Final Report Summary - ACTIVITY & PLANETS (The effect of stellar magnetic activity on protoplanetary discs and exoplanet detection) Executive Summary:Our Sun is known to harbour magnetic fields which cause myriad of phenomena, e.g. starspots, flares, and coronal mass ejections. The strength of the magnetic field and the frequency of the associated phenomena is strongly linked to the rotation of the star, with rapid rotation enhancing the field generation. Most stars are born as rapid rotators, and therefore young solar-like stars have a strong dynamo created magnetic field, which manifests itself as a high level of magnetic activity. All these energetic events can heat the gas and dust disc that was left over from the star formation process and is now surrounding the young star. These discs are the location of planet formation and the extra heating provided by the activity can have an impact on the composition of the disc, and thus also affecting the planet and planetary system formation process. Even older cool stars retain some of their activity, as is seen in the results from the Kepler satellite which have shown that many old solar-like stars are more active than the Sun. The phenomena caused by the stellar magnetic activity can also show spectral effects that can be interpreted as the stellar radial velocity changes caused by orbiting planets. This so-called 'jitter' makes it at times difficult to distinguish between planets and activity signatures.The aims of the Marie Curie fellowship ACTIVITY&PLANETS were twofold:1) Studying radial velocity jitter using a realistic stellar activity patterns on different types of stars. Synthetic observations are used to probe the errors the different activity cases introduce to the orbital parameters of the planets.2) Using mid-infrared and sub-millimetre observations for studying the effect of the stellar magnetic activity on protoplanetary discs.PLANET DETECTABILITY SUB-PROJECTThe planet detectability sub-project was started by investigating in detail realistic spot models. The amount of 'jitter' is highly dependent on the amount of spots, and also on their exact configurations. Our investigation concentrated on solar-like stars, which are of interest for finding a real Earth's twin. Another class of stars that is especially interesting for studying the effect of magnetic activity on the exoplanets and their detection are the cool main sequence stars, M dwarfs. Due to their abundance, long lifetimes, and low mass and luminosity, M dwarfs are considered prime targets for planet searches. The fainter and less massive the star, the easier planets are detected around them. In addition, since low-mass M dwarfs are much cooler than Sun-like stars, the zone around the star where the temperature is right for water to exist is much closer to the star, making a "Goldilocks Planet" that is just right for life easier to detect. However M dwarfs can be magnetically very active, which causes considerable noise in the exoplanet detection, and also raises serious questions on their habitabilityWe have investigated the activity patterns and the 'jitter' they cause in solar-like stars and M dwarfs. Solar-like activity patterns, activity patterns seen in very active stars, and also patterns predicted by simulations were used as starting points. In addition, the cyclically changing amount of spots and their effect on 'jitter' were studied. We used stellar atmosphere models when creating spectral line-profiles arising from different activity patterns. We confirm the earlier results that the amount of 'jitter' is wavelength dependent and decreases towards redder wavelengths. In addition we discovered that the amount of 'jitter' increases with the decreasing surface temperature of the star, even when the effects of the temperature contrast between the unspotted stellar surface and the spot are taken into account.The main effort of this sub-project concentrated in investigating the effect of activity in the determined orbital parameters of the planets. For this work we introduced planets to the spectra that already included the signatures of cool spots. We processed the synthetic spectra the same way as would have been done when searching for exoplanets using radial velocity method, including analysing the obtained radial velocities and determining the orbital parameters of the planets. We then could compare the obtained results to the real orbital parameters of the planet that was introduced to the spectra. Our results show that even small amounts of stellar activity causes errors in the orbital parameters of the detected planets (Korhonen et al., 2013 MNRAS, see later).ACTIVITY AND PROTOPLANETARY DISCS SUB-PROJECT:Theoretical calculations show that X-ray emission from the central object strongly enhances H3+ creation in the circumstellar disc, which on the other hand can have serious implications on the disc chemistry. H3+ is the starting point for the evolution of the oxygen, carbon, and nitrogen chemistries and thus crucial for formation of numerous molecules. Under standard CO abundances H3+ is efficiently removed through reaction with CO which creates HCO+ and H2 molecules. Investigating HCO+ and H3+ in the discs around young stars experiencing high X-ray flux, related to the magnetic activity of the star, is of utmost importance in understanding the effect of stellar X-rays on the disc chemistry.For a pilot study using the Atacama Large Millimeter/submillimeter Array (ALMA) we proposed to investigate HCO+ and CO molecular emission in three young, X-ray luminous, solar mass stars in the Orion Nebula Cluster. They were found during the Chandra Orion Ultradeep Project which detected 1616 X-ray sources, from which more than 1400 are confirmed to belong to the Orion starforming region. From the detected 28 solar mass stars we selected three most X-ray luminous sources which also have a disc in a low accretion state for an ALMA path-finder study. The ALMA allocation committee comments to this proposal were very encouraging. Still, during the Cycle 1, where the array is being constructed, only very limited number of proposal can be carried out and it is very unlikely that our observations will be executed. We will reapply in Cycle 2 (deadline December 2013) taking into account the comments from the allocation committee.In addition, we investigated H3+ directly using mid-infrared spectroscopy. H3+ has several strong transitions around 3.5-4.0 micrometres. In a first pathfinder project we proposed to use CRIRES high resolution infrared spectrograph at the European Southern Observatory's flagship facility Very Large Telescope to detect H3+ in an optimum target. This project would pave a way for a more detailed observational study to understand the role of stellar X-ray luminosity on disc chemistry, using a sample of pre-main sequence stars with a range of X-ray luminosities. We were granted observing time with CRIRES and the observations for the pilot project were carried out in June 2013. We have done the preliminary data reduction and the spectra show possible indications of very intriguing emission features close to the wavelengths of the two strongest transitions of H3+. We are working on the final data reduction to verify the existence of these emission features. If these features are verified, they provide the first direct measurement of H3+ in a circumstellar disc and will enable us to determine total column density of H3+ and the ionisation fraction in the inner disc. All this would warrant a high level publication.
