Navegando por Autor "Castro, Matthieu"
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Artigo HIP 10725: the first solar twin/analogue field blue straggler(EDP Sciences, 2015-10-02) Schirbel, Lucas; Meléndez, Jorge; Karakas, Amanda I.; Ramírez, Iván; Castro, Matthieu; Faria, Marcos A.; Lugaro, Maria; Asplund, Martin; Maia, Marcelo Tucci; Yong, David; Howes, Louise; Nascimento Júnior, José Dias doContext. Blue stragglers are easy to identify in globular clusters, but are much harder to identify in the field. Here we present the serendipitous discovery of one field blue straggler, HIP 10725, that closely matches the Sun in mass and age, but with a metallicity slightly lower than solar. Aims. We characterise the solar twin/analogue HIP 10725 to assess whether this star is a blue straggler. Methods. We employed spectra with high resolution (R ∼ 105) and high signal-to-noise ratio (330) obtained with UVES at the VLT to perform a differential abundance analysis of the solar analogue HIP 10725. Radial velocities obtained by other instruments were also used to check for binarity. We also studied its chromospheric activity, age, and rotational velocity. Results. HIP 10725 is severely depleted in beryllium ([Be/H] ≤ −1.2 dex) for its stellar parameters and age. The abundances relative to solar of the elements with Z ≤ 30 show a correlation with condensation temperature, and the neutron capture elements produced by the s-process are greatly enhanced, while the r-process elements seem normal. We found its projected rotational velocity (v sin i = 3.3 ± 0.1 kms−1) to be significantly higher than solar and incompatible with its isochrone-derived age. Radial velocity monitoring shows that the star has a binary companion. Conclusions. Based on the high s-process element enhancements and low beryllium abundance, we suggest that HIP 10725 has been polluted by mass transfer from an AGB star that probably had an initial mass of about 2 M . The radial velocity variations suggest the presence of an unseen binary companion, probably the remnant of a former AGB star. Isochrones predict a solar-age star, but this disagrees with the high projected rotational velocity and high chromospheric activity. We conclude that HIP 10725 is a field blue straggler, rejuvenated by the mass-transfer process of its former AGB companionArtigo Optimized cutting off transit algorithm to study stellar rotation from PLATO mission light curves(Springer, 2020-06-16) Costa, Jefferson Soares da; Almeida, Leandro de; Anthony, Francys; Mattiuci, Ana Carolina; Castro, Matthieu; Samadi, Reza; Nascimento Júnior, José Dias doMeasuring the stellar rotation of one of the components in eclipsing binaries (EBs) or planetary systems is a challenge task. The difficulty is mainly due to the complexity of analyzing, in the same light curve, the signal from the stellar rotation mixed with the transit signal of a stellar or substellar companion, like a brown dwarf or planet. There are many methods to correct the long-term trend of the light curve. However, the correction often erases the signal of the stellar rotation from spots crossing the visible stellar disk and other weaker signals like planets. In this work, we present the DiffeRencial flUx Method of cuTting Off biNariES (DRUM TONES) to identify the signal of the binary transits and disentangle it from stellar rotation planet signals. We present our technique with applications to EBs from CoRoT, Kepler, Kepler K2 and TESS missions. We also applied our method to simulated synthetic EB from the PLATO mission. Our method shows good agreement in the determination of stellar rotation periods for few observed targets from last space missions, as well it is naturally useful for future European mission, such as PLAnetary Transits and Oscillations of stars (PLATO)