A deep dive into NGC 604 with Gemini/NIRI imaging

The giant HII region NGC 604 constitutes a complex and rich population to studying 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 star-formation 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. A extinction map obtained based on narrow-band images is also shown.Comment: 4 pages, 4 figures. To appear in the proceedings of IAU Symposium 266, Star Clusters: Basic Galactic Building Blocks Throughout Time and Space, eds. R. de Grijs and J. Lepin

Procesamiento de imágenes astronómicas con el equipo HP-1000 de la FCAGLP

As the HP-1000 computer of the FCAGLP will next be out of service, after thirteen years of use in Astrophysics, we present a summary of the software that was developed in the last years for its use in digital data handling (spectra and 2-D images).Asociación Argentina de Astronomí

The eccentric short-period orbit of the supergiant fast X-ray transient HD 74194 (=LM Vel)

Aims. We present the first orbital solution for the O-type supergiant star HD 74194, which is the optical counterpart of the supergiant fast X-ray transient IGR J08408-4503. Methods. We measured the radial velocities in the optical spectrum of HD 74194, and we determined the orbital solution for the first time. We also analysed the complex Hα profile. Results. HD 74194 is a binary system composed of an O-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 with the orbital period, but seems to vary in a superorbital period (P = 285 ± 10 d) nearly 30 times longer than the orbital one.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Spectroscopic study of the N159/N160 complex in the Large Magellanic Cloud

We 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.Comment: 36 pages, 24 figures (127 spectra mostly OB stars, 4 field images). Published in The Astronomical Journa

Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

Context. B[e] supergiants are evolved massive stars, enshrouded in a dense wind and surrounded by a molecular and dusty disk. The mechanisms that drive phases of enhanced mass loss and mass ejections, responsible for the shaping of the circumstellar material of these objects, are still unclear. Aims. We aim to improve our knowledge on the structure and dynamics of the circumstellar disk of the Large Magellanic Cloud B[e] supergiant LHA 120-S 73. Methods. High-resolution optical and near-infrared spectroscopic data were obtained over a period of 16 and 7 yr, respectively. The spectra cover the diagnostic emission lines from [Ca II] and [O I], as well as the CO bands. These features trace the disk at different distances from the star. We analyzed the kinematics of the individual emission regions by modeling their emission profiles. A low-resolution mid-infrared spectrum was obtained as well, which provides information on the composition of the dusty disk. Results. All diagnostic emission features display double-peaked line profiles, which we interpret as due to Keplerian rotation. We find that the profile of each forbidden line contains contributions from two spatially clearly distinct rings. In total, we find that LHA 120-S 73 is surrounded by at least four individual rings of material with alternating densities (or by a disk with strongly non-monotonic radial density distribution). Moreover, we find that the molecular ring must have gaps or at least strong density inhomogeneities, or in other words, a clumpy structure. The optical spectra additionally display a broad emission feature at 6160-6180 Å, which we interpret as molecular emission from TiO. The mid-infrared spectrum displays features of oxygen-and carbon-rich grain species, which indicates a long-lived, stable dusty disk. We cannot confirm the previously reported high value for the stellar rotation velocity. He I λ 5876 is the only clearly detectable pure atmospheric absorption line in our data. Its line profile is strongly variable in both width and shape and resembles of those seen in non-radially pulsating stars. A proper determination of the real underlying stellar rotation velocity is hence not possible. Conclusions. The existence of multiple stable and clumpy rings of alternating density recalls ring structures around planets. Although there is currently insufficient observational evidence, it is tempting to propose a scenario with one (or more) minor bodies or planets revolving around LHA 120-S 73 and stabilizing the ring system, in analogy to the shepherd moons in planetary systems.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

An HST/NICMOS view of the prototypical giant HII region NGC604 in M33

We present the first high-spatial resolution near-infrared (NIR) imaging of NGC 604, obtained with the NICMOS camera aboard the Hubble Space Telescope (HST). These NICMOS broadband images reveal new NIR point sources, clusters, and diffuse structures. We found an excellent spatial correlation between the 8.4 GHz radio continuum and the 2.2mu-m 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 of them was previously known. This preliminary analysis of the NICMOS images shows the complexity of the stellar content of the NGC 604 nebula.Comment: Paper presented in the Workshop "Young massive star clusters: initial conditions and environments" (Granada, Spain - Sept 2007). Astrophysics & Space Science in press, 7 pages, 4 figure

The little-studied cluster Berkeley 90 : I. LS III +46 11: a very massive O3.5 If* + O3.5 If* binary

Context. It appears that most (if not all) massive stars are born in multiple systems. At the same time, the most massive binaries are hard to find owing to their low numbers throughout the Galaxy and the implied large distances and extinctions. Aims. We want to study LS III +46 11, identified in this paper as a very massive binary; another nearby massive system, LS III +46 12; and the surrounding stellar cluster, Berkeley 90. Methods. Most of the data used in this paper are multi-epoch high S/N optical spectra, although we also use Lucky Imaging and archival photometry. The spectra are reduced with dedicated pipelines and processed with our own software, such as a spectroscopic-orbit code, CHORIZOS, and MGB. Results. LS III +46 11 is identified as a new very early O-type spectroscopic binary [O3.5 If* + O3.5 If*] and LS III +46 12 as another early O-type system [O4.5 V((f))]. We measure a 97.2-day period for LS III +46 11 and derive minimum masses of 38.80 ± 0.83 M⊙ and 35.60 ± 0.77 M⊙ for its two stars. We measure the extinction to both stars, estimate the distance, search for optical companions, and study the surrounding cluster. In doing so, a variable extinction is found as well as discrepant results for the distance. We discuss possible explanations and suggest that LS III +46 12 may be a hidden binary system where the companion is currently undetected.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

The little-studied cluster Berkeley 90 I. LS III +46 11: a very massive O3.5 If* + O3.5 If* binary

Context. It appears that most (if not all) massive stars are born in multiple systems. At the same time, the most massive binaries are hard to find owing to their low numbers throughout the Galaxy and the implied large distances and extinctions. Aims. We want to study LS III +46 11, identified in this paper as a very massive binary; another nearby massive system, LS III +46 12; and the surrounding stellar cluster, Berkeley 90. Methods. Most of the data used in this paper are multi-epoch high S/N optical spectra, although we also use Lucky Imaging and archival photometry. The spectra are reduced with dedicated pipelines and processed with our own software, such as a spectroscopic-orbit code, CHORIZOS, and MGB. Results. LS III +46 11 is identified as a new very early O-type spectroscopic binary [O3.5 If* + O3.5 If*] and LS III +46 12 as another early O-type system [O4.5 V((f))]. We measure a 97.2-day period for LS III +46 11 and derive minimum masses of 38.80 ± 0.83 M⊙ and 35.60 ± 0.77 M⊙ for its two stars. We measure the extinction to both stars, estimate the distance, search for optical companions, and study the surrounding cluster. In doing so, a variable extinction is found as well as discrepant results for the distance. We discuss possible explanations and suggest that LS III +46 12 may be a hidden binary system where the companion is currently undetected.J.M.A. and A.S. acknowledge support from [a] the Spanish Government Ministerio de Economía y Competitividad (MINECO) through grants AYA2010-15 081, AYA2010-17 631, and AYA2013-40 611-P and [b] the Consejería de Educación of the Junta de Andalucía through grant P08-TIC-4075. J.M.A. was also supported by the George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy and he is grateful to the Department of Physics and Astronomy at Texas A&M University for their hospitality during some of the time this work was carried out. I.N., A.M., J.A., and J.L. acknowledge support from [a] the Spanish Government Ministerio de Economía y Competitividad (MINECO) through grant AYA2012-39 364-C02-01/02, [b] the European Union, and [c] the Generalitat Valenciana through grant ACOMP/2014/129. R.H.B. acknowledges support from FONDECYT Project 1 140 076. S.S.-D. acknowledges funding by [a] the Spanish Government Ministerio de Economía y Competitividad (MINECO) through grants AYA2010-21 697-C05-04, AYA2012-39 364-C02-01, and Severo Ochoa SEV-2011-0187 and [b] the Canary Islands Government under grant PID2 010 119. J.S.-B. acknowledges support by the JAE-PreDoc program of the Spanish Consejo Superior de Investigaciones Científicas (CSIC). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555