Comunicación oral presentada al congreso: The Past, Present, and Future of the VLA: Celebrating 40 Years - the meeting will be held virtually on August 4 - 6, 2021, broadcasting from Socorro, NM, USA, and will conclude with a virtual public event on Saturday, August 7th-. ; The detection of young stellar objects (YSOs) in early VLA observations was essentially limited to the strongest sources, namely free-free thermal emission from photoionized HII regions associated with young massive stars and non-thermal gyrosynchrotron emission from the active magnetosphere of some low-mass PMS stars (typically T-Tauris). Current VLA observations can reach microJy sensitivities and radio emission from a wide variety of YSOs, including the youngest deeply embedded protostars, is readily detected. Thermal free-free radio jets have been found associated with protostars spanning a wide range of masses and luminosities, from the most massive O-type protostars to very low-luminosity objects (VeLLOs) and proto-brown dwarf candidates. Non-thermal synchrotron radio emission, probably associated with strong shocks, has also been identified in the lobes of jets at relatively large distances from the source. Finally, cm radio emission has also been found associated with accretion disks around YSOs, either tracing the ionized photoevaporating disk or the dust emission. However, establishing the nature of a radio source is often not an easy task. I will summarize our current knowledge of radio emission from YSOs, with emphasis on radio jets, to build a self-consistent picture for the interpretation of their properties, to distinguish them from photoionized HII regions, and to relate the radio emission to the luminosity and evolutionary stage of protostars of all masses. ; With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709
Our nearest neighbor, Proxima Centauri, hosts a temperate terrestrial planet. We detected in radial velocities evidence of a possible second planet with minimum mass mc sin ic = 5.8 ± 1.9M⊕ and orbital period P c = 5.21 −0.22 +0.26 years. The analysis of photometric data and spectro-scopic activity diagnostics does not explain the signal in terms of a stellar activity cycle, but follow-up is required in the coming years for confirming its planetary origin. We show that the existence of the planet can be ascertained, and its true mass can be determined with high accuracy, by combining Gaia astrometry and radial velocities. Proxima c could become a prime target for follow-up and characterization with next-generation direct imaging instrumentation due to the large maximum angular separation of ~1 arc second from the parent star. The candidate planet represents a challenge for the models of super-Earth formation and evolution. ; Progetto Premiale 2015 FRONTIERA funding scheme of the Italian Ministry of Education, University, and Research Italian Space Agency INAF Italian Space Agency Science & Technology Facilities Council (STFC) Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT CONICYT project Basal Spanish MINECO State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award Science & Technology Facilities Council (STFC) European Union (EU)
Context. Variability caused by stellar activity represents a challenge to the discovery and characterization of terrestrial exoplanets and complicates the interpretation of atmospheric planetary signals. Aims. We aim to use a detailed modeling tool to reproduce the effect of active regions on radial velocity measurements, which aids the identification of the key parameters that have an impact on the induced variability. Methods. We analyzed the effect of stellar activity on radial velocities as a function of wavelength by simulating the impact of the properties of spots, shifts induced by convective motions, and rotation. We focused our modeling effort on the active star YZ CMi (GJ 285), which was photometrically and spectroscopically monitored with CARMENES and the Telescopi Joan Oró. Results. We demonstrate that radial velocity curves at different wavelengths yield determinations of key properties of active regions, including spot-filling factor, temperature contrast, and location, thus solving the degeneracy between them. Most notably, our model is also sensitive to convective motions. Results indicate a reduced convective shift for M dwarfs when compared to solar-Type stars (in agreement with theoretical extrapolations) and points to a small global convective redshift instead of blueshift. Conclusions. Using a novel approach based on simultaneous chromatic radial velocities and light curves, we can set strong constraints on stellar activity, including an elusive parameter such as the net convective motion effect. ; With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)
Aims. We report on radial velocity time series for two M0.0 V stars, GJ 338 B and GJ 338 A, using the CARMENES spectrograph, complemented by ground-telescope photometry from Las Cumbres and Sierra Nevada observatories. We aim to explore the presence of small planets in tight orbits using the spectroscopic radial velocity technique. Methods. We obtained 159 and 70 radial velocity measurements of GJ 338 B and A, respectively, with the CARMENES visible channel between 2016 January and 2018 October. We also compiled additional relative radial velocity measurements from the literature and a collection of astrometric data that cover 200 a of observations to solve for the binary orbit. Results. We found dynamical masses of 0.64 ± 0.07 M° for GJ 338 B and 0.69 ± 0.07 M° for GJ 338 A. The CARMENES radial velocity periodograms show significant peaks at 16.61 ± 0.04 d (GJ 338 B) and 16.3-1.3+3.5 d (GJ 338 A), which have counterparts at the same frequencies in CARMENES activity indicators and photometric light curves. We attribute these to stellar rotation. GJ 338 B shows two additional, significant signals at 8.27 ± 0.01 and 24.45 ± 0.02 d, with no obvious counterparts in the stellar activity indices. The former is likely the first harmonic of the star's rotation, while we ascribe the latter to the existence of a super-Earth planet with a minimum mass of 10.27-1.38+1.47 M⊕ orbiting GJ 338 B. We have not detected signals of likely planetary origin around GJ 338 A. Conclusions. GJ 338 Bb lies inside the inner boundary of the habitable zone around its parent star. It is one of the least massive planets ever found around any member of stellar binaries. The masses, spectral types, brightnesses, and even the rotational periods are very similar for both stars, which are likely coeval and formed from the same molecular cloud, yet they differ in the architecture of their planetary systems. ; With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)
We have conducted a survey of 328 protostars in the Orion molecular clouds with the Atacama Large Millimeter/submillimeter Array at 0.87 mm at a resolution of similar to 0.'' (40au), including observations with the Very Large Array at 9 mm toward 148 protostars at a resolution of similar to 0.'' 08 (32 au) This is the largest multiwavelength survey of protostars at this resolution by an order of magnitude. We use the dust continuum emission at 0.87 and 9 mm to measure the dust disk radii and masses toward the Class 0, Class I, and flat-spectrum protostars, characterizing the evolution of these disk properties in the protostellar phase. The mean dust disk radii for the Class 0, Class I, and flat-spectrum protostars are 44.9(-3.4)(+5.8), 37.0(-3.0)(+4.9), and 28.5(-2.3)(+3.7) au, respectively, and the mean protostellar dust disk masses are 25.9(-4.0)(+7.7), 14.9(-2.2)(+3.8), 1.6(-1.9)(+3.5) M-circle plus, respectively. The decrease in dust disk masses is expected from disk evolution and accretion, but the decrease in disk radii may point to the initial conditions of star formation not leading to the systematic growth of disk radii or that radial drift is keeping the dust disk sizes small. At least 146 protostellar disks (35% of 379 detected 0.87 mm continuum sources plus 42 nondetections) have disk radii greater than 50 au in our sample. These properties are not found to vary significantly between different regions within Orion. The protostellar dust disk mass distributions are systematically larger than those of Class II disks by a factor of >4, providing evidence that the cores of giant planets may need to at least begin their formation during the protostellar phase. ; National Science Foundation (NSF): AST-1814762, AST-1716259, 1815784, 1910106 Homer L. Dodge Endowed Chair National Aeronautics & Space Administration (NASA): 80NSSC18K1095 European Union (EU): AYA2017-84390-C2-1-R State Agency for Research of the Spanish MCIU through "Center of Excellence Severo Ochoa" award: SEV-20170709 Huygens fellowship from Leiden University