Spectral energy distribution analysis of class i and class ii fu orionis stars

FU Orionis stars (FUors) are eruptive pre-main sequence objects thought to represent quasi-periodic or recurring stages of enhanced accretion during the low-mass star-forming process. We characterize the sample of known and candidate FUors in a homogeneous and consistent way, deriving stellar and circumstellar parameters for each object. We emphasize the analysis in those parameters that are supposed to vary during the FUor stage. We modeled the spectral energy distributions of 24 of the 26 currently known FUors, using the radiative transfer code of Whitney et al. We compare our models with those obtained by Robitaille et al. for Taurus class II and I sources in quiescence periods by calculating the cumulative distribution of the different parameters. FUors have more massive disks: we find that ~80% of the disks in FUors are more massive than any Taurus class II and I sources in the sample. Median values for the disk mass accretion rates are ~10–7 M ☉ yr–1 versus ~10–5 M ☉ yr–1 for standard young stellar objects (YSOs) and FUors, respectively. While the distributions of envelope mass accretion rates for class I FUors and standard class I objects are similar, FUors, on average, have higher envelope mass accretion rates than standard class II and class I sources. Most FUors (~70%) have envelope mass accretion rates above 10–7 M ☉ yr–1. In contrast, 60% of the classical YSO sample has an accretion rate below this value. Our results support the current scenario in which changes experimented by the circumstellar disk explain the observed properties of these stars. However, the increase in the disk mass accretion rate is smaller than theoretically predicted, although in good agreement with previous determinations.Fil: Gramajo, Luciana Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Rodón Javier A.. European Southern Observatory. Santiago; ChileFil: Gomez, Mercedes Nieves. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentin

Espectros en el infrarrojo medio de discos de escombros

Se presentan espectros en el infrarrojo medio de 3 estrellas (edades de 107 – 109 a˜nos) asociadas con discos de escombros. Los espectros se compararon con perfiles de absorci´on de compuestos de tipo amorfo y cristalino. La presencia de bandas de absorci´on no puede explicarse considerando s´olo compuestos del tipo amorfo sugiriendo la existencia de compuestos del tipo cristalino. Adem´as, las part´ıculas de polvo tendr´ıan tama˜nos > 1.5 µm. Esto evidenciar´ıa que el material de los discos de escombros se encuentra en un estado evolutivo m´as avanzado que en los discos en estrellas de tipo T - Tauri (∼ 106 a˜nos) o del medio interestelar, poblados principalmente por part´ıculas de polvo con tama˜nos de ∼ 0.1 µm constituidas por silicatos del tipo amorfo.In this contribution we report mid-infrared spectra of 3 stars (ages 107 – 109 yrs) with known debris disks. These spectra are compared with the absorption profiles of crystalline and amorphous silicates. The presence of absorption bands can be explained by considering the existence of amorphous compounds together with those of the crystalline type. In addition, dust particles may have typical sizes > 1.5 µm. This would indicate that the material in the debris disks is in a more advanced evolutionary state than in disks around T - Tauri stars (∼ 106 years) or in the interstellar medium, populated by dust particles with sizes ∼ 0.1 µm consisting of amorphous silicates.Fil: García, Luciano Héctor. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gomez, Mercedes Nieves. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Modeling of debris disks in single and binary stars

Infrared space observatories such as Spitzer and Herschel have allowed the detection of likely analogs to the Kuiper Belt in single as well as binary systems. The aim of this work is to characterize debris disks in single and binary stars and to identify features shared by the disks in both types of systems, as well as possible differences. We compiled a sample of 25 single and 14 binary stars (ages > 100 Myr) and flux measurements at lambda > 100 microns and evidence of infrared excesses attributed to the presence of debris disks. Then, we constructed and modeled the observed spectral energy distributions (SEDs), and compared the parameters of the disks of both samples. Both types of disks are relatively free of dust in the inner region ( 100 × 106 años) con flujos observados para λ > 100 µm y evidencia de excesos en emisión en el infrarrojo atribuidos a la presencia de disco. Luego, se construyeron y modelaron las distribuciones espectrales de energía (SEDs), y se compararon los parámetros obtenidos para los discos de ambas muestras. En general, los discos tienen una región interna (< 3-5 UA), relativamente libre de polvo y se extenderían más allá de 100 UA. No se encontraron diferencias significativas en las distribuciones de masa y de tamaño de las partículas de polvo de ambas muestras.Fil: García, Luciano Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaFil: Gomez, Mercedes Nieves. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentin

The distant young embedded stellar cluster CBJC 8 associated with G085.40-0.00

The infrared cluster CBJC 8 is associated with a 6.7 GHz methanol maser and a compact radio-continuum source, G85.40-0.00. It is located at a distance of about 8 kpc. Aims. The aim is to study the characteristics of this distant and compact embedded cluster and derive the properties of its stellar population. Methods. We present new ground-based near- and mid-infrared imaging observations of this region. The calibrated images were analysed together with archive Spitzer IRAC images. Results. Based on the discovery of a considerable fraction of embedded sources with infrared excess emission that are concentrated within a radius around 16" centred near the position of the compact HII region G85.40-0.00, we were able to confirm the presence of a very young embedded cluster. It was found to contain more than 58 members brighter than MK = 2.6, two-thirds of which showing significant near- or mid-IR excess emission. We present spectral energy distributions and extrapolated total luminosities for nine sources with large mid-infrared excesses that were measured in all four IRAC bands. For the brightest of these, G8540A, which is associated with a methanol maser and a compact HII region, we fitted a model of an infalling envelope plus disc plus central star to its observed 1.6 to 850 μm fluxes to get an idea of its physical properties. We also report a single 2.12 μm molecular hydrogen line emission knot near the centre of the cluster, which support the idea about an outflow activity. © 2010 ESO.Fil: Persi, P.. Istituto di Astrofisica Spaziale e Fisica Cosmica, Sezione di Roma; ItaliaFil: Tapia, M.. Universidad Nacional Autónoma de México; MéxicoFil: Gomez, Mercedes Nieves. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Herschel, Spitzer and Magellan infrared observations of the star-forming region RCW 121 (IRAS 17149−3916)

We present new deep near-infrared broad- and narrow-band imaging and low-resolution spec-troscopy of the star formation region RCW 121 (IRAS 17149−3916) which we analyse incombination withHerschel(70, 160, 250, 350 and 500μm) andSpitzer(3.6, 4.5, 5.8 and 8μm)images. The near-infrared photometry reveals the presence of a stellar cluster of approximatesize of 92 arcsec which is composed of at least 264 members, approximately 25 per cent ofthese showing excess emission atλ>2.0μm, indicative of circumstellar discs. Isochronescorresponding to ages 0.5–1.0 Myr andAV=7.8 fit well the position of a large fraction of likelycluster members in theKsversusH−Ksdiagram. We find three massive star-forming coreslocated in the boundaries of an expanding HIIregion ionized by a central O-type star. Fromtheir far-infrared spectral energy distributions (SEDs) we derive masses and temperatures ofthe dense cores. When these young stellar objects (YSOs) have warm emission components,the 1.2–500μm SEDs are fitted with Robitaille et al.’s star–disc-envelope model to obtain theirphysical parameters. The masses of the three YSOs are between 8 and 10 M . The youngestsite (core I) is undetected atλ<100μm and is at the earliest evolutionary stage that cancurrently be detected. The other two cores (II and III) contain YSOs of similar masses andhave near-infrared counterparts, which imply a more advanced evolutionary stage. The YSOat core II has been found to have associated a jet, with strong H2line emission, co-existingwith an H2O maser source. RCW 121 is another example of multiple star formation beingtriggered by the expansion of a single HIIregion.Fil: Tapia, M.. Universidad Nacional Autónoma de México; MéxicoFil: Persi, P.. Istituto Astrofisica e Planetologia Spaziale. Roma; ItaliaFil: Roth, Markus Albert. Las Campanas Observatory. La Serena; ChileFil: Elia, D.. Istituto Astrofisica e Planetologia Spaziale. Roma; ItaliaFil: Molinari, S.. Istituto Astrofisica e Planetologia Spaziale. Roma; ItaliaFil: Saldaño, Hugo Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; ArgentinaFil: Gomez, Mercedes Nieves. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentin

Espectroscopía de la binaria simbiótica PU Vul

En el presente trabajo se expone un análisis espectroscópico preliminar de la nova simbiótica PU Vul, con datos recopilados durante más de 20 años de observaciones. Con el objetivo de realizar un análisis global de la evolución del sistema desde su estallido en 1979, se determinan temperaturas y luminosidades de la nebulosa a lo largo de su evolución y se consideran diferentes escenarios para el sistema. Este análisis permitirá determinar la geometría de la binaria y ayudará a comprender los procesos que tienen lugar en este sistema en permanente cambio.Fil: Cuneo, Virginia. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Kenyon, S.. Harvard-Smithsonian Center for Astrophysics; Estados UnidosFil: Gomez, Mercedes Nieves. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; ArgentinaTerceras Jornadas de Astrofísica EstelarCórdobaArgentinaObservatorio Astronómico de CórdobaUniversidad Nacional de Córdob

High-contrast imaging of HD 29992 and HD 196385 with the Gemini Planet Imager

Based on high contrast images obtained with the Gemini Planet Imager (GPI), we report the discovery of two point-like sources at angular separations of ∼ 0.1800 and ∼ 0.8000 from the stars HD 29992 and HD 196385. A combined analysis of the new GPI observations and images from the literature indicates that the source close to HD 29992 could be a companion to the star. Concerning HD 196385, the small number of contaminants (∼ 0.5) suggests that the detected source may be gravitationally bound to the star. For both systems, we discarded the presence of other potential companions with > 75 MJup at ∼ 0.3−1.3 00. From stellar model atmospheres and low-resolution GPI spectra, we derive masses of ∼ 0.2 - 0.3 M for these sources. Using a Markov-chain Monte Carlo approach, we performed a joint fit of the new astrometry measurements and published radial velocity data to characterize the possible orbits. For HD 196385B, the median dynamic mass is in agreement with that derived from model atmospheres, whilst for HD 29992B, the orbital fit favors masses close to the brown dwarf regime(∼ 0.08 M). HD 29992 and HD 196385 might be two new binary systems with M-type stellar companions. However, new high angular resolution images would help to definitively confirm whether the detected sources are gravitationally bound to their respective stars, and permittighter constraints on the orbital parameters of both systems.Fil: García, Luciano Héctor. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Petrucci, Romina Paola. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Jofre, Jorge Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; ArgentinaFil: Gomez, Mercedes Nieves. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentin

Abundancias químicas y parámetros físicos de estrellas con planetas

La elevada metalicidad en las estrellas con planetas podría favorecer la formación de planetas ya sea a través del modelo de acreción de núcleos o de la inestabilidad del disco. Debido a esto hay un gran interés en estudiar las atmósferas de estrellas que albergan planetas. Presentamos resultados del estudio de atmósferas de este tipo de estrellas, analizando abundancias de algunos elementos químicos relevantes y parámetros estelares tales como temperatura efectiva, gravedad superficial y velocidad de microturbulencia. Estos objetos estudiados, con tipos espectrales no estrictamente solares, fueron observados con el espectrógrafo EBASIM de CASLEO.The high metallicity in stars with planets could favor the formation of planets either through the model of nuclei accretion or the instability of the disk. Because of this there is great interest in studying the atmospheres of stars that host planets. We present results of the study of atmospheres of this type of stars, analyzing abundances of some relevant chemical elements and stellar parameters such as effective temperature, surface gravity and microturbulence velocity. These objects studied, with spectral types not strictly solar, were observed with the CASLEO EBASIM spectrograph.Fil: Vendemmia, Estefania Beatriz. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Pintado, Olga Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; ArgentinaFil: Gomez, Mercedes Nieves. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin

Transit timing variation analysis in southern stars: the case of WASP-28

We present four new transit observations of the exoplanet WASP-28b observed between 2011 August and 2013 October. Employing another 11 transits available in the literature we compute new ephemeris and redetermine the physical parameters of the star and the exoplanet. Considering 3 yr of observations, we find no periodic transit timing variations (TTVs) or long-term variations of the inclination of the orbit, i, or the depth of the transit, k, that could be attributable to the presence of another planetary-mass body in the system. We also study the relations between i and k with different factors that characterize the light curves. The fits suggest a possible weak correlation between k with the red noise factor, β, and the photometric noise rate, PNR, and a weak anticorrelation between i and PNR, although more points are needed to confirm these trends. Finally, the kinematic study suggests that WASP-28 is a thin-disc star.Fil: Petrucci, Romina Paola. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Jofre, Jorge Emiliano. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Melita, Mario Daniel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Gomez, Mercedes Nieves. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mauas, Pablo Jacobo David. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Discarding orbital decay in WASP-19b after one decade of transit observations

We present an empirical study of orbital decay for the exoplanet WASP-19b, based on mid-time measurements of 74 complete transits (12 newly obtained by our team and 62 from the literature), covering a 10-yr baseline. A linear ephemeris best represents the mid-transit times as a function of epoch. Thus, we detect no evidence of the shortening of WASP-19b's orbital period and establish an upper limit of its steady changing rate, P' = −2.294 ms yr−1, and a lower limit for the modified tidal quality factor Q'* = (1.23 ± 0.231) × 106. Both are in agreement with previous works. This is the first estimation of Q' directly derived from the mid-times of WASP-19b obtained through homogeneously analysed transit measurements. Additionally, we do not detect periodic variations in the transit timings within the measured uncertainties in the mid-times of transit. We are therefore able to discard the existence of planetary companions in the system down to a few M in the first-order mean-motion resonances 1:2 and 2:1 with WASP-19b, in the most conservative case of circular orbits. Finally, we measure the empirical Q'* values of 15 exoplanet host stars, which suggest that stars with Teff ≲ 5600 K dissipate tidal energy more efficiently than hotter stars. This tentative trend needs to be confirmed with a larger sample of empirically measured Q'*.Fil: Petrucci, Romina Paola. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; ArgentinaFil: Jofre, Jorge Emiliano. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Universidad Nacional Autónoma de México; México. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gómez Maqueo Chew, Y.. Universidad Nacional Autónoma de México; MéxicoFil: Hinse, T. C.. Chungnam National University; Corea del SurFil: Mazek, M.. Institute Of Physics Czech Academy Of Sciences; República ChecaFil: Tan, T. -G.. Perth Exoplanet Survey Telescope; AustraliaFil: Gomez, Mercedes Nieves. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentin