Related papers: Periodic X-ray Emission from the O7 V Star theta^1…

Magnetic fields have been frequently invoked as a likely source of variability and confinement of the winds of massive stars. To date, the only magnetic field detected in O-type stars are those of theta 1 Ori C (HD 37022; Donati et al.…

The young O-type star theta1 OriC, the brightest star of the Trapezium cluster in Orion, is one of only two known magnetic rotators among the O stars. However, not all spectroscopic variations of this star can be explained by the magnetic…

Massive stars rarely show intrinsic X-ray variability. The only O-stars credited to be intrinsically variable are theta1 Ori C due to effects from magnetic confinement of its wind, and theta2 Ori A suspected of similar activity. Early…

We present the results of a spectroscopic analysis of the Trapezium cluster stars inside the Orion Nebula. The rotational velocities have been obtained using Fourier analysis method, finding agreement with values derived from the usual…

We analyzed high resolution X-ray spectra in the wavelength range of 1.5 -- 25 A of three of its X-ray brightest members obtained with the High Energy Transmission Grating Spectrometer (HETGS) on-board the Chandra X-ray Observatory. The DEM…

Theta^1 Ori is thought to be a hot analog of Bp variables because its optical and UV line and X-ray continuum fluxes modulate regularly over the magnetic/rotational period. A flattened magnetosphere surrounding co-rotates with these stars,…

Young O stars are strong, hard, and variable X-ray sources, properties which strongly affect their circumstellar and galactic environments. After ~1 Myr, these stars settle down to become steady sources of soft X-rays. I use high-resolution…

The Orion Nebula Cluster and the molecular cloud in its vicinity have been observed with the ACIS-I detector on board the Chandra X-ray Observatory with 23 hours exposure. We detect 1075 X-ray sources: 91% are spatially associated with…

We investigate the spatial distribution of X-ray emitting plasma in a sample of young Orion Nebula Cluster stars by modulation of their X-ray light-curves due to stellar rotation. The study, part of the Chandra Orion Ultradeep Project…

The X-ray properties of twenty ~1 Myr old O, B, and A stars of the Orion Trapezium are examined with data from the Chandra Orion Ultradeep Project (COUP). On the basis of simple theories for X-ray emission, we define two classes separated…

Located in the Orion Trapezium cluster, Theta 1 Orionis C is one of the youngest and nearest high-mass stars (O5-O7) and also known to be a close binary system. Using new multi-epoch visual and near-infrared bispectrum speckle…

We have obtained high-dispersion spectra for 256 pre-main-sequence stars in the Orion Nebula Cluster in order to measure their projected rotational velocities and study the rotational evolution and physical properties of young, low-mass…

We used the Very Large Array to carry out a multi-epoch radio continuum monitoring of the Orion Nebula Cluster and Orion Molecular Cloud. Our observations reveal the presence of 19 sources. With the exception of the sources BN and C the…

A recent Chandra/ACIS observation of the Orion Nebula Cluster detected 1075 sources (Feigelson et al. 2002), providing a uniquely large and well-defined sample to study the dependence of magnetic activity on bulk properties for stars…

High-resolution X-ray spectra of high-mass stars and low-mass T-Tauri stars obtained during the first year of the Chandra mission are providing important clues about the mechanisms which produce X-rays on very young stars. For zeta Puppis…

We used the Aladin Virtual Obsrvatory tool and High Resolution Imager ROSAT archival data to search for X-ray variability in scale of days in 23 young stars in the sigma Orionis cluster and a background galaxy. Five stars displayed…

The young O9.5 V spectroscopic binary Theta 2 Ori A shows moderately hard X-ray emission and relatively narrow X-ray lines, suggesting that it may be a Magnetically Confined Wind Shock (MCWS) source, similar to its more massive analogue…

We report on four Chandra grating observations of the oblique magnetic rotator theta^1 Ori C (O5.5 V) covering a wide range of viewing angles with respect to the star's 1060 G dipole magnetic field. We employ line-width and centroid…

We present a statistical analysis of simultaneous optical and X-ray light curves, spanning 600 ks, for 814 pre-main-sequence (PMS) stars in the Orion Nebula Cluster. The aim of this study is to establish the relationship, if any, between…

Eighteen fields in the Orion Nebula Cluster (ONC) have been monitored for one or more observing seasons from 1990-99 with a 0.6-m telescope at Wesleyan University. Photometric data were obtained in Cousins I on 25-40 nights per season.…