Did you know about XO-2b? This hot-Jupiter, discovered in 2007 by Burke et al., orbits its parent star XO-2N which is a component of a wide binary system. The companion star XO-2S is
separated by a projected distance of ~4600 AU, with both stars being almost twins (and similar to our Sun, but older) and sharing an equal proper motion. Thanks to radial velocity measurements collected with the spectrograph HARPS-N at the Telescopio Nazionale Galileo in the framework of the Italian program GAPS (Global Architecture of Planetary Systems), Desidera et al. discovered a couple of planets orbiting XO-2S, one slightly more massive than Jupiter at 0.48 AU, and a Saturn-mass planet at 0.13 AU. This is the first confirmed case of a wide binary whose components both host planets, one of which is transiting, and this makes the XO-2 system a unique laboratory for understanding the diversity of planetary systems.
As described in the paper, the APACHE survey provided an important contribution to the discovery. Both the bright stars of the XO-2 system were scheduled for a photometric follow-up with one of the APACHE telescopes right after it became clear that XO-2S was orbited by companions of planetary origin. The follow-up aimed to look for possible transits of the inner planet and to attempt a measurement of the star rotation period, a very relevant information necessary to confirm the keplerian nature of the signals found in the radial velocities. The XO-2 field was monitored by APACHE for more than 40 nights and data did not revealed any signal related to spin-axis stellar rotation close to the ~18 days orbital period of the inner planet. It seems that the star is rotating at ~25 days, even if, being a quiet star, the observed photometric modulation could not be related to the rotation of the star. On the other hand, thanks to the APACHE photometry it was possible to measure with high confidence the rotation period of the more active companion XO-2N, which appears to be ~40 days.
It has been a real great pleasure for all the members of the APACHE Project to have two members of the MEarth Project team as guests of the Astronomical Observatory of the Aosta Valley. Prof. David Charbonneau (Harvard University) and Dr. Zach Berta-Thompson (Torres Fellow for Exoplanetary Research at the Massachusetts Institute of Technology) came to visit us and to share their long experience matured after 6 years since the first light of the MEarth telescopes, operating at Fred Lawrence Whipple Observatory (FLWO) on Mount Hopkins (Arizona), with now eight “twins” regularly observing at Cerro Tololo Inter-American Observatory (CTIO) on Cerro Tololo (Chile). It has been a nice and very productive discussion, and we all hope that a strong synergy between the different surveys in the world devoted primarily to the search for planets around M dwarfs could be established in the very near future. Indeed, small telescopes used for observing cool stars are really cool!
The Astronomical Observatory of the Autonomous Region of the Aosta Valley will host the 23rd edition of the Star Party on 2014, September 26-28. This edition will be particularly rich of events for all the amateur astronomers, and a dedicated Web site is available for any information: www.starparty.it
The APACHEs welcome every lover of the starry sky who is interested to participate!
Mario Damasso will attend the meeting Exclimes III – The diversity of planetary atmospheres in Davos (Switzerland). He will present a poster about the APACHE Project, showing some results of the first observing season.
Planets transiting their parent M dwarf are very important targets for studying their atmosphere, and APACHE is expected to provide a relevant contribution in this field by detecting new exoplanets.
As reported few days ago in a very interesting article published on the BBC site, after the M3 candidate mission presentations in Paris, the recommendation to the Science Programme Committee (SPC) has been made: PLATO 2.0 is uniquely proposed for M3 selection. The final decision will be made only in February 19-20, but the community of all the planet hunters can be very optimistic. We invite the Italian astronomical community and all the amateur astronomers to read an interesting article appeared today in the national newspaper Il Sole 24ore.
EChO (Exoplanet Characterisation Observatory) is one of the ESA M3 mission candidates currently assessed for an expected launch in 2022 and it designed for looking at the atmospheres of planets that transit their host star. Extrasolar planets transiting M dwarfs are among the most appealing targets for ECho ad the APACHE survey can contribute significantly in the target selection to be observed from space. In a very recent paper (http://arxiv.org/abs/1401.4611) G. Micela et al. analyse the targets suitable for EChO observations which are expected to result from a sample of present and forthcoming detection surveys, such as APACHE.
On January 20 Mario Damasso will give a talk about the APACHE survey at IPAG (Institut de Planétologie et d’Astrophysique de Grenoble). During the talk will be described the milestones of the Project and discussed some results from the first observing season.
A new paper from the APACHE team presenting the discovery and first characterization of more than 80 variable stars has been accepted for publication in The Journal of the American Association of Variable Star Observers (JAAVSO).
M. Damasso et al. New variable stars discovered by the APACHE survey. I. Results after the first observing season
Abstract - We present more than 80 new variable stars discovered during the first observing season of the APACHE survey. APACHE is a project aimed at detecting extrasolar planets transiting nearby, bright M dwarfs by using an array of small-aperture telescopes. Despite the survey is targeted to a well defined sample of cool stars, we reduce and analyze data also for all the detected field stars. Since July 2012 dozens of different stellar fields have been monitored, leading to the detection of several variables for which we propose a classification and estimate a period, when a periodicity is evident in the data. Thanks to the SuperWASP public archive, we have also retrieved and analyzed photometric data collected by the SWASP survey, which helped us to refine the classification and the period estimation of many variables found in the APACHE database. Some of the variables present peculiarities and thus are discussed separately.
The paper will be soon accessible at this address http://www.aavso.org/ejaavso
On 8 December 2013 the Government of South Africa proclaimed the Day of Prayer and Reflection for Nelson Mandela. On that occasion, the researchers carrying out the APACHE Project at the Astronomical Observatory of the Autonomous Region of the Aosta Valley have dedicated their scientific work and observations to his memory.
Nelson Mandela (1918-2013) was awarded the Nobel Peace Prize in 1993 together with Frederik Willem de Klerk for their work for the peaceful termination of the apartheid regime. He was the first President of South Africa elected in a fully represented democratic election on 27 April 1994 and the first black President of his country. Nelson Mandela passed away on 5 December 2013. He firmly believed that the struggle for political freedom and democracy was closely associated with the development of scientific and technological capacity and, as a statesman, he favoured policies with this goal. African astronomers and astrophysicist owe also to this vision the fact that world level state-of-the-art astronomical facilities such as the South Africa Large Telescope (SALT) and the Square Kilometer Array (SKA) are based in the African continent.
In 2011 the International Astronomical Union, the largest body of professional astronomers in the world, has set up the Office of Astronomy for Development in partnership with the South African National Research Foundation with the purpose “to use astronomy to make the world a better place”. Of course, South Africa scientists take part to International projects for the search for exoplanets too. As researchers of the APACHE Project, we hope that our study can give a contribution, even a little one, to make the world a better place. Hamba Kahle Madiba!
An article titled Astronomers revisit dwarf stars’ promise appeared in the News section of the Nature journal on October 31th. The APACHE Project is cited together with analogous present and future surveys, primarly MEarth. In the article, the efforts of ground-based surveys targeted to M dwarfs are discussed in light of the findings made by the Kepler satellite. The essence of this publication is that the hard work of the Apaches is indeed required, and ground-based intensive observations are very important to increase the statistics of exoplanets orbiting cool stars. Our sleeves are always rolled up!