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

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

A survey of N IV and O IV features near 3400 Å in O2-O5 spectra

We have conducted a survey of little-known N IV and O IV multiplets near 3400 Å in an extensive sample of well-classified, very early O-type spectra. The initial motivation was to search for additional useful classification criteria for these types, but an unexpected result is the high sensitivity of these features to evolutionary CNO processing. We have found a useful discriminant between O2 and later types in the relative strengths of the O IV multiplets, one of which is subject to selective emission in the hottest spectra; the overall strengths of these lines also decrease between spectral types O4 and O5. More remarkable, however, are the variations in the N/O ratios among both individual stars and clusters. For instance, several O4 If + spectra have very large ratios, while main-sequence stars in the Carina Nebula generally have smaller values than others of the same spectral types in other regions. These effects correspond to different degrees of mixing of processed material as a function of evolutionary age and initial rotational velocities; the second effect provides significant further evidence that very massive stars mix while still on the main sequence. Thus, further analysis of these features will likely provide valuable diagnostics of important evolutionary parameters.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

OWN Survey: A spectroscopic monitoring of Southern Galactic O and WN-type stars

We summarize the status and results of the OWN Survey, a high-resolution monitoring program of Southern Galactic O-and WN-Type stars, after twelve years of observing campaign.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

OWN Survey: A spectroscopic monitoring of Southern Galactic O and WN-type stars

We summarize the status and results of the OWN Survey, a high-resolution monitoring program of Southern Galactic O-and WN-Type stars, after twelve years of observing campaign.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísica

The infrared Hourglass cluster in M8

A detailed study of the Hourglass nebula in the M8 star-forming region is presented. The study is mainly based on recent subarcsec-resolution JHKs images taken at Las Campanas Observatory and complemented with archival Hubble Space Telescope (HST) images and long-slit spectroscopy retrieved from the European Southern Observatory Archive Facility. Using the new numerical code chorizos, we estimate the distance to the earliest stars in the region to be 1.25 kpc. Infrared photometry of all the sources detected in the field is given. From analysis of the JHKs colour-colour diagrams, we find that an important fraction of these sources exhibit significant infrared excess. These objects are candidates to be low- and intermediate-mass pre-main-sequence stars. Based on HST observations, the spatial distribution of gas, dust and stars in the region is analysed. A morphological analysis of these images also reveals a rich variety of structures related to star formation (proplyds, jets, bow shocks), similar to those observed in M16 and M42, along with the detection of the first four Herbig-Haro objects in the region. Furthermore, a long-slit spectrum obtained with the New Technology Telescope confirms the identification of one of them (HH 870) in the core of the Hourglass nebula, providing the first direct evidence of active star formation by accretion in M8.Facultad de Ciencias Astronómicas y Geofísica

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

The massive double-lined O-type binary HD 165052

We present a new optical spectroscopic study of the O-type binary HD 165052 based on high-and intermediate-resolution CCD observations. We re-investigated the spectral classification of the binary components, obtaining spectral types of O6.5 V and O7.5 V for the primary and secondary, respectively, finding that both stars display weak CIII λ5696 emission in their spectra. We also determined a radial-velocity orbit for HD 165052 with a period of 2.95510 ± 0.00001 d, and semi-amplitudes of 94.8 and 104.7 ± 0.5km s-1, resulting in a mass ratio Q = 0.9. From a comparison with previous radial-velocity determinations, we found evidence of apsidal motion in the system. Several signatures of wind-wind collision, such as phase-locked variability of the X-ray flux and the Struve-Sahade effect, are also considered. It was also found that the reddening in the region should be normal, in contrast with previous determinations.Facultad de Ciencias Astronómicas y Geofísica

Observational Constraints on the HD 5980 Wind-Wind Collision

Se presentan observaciones recientes del sistema m´ultiple HD 5980 ubicado en la Nube Menor de Magallanes que se complementan con los resultados de observaciones efectuadas desde los a˜nos 1950s. Encontramos que la componente Star A, que actualmente posee el espectro dominante tipo Wolf-Rayet, siempre ha sido la estrella con el viento m´as intenso. Las variaciones en los perfiles de l´ıneas en emisi´on se explican con una combinaci´on de los siguientes procesos: eclipses atmosf´ericos, emisi´on y absorci´on proveniente de la zona de interacci´on de los vientos, y ocultamiento de regiones de esta misma zona. Las observaciones de 2017-2020 indican un incremento en el nivel de actividad comparado con los a˜nos 2010-2015.Analysis of spectral line profile variations observed over 6 decades in the WolfRayet system HD 5980 lead to the conclusion that Star A, the variable member of the system, has always dominated the wind collision zone (WCZ), contrary to suggestions that before 1994 the stronger wind belonged to its close companion, Star B. The observed variations are caused by a combination of physical occultations, wind eclipses and emission and absorption originating in the WCZ. The effects caused by the leading WCZ branch, which folds around Star B, are clearly seen as it crosses our line of sight to Star A during the secondary eclipse. These effects can inform on the WCZ velocity and density structures. We speculate that differences in line profiles at the same orbital phase but at different epochs may be linked to changes in the WCZ radiative properties. The 2017-2020 spectra indicate that HD 5980 was in a higher activity state than during 2010-2015.Fil: Koenigsberger, G.. Universidad Nacional Autonoma de Mexico. Instituto de Astronomia; MéxicoFil: Morrell, Nidia. Observatorio Las Campanas, Carnegie Institution; ChileFil: John Hillier, D.. University of Pittsburgh; Estados UnidosFil: Schmutz, Werner. No especifíca;Fil: 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: Arias, Julia Inés. Universidad de La Serena; ChileFil: Barbá, Rodolfo. Universidad de La Serena; ChileFil: Ferrero, Gabriel. 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; Argentin