In this paper, we present a new multifrequency study of the giant star-forming complex RCW\,122. We used molecular data obtained with the ASTE 10 m and the APEX 12 m telescopes, along with infrared ...observations spanning from 3.6 to 870 obtained from available databases. We also incorporated a range of public datasets, including the radio continuum at 3 GHz, narrowband Halpha images, and deep JHK photometry. Our analysis focuses mostly on cataloged ATLASGAL sources, showcasing a spectrum of evolutionary stages from infrared dark cloud (IRDC)/high-mass protostellar object (HMPO) to ultra-compact HII region (UCHII), as inferred from preliminary inspections of the public dataset. Based on ASTE HCO$^+$(4--3) and CO(3--2) data, we identified five molecular clumps, designated A, B, C, D, and E, as molecular counterparts of the ATLASGAL sources. These clumps have radial velocities ranging from sim --15 to --10 confirming their association with RCW\,122. In addition, we report the detection of 20 transitions from 11 distinct molecules in the APEX spectra in the frequency ranges from 228.538 GHz to 232.538 GHz and 218.3 to 222.3 GHz, unveiling a diverse chemical complexity among the clumps. Utilizing CO(2--1) and C18O(2--1) data taken from the observations with the APEX telescope we estimated the total LTE molecular mass, ranging from 200 $M_ odot $ (clump A) to 4400 $M_ odot $ (clump B). Our mid- to far-infrared (MIR-FIR) flux density analysis yielded minimum dust temperatures of 23.7 K (clump A) to maximum temperatures of 33.9 K (clump B), indicating varying degrees of internal heating among the clumps. The bolometric luminosities span 1.7times 10$^3$ L$_ odot $ (clump A) to 2.4times 10$^5$ L$_ odot $ (clump B), while the total (dust+gas) mass ranges from 350 $M_ odot $ (clump A) to 3800 $M_ odot $ (clump B). Our analysis of the molecular line richness, $L/M$ ratios, and CH$_3$CCH and dust temperatures reveals an evolutionary sequence of A/Erightarrow Crightarrow D/B, consistent with preliminary inferences of the ATLASGAL sources. In this context, clumps A and E exhibit early stages of collapse, with clump A likely in an early HMPO phase, which is supported by identifying a candidate molecular outflow. Clump E appears to be in an intermediate stage between IRDC and HMPO. Clumps D and B show evidence of being in the UCHII phase, with clump B likely more advanced. Clump C likely represents an intermediate stage between HMPO and HMC. Our findings suggest clump B is undergoing ionization and heating by multiple stellar and protostellar members of the stellar cluster DBS\,119. Meanwhile, other cluster members may be responsible for ionizing other regions of RCW\,122 that have evolved into fully developed HII regions, beyond the molecular dissociation stage.
Context. The OWN Survey has detected several O-type stars with composite spectra whose individual components show very different line broadening. Some of these stars have been revealed as binary ...systems whose components are asynchronous. This fact may be related to the processes acting in these systems (e.g., angular-momentum transfer, tidal forces, etc.) or to the origin of the binaries themselves. Aims. We aim to determine the orbital and physical parameters of the massive star HD 96264A in order to confirm its binary nature and to constrain the evolutionary status of its stellar components. Methods. We computed the spectroscopic orbit of the system based on the radial velocity analysis of 37 high-resolution, high-S/N, multi-epoch optical spectra. We disentangled the composite spectrum and determined the physical properties of the individual stellar components using FASTWIND models incorporated to the IACOB-GBAT tool. We also computed a set of evolutionary models to estimate the age of the system and explore its tidal evolution. Results. HD 96264A is a binary system composed of an O9.2 IV primary and a B0 V(n) secondary, with minimum masses of 15.0 ± 0.5 M⊙ and 9.9 ± 0.4 M⊙, respectively, in a wide and eccentric orbit (P = 124.336 ± 0.008 d; e = 0.265 ± 0.005). The primary and secondary components have different projected rotational velocities (∼40 and ∼215 km s−1 respectively), and the physical properties derived through quantitative spectroscopic analyses include masses of ∼20.5 M⊙ and 16.8 M⊙, respectively. The evolutionary models indicate an approximate age of 4.5 Myr for both stars in the pair, corresponding to current masses and radii of 26.0 M⊙ and 10.8 R⊙ for the primary, and 17.9 M⊙ and 7.0 R⊙ for the secondary. Conclusions. The youth and wide orbit of the system indicate that the non-synchronous rotational nature of its components is a consequence of the stellar formation process rather than tidal evolution. This circumstance should be accounted for in theories of binary star formation.
We describe the public ESO near-IR variability survey (VVV) scanning the Milky Way bulge and an adjacent section of the mid-plane where star formation activity is high. The survey will take 1929
h of ...observations with the 4-m VISTA telescope during 5 years (2010–2014), covering ∼10
9 point sources across an area of 520
deg
2, including 33 known globular clusters and ∼350 open clusters. The final product will be a deep near-IR atlas in five passbands (0.9–2.5
μm) and a catalogue of more than 10
6 variable point sources. Unlike single-epoch surveys that, in most cases, only produce 2-D maps, the VVV variable star survey will enable the construction of a 3-D map of the surveyed region using well-understood distance indicators such as RR Lyrae stars, and Cepheids. It will yield important information on the ages of the populations. The observations will be combined with data from MACHO, OGLE, EROS, VST, Spitzer, HST, Chandra, INTEGRAL, WISE, Fermi LAT, XMM-Newton, GAIA and ALMA for a complete understanding of the variable sources in the inner Milky Way. This public survey will provide data available to the whole community and therefore will enable further studies of the history of the Milky Way, its globular cluster evolution, and the population census of the Galactic Bulge and center, as well as the investigations of the star forming regions in the disk. The combined variable star catalogues will have important implications for theoretical investigations of pulsation properties of stars.
The periodic spectroscopic events in eta Carinae are now well established and occur near the periastron passage of two massive stars in a very eccentric orbit. Several mechanisms have been proposed ...to explain the variations of different spectral features, such as an eclipse by the wind-wind collision (WWC) boundary, a shell ejection from the primary star or accretion of its wind onto the secondary. All of them have problems explaining all the observed phenomena. To better understand the nature of the cyclic events, we performed a dense monitoring of eta Carinae with five Southern telescopes during the 2009 low-excitation event, resulting in a set of data of unprecedented quality and sampling. The intrinsic luminosity of the He II lambda4686 emission line (L ~ 310 L sub(middot in circle)) just before periastron reveals the presence of a very luminous transient source of extreme UV radiation emitted in the WWC region. Clumps in the primary's wind probably explain the flare-like behavior of both the X-ray and He II lambda4686 light curves. After a short-lived minimum, He II lambda4686 emission rises again to a new maximum, when X-rays are still absent or very weak. We interpret this as a collapse of the WWC onto the "surface" of the secondary star, switching off the hard X-ray source and diminishing the WWC shock cone. The recovery from this state is controlled by the momentum balance between the secondary's wind and the clumps in the primary's wind.
Context. About 2500 planetary nebulae are known in our Galaxy but only 224 have central stars with reported spectral types in the Strasbourg-ESO Catalogue of Galactic Planetary Nebulae (Acker et al. ...1992; Acker et al. 1996). Aims. We have started an observational program aiming to increase the number of PN central stars with spectral classification. Methods. By means of spectroscopy and high resolution imaging, we identify the position and true nature of the central star. We carried out low resolution spectroscopic observations at CASLEO telescope, complemented with medium resolution spectroscopy performed at Gemini South and Magellan telescopes. Results. As a first outcome of this survey, we present for the first time the spectra of the central star of the PN Th 2-A. These spectra show emission lines of ionized C and O, typical in Wolf-Rayet stars. Conclusions. We identify the position of that central star, which is not the brightest one of the visual central pair. We classify it as of type WO 3pec, which is consistent with the high excitation and dynamical age of the nebula.
Context.
The OWN Survey has detected several O-type stars with composite spectra whose individual components show very different line broadening. Some of these stars have been revealed as binary ...systems whose components are asynchronous. This fact may be related to the processes acting in these systems (e.g., angular-momentum transfer, tidal forces, etc.) or to the origin of the binaries themselves.
Aims.
We aim to determine the orbital and physical parameters of the massive star HD 96264A in order to confirm its binary nature and to constrain the evolutionary status of its stellar components.
Methods.
We computed the spectroscopic orbit of the system based on the radial velocity analysis of 37 high-resolution, high-S/N, multi-epoch optical spectra. We disentangled the composite spectrum and determined the physical properties of the individual stellar components using
FASTWIND
models incorporated to the
IACOB-GBAT
tool. We also computed a set of evolutionary models to estimate the age of the system and explore its tidal evolution.
Results.
HD 96264A is a binary system composed of an O9.2 IV primary and a B0 V(n) secondary, with minimum masses of 15.0 ± 0.5
M
⊙
and 9.9 ± 0.4
M
⊙
, respectively, in a wide and eccentric orbit (
P
= 124.336 ± 0.008 d;
e
= 0.265 ± 0.005). The primary and secondary components have different projected rotational velocities (∼40 and ∼215 km s
−1
respectively), and the physical properties derived through quantitative spectroscopic analyses include masses of ∼20.5
M
⊙
and 16.8
M
⊙
, respectively. The evolutionary models indicate an approximate age of 4.5 Myr for both stars in the pair, corresponding to current masses and radii of 26.0
M
⊙
and 10.8
R
⊙
for the primary, and 17.9
M
⊙
and 7.0
R
⊙
for the secondary.
Conclusions.
The youth and wide orbit of the system indicate that the non-synchronous rotational nature of its components is a consequence of the stellar formation process rather than tidal evolution. This circumstance should be accounted for in theories of binary star formation.
Double-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.
ABSTRACT
Eta Carinae (
η
Car) is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He
ii
λ
4686 line increases rapidly ...in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of the He
ii
λ
4686 emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of the line equivalent width (EW), radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW variations, combined with other measurements, yield an orbital period of 2022.7 ± 0.3 days. The observed variability of the EW was reproduced by a model in which the line flux primarily arises at the apex of the wind–wind collision and scales inversely with the square of the stellar separation, if we account for the excess emission as the companion star plunges into the hot inner layers of the primary’s atmosphere, and including absorption from the disturbed primary wind between the source and the observer. This model constrains the orbital inclination to 135°–153°, and the longitude of periastron to 234°–252°. It also suggests that periastron passage occurred on
days). Our model also reproduced EW variations from a polar view of the primary star as determined from the observed He
ii
emission scattered off the Homunculus nebula.
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![He II [lambda]4686 IN [eta]...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0004-637X/small "He II [lambda]4686 IN [eta] CARINAE: COLLAPSE OF THE WIND-WIND COLLISION REGION DURING PERIASTRON PASSAGE")
