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X-ray observations of the double-binary OB-star system QZ Car (HD 93206) obtained with the Chandra X-ray Observatory over a period of roughly 2 years are presented. The respective orbits of systems A (O9.7 I+b2 v, P
A = 21 days) and B (O8 III+o9 v, P
B = 6 days) are reasonably well sampled by the observations, allowing the origin of the X-ray emiss...
Contexts in source publication
Context 1
... total of nine observations over a period of roughly two years, and combining relatively on-axis and far off-axis expo- sures taken with both the I-array and the S-array, have been obtained for QZ Car (Table 3). Due to the brightness of the central source the I-array observation (Obs ID 9482) was af- fected by photon pile-up, which we account for in our analy- sis (see § 3). ...
Context 2
... mass transfer (for an alternative scenario see § 4.3). Com- ponent A1-O is the faintest emitter (noting that component A1-O is bright for a brief period around periastron which is not sampled by our observations -see the φ A 's in Table 3), followed by the EWSs (≈ 4.4 × 10 −13 erg s −1 cm −2 ), both of which are fainter than the contribution from the MWC (Ta- ble 5). However, before making a detailed comparison with the best-fit values from the spectral fits we can improve our predictions by considering the energy dependence of the in- trinsic and attenuated flux. ...
Context 3
... intrinsic spectrum is then scaled so that the inte- grated 0.5-8 keV fluxes are equal to the orbital phase depen- dent values, which for components A1-O and B1-O are shown in Fig. 4e. The top panel of Fig. 5 shows the intrinsic spectra calculated for components A1-O, B1-O, the EWSs, and the MWC for Obs ID 6402 (see Table 3 for the respective orbital phases of systems A and B). The EWSs clearly contribute the softest spectrum. ...
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... The variable QZ Car is the brightest object in the Collinder 228 cluster and ID#46 in our distance survey (Shull & Danforth 2019). This is a double-line (SB1+SB1) binary (Parkin et al. 2011), consisting of system A (O9.7 Ib + b2 v) and system B (O8 III + o9 v). GOSS gives a combined classification of O9.7 Ib (S14) with V J,0 = 4.206 ± 0.018 and A V,J = 2.106 ± 0.022 (MAB18), presumably including all four stars in HD 93206AB. ...
Using offset-corrected Gaia EDR3 parallax measurements and spectrophotometric methods, we have determined distances for 69 massive stars in the Carina OB1 association and associated clusters: Trumpler 16 (21 stars), Trumpler 14 (20 stars), Trumpler 15 (three stars), Bochum 11 (five stars), and South Pillars region (20 stars). Past distance estimates to the Carina Nebula range from 2.2 to 3.6 kpc, with uncertainties arising from photometry and anomalous dust extinction. The EDR3 parallax solutions show considerable improvement over DR2, with typical errors σ ϖ /ϖ ≈ 3%-5%. The O-type stars in the Great Carina Nebula lie at essentially the same distance (2.35 ± 0.08 kpc), quoting mean and rms variance. The clusters have distances of 2.32 ± 0.12 kpc (Tr 16), 2.37 ± 0.15 kpc (Tr 14), 2.36 ± 0.09 kpc (Tr 15), and 2.33 ± 0.12 kpc (Bochum 11) in good agreement with the η Car distance of around 2.3 kpc. O-star proper motions suggest internal (3D) velocity dispersions ∼4 km s-1 for Tr 14 and Tr 16. Reliable distances allow estimates of cluster sizes, stellar dynamics, luminosities, and fluxes of photoionizing radiation incident on photodissociation regions in the region. We estimate that Tr 14 and Tr 16 have half-mass radii r h = 1.5-1.8 pc, stellar crossing times t cr = r h/v m ≈ 0.7-0.8 Myr, and two-body relaxation times t rh ≈ 40-80 Myr. The underlying velocity dispersion for Tr 14, if a bound cluster, would be vm ≈ 2.1-0.4+0.7 km s-1 for N=7600-2600+5800 stars. With the higher dispersions of the O stars, inward drift would occur slowly, on timescales of 3-6 Myr. © 2021. The American Astronomical Society. All rights reserved..
... In multiple systems, the quoted magnitude is that of the brightest stellar component. We analyze HD93129A and HD 93206A as binary systems (Aa, Ab)-seeGruner et al. (2019),Parkin et al. (2011), and further discussion in the Appendix. ...
For application to surveys of interstellar matter and Galactic structure, we compute new spectrophotometric distances to 139 OB stars frequently used as background targets for UV spectroscopy. Many of these stars have updated spectral types and digital photometry with reddening corrections from the Galactic O-Star (GOS) spectroscopic survey. We compare our new photometric distances to values used in previous International Ultraviolet Explorer and Far Ultraviolet Spectroscopic Explorer surveys and to parallax distances derived from Gaia -DR2, after applying a standard (0.03 mas) offset from the quasar celestial reference frame. We find substantial differences between photometric and parallax distances at d > 1.5 kpc, with increasing dispersion when parallax errors exceed 8%. Differences from previous surveys arise from new GOS stellar classifications, especially luminosity classes, and from reddening corrections. We apply our methods to two OB associations. For Perseus OB1 (nine O stars) we find mean distances of 2.47 ± 0.57 kpc ( Gaia parallax) and 2.99 ± 0.14 kpc (photometric) using a standard grid of absolute magnitudes. For 29 O stars in Car OB1 associated with Trumpler 16, Trumpler 14, Trumpler 15, and Collinder 228 star clusters, we find 2.87 ± 0.73 kpc ( Gaia ) and 2.60 ± 0.28 kpc (photometric). Using an alternative grid of O-star absolute magnitudes shifts these photometric distances ∼7% closer. Improving the distances to OB stars will require attention to spectral types, photometry, reddening, binarity, and the grid of absolute magnitudes. We anticipate that future measurements in Gaia -DR3 will improve the precision of distances to massive star-forming regions in the Milky Way.
... The X-ray emission can be described by a three temperature thermal plasma model with the hottest component at 2 keV and as a combination of contributions from the single stars and the mutual wind-wind collision. The wind-wind collisions in systems A and B are probably not contributing to the observed X-ray flux as a wind-wind momentum balance does not occur [152]. No non-thermal emission towards QZ Car has been observed. ...
... 43 ± 3 19 +3 -7 30 ± 3 20 ± 3 Table 4.10: Mass-loss rates and terminal wind velocities for the components of the double binary system QZ Car [152], masses [145]. ...
Das außergewöhnliche Doppelsternsystem Eta Carinae fasziniert WissenschaftlerInnen und BeobachterInnen auf der südlichen Erdhalbkugel seit hunderten Jahren. Nach einem Supernova-ähnlichem Ausbruch war Eta Carinae zeitweise der hellste Stern am Nachthimmel. Heute sind durch zahlreiche Beobachtungen, von Radiowellen bis zu Röntgenstrahlung, der Aufbau des Sternsystems und die Eigenschaften seiner Strahlung bis zu Energien von ~ 50 keV gut erforscht. Das Doppelsternsystem besteht aus zwei massiven Sternen (~ 30 und ~ 100 Sonnenmassen Gewicht) mit starken Sternwinden, über die sie kontinuierlich einen Teil ihrer Masse verlieren. Wenn diese Sternwinde kollidieren, entsteht auf beiden Seiten ein Kompressionsschock der das Plasma in der Kollisionszone aufheizt, was sich in Röntgenstrahlung beobachten lässt. Bei Energien oberhalb von ~ 50 keV ist der Ursprung der Strahlung nicht mehr thermisch: um ein Plasma auf die entsprechende Temperatur zu bringen, wird mehr mechanische Energie benötigt, als in den Sternwinden vorhanden. In hoch-energetischer Gamma-Strahlung ist Eta Carinae das einzige eindeutig detektierte Sternsystem seiner Art und sein Energiespektrum reicht bis zu ~ hundert GeV. Bodengebundene Gamma-Strahlungsexperimente haben in diesem Energiebereich den Vorteil von großen Detektorflächen. H.E.S.S. ist das einzige bodengebundene Gamma-Strahlungsexperiment auf der Südhalbkugel und somit in der Lage, Eta Carinae in diesen Energien zu beobachten. H.E.S.S. misst Gamma-Strahlung mit Hilfe der elektromagnetischen Teilchenschauer, die sehr hoch-energetische Photonen in der Atmosphäre auslösen. Die größte Herausforderung der Messung von Eta Carinaes Strahlung mit H.E.S.S. ist die ultraviolette Strahlung des Carina Nebels, die zu einem Hintergrund führt, der bis zu zehn mal stärker ist als der Durchschnitt in H.E.S.S. In dieser Arbeit wird die erste Detektion eines Doppelsternsystems mit kollidierenden Sternwinden in sehr hoch-energetischer Gamma-Strahlung präsentiert und die Studien, die diese ermöglicht haben. Das differentielle Gamma-Strahlungsspektrum bis 700 GeV wird untersucht. Hadronische und leptonische Szenarios für den Ursprung der Gamma-Strahlung werden diskutiert und das hadronische Szenario wird aufgrund eines Vergleichs der Kühlzeiten bevorzugt.
... In the case of the trapezium-like system QZ Car which hosts two binary systems with O9.7 I and O8 III primaries, Parkin et al. (2011a) noted from simple analytical considerations that the wind interaction in the binary containing the O8 III star should produce an X-ray emission 10 times stronger than the one observed with Chandra. Parkin et al. (2011a) suggest that in this system, the wind interaction could be disrupted by mass transfer via Roche lobe overflow from the O8 III star towards its companion. ...
... In the case of the trapezium-like system QZ Car which hosts two binary systems with O9.7 I and O8 III primaries, Parkin et al. (2011a) noted from simple analytical considerations that the wind interaction in the binary containing the O8 III star should produce an X-ray emission 10 times stronger than the one observed with Chandra. Parkin et al. (2011a) suggest that in this system, the wind interaction could be disrupted by mass transfer via Roche lobe overflow from the O8 III star towards its companion. ...
Previous generations of X-ray observatories revealed a group of massive
binaries that were relatively bright X-ray emitters. This was attributed to
emission of shock-heated plasma in the wind-wind interaction zone located
between the stars. With the advent of the current generation of X-ray
observatories, the phenomenon could be studied in much more detail. In this
review, we highlight the progress that has been achieved in our understanding
of the phenomenon over the last 15 years, both on theoretical and observational
grounds. All these studies have paved the way for future investigations using
the next generation of X-ray satellites that will provide crucial information
on the X-ray emission formed in the innermost part of the wind-wind
interaction.
... See also the previous works by Leung et al. (1979) and Morrison & Conti (1980). The spectral types of Parkin et al. (2011) are consistent with our combined classification (we do not see double lines in the GOSSS data). ...
We present the second installment of GOSSS, a massive spectroscopic survey of Galactic O stars, based on new homogeneous, high signal-to-noise ratio, R ~ 2500 digital observations from both hemispheres selected from the Galactic O-Star Catalog (GOSC). In this paper we include bright stars and other objects drawn mostly from the first version of GOSC, all of them south of delta = -20 degrees, for a total number of 258 O stars. We also revise the northern sample of paper I to provide the full list of spectroscopically classified Galactic O stars complete to B = 8, bringing the total number of published GOSSS stars to 448. Extensive sequences of exceptional objects are given, including the early Of/WN, O Iafpe, Ofc, ON/OC, Onfp, Of?p, and Oe types, as well as double/triple-lined spectroscopic binaries. The new spectral subtype O9.2 is also discussed. The magnitude and spatial distributions of the observed sample are analyzed. We also present new results from OWN, a multi-epoch
high-resolution spectroscopic survey coordinated with GOSSS that is assembling the largest sample of Galactic spectroscopic massive binaries ever attained. The OWN data combined with additional information on spectroscopic and visual binaries from the literature indicate that only a very small fraction (if any) of the stars with masses above 15-20 M_Sol are born as single systems. In the future we will publish the rest of the GOSSS survey, which is expected to include over 1000 Galactic O stars.
The hot nine-component system HD 93206, which contains a gravitationally bounded eclipsing Ac1+Ac2 binary ( P = 5.9987 d) and a spectroscopic Aa1+Aa2 ( P = 20.734 d) binary can provide important insights into the origin and evolution of massive stars. Using archival and new spectra, and a rich collection of ground-based and space photometric observations, we carried out a detailed study of this object. We provide a much improved description of both short orbits and a good estimate of the mutual period of both binaries of about 14 500 d (i.e. 40 years). For the first time, we detected weak lines of the fainter component of the 6.0 d eclipsing binary in the optical region of the spectrum, measured their radial velocities, and derived a mass ratio of M Ac2 / M Ac1 = 1.29, which is the opposite of what was estimated from the International Ultraviolet explorer (IUE) spectra. We confirm that the eclipsing subsystem Ac is semi-detached and is therefore in a phase of large-scale mass transfer between its components. The Roche-lobe filling and spectroscopically brighter component Ac1 is the less massive of the two and is eclipsed in the secondary minimum. We show that the bulk of the H α emission, so far believed to be associated with the eclipsing system, moves with the primary O9.7 I component Aa1 of the 20.73 d spectroscopic binary. However, the weak emission in the higher Balmer lines seems to be associated with the accretion disc around component Ac2. We demonstrate that accurate masses and other basic physical properties including the distance of this unique system can be obtained but require a more sophisticated modelling. A first step in this direction is presented in the accompanying Paper II (Brož et al.).
Context . In wind-powered X-ray binaries, the radiatively driven stellar wind from the primary may be inhibited by the X-ray irradiation. This creates the feedback that limits the X-ray luminosity of the compact secondary. Wind inhibition might be weakened by the effect of small-scale wind inhomogeneities (clumping) possibly affecting the limiting X-ray luminosity.
Aims . We study the influence of X-ray irradiation on the stellar wind for different radial distributions of clumping.
Methods . We calculate hot star wind models with external irradiation and clumping using our global wind code. The models are calculated for different parameters of the binary. We determine the parameters for which the X-ray wind ionization is so strong that it leads to a decrease of the radiative force. This causes a decrease of the wind velocity and even of the mass-loss rate in the case of extreme X-ray irradiation.
Results . Clumping weakens the effect of X-ray irradiation because it favours recombination and leads to an increase of the wind mass-loss rate. The best match between the models and observed properties of high-mass X-ray binaries (HMXBs) is derived with radially variable clumping. We describe the influence of X-ray irradiation on the terminal velocity and on the mass-loss rate in a parametric way. The X-ray luminosities predicted within the Bondi-Hoyle-Lyttleton theory agree nicely with observations when accounting for X-ray irradiation.
Conclusions . The ionizing feedback regulates the accretion onto the compact companion resulting in a relatively stable X-ray source. The wind-powered accretion model can account for large luminosities in HMXBs only when introducing the ionizing feedback. There are two possible states following from the dependence of X-ray luminosity on the wind terminal velocity and mass-loss rate. One state has low X-ray luminosity and a nearly undisturbed wind, and the second state has high X-ray luminosity and exhibits a strong influence of X-rays on the flow.
Characterization of the dynamics of massive star systems and the astrophysical properties of the interacting components are a prerequisite for understanding their formation and evolution. Optical interferometry at milliarcsecond resolution is a key observing technique for resolving high-mass multiple compact systems. Here we report on VLTI/GRAVITY, Magellan/FIRE, and MPG2.2m/FEROS observations of the late-O/early-B type system HD 93206 A, which is a member of the massive cluster Collinder 228 in the Carina nebula complex. With a total mass of about 90 M_sun, it is one of the most compact massive-quadruple systems known. In addition to measuring the separation and position angle of the outer binary Aa - Ac, we observe BrG and HeI variability in phase with the orbital motion of the two inner binaries. From the differential phases analysis, we conclude that the BrG emission arises from the interaction regions within the components of the individual binaries, which is consistent with previous models for the X-ray emission of the system based on wind-wind interaction. With an average 3-sigma deviation of ~15 deg, we establish an upper limit of p ~ 0.157 mas (0.35 AU) for the size of the BrG line-emitting region. Future interferometric observations with GRAVITY using the 8m UTs will allow us to constrain the line-emitting regions down to angular sizes of 20 uas (0.05 AU at the distance of the Carina nebula).
New high-resolution spectroscopy and BVR photometry together with literature data on the complex massive quaternary star QZ Car are collected and analysed. Absolute parameters are found as follows : System A: M1 = 43 (±3), M2 = 19 (+3 –7), R1 = 28 (±2), R2 = 6 (±2), (⊙); T1 ∼28000, T2 ∼33000 K; System B: M1 = 30 (±3), M2 = 20 (±3), R1 = 10 (±0.5), R2 = 20 (±1), (⊙); T1 ∼36000, T2 ∼30000 K (model dependent temperatures). The wide system AB: Period = 49.5 (±1) y, Epochs, conjunction = 1984.8 (±1), periastron = 2005.3 (±3) y, mean separation = 65 (±3), (AU); orbital inclination = 85 (+5 –15) deg, photometric distance ∼2700 (±300) pc, age = 4 (±1) My. Other new contributions concern (a) analysis of the timing of minima differences (O – C)s for the eclipsing binary (System B), (b) the width of the eclipses, pointing to relatively large effects of radiation pressure, (c) inferences from the rotational widths of lines for both Systems A and B, and (d) implications for theoretical models of early type stars. While feeling greater confidence on the quaternary’s general parametrization, observational complications arising from strong wind interactions or other, unclear, causes still inhibit precision and call for continued multiwavelength observations. Our high inclination value for the AB system helps to explain failures to resolve the wide binary in previous years. The derived young age independently confirms membership of QZ Car to the open cluster Collinder 228.
Binaries with hot massive components are strong X-ray sources. Besides the
intrinsic X-ray emission of individual binary members originating in their
winds, X-ray emission stems from the accretion on the compact companion or from
wind collision. Since hot star winds are driven by the light absorption in the
lines of heavier elements, wind acceleration is sensitive to the ionization
state. Therefore, the over-ionization induced by external X-ray source strongly
influences the winds of individual components. We studied the effect of
external X-ray irradiation on hot star winds. We used our kinetic equilibrium
(NLTE) wind models to estimate the influence of external X-ray ionization for
different X-ray luminosities and source distances. The models are calculated
for parameters typical of O stars. The influence of X-rays is given by the
X-ray luminosity, by the optical depth between a given point and the X-ray
source, and by a distance to the X-ray source. Therefore, the results can be
interpreted in the diagrams of X-ray luminosity vs.~the optical depth
parameter. X-rays are negligible in binaries with low X-ray luminosities or at
large distances from the X-ray source. The influence of X-rays is stronger for
higher X-ray luminosities and in closer proximity of the X-ray source. There is
a forbidden area with high X-ray luminosities and low optical depth parameters,
where the X-ray ionization leads to wind inhibition. There is excellent
agreement between the positions of observed stars in these diagrams and our
predictions. All wind-powered high-mass X-ray binary (HMXB) primaries lie
outside the forbidden area. Many of them lie close to the border of the
forbidden area, indicating that their X-ray luminosities are self-regulated. We
discuss the implications of our work for other binary types.
