1,720,995 research outputs found
Multiwavelength study of RCW 108 as a massive star forming region
Full text linkNGC 6193 is an open cluster embedded in an HII region (RCW 108, Rodgers et al. 1960) located 15^´ eastwards of NGC 6188. The later is a bright rimmed cloud that stretches over 30^´ in the north-south direction, and marks the interface between RCW 108 and nearby dark clouds. RCW 108 is being powered by the multiple O-type star systems, namely HD 150135-HD 150136 (Niemela & Gamen 2005) in the core of NGC 6193. The UV photons emitted by these stars may drive photoinization-induced shocks into the nearby molecular clouds, possibly originating the well studied infrared cluster RCW 108-IR (Comerón et al. 2005, and references therein). In this work we describe the morphology of the distribution of the photoionized and shock-excited gas based on Hα, [O III] and [S II] images, ^{13}CO observations, and infrared data (2MASS, MSX).Fil: Romero, Gisela Andrea. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de la Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Arnal, Edmundo Marcelo. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin
Pre-main-sequence stars in the Lagoon Nebula (M8)
Full text linkWe report the discovery of new pre-main-sequence (PMS) stars in the Lagoon Nebula (M8) at a distance of 1.25 kpc, based on intermediate-resolution spectra obtained with the Boiler & Chivens spectrograph at the 6.5-m Magellan I Telescope (Las Campanas Observatory, Chile). According to the spectral types, the presence of emission lines and the lithium λ 6708 absorption line, we are able to identify 27 classical T Tauri stars, seven weak-lined T Tauri stars and three PMS emission objects with spectral type G, which we include in a separate stellar class denominated 'PMS Fe/Ge class'. Using near-infrared photometry either from the Two-Micron All-Sky Survey or from our own previous work, we derive effective temperatures and luminosities for these stars and locate them in the Hertzsprung-Russell diagram, in order to estimate their masses and ages. We find that almost all of our sample stars are younger than 3 × 106 yr and span over a range of masses between 0.8 and 2.5 M⊙. A cross-correlation between our spectroscopic data and the X-ray sources detected with the Chandra ACIS instrument is also presented.Fil: Arias, Julia Ines. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de La Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Morrell, Nidia Irene. Las Campanas Observatory; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
A ~ 40 year variability cycle in the luminous blue variable/Wolf-Rayet Binary System HD 5980?
Full text linkThe massive Wolf-Rayet stellar system HD 5980 in the Small Magellanic Cloud entered a sudden and brief ~ 1-3 mag eruptive state in the mid-1990s. The cause of the instability is not yet understood, but mechanisms similar to those in luminous blue variables are suspected. Using a previously unreported set of spectroscopic data obtained in 1955-1967 and recently acquired optical and HST/STIS spectra, we find that (1) the brief eruptions of 1993 and 1994 occurred at the beginning of an extended (~ decades) high state of activity characterized by large emission-line intensities; (2) the level of activity is currently subsiding; and (3) another strong emission-line episode appears to have occurred between 1960 and 1965, suggesting the possibility that the long-term cyclical variability may be recurrent on a ~ 40 year timescale. These characteristics suggest the possible classification of HD 5980 as an S Doradus-type variable. The effects due to binary interactions in the system are discussed, and we tentatively suggest that the short duration and relatively hot spectral type (WN11/B1.5I) observed during maximum in the visual light curve may be attributed to these interactions.Fil: Koenigsberger, Gloria. Universidad Nacional Autónoma de México; MéxicoFil: Georgiev, Leonid. Universidad Nacional Autónoma de México; MéxicoFil: Hillier, D. John. University Of Pittsburgh; Estados UnidosFil: Morrell, Nidia Irene. The Carnegie Observatories. Las Campanas Observatory; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barba, Rodolfo Hector. Consejo Nacional de Investigaciones Cientiâficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina. Universidad de la Serena; ChileFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Astrofísica de la Plata; Argentin
The eccentric short-period orbit of the supergiant fast X-ray transient HD 74194 (=LM Vel)
Full text linkAims. We present the first orbital solution for the O-type supergiantstar HD 74194, which is the optical counterpart of the supergiant fastX-ray transient IGR J08408-4503. Methods. We measured the radialvelocities in the optical spectrum of HD 74194, and we determined theorbital solution for the first time. We also analysed the complexHα profle. Results. HD 74194 is a binary system composed of anO-type supergiant and a compact object in a short-period (P=9.5436± 0.0002 d) and high-eccentricity (e=0.63 ± 0.03) orbit.The equivalent width of the Hα line is not modulated entirely withthe orbital period, but seems to vary in a superorbital period (P=285± 10 d) nearly 30 times longer than the orbital one.Fil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Astrofísica de la Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de la Serena; ChileFil: Walborn, N. R.. Space Telescope Science Institute; Estados UnidosFil: Morrell, Nidia Irene. Universidad de la Serena; ChileFil: Arias, Julia Ines. Universidad de la Serena; ChileFil: Maíz Apellániz, J.. Consejo Superior de Investigaciones Cientificas; EspañaFil: Sota, A.. Consejo Superior de Investigaciones Cientificas; EspañaFil: Alfaro, E. J.. Consejo Superior de Investigaciones Cientificas; Españ
A Hubble Space Telescope/NICMOS view of the prototypical giant H ii region NGC604 in M33
Full text linkWe present the first high-spatial-resolution nearinfrared (NIR) imaging of NGC604, obtained with the NICMOS camera onboard the Hubble Space Telescope (HST). These NICMOS broad-band images reveal new NIR point sources, clusters, and diffuse structures. We find an excellent spatial correlation between the 8.4 GHz radio continuum and the 2.2 µm nebular emission. Moreover, massive young stellar object candidates appear aligned with these radio peaks, reinforcing the idea that those areas are star-forming regions. Three different scaled OB associations are recognized in the NICMOS images. The brightest NIR sources in our images have properties that suggest that they are red supergiant stars, of which one was previously known. This preliminary analysis of the NICMOS images shows the complexity of the stellar content of the NGC604 nebula.Fil: Barba, Rodolfo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Maíz Apellániz, Jesús. Instituto de Astrofísica de Andalucía; EspañaFil: Pérez, Enrique. Instituto de Astrofísica de Andalucía; EspañaFil: Rubio, Mónica. Universidad de Chile; ChileFil: Bolatto, Alberto. University of Maryland; Estados UnidosFil: Fariña, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Bosch, Guillermo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Walborn, Nolan Revere. Space Telescope Science Institute; Estados Unido
Spectroscopic study of the N159/N160 complex in the Large Magellanic Cloud
Full text linkWe present a spectroscopic study of the N159/N160 massive star-forming region south of 30 Doradus in the Large Magellanic Cloud, classifying a total of 189 stars in the field of the complex. Most of them belong to O and early B spectral classes; we have also found some uncommon and very interesting spectra, including members of the Onfp class, a Be P Cygni star, and some possible multiple systems. Using spectral types as broad indicators of evolutionary stages, we considered the evolutionary status of the region as a whole. We infer that massive stars at different evolutionary stages are present throughout the region, favoring the idea of a common time for the origin of recent star formation in the N159/N160 complex as a whole, while sequential star formation at different rates is probably present in several subregions.Fil: Fariña, Cecilia Silvia. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Bosch, Guillermo Luis. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Morrell, Nidia Irene. Las Campanas Observatory; ChadFil: Barba, Rodolfo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico ; ArgentinaFil: Walborn, Nolan Revere. Space Telescope Science Institute; Estados Unido
The new Wolf-Rayet binary system WR62a
Full text linkA significant number of the Wolf-Rayet stars seem to be binary or multiple systems, but the nature of many of them is still unknown. Dedicated monitoring of WR stars favours the discovery of new systems. Aims. We explore the possibility that WR62a is a binary system. Methods. We analysed the spectra of WR62a, obtained between 2002 and 2010, to look for radial-velocity and spectral variations that would suggest there is a binary component. We searched for periodicities in the measured radial velocities and determined orbital solutions. A period search was also performed on the “All-Sky Automated Survey” photometry. Results. We find that WR62a is a double-lined spectroscopic binary with a WN5 primary star and an O 5.5–6 type secondary component in orbit with a period of 9.1447 d. The minimum masses range between 21 and 23 M for the WN star and between 39 and 42 M for the O-type star, thus indicating that the WN star is less massive than the O-type component. We detect a phase shift in the radial-velocity curve of the He ii λ4686 emission line relative to the other emission line curves. The equivalent width of this emission line shows a minimum value when the WN star passes in front of the system. The analysis of the ASAS photometry confirms the spectroscopic periodicity, presenting a minimum at the same phase.Fil: Collado, Ana Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica la Plata; ArgentinaFil: Barba, Rodolfo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentina. Universidad de la Serena; Chil
The massive Wolf-Rayet Binary LSS1964 (=WR29), II: the V light curve
Full text linkContext. WR 29 is a known WN7h+O double-lined binary system with a rather short period (3.164 days). Aims. We search for light variations to determine the inclination of the system and thus the absolute masses of both components. Methods. We observed photometrically the field of WR 29 between December, 2002, and February, 2006. Results. We find that the V light of WR 29 varies in phase with the spectroscopic period of 3.16412 days, presenting two minima corresponding to the conjunctions of the binary components. Numerical models fitted to the light curve indicate an orbital inclination of about 44◦, and masses of 53 M and 42 M for the O- and WN-type components, respectively.Fil: Gamen, Roberto Claudio. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Fernandez Lajus, Eduardo Eusebio. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Niemela, Virpi Sinikka. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; Argentin
A new massive double-lined spectroscopic binary system: The Wolf-Rayet star WR68a
Full text linkDouble-lined spectroscopic binary systems, containing a Wolf-Rayet and a massive O-type star, are key objects for the study of massive star evolution because these kinds of systems allow the determination of fundamental astrophysical parameters of their components. We have performed spectroscopic observations of the star WR 68a as part of a dedicated monitoring program of WR stars to discover new binary systems. We identified spectral lines of the two components of the system and disentangled the spectra. We measured the radial velocities in the separated spectra and determined the orbital solution. We discovered that WR 68a is a double-lined spectroscopic binary with an orbital period of 5.2207 days, very small or null eccentricity, and inclination ranging between 75 and 85 deg. We classified the binary components as WN6 and O5.5-6. The WN star is less massive than the O-type star with minimum masses of 15 ± 5 M⊙ and 30 ± 4 M⊙, respectively. The equivalent width of the He ii λ4686 emission line shows variations with the orbital phase, presenting a minimum when the WN star is in front of the system. The light curve constructed from available photometric data presents minima in both conjunctions of the system.Fil: Collado, Ana Elisa. Consejo Nacional de Investigaciones CientiÂficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Fisicas y Naturales; ArgentinaFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad de la Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Morrell, Nidia Irene. Carnegie Observatories; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
G287.84-0.82: An infrared star cluster in the Carina nebula
Full text linkWe have studied the properties of an infrared cluster embedded in the gas and dust of the southern part of the Carina nebula (NGC 3372), where the probable existence of current star formation has already been predicted. We used mid-infrared (A and C bands) and near-infrared (JHKs) images from the Midcourse Space Experiment and the Two-Micron All-Sky Survey, respectively, combined with an optical Ha narrow-band filter image obtained at the Cerro Tololo Inter-American Observatory. The infrared star cluster has at least 17 members, and its parameters, radius and stellar density are in very good agreement with high- to intermediate-mass star formation scenarios. The detected infrared sources have roughly the same intrinsic infrared excess determined from their position in colour-colour and colour-magnitude diagrams, suggesting that these objects could be related to pre-main-sequence stars of high to intermediate mass. Furthermore, we present a low-dispersion spectrum of the LS 1883 (O9.5V) star located near the centre of the infrared cluster. The position of this object in the colour-colour and colour-magnitude infrared diagrams lies close to the reddening vector of a zero-age main-sequence O9V spectral-type star, and it seems to be the first star of this cluster to emerge. All these facts are consistent with the current star-forming scenarios associated with highly embedded star clusters.Fil: Hägele, Guillermo Federico. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Albacete Colombo, Juan Facundo. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barba, Rodolfo Hector. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Universidad de La Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bosch, Guillermo Luis. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
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