decrease in the planet frequency for very close pairs.

Simulation of Extrasolar Planet Detection with Rotationally Shearing Interferometer at 10 µm

We simulate the interferometric fringe patterns for the case of an extrasolar planet system with two planets. We show that the incidence distributions become more complicated, yet their interpretation is feasible. The generalized fringe distributions rotate when the Dove prism is rotated. Likewise, the number of fringes changes with the angle of rotation of the Dove prism.

Ross 128 – GL 447

Context. Long-term chromospheric activity in slow-rotating fully convective stars has scarcely been explored. Ross 128 (Gl 447) is a slow-rotator and inactive dM4 star that has been extensively observed. It hosts the fourth closest extrasolar planet. Aims. Ross 128 is an ideal target to test dynamo theories in slow-rotating low-mass stars. Methods. To characterize the magnetic activity of Ross 128, we studied the SK-indexes derived from CASLEO, HARPS, FEROS, UVES, and X-shooter spectra. Using the generalized Lomb-Scargle and CLEAN periodograms, we analyzed the whole SK time-series obtained between 2004 and 2018. We performed a similar analysis for the Na I-index, and we analyzed its relation with the SK-index. Results. From both indexes, we obtain a possible activity cycle with a period of about five years, which is one of a small handful of activity cycles that have been reported for a slow-rotating fully convective star.

Matrix-propagator approach to compute fluid Love numbers and applicability to extrasolar planets

Context.The mass and radius of a planet directly provide its bulk density, which can be interpreted in terms of its overall composition. Any measure of the radial mass distribution provides a first step in constraining the interior structure. The fluid Love numberk2provides such a measure, and estimates ofk2for extrasolar planets are expected to be available in the coming years thanks to improved observational facilities and the ever-extending temporal baseline of extrasolar planet observations.Aims.We derive a method for calculating the Love numbersknof any object given its density profile, which is routinely calculated from interior structure codes.Methods.We used the matrix-propagator technique, a method frequently used in the geophysical community.Results.We detail the calculation and apply it to the case of GJ 436b, a classical example of the degeneracy of mass-radius relationships, to illustrate how measurements ofk2can improve our understanding of the interior structure of extrasolar planets. We implemented the method in a code that is fast, freely available, and easy to combine with preexisting interior structure codes. While the linear approach presented here for the calculation of the Love numbers cannot treat the presence of nonlinear effects that may arise under certain dynamical conditions, it is applicable to close-in gaseous extrasolar planets like hot Jupiters, likely the first targets for whichk2will be measured.