Search

Your search keyword '"Garatti, A. Caratti O."' showing total 9 results
Start Over Author "Garatti, A. Caratti O." Topic astrophysics
9 results on '"Garatti, A. Caratti O."'

1. Molecular jets driven by high-mass protostars: a detailed study of the IRAS 20126+4104 jet

Author

Garatti, A. Caratti o, Froebrich, D., Eisloeffel, J., Giannini, T., and Nisini, B.

Subjects
Astrophysics
Abstract

We present here an extensive analysis of the protostellar jet driven by IRAS 20126+4104, deriving the kinematical, dynamical, and physical conditions of the H2 gas along the flow. The jet has been investigated by means of near-IR H2 and [FeII] narrow-band imaging, high resolution spectroscopy of the 1-0S(1) line (2.12 um), NIR (0.9-2.5 um) low resolution spectroscopy, along with ISO-SWS and LWS spectra (from 2.4 to 200 um). The flow shows a complex morphology. In addition to the large-scale jet precession presented in previous studies, we detect a small-scale wiggling close to the source, that may indicate the presence of a multiple system. The peak radial velocities of the H2 knots range from -42 to -14 km s^-1 in the blue lobe, and from -8 to 47 km s^-1 in the red lobe. The low resolution spectra are rich in H_2 emission, and relatively faint [FeII] (NIR), [OI] and [CII] (FIR) emission is observed in the region close to the source. A warm H2 gas component has an average excitation temperature that ranges between 2000 K and 2500 K. Additionally, the ISO-SWS spectrum reveals the presence of a cold component (520 K), that strongly contributes to the radiative cooling of the flow and plays a major role in the dynamics of the flow. The estimated L(H2) of the jet is 8.2+/-0.7 L_sun, suggesting that IRAS20126+4104 has an accretion rate significantly increased compared to low-mass YSOs. This is also supported by the derived mass flux rate from the H2 lines (Mflux(H2)~7.5x10^-4 M_sun yr^-1). The comparison between the H2 and the outflow parameters strongly indicates that the jet is driving, at least partially, the outflow. As already found for low-mass protostellar jets, the measured H2 outflow luminosity is tightly related to the source bolometric luminosity., Comment: 16 pages, 12 figures. A&A accepted

Published
2008
Full Text
View/download PDF

2. Molecular line emission in HH54: a coherent view from near to far infrared

Author

Giannini, T., McCoey, C., Nisini, B., Cabrit, S., Garatti, A. Caratti o, Calzoletti, L., and Flower, D. R.

Subjects
Astrophysics
Abstract

Aims. We present a detailed study of the infrared line emission (1-200 micron) in the Herbig-Haro object HH54. Our database comprises: high- (R~9000) and low- (R~600) resolution spectroscopic data in the near-infrared band (1-2.5 micron); mid-infrared spectrophotometric images (5-12 micron); and, far-IR (45-200 micron, R~200) spectra acquired with the ISO satellite. As a result, we provide the detection of and the absolute fluxes for more than 60 molecular features (mainly from H2 in the near- and mid-infrared and from H2O, CO and OH in the far-infrared) and 23 ionic lines. Methods. The H2 lines, coming from levels from v=0 to v=4 have been interpreted in the context of a state-of-art shock code, whose output parameters are adopted as input to a Large Velocity Gradient computation in order to interpret the FIR emission of CO, H2O and OH. Results. The H2 emission can be interpreted as originating in either steady-state J-type shocks or in quasi-steady J-type shocks with magnetic precursor. However, our multi-species analysis shows that only a model of a J-type shock with magnetic precursor (v_shock=18 km/s, n_H=10^4 cm^-3, B=100 microG, age=400 yr) can account for both the observed H2 emission and the CO and H2O lines. Such a model predicts a H2O abundance of ~ 7 10^-5, in agreement with estimations from other shock models for outflows associated with low mass protostars. We can exclude the possibility that the observed atomic lines arise in the same shock as the molecular lines, and give arguments in favour of the presence of a further high-velocity, fully dissociative shock component in the region. Finally, in view of the forthcoming spectroscopic facilities on board of the Herschel satellite, we provide predictions for H2O lines considered to be the most suitable for diagnostic purposes.

Published
2006
Full Text
View/download PDF

3. H2 active jets in the near IR as a probe of protostellar evolution

Author

Garatti, A. Caratti o, Giannini, T., Nisini, B., and Lorenzetti, D.

Subjects
Astrophysics
Abstract

We present a NIR analysis of a sample of H2 outflows from young embedded sources to compare the physical properties and cooling mechanisms of the different flows. The sample comprises 23 outflows driven by Class 0 and I sources having low-intermediate luminosity. We have obtained narrow band images in H2 2.12um and FeII 1.64um and spectroscopic observations in the range 1-2.5um. H2 line ratios have been used to estimate the visual extinction and average temperature of the molecular gas. Av values range from 2 to 15mag; average temperatures range between 2000 and 4000K. In several knots a stratification of temperatures is found with maximum values up to 5000K. Such a stratification is more commonly observed in those knots which also show FeII emission, while a thermalized gas at a single temperature is generally found in knots emitting only in molecular lines. Combining narrow band imaging with the parameters derived from the spectral analysis, we are able to measure the total luminosity of the H2 and FeII shocked regions in each flow. H2 is the major IR coolant with an average L(H2)/L(FeII) ratio of 10^{-2}. 83% of the sources have a L(H2)/L(bol) ratio of 0.04, irrespective of the Class of the driving source, while a smaller group of sources have L(H2)/L(bol) an order of magnitude smaller.Such a separation reveals the non-homogeneous behaviour of ClassI, where sources with very different outflow activity can be found. This is consistent with other studies showing that among ClassI one can find objects with different accretion properties and it demonstrates that the H2 power in the jet can be a powerful tool to identify the most active sources of this class., Comment: 35 pages, 19 figures. To be published in Astronomy and Astrophysics

Published
2005

4. On the excitation of the infrared knots in the HH99 outflow

Author

McCoey, C., Giannini, T., Flower, D. R., and Garatti, A. Caratti o

Subjects
Astrophysics
Abstract

We present near infrared (IR) spectra (0.98--2.5 mu m) from the group of Herbig-Haro (HH) objects comprising HH99: a series of knots forming a bow, HH99B, and a separate knot, HH99A. Observations of H2, [Fe II] and [C I] are used to constrain shock model parameters and determine the origin of the emission. Previous work has shown that it is likely that the atomic and ionic emission arises in regions of higher ionization than the molecular emission. On the basis of observations, it has often been suggested that the [Fe II] and [C I] emission could arise, for example, at the apex of a bow shock, with the H2 emission produced in the wings. Accordingly, we have combined models of C-component and J-type shocks in order to reproduce the observed H2, [Fe II] and [C I] line spectra. We can account for the H2 emission towards the HH99B complex by means of J-type shocks with magnetic precursors. We derive shock velocities of about 30 km s-1 and ages of order 100 yr; the pre-shock gas has a density of approximately 10^4 cm-3 and the magnetic field is approximately 100 mu G. The J-type shocks required to reproduce the intensities of the observed [Fe II] and [C I] lines have velocities of 50 km s-1. It is necessary to assume that Fe has been previously eroded from grains, probably by the earlier passage of a C-type shock wave. Thus, our analysis supports the view that molecular outflows are episodic phenomena whose observed emission arises in shock waves., Comment: 13 pages, 8 figures. MNRAS, in press

Published
2004
Full Text
View/download PDF

5. On the excitation of the infrared knots along protostellar jets

Author

Giannini, T., McCoey, C., Garatti, A. Caratti o, Nisini, B., Lorenzetti, D., and Flower, D. R.

Subjects
Astrophysics
Abstract

The complete near infrared (0.9-2.5 micron) spectra in three different star forming regions (HH24-26, HH72 and BHR71) are presented and analyzed in the framework of shock excitation models. The spectra are dominated by H_2 rovibrational emission (vibrational state nu up to 5, excitation energy T_ex up to 35000 K), while emission from ionized material, recognizable from [Fe II] and [S II] lines, is significantly fainter. The analysis of the H_2 excitation diagrams points to the existence of two different excitation regimes: whilst condensations observed only in the infrared appear to have temperatures rarely exceeding 3000 K and can be modelled in the framework of steady-state C-shock models, the infrared counterparts of Herbig Haro (HH) objects exhibit a temperature stratification with components up to more than 5000 K. The H_2 emission from representative HH objects (HH26A, HH72A and HH320A) has been successfully modelled by planar J-shocks with magnetic precursors, for which the main parameters (pre-shock density, speed) are derived. However, these same models are unable to reproduce the observed atomic and ionic emission, which probably arises from a distinct and perhaps more embedded region with respect to that traced by the H_2. Some of the physical parameters of such regions (fractional ionization, density) have been estimated in HH72, on the basis of the observed ionic lines., Comment: 15 pages, 15 postscript figures, 3 jpeg figures, accepted by Astronomy and Astrophysics

Published
2004
Full Text
View/download PDF

6. Discovery of the heavily obscured supernova 2002cv

Author

Di Paola, A., Larionov, V., Arkharov, A., Bernardi, F., Garatti, A. Caratti o, Dolci, M., Di Carlo, E., and Valentini, G.

Subjects
Astrophysics
Abstract

On the 13th of May 2002, supernova 2002cv was discovered using a near-infrared camera working at the AZT-24 1.1m telescope at Campo Imperatore (AQ-Italy). After the infrared detection a simultaneous photometric follow-up was started at optical wavelengths. The preliminary results confirm a heavily obscured object with a V-K color not lower than 6 magnitudes, making SN 2002cv the most reddened supernova ever observed. This finding, along with the recent discovery of another obscured supernova, suggests a critical revision of the rates known to date. The estimate of the visual extinction and the light curves are provided here. These latter indicate that our SN 2002cv observations are the earliest available for a type-Ia supernova at IR wavelengths., Comment: 4 pages

Published
2002
Full Text
View/download PDF

7. The GRAVITY young stellar object survey

Author

GRAVITY Collaboration, Eupen, F., Labadie, L., Grellmann, R., Perraut, K., Brandner, W., Duch��ne, G., K��hler, R., Sanchez-Bermudez, J., Lopez, R. Garcia, Garatti, A. Caratti o, Benisty, M., Dougados, C., Garcia, P., Klarmann, L., Amorim, A., Baub��ck, M., Berger, J. P., Caselli, P., Cl��net, Y., Foresto, V. Coud�� du, de Zeeuw, P. T., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Ganci, V., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Heissel, G., Henning, Th., Hippler, S., Horrobin, M., Hubert, Z., Jim��nez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyr��re, V., Bouquin, J. B. Le, L��na, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rodr��guez-Coira, G., Rousset, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., Woillez, J., and Wojtczak, A.

Subjects
Techniques: Interferometric, Young stellar object, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, 010309 optics, Stars: Pre-Main Sequence, 0103 physical sciences, Binary star, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Techniques: High Angular Resolution, Orbital elements, Physics, Infrared excess, Herbig Ae/Be, Astronomy and Astrophysics, Mass ratio, Accretion (astrophysics), Binaries: Close, T Tauri star, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Stars: Variables: T Tauri, Astrophysics::Earth and Planetary Astrophysics, Circumbinary planet, Stars: Individual: WW Cha
Abstract

The young T Tauri star WW Cha was recently proposed to be a close binary object with strong infrared and submillimeter excess associated with circum-system emission. This makes WW Cha a very interesting source for studying the influence of dynamical effects on circumstellar as well as circumbinary material. We derive the relative astrometric positions and flux ratios of the stellar companion in WW Cha from the interferometric model fitting of observations made with the VLTI instruments AMBER, PIONIER, and GRAVITY in the near-infrared from 2011 to 2020. For two epochs, the resulting uv-coverage in spatial frequencies permits us to perform the first image reconstruction of the system in the K band. The positions of nine epochs are used to determine the orbital elements and the total mass of the system. We find the secondary star orbiting the primary with a period of T=206.55 days, a semimajor axis of a=1.01 au, and a relatively high eccentricity of e=0.45. Combining the orbital solution with distance measurements from Gaia DR2 and the analysis of evolutionary tracks, the dynamical mass of Mtot=3.20 Msol can be explained by a mass ratio between ~0.5 and 1. The orbital angular momentum vector is in close alignment with the angular momentum vector of the outer disk as measured by ALMA and SPHERE. The analysis of the relative photometry suggests the presence of infrared excess surviving in the system and likely originating from truncated circumstellar disks. The flux ratio between the two components appears variable, in particular in the K band, and may hint at periods of triggered higher and lower accretion or changes in the disks' structures. The knowledge of the orbital parameters, combined with a relatively short period, makes WW Cha an ideal target for studying the interaction of a close young T Tauri binary with its surrounding material, such as time-dependent accretion phenomena., Comment: Accepted for publication in A&A; 24 pages, 14 figures, 3 tables; affiliations corrected

Published
2021

8. Multiple star systems in the Orion nebula

Author

GRAVITY Collaboration, Karl, Martina, Pfuhl, Oliver, Eisenhauer, Frank, Genzel, Reinhard, Grellmann, Rebekka, Habibi, Maryam, Abuter, Roberto, Accardo, Matteo, Amorim, Ant��nio, Anugu, Narsireddy, ��vila, Gerardo, Benisty, Myriam, Berger, Jean-Philippe, Bland, Nicolas, Bonnet, Henri, Bourget, Pierre, Brandner, Wolfgang, Brast, Roland, Buron, Alexander, Garatti, Alessio Caratti o, Chapron, Fr��d��ric, Cl��net, Yann, Collin, Claude, Foresto, Vincent Coud�� du, de Wit, Willem-Jan, de Zeeuw, Tim, Deen, Casey, Delplancke-Str��bele, Fran��oise, Dembet, Roderick, Derie, Fr��d��ric, Dexter, Jason, Duvert, Gilles, Ebert, Monica, Eckart, Andreas, Esselborn, Michael, F��dou, Pierre, Finger, Gert, Garcia, Paulo, Dabo, Cesar Enrique Garcia, Lopez, Rebeca Garcia, Gao, Feng, Gandron, ��ric, Gillessen, Stefan, Gont��, Fr��d��ric, Gordo, Paulo, Gr��zinger, Ulrich, Guajardo, Patricia, Guieu, Sylvain, Haguenauer, Pierre, Hans, Oliver, Haubois, Xavier, Haug, Marcus, Hau��mann, Frank, Henning, Thomas, Hippler, Stefan, Horrobin, Matthew, Huber, Armin, Hubert, Zoltan, Hubin, Norbert, Hummel, Christian A., Jakob, Gerd, Jochum, Lieselotte, Jocou, Laurent, Kaufer, Andreas, Kellner, Stefan, Kandrew, Sarah, Kern, Lothar, Kervella, Pierre, Kiekebusch, Mario, Klein, Ralf, K��hler, Rainer, Kolb, Johan, Kulas, Martin, Lacour, Sylvestre, Lapeyr��re, Vincent, Lazareff, Bernard, Bouquin, Jean-Baptiste Le, L��na, Pierre, Lenzen, Rainer, L��v��que, Samuel, Lin, Chien-Cheng, Lippa, Magdalena, Magnard, Yves, Mehrgan, Leander, M��rand, Antoine, Moulin, Thibaut, M��ller, Eric, M��ller, Friedrich, Neumann, Udo, Oberti, Sylvain, Ott, Thomas, Pallanca, Laurent, Panduro, Johana, Pasquini, Luca, Paumard, Thibaut, Percheron, Isabelle, Perraut, Karine, Perrin, Guy, Pfl��ger, Andreas, Duc, Thanh Phan, Plewa, Philipp M., Popovic, Dan, Rabien, Sebastian, Ram��rez, Andr��s, Ramos, Jose, Rau, Christian, Riquelme, Miguel, Rodr��guez-Coira, Gustavo, Rohloff, Ralf-Rainer, Rosales, Alejandra, Rousset, G��rard, Sanchez-Bermudez, Joel, Scheithauer, Silvia, Sch��ller, Markus, Schuhler, Nicolas, Spyromilio, Jason, Straub, Odele, Straubmeier, Christian, Sturm, Eckhard, Suarez, Marcos, Tristram, Konrad R. W., Ventura, Noel, Vincent, Fr��d��ric, Waisberg, Idel, Wank, Imke, Widmann, Felix, Wieprecht, Ekkehard, Wiest, Michael, Wiezorrek, Erich, Wittkowski, Markus, Woillez, Julien, Wolff, Burkhard, Yazici, Senol, Ziegler, Denis, Zins, G��rard, Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, European Southern Observatory (ESO), SIM/IDL Faculdade de Ciências da Universidade de Lisboa (FCUL), University of Lisboa, CENTRA Instituto Superior Tecnico, Laboratoire d'Astrophysique de Grenoble (LAOG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory [Santiago] (ESO), Max-Planck-Institut für Astronomie (MPIA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Astronomie et techniques spatiales, Université Paris Diderot - Paris 7 (UPD7), Physikalisches Institut [Köln], Universität zu Köln, Centro de Astrofísica da Universidade do Porto (CAUP), Universidade do Porto [Porto], State Key Laboratory of Molecular Developmental Biology, Institute of genetics and developmental Biology, CAS, CENTRA, Universidade de Lisboa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), leiden Obsevatory, Universiteit Leiden [Leiden], Laboratoire d'Astrophysique, Laboratoire des interactions plantes micro-organismes (LIPM), Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Matériaux divisés, interfaces, réactivité, électrochimie (MADIREL), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Michigan State University [East Lansing], Michigan State University System, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Universität zu Köln = University of Cologne, Universidade do Porto = University of Porto, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Institut National de la Recherche Agronomique (INRA)-Centre National de la Recherche Scientifique (CNRS), Aix Marseille Université (AMU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), European Project: 8003119(1980), Universidade do Porto, and Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)

Subjects
Initial mass function, Population, FOS: Physical sciences, Star count, Astrophysics, 01 natural sciences, 0103 physical sciences, Orion Nebula, Astrophysics::Solar and Stellar Astrophysics, education, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS, O-type star, Physics, [PHYS]Physics [physics], education.field_of_study, 010308 nuclear & particles physics, Astronomy and Astrophysics, Mass ratio, Accretion (astrophysics), Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium Cluster with the recently comissioned GRAVITY instrument. We observe a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for $\theta ^1$ Ori B, $\theta ^2$ Ori B, and $\theta ^2$ Ori C. We determine a separation for the previously suspected companion of NU Ori. We confirm four companions for $\theta ^1$ Ori A, $\theta ^1$ Ori C, $\theta ^1$ Ori D, and $\theta ^2$ Ori A, all with substantially improved astrometry and photometric mass estimates. We refine the orbit of the eccentric high-mass binary $\theta ^1$ Ori C and we are able to derive a new orbit for $\theta ^1$ Ori D. We find a system mass of 21.7 $M_{\odot}$ and a period of $53$ days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about 2, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints towards a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We exclude collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion., Comment: Accepted for publication in A&A

Published
2018

9. H2 active jets in the near IR as a probe of protostellar evolution

Author

Garatti, A. Caratti O., Giannini, T., Nisini, B., and Dario Lorenzetti

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics
Abstract

We present a NIR analysis of a sample of H2 outflows from young embedded sources to compare the physical properties and cooling mechanisms of the different flows. The sample comprises 23 outflows driven by Class 0 and I sources having low-intermediate luminosity. We have obtained narrow band images in H2 2.12um and FeII 1.64um and spectroscopic observations in the range 1-2.5um. H2 line ratios have been used to estimate the visual extinction and average temperature of the molecular gas. Av values range from 2 to 15mag; average temperatures range between 2000 and 4000K. In several knots a stratification of temperatures is found with maximum values up to 5000K. Such a stratification is more commonly observed in those knots which also show FeII emission, while a thermalized gas at a single temperature is generally found in knots emitting only in molecular lines. Combining narrow band imaging with the parameters derived from the spectral analysis, we are able to measure the total luminosity of the H2 and FeII shocked regions in each flow. H2 is the major IR coolant with an average L(H2)/L(FeII) ratio of 10^{-2}. 83% of the sources have a L(H2)/L(bol) ratio of 0.04, irrespective of the Class of the driving source, while a smaller group of sources have L(H2)/L(bol) an order of magnitude smaller.Such a separation reveals the non-homogeneous behaviour of ClassI, where sources with very different outflow activity can be found. This is consistent with other studies showing that among ClassI one can find objects with different accretion properties and it demonstrates that the H2 power in the jet can be a powerful tool to identify the most active sources of this class., Comment: 35 pages, 19 figures. To be published in Astronomy and Astrophysics

Published
2005
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results