scholarly journals XMM-Newton Detection of Extended X-ray Emission from the Saturn Nebula

2003 ◽  
Vol 209 ◽  
pp. 427-428
Author(s):  
Martín A. Guerrero ◽  
Robert A. Gruendl ◽  
You-Hua Chu
Keyword(s):  
Stellar Wind ◽  
Planetary Nebula ◽  
Emission Measure ◽  
Evolutionary Stage ◽  
Dynamic Effects ◽  
Central Cavity ◽  
Spectral Analyses ◽  
X Ray ◽  
Hot Gas ◽  
Volume Emission

XMM-Newton EPIC observations of the planetary nebula NGC 7009, the Saturn Nebula, have detected extended X-ray emission from its central cavity. The diffuse X-ray emission must originate in the shocked fast stellar wind. Spectral analyses show that the temperature of the hot gas is 1.7 x 106 K. The RMS density derived from the volume emission measure is a few tens H-atom cm-3. The hot gas does not appear over-pressurized with respect to the nebular shell. The Saturn Nebula may represent an evolutionary stage at which the dynamic effects of the hot gas in the central cavity on the cold nebular shell starts to decline due to the diminishing strength of the fast stellar wind and the expansion of the central cavity.

scholarly journals Ablation and Wind Mass-Loading in the Born-Again Planetary Nebula A 30

2011 ◽  
Vol 7 (S283) ◽  
pp. 378-379
Author(s):  
Martín A. Guerrero ◽  
You-Hua Chu ◽  
Wolf-Rainer Hamann ◽  
Lidia Oskinova ◽  
Detlef Schönberner ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Planetary Nebula ◽  
Central Star ◽  
Mass Loading ◽  
Diffuse Emission ◽  
X Ray ◽  
Thermal Pulse ◽  
Born Again

AbstractWe present XMM-Newton and Chandra observations of the born-again planetary nebula A 30. These X-ray observations reveal a bright unresolved source at the position of the central star whose X-ray luminosity exceeds by far the model expectations for photospheric emission and for shocks within the stellar wind. We suggest that a “born-again hot bubble” may be responsible for this X-ray emission. Diffuse X-ray emission associated with the petal-like features and one of the H-poor knots seen in the optical is also found. The weakened emission of carbon lines in the spectrum of the diffuse emission can be interpreted as the dilution of stellar wind by mass-loading or as the detection of material ejected during a very late thermal pulse.

scholarly journals Colliding stellar wind modelling of the X-ray emission from WR 140

2020 ◽  
Vol 500 (4) ◽  
pp. 4837-4848
Author(s):  
Svetozar A Zhekov
Keyword(s):  
Mass Loss ◽  
Effective Mass ◽  
Stellar Wind ◽  
Mass Loss Rate ◽  
Emission Measure ◽  
Strong Line ◽  
Stellar Winds ◽  
Line Profiles ◽  
X Ray ◽  
Binary Orbit

ABSTRACT We modelled the Chandra and Rossi X-ray Timing Explorer X-ray spectra of the massive binary WR 140 in the framework of the standard colliding stellar wind (CSW) picture. Models with partial electron heating at the shock fronts are a better representation of the X-ray data than those with complete temperature equalization. Emission measure of the X-ray plasma in the CSW region exhibits a considerable decrease at orbital phases near periastron. This is equivalent to variable effective mass-loss rates over the binary orbit. At orbital phases near periastron, a considerable X-ray absorption in excess to that from the stellar winds in WR 140 is present. The standard CSW model provides line profiles that in general do not match well the observed line profiles of the strong line features in the X-ray spectrum of WR 140. The variable effective mass-loss rate could be understood qualitatively in CSW picture of clumpy stellar winds where clumps are efficiently dissolved in the CSW region near apastron but not at periastron. However, future development of CSW models with non-spherically symmetric stellar winds might be needed to get a better correspondence between theory and observations.

scholarly journals The Bubble Nebula NGC 7635 – testing the wind-blown bubble theory

2020 ◽  
Vol 495 (3) ◽  
pp. 3041-3051
Author(s):  
J A Toalá ◽  
M A Guerrero ◽  
H Todt ◽  
L Sabin ◽  
L M Oskinova ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Massive Stars ◽  
Stellar Atmosphere ◽  
The Other ◽  
X Ray ◽  
Hot Gas ◽  
San Pedro ◽  
Kinematic Study ◽  
Fast Motion ◽  
Echelle Spectrometer

ABSTRACT We present a multiwavelength study of the iconic Bubble Nebula (NGC 7635) and its ionizing star BD+60○2522. We obtained XMM–Newton EPIC X-ray observations to search for extended X-ray emission as in other similar wind-blown bubbles around massive stars. We also obtained San Pedro Mártir spectroscopic observations with the Manchester Echelle Spectrometer to study the dynamics of the Bubble Nebula. Although our EPIC observations are deep, we do not detect extended X-ray emission from this wind-blown bubble. On the other hand, BD+60○2522 is a bright X-ray source similar to other O stars. We used the stellar atmosphere code PoWR to characterize BD+60○2522 and found that this star is a young O-type star with stellar wind capable of producing a wind-blown bubble that in principle could be filled with hot gas. We discussed our findings in line with recent numerical simulations proposing that the Bubble Nebula has been formed as the result of the fast motion of BD+60○2522 through the medium. Our kinematic study shows that the Bubble Nebula is composed by a series of nested shells, some showing blister-like structures, but with little signatures of hydrodynamical instabilities that would mix the material producing diffuse X-ray emission as seen in other wind-blown bubbles. Its morphology seems to be merely the result of projection effects of these different shells.

scholarly journals X-ray Shaping of Planetary Nebulae

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 98
Author(s):  
Martín Guerrero
Keyword(s):  
Stellar Wind ◽  
Essential Role ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Stellar Winds ◽  
Physical Processes ◽  
X Ray ◽  
Hot Gas ◽  
Energy And Momentum ◽  
Central Stars

The stellar winds of the central stars of planetary nebulae play an essential role in the shaping of planetary nebulae. In the interacting stellar winds model, the fast stellar wind injects energy and momentum, which are transferred to the nebular envelope through an X-ray-emitting hot bubble. Together with other physical processes, such as the ionization of the nebular envelope, the asymmetrical mass-loss in the asymptotic giant branch (AGB), and the action of collimated outflows and magnetic fields, the pressurized hot gas determines the expansion and evolution of planetary nebulae. Chandra and XMM-Newton have provided us with detailed information of this hot gas. Here in this talk I will review our current understanding of the effects of the fast stellar wind in the shaping and evolution of planetary nebulae and give some hints of the promising future of this research.

scholarly journals X-ray and UV Views of Hot Gas in Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 415-424 ◽  
Author(s):  
You-Hua Chu ◽  
Martín A. Guerrero ◽  
Robert A. Gruendl
Keyword(s):  
Planetary Nebula ◽  
Dynamical Evolution ◽  
Planetary Nebulae ◽  
Central Star ◽  
X Ray ◽  
Physical Conditions ◽  
Hot Gas ◽  
Fast Wind

The interior of a planetary nebula (PN) is expected to be filled with shocked fast wind from the central star. This hot gas plays the most important role in the dynamical evolution of the PN; however, its physical conditions are not well-known because useful X-ray and far-UV observations were not available until the advent of Chandra, XMM-Newton, and FUSE. This paper reviews X-ray observations of the hot gas in PN interiors and far-UV observations of the interfaces between the hot gas and the dense nebular shells.

scholarly journals High Spectral Resolution Observations of Coronal X-Ray Emission from the RS CVn Binary Sigma Corona Borealis

1984 ◽  
Vol 86 ◽  
pp. 143-146
Author(s):  
G.R. Riegler ◽  
P.C. Agrawal ◽  
T.H. Markert
Keyword(s):  
Spectral Resolution ◽  
Emission Measure ◽  
High Spectral Resolution ◽  
Loop Model ◽  
X Ray ◽  
Resolution Observation ◽  
Volume Emission ◽  
Best Fit ◽  
Spectral Scan ◽  
Prominent Peak

Results of a high spectral resolution observation of the RS CVn binary σ Cr B, made with the Focal Plane Crystal Spectrometer (FPCS) on the Einstein Observatory, are reported. A spectral scan in the 800–840 eV interval shows clear presence of an X-ray emission line at 826 eV identified with the 1S0 − 1P1 transition of Fe XVII. A prominent peak at 1007 eV in the scan band 987–1013 eV is attributed to a blend of lines due to Fe XVII and Fe XXI. Using the observed line fluxes and the Raymond-Smith model, best fit values of corona temperature and volume emission measure, with associated 90% confidence level uncertainties, are derived to be (6.9 ± 0.8) × 106 K and (1.7 ± 0.7) × 1053 cm−3, respectively. Pressure and density of the X-ray emitting plasma and loop length are deduced by applying a Constant Pressure Coronal Loop Model.

scholarly journals Fluctuations in the Diffuse Soft X-ray Background; Probably of Galactic Halo Origin

1997 ◽  
Vol 166 ◽  
pp. 333-336
Author(s):  
T.J. Sumner ◽  
S.D. Sidher ◽  
J.J. Quenby ◽  
M. Hernandez ◽  
A. Mian ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Emission Measure ◽  
Local Bubble ◽  
Spherical Distribution ◽  
X Ray ◽  
Hot Gas ◽  
Galactic Emission ◽  
Global Trend ◽  
Background Data ◽  
X Ray Background

AbstractSoft X-ray background data from the ROSATPSPC have been fitted by a model including emission from the local bubble, embedded hot gas within the disk, hot gas in the Galactic halo and extra-galactic emission, together with local and disk absorption. In all directions a halo component at 106.2 K (0.2 keV) is required for an acceptable fit. The halo emission measure shows spatial variability and the global trend suggests a disk-like planar rather than more extended spherical distribution. New values for the emission measure within the local bubble are derived.

scholarly journals X-ray Shaping of Planetary Nebulae

2018 ◽  
Author(s):  
Martin A Guerrero
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Essential Role ◽  
Planetary Nebulae ◽  
Stellar Winds ◽  
Physical Processes ◽  
X Ray ◽  
Hot Gas ◽  
Energy And Momentum ◽  
Central Stars

The stellar winds of the central stars of planetary nebulae play an essential role in planetary nebulae shaping. In the interacting stellar winds model, the fast stellar wind injects energy and momentum which are transfered to the nebular envelope through an X-ray-emitting hot bubble. Together with other physical processes, such as the ionization of the nebular envelope, the asymmetrical mass-loss in the AGB, and the action of collimated outflows and magnetic fields, the presurized hot gas determines the expansion and evolution of planetary nebulae. \emph{Chandra} and \emph{XMM-Newton} have provided us with detailed information of this hot gas. Here in this talk I will review our current understanding of the effects of the fast stellar wind in the shaping and evolution of planetary nebulae and give some hints of the promissing future of this research.

Pathways for penetration of iron and negative stain across the protein shell of ferritin: Ultrastructural perspectives

1992 ◽  
Vol 50 (2) ◽  
pp. 1012-1013
Author(s):  
William H. Massover
Keyword(s):  
Outer Shell ◽  
X Ray Diffraction ◽  
Central Cavity ◽  
X Ray ◽  
Subunit Dissociation ◽  
Negative Stain ◽  
Analogous Question ◽  
Protein Shell

Molecules of the metalloprotein, ferritin, have an outer shell comprised of a polymeric assembly of 24 polypeptide subunits (apoferritin). This protein shell encloses a hydrated space, the central cavity, within which up to several thousand iron atoms can be deposited as the biomineral, ferrihydrite. The actual pathway taken by iron moving across the protein shell is not known; an analogous question exists for the demonstrated entrance of negative stains into the central cavity. Intersubunit interstices at the 4-fold and 3-fold symmetry axes have been defined with x-ray diffraction, and were hypothesized to provide a pathway for penetration through the outer shell; however, since these channels are only 4Å in width, they are much too small to allow simple permeation of either hydrated iron or stain ions. A different hypothesis, based on studies of subunit dissociation from highly diluted ferritin, proposes that transient gaps in the protein shell are created by a rapid reversible subunit release and permit the direct passage of large ions into the central cavity.

High‐Resolution X‐Ray Image of the Hydrogen‐deficient Planetary Nebula Abell 30

1997 ◽  
Vol 482 (2) ◽  
pp. 891-896 ◽  
Author(s):  
You‐Hua Chu ◽  
Thomas H. Chang ◽  
Gail M. Conway
Keyword(s):  
High Resolution ◽  
Planetary Nebula ◽  
X Ray
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