scholarly journals Conditions in the WR 140 wind-collision region revealed by the 1.083-μm He i line profile.

2021 ◽  
Author(s):  
Peredur M Williams ◽  
Watson P Varricatt ◽  
André-Nicolas Chené ◽  
Michael F Corcoran ◽  
Ted R Gull ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Time Scales ◽  
Line Profile ◽  
Absorption Component ◽  
Absorption And Emission ◽  
X Ray ◽  
Collision Region ◽  
Peak Flux ◽  
Orbital Phase ◽  
Phase Range

Abstract We present spectroscopy of the P Cygni profile of the 1.083-μm He i line in the WC7 + O5 colliding-wind binary (CWB) WR 140 (HD 193793), observed in 2008, before its periastron passage in 2009, and in 2016–17, spanning the subsequent periastron passage. Both absorption and emission components showed strong variations. The variation of the absorption component as the O5 star was occulted by the wind-collision region (WCR) sets a tight constraint on its geometry. While the sightline to the O5 star traversed the WCR, the strength and breadth of the absorption component varied significantly on time-scales of days. An emission sub-peak was observed on all our profiles. The variation of its radial velocity with orbital phase was shown to be consistent with formation in the WCR as it swung round the stars in their orbit. Modelling the profile gave a measure of the extent of the sub-peak forming region. In the phase range 0.93–0.99, the flux in the sub-peak increased steadily, approximately inversely proportionally to the stellar separation, indicating that the shocked gas in the WCR where the line was formed was adiabatic. After periastron, the sub-peak flux was anomalously strong and varied rapidly, suggesting formation in clumps down-stream in the WCR. For most of the time, its flux exceeded the 2–10-keV X-ray emission, showing it to be a significant coolant of the shocked wind.

scholarly journals Surprises in the simultaneous X-ray and optical monitoring of π Aquarii

2019 ◽  
Vol 632 ◽  
pp. A23 ◽  
Author(s):  
Yaël Nazé ◽  
Gregor Rauw ◽  
Myron Smith
Keyword(s):  
Radial Velocity ◽  
Line Strength ◽  
Optical Data ◽  
Optical Monitoring ◽  
Absorption Component ◽  
X Ray ◽  
Orbital Cycles ◽  
Orbital Phase ◽  
Velocity Variations

To help constrain the origin of the peculiar X-ray emission of γ Cas stars, we conducted a simultaneous optical and X-ray monitoring of π Aqr in 2018. At that time, the star appeared optically bright and active, with a very strong Hα emission. Our monitoring covers three 84 d orbital cycles, allowing us to probe phase-locked variations as well as longer-term changes. In the new optical data, the radial velocity variations seem to span a smaller range than previously reported, which might indicate possible biases. The X-ray emission is variable, but without any obvious correlation with orbital phase or Hα line strength. Furthermore, the average X-ray flux and the relative range of flux variations are similar to those recorded in previous data, although the latter data were taken when the star was less bright and its disk had nearly entirely disappeared. Only the local absorption component in the X-ray spectrum appears to have strengthened in the new data. This absence of large changes in X-ray properties despite dramatic disk changes appears at odds with previous observations of other γ Cas stars. It also constrains scenarios proposed to explain the γ Cas phenomenon.

Orbital resolved spectroscopy of GX 301–2: wind diagnostics

2018 ◽  
Vol 14 (S346) ◽  
pp. 59-61
Author(s):  
Nazma Islam
Keyword(s):  
Equivalent Width ◽  
Column Density ◽  
High Mass ◽  
Absorption Column ◽  
Iron Line ◽  
X Ray ◽  
Orbital Phase ◽  
Stable Periodic ◽  
Phase Range ◽  
Using Data

AbstractGX 301–2, a bright high-mass X-ray binary with an orbital period of 41.5 days, exhibits stable periodic orbital intensity modulations with a strong pre-periastron X-ray flare. Several models have been proposed to explain the accretion at different orbital phases. In Islam & Paul (2014), we presented results from an orbital resolved spectroscopic study of GX 301–2 using data from MAXI Gas Slit Camera. We have found a strong orbital dependence of the absorption column density and equivalent width of the iron emission line. A very large equivalent width of the iron line along with a small value of the column density in the orbital phase range 0.1–0.3 after the periastron passage indicates the presence of high density accretion stream. We aim to further investigate the characteristics of the accretion stream with an AstroSat observation of the system.

Microstructure of post-deformed ECAP-Ti investigated by Multiple X-Ray Line Profile Analysis

2006 ◽  
Vol 2006 (suppl_23_2006) ◽  
pp. 129-134 ◽  
Author(s):  
E. Schafler ◽  
K. Nyilas ◽  
S. Bernstorff ◽  
L. Zeipper ◽  
M. Zehetbauer ◽  
...  
Keyword(s):  
Line Profile ◽  
Profile Analysis ◽  
Line Profile Analysis ◽  
X Ray

scholarly journals The study of multipeaked type-I X-ray bursts in the neutron star low-mass X-ray binary 4U 1636 − 536 with RXTE

2020 ◽  
Vol 501 (1) ◽  
pp. 168-178
Author(s):  
Chen Li ◽  
Guobao Zhang ◽  
Mariano Méndez ◽  
Jiancheng Wang ◽  
Ming Lyu
Keyword(s):  
Neutron Star ◽  
Flux Ratio ◽  
Light Curves ◽  
Type I ◽  
X Ray ◽  
Soft State ◽  
Peak Flux ◽  
Low Mass ◽  
Two Peaks ◽  
Second Peak

ABSTRACT We have found and analysed 16 multipeaked type-I bursts from the neutron-star low-mass X-ray binary 4U 1636 − 53 with the Rossi X-ray Timing Explorer (RXTE). One of the bursts is a rare quadruple-peaked burst that was not previously reported. All 16 bursts show a multipeaked structure not only in the X-ray light curves but also in the bolometric light curves. Most of the multipeaked bursts appear in observations during the transition from the hard to the soft state in the colour–colour diagram. We find an anticorrelation between the second peak flux and the separation time between two peaks. We also find that in the double-peaked bursts the peak-flux ratio and the temperature of the thermal component in the pre-burst spectra are correlated. This indicates that the double-peaked structure in the light curve of the bursts may be affected by enhanced accretion rate in the disc, or increased temperature of the neutron star.

scholarly journals Stellar noise and planet detection. I. Oscillations, granulation and sun-like spots

2010 ◽  
Vol 6 (S276) ◽  
pp. 527-529
Author(s):  
Xavier Dumusque ◽  
Nuno C. Santos ◽  
Stéphane Udry ◽  
Cristophe Lovis ◽  
Xavier Bonfils
Keyword(s):  
Radial Velocity ◽  
Time Scales ◽  
High Precision ◽  
Habitable Zone ◽  
Planet Detection ◽  
Solar Type ◽  
Physical Phenomena ◽  
Instrumental Precision ◽  
Observational Strategy ◽  
Different Time Scales

AbstractSpectrographs like HARPS can now reach a sub-ms−1 precision in radial-velocity (RV) (Pepe & Lovis 2008). At this level of accuracy, we start to be confronted with stellar noise produced by 3 different physical phenomena: oscillations, granulation phenomena (granulation, meso- and super-granulation) and activity. On solar type stars, these 3 types of perturbation can induce ms−1 RV variation, but on different time scales: 3 to 15 minutes for oscillations, 15 minutes to 1.5 days for granulation phenomena and 10 to 50 days for activity. The high precision observational strategy used on HARPS, 1 measure per night of 15 minutes, on 10 consecutive days each month, is optimized, due to a long exposure time, to average out the noise coming from oscillations (Dumusque et al. 2011a) but not to reduce the noise coming from granulation and activity (Dumusque et al. 2011a and Dumusque et al. 2011b). The smallest planets found with this strategy (Mayor et al. 2009) seems to be at the limit of the actual observational strategy and not at the limit of the instrumental precision. To be able to find Earth mass planets in the habitable zone of solar-type stars (200 days for a K0 dwarf), new observational strategies, averaging out simultaneously all type of stellar noise, are required.

scholarly journals From Femtoseconds to Hours–Measuring Dynamics over 18 Orders of Magnitude with Coherent X-rays

2021 ◽  
Vol 11 (13) ◽  
pp. 6179
Author(s):  
Felix Lehmkühler ◽  
Wojciech Roseker ◽  
Gerhard Grübel
Keyword(s):  
Time Scales ◽  
Free Electron Laser ◽  
Photon Correlation Spectroscopy ◽  
Signal To Noise Ratio ◽  
Coherent Scattering ◽  
Correlation Spectroscopy ◽  
X Rays ◽  
Photon Correlation ◽  
X Ray ◽  
Scattering Technique

X-ray photon correlation spectroscopy (XPCS) enables the study of sample dynamics between micrometer and atomic length scales. As a coherent scattering technique, it benefits from the increased brilliance of the next-generation synchrotron radiation and Free-Electron Laser (FEL) sources. In this article, we will introduce the XPCS concepts and review the latest developments of XPCS with special attention on the extension of accessible time scales to sub-μs and the application of XPCS at FELs. Furthermore, we will discuss future opportunities of XPCS and the related technique X-ray speckle visibility spectroscopy (XSVS) at new X-ray sources. Due to its particular signal-to-noise ratio, the time scales accessible by XPCS scale with the square of the coherent flux, allowing to dramatically extend its applications. This will soon enable studies over more than 18 orders of magnitude in time by XPCS and XSVS.

scholarly journals Transient absorption spectroscopy using high harmonic generation: a review of ultrafast X-ray dynamics in molecules and solids

2019 ◽  
Vol 377 (2145) ◽  
pp. 20170463 ◽  
Author(s):  
Romain Geneaux ◽  
Hugo J. B. Marroux ◽  
Alexander Guggenmos ◽  
Daniel M. Neumark ◽  
Stephen R. Leone
Keyword(s):  
Time Scales ◽  
Harmonic Generation ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
High Harmonic ◽  
High Harmonic Generation ◽  
Transient Absorption Spectroscopy ◽  
Spectroscopic Techniques ◽  
X Rays ◽  
X Ray

Attosecond science opened the door to observing nuclear and electronic dynamics in real time and has begun to expand beyond its traditional grounds. Among several spectroscopic techniques, X-ray transient absorption spectroscopy has become key in understanding matter on ultrafast time scales. In this review, we illustrate the capabilities of this unique tool through a number of iconic experiments. We outline how coherent broadband X-ray radiation, emitted in high-harmonic generation, can be used to follow dynamics in increasingly complex systems. Experiments performed in both molecules and solids are discussed at length, on time scales ranging from attoseconds to picoseconds, and in perturbative or strong-field excitation regimes. This article is part of the theme issue ‘Measurement of ultrafast electronic and structural dynamics with X-rays’.

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