Geysers in the Lagoon: New Herbig-Haro objects in M 8

Aims. We search for direct evidence of ongoing star formation by accretion in the Lagoon Nebula (M 8), using optical wide-field narrow-band imaging obtained at La Silla Observatory. Methods. We examine [S II] and Hα images for line-emission features that could be interpreted as signatures of outflow activity of the exciting sources. Results. We discover five new Herbig-Haro objects, study in detail their morphology and attempt to identify their potential driving sources among the population of T Tauri stars and embedded sources in the surroundings. Conclusions. The results reported here conclusively demonstrate the existence of very young stars going through the accreting phase in the M 8 region.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Un paso más en el entendimiento de W Serpentis

W Serpentis (HD 166126) es una binaria interactuante, cuyas propiedades espectroscópicas y fotométricas la convierten en un objeto único. Dicha binaria fue observada espectrográficamente en alta dispersión en Cerro Tololo (Junio de 1991) y en dispersión media en el CASLEO (Agosto de 1992). Este material ha permitido analizar detalles espectrales asociados con las dos componentes estelares del sistema. Es la primera vez que se detectan líneas espectrales asociadas con la componente que está al frente en el mínimo de luz profundo. Se sugieren valores posibles de distintos parámetros físicos del sistema. Por último, se discute la estructura gaseosa del sistema (envolturas circumbinaria y circunestelares, disco de acreción, corriente gaseosa, etc.) sugiriéndose un modelo tentativo para el mismo.Asociación Argentina de Astronomí

Resultados del primer estudio de W Serpentis con altas resoluciones temporal y espectral

The interacting binary system W Serpentis was observed at the CTIO 1.52m telescope, with the BME spectrograph, from June 26 through July 1, 1991, through the phase interval 0.93P - 0.28P. The spectral region AA5510-6980 Å was covered. The spectra show the following behavior: a) Hα is the most prominent emission present, b) He I λ5876 emission is present on all the spectra, c) Na I, Si II, Fe II and Ba II are present as variable emissions, d) [Fe II] and [O I] emissions are possibly present, e) narrow and associated variable shallow absorption of Na I, Si II, Sc II and Fe II are present, f) shallow and variable absorption of Ca I and Fe I are present, g) diffuse interstellar absorptions are present, and suggest E(B — V) ∼ 0.5.Asociación Argentina de Astronomí

A deep dive into NGC604 with Gemini/NIRI imaging

The giant HII region NGC 604 constitutes a complex and rich population to study in detail many aspects of massive star formation, such as their environments and physical conditions, the evolutionary processes involved, the initial mass function for massive stars and starformation rates, among many others. Here, we present our first results of a near-infrared study of NGC 604 performed with NIRI images obtained with Gemini North. Based on deep JHK photometry, 164 sources showing infrared excess were detected, pointing to the places where we should look for star-formation processes currently taking place. In addition, the color-color diagram reveals a great number of objects that could be giant/supergiant stars or unresolved, small, tight clusters. An extinction map obtained based on narrow-band images is also shown.Facultad de Ciencias Astronómicas y Geofísica

Unveiling the new generation of stars in NGC604 with Gemini-NIRI

We present a near-infrared study focused on the detection and characterization of the youngest stellar component of the NGC604 giant star-forming region in the Triangulum galaxy (M33). By means of color-color diagrams derived from the photometry of JHKs images taken with the Gemini Near Infrared Imaging and Spectrometer (NIRI), we have found 68 candidate massive young stellar objects. The spatial distribution of these sources matches the areas where previous studies suggested that star formation might be taking place, and the high spatial resolution of our deep NIRI imaging allows us to pinpoint the star-forming knots. An analysis of the fraction of objects that show infrared excess suggests that the star formation is still active, supporting the presence of a second generation of stars being born, although the evidence for or against sequential star formation does not seem to be conclusive.Facultad de Ciencias Astronómicas y Geofísica

The new Wolf-Rayet binary system WR62a

Context. A 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.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Pre-main-sequence stars in the Lagoon Nebula (M8)

We 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.Facultad de Ciencias Astronómicas y Geofísica

Geysers in the Lagoon: New Herbig-Haro objects in M 8

Aims. We search for direct evidence of ongoing star formation by accretion in the Lagoon Nebula (M 8), using optical wide-field narrow-band imaging obtained at La Silla Observatory. Methods. We examine [S II] and Hα images for line-emission features that could be interpreted as signatures of outflow activity of the exciting sources. Results. We discover five new Herbig-Haro objects, study in detail their morphology and attempt to identify their potential driving sources among the population of T Tauri stars and embedded sources in the surroundings. Conclusions. The results reported here conclusively demonstrate the existence of very young stars going through the accreting phase in the M 8 region.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

Further insights into the structure of 30 Doradus from the Hubble space telescope instruments

New observations with the Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2), combined with prior archival data, provide nearly complete coverage of the inner 30 Doradus Nebula in both nebular lines and continuum at 0″.1 resolution. The developing windblown cavity surrounding the massive first-generation, central cluster and its interface with the remanent molecular clouds, the site of second-generation, triggered star formation, are imaged in their entirety. Dithered Planetary Camera observations with 0″.03 resolution of Knots 1-3 reveal further structural details of the large dust pillars oriented toward the central cluster and the newborn, massive multiple systems of the second generation in those fields. The new data also provide the first WFPC2 coverage of the fields of two interesting, luminous infrared sources observed in our previous Near Infrared Camera and Multi-Object Spectrometer program; comparisons of the high-resolution optical and IR images are illuminating. In addition, we have obtained Space Telescope Imaging Spectrograph optical, long-slit observations of seven O-type multiple systems in the region, including those in Knots 1-3 and four representatives of the older generation. The spatially resolved spectrograms and classifications of the close pairs, with separations ranging from 0″.09 to 1″.18, are presented, as well as WFPC2 photometry of the individual components and the compact clusters of fainter stars associated with them. These new observations, and planned further analysis of them, offer significant new information about the intricate structure and evolution of the two-stage starburst in 30 Dor.Facultad de Ciencias Astronómicas y Geofísica

Multiwavelength study of RCW 108 as a massive star forming region

NGC 6193 is an open cluster embedded in an Hii region (RCW 108, Rodgers et al. 1960) located 15 0 eastwards of NGC 6188. The later is a bright rimmed cloud that stretches over 30 0 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 RCW108- 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, 13CO observations, and infrared data (2MASS, MSX).Facultad de Ciencias Astronómicas y Geofísica