K. Hamaguchi

η Carinae across the 2003.5 minimum: Spectroscopic evidence for massive binary interactions

We have analyzed high spatial, moderate spectral resolution observations of η Carinae (η Car) obtained with the STIS from 1998.0 to 2004.3. The data were obtained at discrete times covering an entire 2024 day spectroscopic cycle, with focus on the X-ray/ionization low state that began in 2003 June. The spectra show prominent P Cygni lines in H I, Fe II, and He I, which are complicated by blends and contamination by nebular emission and absorption. All lines show phase- and species-dependent variations in emission and absorption. For most of the cycle the He I emission is blueshifted relative to the H I and Fe II P Cygni emission lines, which are centered at approximately system velocity. The blueshifted He I absorption components vary in intensity and velocity throughout the 2024 day period. We construct radial velocity curves for the absorption component of the He I and H I lines. The He I absorption shows significant radial velocity variations throughout the cycle, with a rapid change of over 200 km s-1 near the 2003.5 event. The H I velocity curve is similar to that of the He I absorption, although offset in phase and reduced in amplitude. We interpret the complex line profile variations in He I, H I, and Fe II to be a consequence of the dynamic interaction of the dense wind of η Car A with the less dense, faster wind plus the radiation field of a hot companion star, η Car B. We use the variations seen in He I and the other P Cygni lines to constrain the geometry of the orbit and the character of η Car B.

CHANDRA X-RAY GRATING SPECTROMETRY OF η CARINAE NEAR X-RAY MINIMUM. I. VARIABILITY OF THE SULFUR AND SILICON EMISSION LINES

We reportonvariationsinimportant X-ray emissionlines ina seriesof Chandragrating spectra of the supermassive colliding wind binary starCar, including key phases around the X-ray minimum/periastron passage in 2003.5. The X-raysarisefromthecollisionof theslow,densewindofCarwiththefast,low-densitywindof anotherwisehidden companion star. The X-ray emission lines provide the only direct measure of the flow dynamics of the companions wind along the wind-wind collision zone. We concentrate here on the silicon and sulfur lines, which are the strongest and best-resolved lines in the X-ray spectra. Most of the line profiles can be adequately fit with symmetric Gaussians with little significant skewness. Both the silicon and sulfur lines show significant velocity shifts and correlated increases in line widths through the observations. The R = forbidden-to-intercombination ratio from the Si xiii and S xv triplets is near or above the low-density limit in all observations, suggesting that the line-forming region is >1.6 stellar radii from the companion star. We show that simple geometrical models cannot simultaneously fit both the observed centroid variations and changes in line width as a function of phase. We show that the observed profiles can be fitted with synthetic profiles with a reasonable model of the emissivity along the wind-wind collision boundary. Weusethisanalysistohelpconstrainthelineformationregionasafunctionof orbitalphase,andtheorbitalgeometry. Subject headingg stars: early-type — stars: individual (� Car) — X-rays: stars

Chandra Observations of High-Mass Young Stellar Objects in the Monoceros R2 Molecular Cloud

We observed the Monoceros R2 molecular cloud with the ACIS-I array on board the Chandra X-Ray Observatory. From the central 32 × 32 region, we detect 154 sources above the detection limit of ~5 × 10-16 ergs s -1 cm -2 with a 100 ks exposure. About 85% of the X-ray sources are identified with an infrared counterpart, including four high-mass stars in the zero-age main-sequence (ZAMS) and/or pre-main-sequence (PMS) phase. The X-ray spectra of the high-mass ZAMS and PMS stars are represented by a thin thermal plasma model of a temperature above ~2 keV. The X-rays are time variable and exhibit rapid flares. This high-temperature plasma and flaring activity is similar to that seen in low-mass PMS stars and is contrary to the behavior observed in high-mass main-sequence stars.The X-ray luminosity increases as the intrinsic K-band flux increases. However, the X-ray luminosity saturates at a level of ~1031 ergs s-1. We conclude that high-mass ZAMS and PMS stars emit X-rays, possibly because of magnetic activity such as that of low-mass stars.

He II λ4686 EMISSION FROM THE MASSIVE BINARY SYSTEM IN η CAR: CONSTRAINTS TO THE ORBITAL ELEMENTS AND THE NATURE OF THE PERIODIC MINIMA* ** *** ****

{\eta} Carinae is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He II

A Coordinated X-Ray and Optical Campaign of the Nearest Massive Eclipsing Binary, δ Orionis Aa. II. X-Ray Variability

\lambda 4686

The wind-wind collision hole in eta Car

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

THE DISK AND ENVIRONMENT OF A YOUNG VEGA ANALOG: HD 169142

\lambda 4686

Erratum: “Chandra Observations of High-Mass Young Stellar Objects in the Monoceros R2 Molecular Cloud” (ApJ, 567, 423 [2002])

emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of EW(He II

The Potential of High Angular Resolution and Contrast FUV Imagery for Studies of Star and Planetary System Formation

\lambda 4686

The Discovery of a Photoevaporation-Driven Molecular Outflow from the T Tauri Transitional Disk GM Aur

), the line radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW(He II