Structure & Components of the Galaxy

 


Research lines

Tracing the outer Milky Way Spiral Arms: the Perseus arm

We have carried out a uvbyHbeta Strömgren photometric survey covering 16 square degrees in the anticentre direction using the Wide Field Camera at the Isaac Newton Telescope (Monguió et al 2013). This is the natural system to identify young stars and obtaining accurate distances and ages. The limiting magnitude of the survey is of V~17mag in the central 8 squared degrees and 15.5 in the surrounding area. We have developed a new method to derive the physical parameters using atmospheric grids and evolutionary tracks. Using this catalogue we have been able to detect the Perseus spiral arm in the anticentre direction (M. Monguió, 2013, Ph D thesis, and Monguió et al., 2013; 2014;2015).
In parallel, we are reducing spectroscopic data using the WYFFOS at the William Herschel Telescope, that will allow us to detect kinematic effects of the Perseus spiral arm.

Characterization of stellar population of the coronas of open clusters

High quality proper motions on an extended area of a selection of around 40 Open Clusters have been obtained in collaboration with the Real Observatorio de San Fernando (ROA). This data will let us study their kinematics and in particular their coronas with unprecedented accuracy. We are finishing the process of obtaining astrometry with the automatic meridian circles CMASF at El Leoncito (Argentina) and CTA at La Palma of an area few times the known radius (from Webda ) of the OCs. We will make use of Strömgren wide-field photometry to complement their characterization. We derive proper motions by using POSS-I positions as first epoch, which can be used to reject clear non-cluster members. Forty clusters have been completed up to a magnitude of r’~17. Preliminary results for NGC2682, NGC1817, NGC2509 and NGC2264 and a comparison with previous determinations of proper motions have been already published (Jordi et al., 2013; Balaguer-Núñez et al, 2012). These high-precision proper motions and radial velocities from GES will allow to perform the kinematic analysis of the selected clusters. Detailed analysis of the data is on-going.

Absolute Properties of the Low-Mass stars

Spectroscopic and eclipsing binary systems offer the best means for determining accurate physical properties of stars, including their masses and radii. The data available for low-mass stars have yielded firm evidence that stellar structure models predict smaller radii and higher effective temperatures than observed, but the number of systems with detailed analyses is still small. We have done an extensive analysis of low-mass eclipsing binaries and field stars to evaluate the impact of the stellar activity on the light curves and on the stellar structure and evolutionary models, in order to reconcile both theory and observations.

We found that the stellar activity (a) distorts the light curves yielding an overestimation of the measured radii by about 3% in case of permanent coverage of polar spots, (b) forces the star to increase its radius by about 2% to compensate the low radiation efficiency of the spots, and (c) and additional increase of the radius in the range 0-4% is needed to compensate the low efficiency of convection in case of large rotation (Morales Ph D thesis, Morales et al., 2009; 2010). We used activity-rotation velocity relations for low-mass stars with a convective envelope to study the dependence of the position in the activity-vsini diagram on the stellar axis inclination (Herrero et al., 2011). This has been used to elaborate a method to increase the efficiency of a targeted exoplanet search with the transit technique by pre-selecting a subset of candidates from large catalogues of stars. Assuming spin-orbit alignment, this can be achieved by considering stars that have a higher probability to be oriented nearly equator-on (inclination close to 90°).

Currently, a simulation of stellar surfaces accounting for bright and dark spots is being developed. The presence of such spots induces jitters in astrometric, photometric and spectroscopic measurements that we are evaluating (E. Herrero, PhD thesis 2014).

Related thesis

Publications

  • Morales et al 2009

 

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