It is sunrise here in the Alps and a very good night has just gone by. While analyzing the data collected last night, we observed an M dwarf of the Apache Input Catalogue flaring (see the light curve in figure. Time (HJD) is on the X-axis). Instead, tonight the star was quite all the time. Since July 2012, when APACHE officially started, it is the first time that we clearly observe a stellar flare occurring on one of our target stars. This should mean that our observing strategy is sensible to flares, which usually last just for few minutes. The star seems to be a mid M dwarf and it should be located at nearly 75 light years from us: when the flare occurred, the Earth was plagued by the Second World War. We did not find in literature any information concerning the activity of this red dwarf, so this appears to be a new finding from APACHE!
Andrea Bernagozzi, scientific researcher at the OAVdA and member of the APACHE research team, will give on Monday, March 25th a talk about extrasolar planets for a refresher course oriented towards Italian high school science teachers.
The talk will be presented at 15.30 hour at the Science Museum of the University of Camerino, Italy (http://www.unicam.it/museoscienzenaturali/docfile/seminari_per%20insegnanti_2013-1-2-3.pdf).
This is for sure a very hot topic! The lively debate concerning the occurrence rate of habitable terrestrial planets around red dwarfs produced a new paper by R. Kopparapu (Penn State University) accepted by the Astrophysical Journal Letters and available here as a pre-print. The manuscript entitled A revised estimate of the occurrence rate of terrestrial planets in the habitable zones around Kepler M-dwarfs is an update of the recent paper by Dressing & Charbonneau that we have advertised in a previous post. According to the new calculations of Kopparapu, based on the Kepler data and new estimated limits for the Habitable Zone (HZ) boundaries, the frequency of terrestrial planets (0.5-1.4 Earth radius) in the HZ of cool stars is increased to 0.48-0.53, while Dressing & Charbonneau calculated the lower value 0.15. Assuming Earth-size planets with 0.5 – 2 Earth radius, the frequency increases to 0.51-0.61 planet/star. So, the potential for finding Earth-like planets around M dwarfs may be higher than previously reported, and the Apaches will search for them with greater enthusiasm!
On 8th of March we had the pleasure to host dr. ZengHua Zhang at the Astronomical Observatory Of the Autonomous Region of the Aosta Valley (OAVdA). He has got his PhD at the Centre for Astrophysics Research (University of Hertfordshire).
ZengHua, during a brief permanence at the INAF – Astrophysical Observatory of Torino, has found the time to come to visit our Observatory and the APACHE telescope array. His research topics include the discovery and characterization of low mass stars and brown dwarfs in large area surveys, the study of the physical properties of disk and halo with benchmarks in binary systems, and the search for the extreme ultracool objects in near-infrared surveys. He gave a very interesting seminar for the OAVdA staff about the ultracool dwarfs in the Galactic Halo (see the picture, of course ZengHua is the one in the middle!), leaving us with an increased curiosity about such celestial objects and about the possibility of existence of planets orbiting ultracool dwarfs.
Here it is the personal Web page of ZengHua.
The paper A Spectroscopic Catalog of the Brightest (J<9) M Dwarfs in the Northern Sky by S. Lépine and collaborators has been accepted for publication in The Astronomical Journal, and it is available as a preprint in the arXiv database (http://arxiv.org/abs/1206.5991).
In the manuscript, a spectroscopic catalog of the 1,564 brightest (J<9) M dwarf candidates in the northern sky is presented, in particular providing fresh information about the spectral subtype and the stellar activity as measured in the H-alpha line. Many of the stars in the Lépine et al. spectroscopic catalogue are in common with those in the Apache Input Catalogue, and some of the latter did not have a reliable spectral subtype. Then, the results from Lépine et al. work are very useful for us for a better definition of the APACHE target list and the observing priorities to assign to each star.
As recently reiterated in a paper by C. D. Dressing and D. Charbonneau (The Occurrence Rate of Small Planets around Small Stars, http://arxiv.org/abs/1302.1647), looking for habitable planets around low-mass stars is a very promising research field. The APACHE Project is working on it every night, when the sky collaborates. Since August, some of the M dwarfs stars observed by the APACHE telescopes are targets also observed by the spectrograph HARPS-N, hosted by the Telescopio Nazionale Galileo (TNG) at the top of La Palma island in the Canary archipelago, in the framework of the very ambitious, challenging and long-term observational programme GAPS (Characterizing the Global Architectures of Planetary Systems).
Today we have received and mounted the telescope number 5 of the APACHE array. In few days it will be operating with the other four already functioning since July, 2012.
Observing the same star for several nights in a row is the way the APACHE team hopes mainly to find a planet around it. But many, nearly consecutive photometric observations of a star could allow us to measure its rotation period. If the star is covered by spots -and this indeed should be the case for M dwarfs- we can infer the rotation period from the sinusoid-like modulation observed in the light curve. The modulation is interpreted to be due to the periodic appearance and disappearance of the spot(s) with respect to the observer’s line of sight.
One of the stars observed by APACHE shows such modulation, with a period of ~3.2 days. We have run a first version of a star-spots model, which fits the light curve under the hypothesis that one single spot on the star surface is responsible for the observed photometric variability. According to our simulation, the rotation axis of the star should have an inclination of ~50° and the spot should be at a latitude of ~-30°. We cannot travel to the star to check directly if this is true, but this is a way to imagine how the surface of this M dwarf should look like to an hypothetic near observer.
Recently, the Astronomical Observatory of the Aosta Valley has renewed its infrastructure, now taking greater care of the environment. Solar panels have been installed, providing 2.5 kW of power, and 4 geothermal wells have been dug at 120 mt of depth, providing 6 kW of power through an heat pump. If a rocky planet will be discovered by the APACHE project, it will be for sure an…ecological planet!