Articoli con tag M. Damasso
Since February 2012 we started a National collaboration aimed at spectroscopically characterizing dozens of M dwarfs which are listed in the APACHE Input Catalog.
Low-resolution spectra are acquired with the Copernico (182 cm) and Galileo (122 cm) telescopes at the Asiago Astrophysical Observatory, and they will be used mostly:
1) to determine an accurate spectral type of the stars;
2) to search for evidence of chromospheric activity.
The red dwarfs photometrically observed by the APACHE team represent a major component of the stars observed at the Asiago Observatory, and the collected spectra are of great importance for an optimal selection and prioritization of the target to be monitored by the APACHE telescopes.
The spectroscopic survey at Asiago, that will last for at least 2 years, is a collaboration among the APACHE team and astronomers from the University of Padova, the Astronomical Observatory of Padova and the Astronomical Observatory of Palermo, the last two being part of the National Institute for Astrophysics (INAF).
The project APACHE will be presented on June 2012 during the Workshop Transiting Planets in the House of the Sun. Mario Damasso will attend the course about M dwarfs and their extrasolar planets, and his speech Photometric transit search for planets around cool stars from the western Italian Alps: the Apache Project is scheduled on Wednesday, June 6.
During the commissioning phase of the new APACHE telescopes, two new variable stars have been discovered and included in the International Variable Star Index. Their identifiers are VSX J071108.7+695227 and VSX J021148.2+514212, and both are eclipsing variables of W UMa type (EW), i.e. two stars orbiting each other with short periods (and at short distances).
In particular, the variable star VSX J071108.7+695227 has the very short period P=0.238 days, and probably it is composed of two main sequence stars.
According to the present knowledge, EW variables composed of two main sequence stars seem to have a cut-off period of ~0.22 days, so that our new variable is very close to this lower limit. We are planning a spectroscopic investigation to better characterize this system.
After several days of intense snow and strong wind (but, fortunately, a warm wind which makes this winter less severe), we started testing the first two telescopes of the APACHE array. How the systems react to a multi-pointing observing sessions? At regime, each telescope will point automatically several targets, one after the other, repeating multiple cycles during the night. How much each telescope is stable under such a stress? How precise are the multiple pointings of the same target, when the telescope is back to the same stellar field after completing one cycle?
These are only some of the concerns we are facing at the moment, which we need to investigate to produce very precise photometry, but the time when we will begin the survey is approaching!
The search for habitable planets around nearby M dwarfs is really a very appealing topic in the field of exoplanets. This fact is confirmed by the recently announced meeting Transiting Planets in the House of the Sun – A Workshop on M Dwarf Stars and Their Planets, to be held in the island of Maui (Hawaii, US) on June 3-6 2012.
On 5th December the scientific team of the Kepler space telescope announced the discovery, made with the photometric transit method, of the first potentially habitable planet around a star very similar to our Sun.
The scientific community (and not only) is now waiting for the paper to appear in The Astrophysical Journal but, even if this announcement represents a milestone for the search for an Earth twin, some caveats should be kept in mind when discussing the results: realistically, should Kepler-22b be still considered a candidate instead of a confirmed planet? Even if its orbital period is compatible with its parent star’s habitable zone, is Kepler-22b really well characterized as a planet, despite it has a small radius (roughly 2.4 times the radius of Earth)? (continua…)
Today a paper by J. A. Johnson and collaborators appeared in Astro-ph (http://arxiv.org/pdf/1112.0017), reporting the confirmation and characterization of the first Hot Jupiter discovered orbiting a red dwarf (in this case an early-type M dwarf). The paper has not been submitted yet. The planet has a period of ~2.5 days and a radius very close to the radius of Jupiter, and was originally discovered by the Kepler mission using the photometric transit method. Despite the faintness of the star KOI-254 (V~17 mag), also known as 2MASS 19312949+4103513), the authors were able to confirm spectroscopically the planetary nature of the companion, estimating for the mass of the planet nearly half the mass of Jupiter.
For a challenging survey as APACHE project it is very important to select the best targets. Almost 3000 M dwarfs must be monitored photometrically, and it is fundamental to find some useful criteria for picking up the most promising stars (anyway, a stroke of luck is always welcome!). For instance, stars with a particularly high level of chromospheric activity seem not to be suitable targets to search for planets, because the star activity makes the measurements of radial velocity -which are necessary to confirm a transiting planetary candidate- very complicated (stellar jitters).
Next Thursday Mario Damasso will present the results of the second year of PhD to professors and colleagues at the Dept. of Astronomy – University of Padova. He will discuss the status of the APACHE project and present the results from the pilot study that we are going to publish very soon.
APACHE is coming up!
You can find more information on Mario Damasso to his personal page on APACHE Project scientific-blog-site.