scholarly journals Feedback from γ Cassiopeiae: Large Expanding Cavity, Accelerating Cometary Globules, and Peculiar X-Ray Emission

2021 ◽  
Vol 922 (2) ◽  
pp. 183
Author(s):  
Xuepeng Chen ◽  
Weihua Guo ◽  
Li Sun ◽  
Jiangchen Feng ◽  
Yang Su ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Neutral Hydrogen ◽  
Expansion Velocity ◽  
Wide Field ◽  
X Ray ◽  
Gas Kinematics ◽  
Velocity Gradients ◽  
Stellar Radiation ◽  
Systemic Velocity ◽  
Co Observations

Abstract We present wide-field multiwavelength observations of γ Cassiopeiae (or γ Cas for short) in order to study its feedback toward the interstellar environment. A large expanding cavity is discovered toward γ Cas in the neutral hydrogen (H i) images at a systemic velocity of about −10 km s−1. The measured dimension of the cavity is roughly 2.°0 × 1.°4 (or 6.0 pc × 4.2 pc at a distance of 168 pc), while the expansion velocity is ∼5.0 ± 0.5 km s−1. The CO observations reveal systematic velocity gradients in IC 63 (∼20 km s−1 pc−1) and IC 59 (∼30 km s−1 pc−1), two cometary globules illuminated by γ Cas, proving fast acceleration of the globules under stellar radiation pressure. The gas kinematics indicate that the cavity is opened by strong stellar wind, which has high potential to lead to the peculiar X-ray emission observed in γ Cas. Our result favors a new scenario that emphasizes the roles of stellar wind and binarity in the X-ray emission of the γ Cas stars.

scholarly journals MOVES III. Simultaneous X-ray and ultraviolet observations unveiling the variable environment of the hot Jupiter HD 189733b

2020 ◽  
Vol 493 (1) ◽  
pp. 559-579 ◽  
Author(s):  
V Bourrier ◽  
P J Wheatley ◽  
A Lecavelier des Etangs ◽  
G King ◽  
T Louden ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Hubble Space Telescope ◽  
Spectral Energy Distribution ◽  
Neutral Hydrogen ◽  
High Energy ◽  
Spectral Energy ◽  
Variable Environment ◽  
X Ray ◽  
Far Ultraviolet ◽  
In Transit

ABSTRACT In this third paper of the MOVES (Multiwavelength Observations of an eVaporating Exoplanet and its Star) programme, we combine Hubble Space Telescope far-ultraviolet (FUV) observations with XMM–Newton/Swift X-ray observations to measure the emission of HD 189733 in various FUV lines, and its soft X-ray spectrum. Based on these measurements we characterize the interstellar medium towards HD 189733 and derive semisynthetic XUV spectra of the star, which are used to study the evolution of its high-energy emission at five different epochs. Two flares from HD 189733 are observed, but we propose that the long-term variations in its spectral energy distribution have the most important consequences for the environment of HD 189733b. Reduced coronal and wind activity could favour the formation of a dense population of Si2+ atoms in a bow-shock ahead of the planet, responsible for pre- and in-transit absorption measured in the first two epochs. In-transit absorption signatures are detected in the Lyman α line in the second, third, and fifth epochs, which could arise from the extended planetary thermosphere and a tail of stellar wind protons neutralized via charge-exchange with the planetary exosphere. We propose that increases in the X-ray irradiation of the planet, and decreases in its EUV irradiation causing lower photoionization rates of neutral hydrogen, favour the detection of these signatures by sustaining larger densities of H0 atoms in the upper atmosphere and boosting charge-exchanges with the stellar wind. Deeper and broader absorption signatures in the last epoch suggest that the planet entered a different evaporation regime, providing clues as to the link between stellar activity and the structure of the planetary environment.

scholarly journals First 3D morpho-kinematic model of supernova remnants. The case of VRO 42.05.01 (G166.0+4.3)

2020 ◽  
Vol 499 (4) ◽  
pp. 5410-5415
Author(s):  
S Derlopa ◽  
P Boumis ◽  
A Chiotellis ◽  
W Steffen ◽  
S Akras
Keyword(s):  
Supernova Remnants ◽  
Ambient Medium ◽  
Kinematic Model ◽  
Three Dimensional ◽  
Expansion Velocity ◽  
Wide Field ◽  
Origin And Evolution ◽  
Systemic Velocity ◽  
Kinematical Behaviour ◽  
Interaction History

ABSTRACT We present the first three-dimensional (3D) morpho-kinematic (MK) model of a supernova remnant (SNR), using as a case study the Galactic SNR VRO 42.05.01. We employed the astrophysical code SHAPE in which wide field imaging and high-resolution spectroscopic data were utilized, to reconstruct its 3D morphology and kinematics. We found that the remnant consists of three basic distinctive components that we call: a ‘shell’, a ‘wing’, and a ‘hat’. With respect to their kinematical behaviour, we found that the ‘wing’  and the ‘shell’  have similar expansion velocities (Vexp = 115 ± 5 km s−1). The ‘hat’  presents the lowest expansion velocity of the remnant (Vexp = 90 ± 20 km s−1), while the upper part of the ‘shell’  presents the highest velocity with respect to the rest of the remnant (Vexp = 155 ± 15 km s−1). Furthermore, the whole nebula has an inclination of ∼3°–5° with respect to the plane of the sky and a systemic velocity of Vsys = −17 ± 3 km s−1. We discuss the interpretation of our model results regarding the origin and evolution of the SNR and we suggest that VRO 42.05.01 had an interaction history with an inhomogeneous ambient medium most likely shaped by the mass outflows of its progenitor star.

scholarly journals Modeling the Lyα transit absorption of the hot Jupiter HD 189733b

2020 ◽  
Vol 638 ◽  
pp. A49 ◽  
Author(s):  
P. Odert ◽  
N. V. Erkaev ◽  
K. G. Kislyakova ◽  
H. Lammer ◽  
A. V. Mezentsev ◽  
...  
Keyword(s):  
Stellar Wind ◽  
Extreme Ultraviolet ◽  
Neutral Hydrogen ◽  
Hydrogen Distribution ◽  
Modeling Framework ◽  
X Ray ◽  
Host Stars ◽  
Excess Absorption ◽  
Hot Jupiter

Context. Hydrogen-dominated atmospheres of hot exoplanets expand and escape hydrodynamically due to the intense heating by the X-ray and extreme ultraviolet (XUV) irradiation of their host stars. Excess absorption of neutral hydrogen has been observed in the Lyα line during transits of several close-in gaseous exoplanets, indicating such extended atmospheres. Aims. For the hot Jupiter HD 189733b, this absorption shows temporal variability. We aim to study if variations in stellar XUV emission and/or variable stellar wind conditions may explain this effect. Methods. We applied a 1D hydrodynamic planetary upper atmosphere model and a 3D magnetohydrodynamic stellar wind flow model to study the effect of variations of the stellar XUV irradiation and wind conditions at the planet’s orbit on the neutral hydrogen distribution. This includes the production of energetic neutral atoms (ENAs) and the related Lyα transit signature. Results. We obtain comparable, albeit slightly higher Lyα absorption than that observed in 2011 with a stellar XUV flux of 1.8 × 104 erg cm−2 s−1, rather typical activity conditions for this star. Flares with parameters similar to that observed eight hours before the transit are unlikely to have caused a significant modulation of the transit signature. We find that the resulting Lyα absorption is dominated by atmospheric broadening, whereas the contribution of ENAs is negligible, as they are formed inside the bow shock from decelerated wind ions that are heated to high temperatures. Thus, within our modeling framework and assumptions, we find an insignificant dependence of the absorption on the stellar wind parameters. Conclusions. Since the transit absorption can be modeled with typical stellar XUV and wind conditions, it is possible that the nondetection of the absorption in 2010 was affected by less typical stellar activity conditions, such as a very different magnitude and/or shape of the star’s spectral XUV emission, or temporal and/or spatial variations in Lyα affecting the determination of the transit absorption.

scholarly journals GJ 436b and the stellar wind interaction: simulations constraints using Lyα and Hα transits

2020 ◽  
Author(s):  
Carolina Villarreal D’Angelo ◽  
Aline A Vidotto ◽  
Alejandro Esquivel ◽  
Gopal Hazra ◽  
Allison Youngblood
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Planetary System ◽  
Neutral Hydrogen ◽  
Hydrogen Atmosphere ◽  
Planetary Atmosphere ◽  
Hydrodynamic Simulations ◽  
Stellar Disc ◽  
Planetary Mass ◽  
Best Fit

Abstract The GJ 436 planetary system is an extraordinary system. The Neptune-size planet that orbits the M3 dwarf revealed in the Lyα line an extended neutral hydrogen atmosphere. This material fills a comet-like tail that obscures the stellar disc for more than 10 hours after the planetary transit. Here, we carry out a series of 3D radiation hydrodynamic simulations to model the interaction of the stellar wind with the escaping planetary atmosphere. With these models, we seek to reproduce the $\sim 56\%$ absorption found in Lyα transits, simultaneously with the lack of absorption in Hα transit. Varying the stellar wind strength and the EUV stellar luminosity, we search for a set of parameters that best fit the observational data. Based on Lyα observations, we found a stellar wind velocity at the position of the planet to be around [250-460] km s−1 with a temperature of [3 − 4] × 105 K. The stellar and planetary mass loss rates are found to be 2 × 10−15 M⊙ yr−1 and ∼[6 − 10] × 109 g s−1, respectively, for a stellar EUV luminosity of [0.8 − 1.6] × 1027 erg s−1. For the parameters explored in our simulations, none of our models present any significant absorption in the Hα line in agreement with the observations.

scholarly journals Chemical Abundances of Early Type Stars

1998 ◽  
Vol 188 ◽  
pp. 224-225
Author(s):  
S. Tanaka ◽  
S. Kitamoto ◽  
T. Suzuki ◽  
K. Torii ◽  
M.F. Corcoran ◽  
...  
Keyword(s):  
Surface Layer ◽  
Stellar Wind ◽  
Nuclear Reactions ◽  
X Rays ◽  
Early Type ◽  
Chemical Abundances ◽  
X Ray ◽  
Low Metallicity ◽  
Early Type Stars

X-rays from early-type stars are emitted by the corona or the stellar wind. The materials in the surface layer of early-type stars are not contaminated by nuclear reactions in the stellar inside. Therefore, abundance study of the early-type stars provides us an information of the abundances of the original gas. However, the X-ray observations indicate low-metallicity, which is about 0.3 times of cosmic abundances. This fact raises the problem on the cosmic abundances.

scholarly journals A Multi-Frequency Study of the Milky Way-Like Spiral Galaxy NGC 6744

2018 ◽  
Vol 35 ◽  
Author(s):  
Miranda Yew ◽  
Miroslav D. Filipović ◽  
Quentin Roper ◽  
Jordan D. Collier ◽  
Evan J. Crawford ◽  
...  
Keyword(s):  
Black Hole ◽  
Milky Way ◽  
Formation Rate ◽  
Radio Continuum ◽  
Starburst Galaxy ◽  
Radio Sources ◽  
Wide Field ◽  
Central Black Hole ◽  
X Ray ◽  
Continuum Data

AbstractWe present a multi-frequency study of the intermediate spiral SAB(r)bc type galaxy NGC 6744, using available data from the Chandra X-Ray telescope, radio continuum data from the Australia Telescope Compact Array and Murchison Widefield Array, and Wide-field Infrared Survey Explorer infrared observations. We identify 117 X-ray sources and 280 radio sources. Of these, we find nine sources in common between the X-ray and radio catalogues, one of which is a faint central black hole with a bolometric radio luminosity similar to the Milky Way’s central black hole. We classify 5 objects as supernova remnant (SNR) candidates, 2 objects as likely SNRs, 17 as H ii regions, 1 source as an AGN; the remaining 255 radio sources are categorised as background objects and one X-ray source is classified as a foreground star. We find the star-formation rate (SFR) of NGC 6744 to be in the range 2.8–4.7 M⊙~yr − 1 signifying the galaxy is still actively forming stars. The specific SFR of NGC 6744 is greater than that of late-type spirals such as the Milky Way, but considerably less that that of a typical starburst galaxy.

scholarly journals Testing a double AGN hypothesis for Mrk 273

2018 ◽  
Vol 611 ◽  
pp. A71 ◽  
Author(s):  
K. Iwasawa ◽  
V. U ◽  
J. M. Mazzarella ◽  
A. M. Medling ◽  
D. B. Sanders ◽  
...  
Keyword(s):  
Alternative Explanation ◽  
Source Model ◽  
Spectral Slope ◽  
Line Flux ◽  
Ionized Gas ◽  
X Ray ◽  
Gas Kinematics ◽  
N Source ◽  
Seyfert Nucleus ◽  
Luminous Infrared Galaxy

The ultra-luminous infrared galaxy (ULIRG) Mrk 273 contains two infrared nuclei, N and SW, separated by 1 arcsecond. A Chandra observation has identified the SW nucleus as an absorbed X-ray source with NH ~ 4 × 1023 cm−2 but also hinted at the possible presence of a Compton-thick AGN in the N nucleus, where a black hole of ~109 M⊙ is inferred from the ionized gas kinematics. The intrinsic X-ray spectral slope recently measured by NuSTAR is unusually hard (Γ ~ 1.3) for a Seyfert nucleus, for which we seek an alternative explanation. We hypothesize a strongly absorbed X-ray source in N, of which X-ray emission rises steeply above 10 keV, in addition to the known X-ray source in SW, and test it against the NuSTAR data, assuming the standard spectral slope (Γ = 1.9). This double X-ray source model gives a good explanation of the hard continuum spectrum, deep Fe K absorption edge, and strong Fe K line observed in this ULIRG, without invoking the unusual spectral slope required for a single source interpretation. The putative X-ray source in N is found to be absorbed by NH = 1.4+0.7−0.4 × 1024 cm−2. The estimated 2−10 keV luminosity of the N source is 1.3 × 1043 erg s−1, about a factor of 2 larger than that of SW during the NuSTAR observation. Uncorrelated variability above and below 10 keV between the Suzaku and NuSTAR observations appears to support the double source interpretation. Variability in spectral hardness and Fe K line flux between the previous X-ray observations is also consistent with this picture.

scholarly journals A 2.5-5 μm spectroscopic study of hard X-ray selected AGNs with AKARI

2013 ◽  
Vol 9 (S304) ◽  
pp. 66-67
Author(s):  
A. Castro ◽  
T. Miyaji ◽  
M. Shirahata ◽  
S. Oyabu ◽  
D. Clark ◽  
...  
Keyword(s):  
Star Formation ◽  
Neutral Hydrogen ◽  
Infrared Camera ◽  
X Ray ◽  
Star Formation Activity ◽  
Hydrogen Column Density ◽  
Polycyclic Aromatic ◽  
Low X

AbstractWe explore the relationships between the 3.3 μm polycyclic aromatic hydrocarbon (PAH) feature and active galactic nucleus (AGN) properties of a sample of 54 hard X-ray selected bright AGNs, including both Seyfert 1 and Seyfert 2 type objects, using the InfraRed Camera (IRC) on board the infrared astronomical satellite AKARI. The sample is selected from the 9-month Swift/BAT survey in the 14-195 keV band and all of them have measured X-ray spectra at E ≲ 10 keV. These X-ray spectra provide measurements of the neutral hydrogen column density (NH) towards the AGNs. We use the 3.3 μm PAH luminosity (L3.3μm) as a proxy for star formation activity and hard X-ray luminosity (L14-195keV) as an indicator of the AGN activity. We searched for possible difference of star-formation activity between type 1 (un-absorbed) and type 2 (absorbed) AGNs. Our regression analysis of log L14-195keV versus log L3.3μm shows a positive correlation and the slope seems steeper for type 1/unobscured AGNs than that of type 2/obscured AGNs. The same trend has been found for the log (L14-195keV/MBH) versus log (L3.3μm/MBH) correlation. Our analysis show that the circum-nuclear star-formation is more enhanced in type 2/absorbed AGNs than type 1/un-absorbed AGNs for low X-ray luminosity/low Eddington ratio AGNs.

scholarly journals Models of X‐Ray Photoionization in LMC X‐4: Slices of a Stellar Wind

1999 ◽  
Vol 519 (1) ◽  
pp. 191-205 ◽  
Author(s):  
Bram Boroson ◽  
Timothy Kallman ◽  
Richard McCray ◽  
S. D. Vrtilek ◽  
John Raymond
Keyword(s):  
Stellar Wind ◽  
X Ray

scholarly journals The 3D structure of fibrous material is fully restorable from its X-ray diffraction pattern

IUCrJ ◽  
2021 ◽  
Vol 8 (4) ◽  
Author(s):  
Hiroyuki Iwamoto
Keyword(s):  
Diffraction Pattern ◽  
Fibrous Material ◽  
3D Structure ◽  
Wide Field ◽  
Fibrous Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fiber Diffraction ◽  
Puzzle Solving ◽  
Diffraction Patterns

X-ray fiber diffraction is potentially a powerful technique to study the structure of fibrous materials, such as DNA and synthetic polymers. However, only rotationally averaged diffraction patterns can be recorded and it is difficult to correctly interpret them without the knowledge of esoteric diffraction theories. Here we demonstrate that, in principle, the non-rotationally averaged 3D structure of a fibrous material can be restored from its fiber diffraction pattern. The method is a simple puzzle-solving process and in ideal cases it does not require any prior knowledge about the structure, such as helical symmetry. We believe that the proposed method has a potential to transform the fiber diffraction to a 3D imaging technique, and will be useful for a wide field of life and materials sciences.

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