scholarly journals Chandra observations of the dwarf starburst and Wolf-Rayet galaxies NGC 4449 and NGC 5253

2003 ◽  
Vol 212 ◽  
pp. 751-752
Author(s):  
Lesley K. Summers ◽  
Ian R. Stevens ◽  
David K. Strickland ◽  
Timothy M. Heckman
Keyword(s):  
Point Source ◽  
Massive Stars ◽  
Stellar Winds ◽  
Diffuse Emission ◽  
X Ray ◽  
Complex Morphology ◽  
Hα Emission ◽  
Supernova Explosions ◽  
Source Populations

We present an analysis of the Chandra observations of two dwarf starburst, Wolf-Rayet galaxies (NGC 4449 and NGC 5253). We have identified at least three different classes of objects within the X-ray point source populations, and we have found the diffuse emission, resulting from the stellar winds and supernova explosions of massive stars, to have a complex morphology and to consist of several components. Comparison with the Hα emission suggests the presence of ~ kpc-scale wind-blown bubbles and ruptured superbubbles.

scholarly journals What Do We Really Know About the Winds of Massive Stars?

2007 ◽  
Vol 3 (S250) ◽  
pp. 89-96
Author(s):  
D. John Hillier
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Standard Theory ◽  
Stellar Winds ◽  
X Rays ◽  
X Ray ◽  
Stellar Photosphere ◽  
Weak Winds ◽  
Ionization Balance ◽  
Loss Rates

AbstractThe standard theory of radiation driven winds has provided a useful framework to understand stellar winds arising from massive stars (O stars, Wolf-Rayet stars, and luminous blue variables). However, with new diagnostics, and advances in spectral modeling, deficiencies in our understanding of stellar winds have been thrust to the forefront of our research efforts. Spectroscopic observations and analyses have shown the importance of inhomogeneities in stellar winds, and revealed that there are fundamental discrepancies between predicted and theoretical mass-loss rates. For late O stars, spectroscopic analyses derive mass-loss rates significantly lower than predicted. For all O stars, observed X-ray fluxes are difficult to reproduce using standard shock theory, while observed X-ray profiles indicate lower mass-loss rates, the potential importance of porosity effects, and an origin surprisingly close to the stellar photosphere. In O stars with weak winds, X-rays play a crucial role in determining the ionization balance, and must be taken into account.

scholarly journals Massive stars shaping the ISM: H I holes and shells in nearby galaxies

1999 ◽  
Vol 193 ◽  
pp. 636-644
Author(s):  
Elias Brinks ◽  
Fabian Walter
Keyword(s):  
Interstellar Medium ◽  
Dwarf Galaxy ◽  
Massive Stars ◽  
Neutral Hydrogen ◽  
Neutral Medium ◽  
Stellar Winds ◽  
X Ray ◽  
Left Behind ◽  
Neutral Gas ◽  
Nearby Galaxies

Neutral hydrogen (H I) is a magnificent tool when studying the structure of the interstellar medium (ISM) as it is relatively easily observable and can be mapped at good spatial and velocity resolution with modern instruments. Moreover, it traces the cool (∼ 100 K) and warm (∼ 5000 K) neutral gas which together make up about 60%, or the bulk, of the ISM. The currently accepted picture is that stellar winds and subsequent supernovae are the origin for the clearly defined holes or bubbles within the more or less smooth neutral medium. The H I can therefore serve indirectly as a tracer of the hot interstellar medium (HIM) left behind after the most massive stars within an OB association have gone off as supernovae. A splendid example is the dwarf galaxy IC 2574 for which we discuss H I, optical and X-ray observations.

scholarly journals X-ray Emission from Massive Stars at the Core of Very Young Clusters

2016 ◽  
Vol 12 (S329) ◽  
pp. 362-365
Author(s):  
Norbert S. Schulz
Keyword(s):  
Massive Stars ◽  
Stellar Winds ◽  
X Rays ◽  
Stellar Clusters ◽  
Orion Nebula ◽  
X Ray ◽  
The Core ◽  
Hot Plasma ◽  
Young Clusters ◽  
Massive Cluster

AbstractMost cores of very young stellar clusters contain one or more massive stars at various evolutionary stages. Observations of the Orion Nebula Cluster, Trumpler 37, NGC 2362, RCW38, NGC 3603 and many others provide the most comprehensive database to study stellar wind properties of these massive cluster stars in X-rays. In this presentation we review some of these observations and results and discuss them in the context of stellar winds and possible evolutionary implications. We argue that in very young clusters such as RCW38 and M17, shock heated remnants of a natal shell could serve as an alternate explanation to the colliding wind paradigm for the hot plasma components in the X-ray spectra.

scholarly journals Bubbles and Superbubbles: Observations and Theory

2007 ◽  
Vol 3 (S250) ◽  
pp. 341-354 ◽  
Author(s):  
You-Hua Chu
Keyword(s):  
Turbulent Mixing ◽  
Thermal Conduction ◽  
Massive Stars ◽  
Ambient Medium ◽  
Surrounding Medium ◽  
Shell Structures ◽  
Stellar Winds ◽  
Hot Gas ◽  
Dense Shell ◽  
Supernova Explosions

AbstractMassive stars inject energy into the surrounding medium and form shell structures. Bubbles are blown by fast stellar winds from individual massive stars, while superbubbles are blown by fast stellar winds and supernova explosions from groups of massive stars. Bubbles and superbubbles share a similar overall structure: a swept-up dense shell with an interior filled by low-density hot gas. Physical properties of a bubble/superbubble can be affected by magnetic field, thermal conduction, turbulent mixing, inhomogeneous ambient medium, etc. I will review recent progresses on observations and compare them to theoretical expectations for (1) swept-up dense shells, (2) hot interiors, and (3) interface between a dense shell and its interior hot gas.

scholarly journals Magnetic fields, winds and X-rays of massive stars in the Orion Nebula Cluster

2008 ◽  
Vol 4 (S259) ◽  
pp. 449-452 ◽  
Author(s):  
Véronique Petit ◽  
G. A. Wade ◽  
L. Drissen ◽  
T. Montmerle ◽  
E. Alecian
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Magnetic Confinement ◽  
Stellar Winds ◽  
X Rays ◽  
Orion Nebula ◽  
X Ray ◽  
Ob Stars ◽  
Complex Processes ◽  
The Relationship

AbstractIn massive stars, magnetic fields are thought to confine the outflowing radiatively-driven wind, resulting in X-ray emission that is harder, more variable and more efficient than that produced by instability-generated shocks in non-magnetic winds. Although magnetic confinement of stellar winds has been shown to strongly modify the mass-loss and X-ray characteristics of massive OB stars, we lack a detailed understanding of the complex processes responsible. The aim of this study is to examine the relationship between magnetism, stellar winds and X-ray emission of OB stars. In conjunction with a Chandra survey of the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS observations to determine the magnetic properties of massive OB stars of this cluster.

scholarly journals Magnetic fields in O-type stars measured with FORS 1 at the VLT

2008 ◽  
Vol 4 (S259) ◽  
pp. 381-382
Author(s):  
Swetlana Hubrig ◽  
M. Schöller ◽  
R. S. Schnerr ◽  
I. Ilyin ◽  
H. F. Henrichs ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Emission Lines ◽  
X Ray ◽  
Wind Variability ◽  
Thermal Radio ◽  
Wide Range ◽  
Long Time ◽  
Hα Emission ◽  
Chemical Peculiarity

AbstractThe presence of magnetic fields in O-type stars has been suspected for a long time. The discovery of such fields would explain a wide range of well documented enigmatic phenomena in massive stars, in particular cyclical wind variability, Hα emission variations, chemical peculiarity, narrow X-ray emission lines and non-thermal radio/X-ray emission. Here we present the results of our studies of magnetic fields in O-type stars, carried out over the last years.

CO 2-1 Mapping of WR16 with AST/RO

2005 ◽  
Vol 13 ◽  
pp. 967-967
Author(s):  
N. F. H. Tothill ◽  
A. P. Marston ◽  
C. L. Martin ◽  
K. Leppik
Keyword(s):  
Massive Stars ◽  
Stellar Winds ◽  
South Pole ◽  
The South ◽  
Supernova Explosions ◽  
Rayet Star

AbstractMassive stars have profound effects on their surroundings, influencing them by their energetic stellar winds, and finally by supernova explosions. We present a CO 2-1 map of the surroundings of the Wolf-Rayet star WR16, taken with AST/RO at the South Pole, which shows some of these effects.

scholarly journals X-RAY POINT-SOURCE POPULATIONS CONSTITUTING THE GALACTIC RIDGE X-RAY EMISSION

2013 ◽  
Vol 766 (1) ◽  
pp. 14 ◽  
Author(s):  
Kumiko Morihana ◽  
Masahiro Tsujimoto ◽  
Tessei Yoshida ◽  
Ken Ebisawa
Keyword(s):  
Point Source ◽  
X Ray ◽  
Source Populations

scholarly journals The Diffuse Emission and a Variable Ultraluminous X‐Ray Point Source in the Elliptical Galaxy NGC 3379

2005 ◽  
Vol 635 (2) ◽  
pp. 1053-1061 ◽  
Author(s):  
Laurence P. David ◽  
Christine Jones ◽  
William Forman ◽  
Steven S. Murray
Keyword(s):  
Point Source ◽  
Elliptical Galaxy ◽  
Diffuse Emission ◽  
X Ray

scholarly journals X-ray diagnostics of massive star winds

2016 ◽  
Vol 12 (S329) ◽  
pp. 151-155
Author(s):  
L. M. Oskinova ◽  
R. Ignace ◽  
D. P. Huenemoerder
Keyword(s):  
High Resolution ◽  
Stellar Wind ◽  
Massive Star ◽  
Massive Stars ◽  
Stellar Winds ◽  
X Rays ◽  
Early Type ◽  
Stellar Rotation ◽  
X Ray ◽  
Early Type Stars

AbstractObservations with powerful X-ray telescopes, such as XMM-Newton and Chandra, significantly advance our understanding of massive stars. Nearly all early-type stars are X-ray sources. Studies of their X-ray emission provide important diagnostics of stellar winds. High-resolution X-ray spectra of O-type stars are well explained when stellar wind clumping is taking into account, providing further support to a modern picture of stellar winds as non-stationary, inhomogeneous outflows. X-ray variability is detected from such winds, on time scales likely associated with stellar rotation. High-resolution X-ray spectroscopy indicates that the winds of late O-type stars are predominantly in a hot phase. Consequently, X-rays provide the best observational window to study these winds. X-ray spectroscopy of evolved, Wolf-Rayet type, stars allows to probe their powerful metal enhanced winds, while the mechanisms responsible for the X-ray emission of these stars are not yet understood.

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