Feedback-limited Accretion: Luminous Signatures from Growing Planets

Planets form in discs of gas and dust around stars, and keep growing by accretion of disc material while available. Massive planets clear a gap in that protoplanetary disc, but still accrete through spiral wakes. On its way to the planet, the gas will settle on a \emph{circumplanetary} disc around the planet and slowly accrete on to it. The energy of the accreted gas will be released, heating the planet surroundings in a feedback process. For high enough accretion rates the planet should be detectable at infrared wavelengths. We aim to find whether detectable planet luminosities, $\gtrsim 10^{-3} \, \textrm{L}_\odot$, can occur when considering that the planet luminosity is coupled to the accretion, and also to study which other effects has the feedback on the dynamics of the circumplanetary and the gap regions. We model a planet with mass ratio $q=10^{-3}$, orbiting at 10 AU from a solar mass star, using a modified version of the 2D code FARGO-AD, which includes a prescription for the accretion and feedback luminosity of the planet. We find that the planetary feedback is able to partially deplete the circumplanetary disc, and to reduce the accretion rate onto the planet. However, detectable luminosities of $L_\textrm{p}\gtrsim 10^{-3}\, \textrm{L}_\odot$ are still produced. The feedback also contributes to partially refilling the gap, to heat up the coorbital region, and to perturb the orbital velocity of the gas.Comment: Submitted to MNRA

Dusty spirals triggered by shadows in transition discs

Context. Despite the recent discovery of spiral-shaped features in protoplanetary discs in the near-infrared and millimetric wavelengths, there is still an active discussion to understand how they formed. In fact, the spiral waves observed in discs around young stars can be due to different physical mechanisms: planet/companion torques, gravitational perturbations or illumination effects. Aims. We study the spirals formed in the gaseous phase due to two diametrically opposed shadows cast at fixed disc locations. The shadows are created by an inclined non-precessing disc inside the cavity, which is assumed to be optically thick. In particular, we analyse the effect of these spirals on the dynamics of the dust particles and discuss their detectability in transition discs. Methods. We perform gaseous hydrodynamical simulations with shadows, then we compute the dust evolution on top of the gaseous distribution, and finally we produce synthetic ALMA observations of the dust emission based on radiative transfer calculations. Results. Our main finding is that mm- to cm-sized dust particles are efficiently trapped inside the shadow-triggered spirals. We also observe that particles of various sizes starting at different stellocentric distances are well mixed inside these pressure maxima. This dynamical effect would favour grain growth and affect the resulting composition of planetesimals in the disc. In addition, our radiative transfer calculations show spiral patterns in the disc at 1.6 {\mu}m and 1.3 mm. Due to their faint thermal emission (compared to the bright inner regions of the disc) the spirals cannot be detected with ALMA. Our synthetic observations prove however that shadows are observable as dips in the thermal emission.Comment: 15 pages, 11 figures, accepted for publication in A&

Producción de Anabaena sp. ATCC 33047 y valorización de la fracción proteica de su biomasa.

La cianobacteria Anabaena sp. ATCC 33047, se ha cultivado en 3 medios de cultivo exentos de nitrógeno, que varían ligeramente en su composición, más otro medio con fuente de nitrógeno asimilable. Con ello se determinó que el uso de fertilizantes agrícolas exentos de nitrógeno en la formulación de éstos, es adecuado para la producción de esta cianobacteria en sistemas a gran escala. Por otro lado, la adición de una fuente de nitrógeno en el medio de cultivo, mejoró la viabilidad y velocidad de crecimiento de la cianobacteria. La biomasa obtenida de Anabaena, se ha utilizado para la obtención de un suplemento nutricional para plantas, mediante la hidrólisis enzimática de las proteínas contenidas en esta biomasa. Este producto, con una concentración en aminoácidos sobre 36 g/L, se obtiene de la separación de la masa sólida residual y de la fase acuosa, de la mezcla hidrolizada enzimáticamente

Estimation of <i>Vs</i> profile using its natural frequency and Rayleigh-wave dispersion characteristics

International audienceThe evaluation of the natural frequency of random Vs profiles before analyzing the fundamental Rayleigh-wave dispersion characteristics is proposed in this paper. The inclusion of this parameter optimizes the effectiveness of random inverse searching to estimate Vs profiles. To demonstrate this method, a numerical test was performed using the "experimental" Rayleigh-wave dispersion curve obtained for a fictitious TEST site

Limiting eccentricity of sub-parsec massive black hole binaries surrounded by self-gravitating gas discs

We study the dynamics of supermassive black hole binaries embedded in circumbinary gaseous discs, with the SPH code Gadget-2. The sub-parsec binary (of total mass M and mass ratio q=1/3) has excavated a gap and transfers its angular momentum to the self--gravitating disc (M_disc=0.2 M). We explore the changes of the binary eccentricity e, by simulating a sequence of binary models that differ in the initial eccentricity e_0, only. In initially low-eccentric binaries, the eccentricity increases with time, while in high-eccentric binaries e declines, indicating the existence of a limiting eccentricity e_crit that is found to fall in the interval [0.6,0.8]. We also present an analytical interpretation for this saturation limit. An important consequence of the existence of e_crit is the detectability of a significant residual eccentricity e_LISA} by the proposed gravitational wave detector LISA. It is found that at the moment of entering the LISA frequency domain e_LISA ~ 10^{-3}-10^{-2}; a signature of its earlier coupling with the massive circumbinary disc. We also observe large periodic inflows across the gap, occurring on the binary and disc dynamical time scales rather than on the viscous time. These periodic changes in the accretion rate (with amplitudes up to ~100%, depending on the binary eccentricity) can be considered a fingerprint of eccentric sub-parsec binaries migrating inside a circumbinary disc.Comment: 10 pages, 7 figures, accepted for publication in MNRA