Deep X-ray view of the Class I YSO Elias 29 with XMM-Newton and NuSTAR

X-ray emission is a characteristic feature of young stellar objects (YSOs) and the result of the interplay between rotation, magnetism, and accretion. For this reason high energy phenomena are key elements to understand the process of star formation, the evolution of their circumstellar disks, and eventually the formation of planets. We investigated the X-ray characteristics of the Class I YSO Elias 29 with joint XMM-Newton and NuSTAR observations of total duration 300 ks and 450 ks, respectively. These are the first observations of a very young (<1 Myr) stellar object in a band encompassing simultaneously both soft and hard X-rays (0.3 − 10 keV in XMM-Newton and ≈3 − 80 keV in NuSTAR). The quiescent spectrum is well described by one thermal component at ∼4.2 keV absorbed by NH ∼ 5.5 × 1022 cm−2. In addition to the hot Fe complex at 6.7 keV, we observed fluorescent emission from Fe at ∼6.4 keV, confirming the previous findings. The line at 6.4 keV is detected during quiescent and flaring states and its flux is variable. The equivalent width is found varying in the range ≈0.15 − 0.5 keV. These values make unrealistic a simple model with a centrally illuminated disk and suggest a role of the cavity containing Elias 29 and possible reverberation processes that could occur in it. We observed two flares that have durations of 20 ks and 50 ks, respectively, and we observed the first flare with both XMM-Newton and NuSTAR. For this flare, we used its peak temperature and timing as diagnostics to infer a loop size of about 1 − 2 R⊙ in length, which is about 20%–30% of the stellar radius. This implies a relatively compact structure. We systematically observed an increase in NH of a factor five during the flares. This behavior has been observed during flares previously detected in Elias 29 with XMM-Newton and ASCA. The phenomenon suggests that the flaring regions could be buried under the accretion streams and at high stellar latitudes because the X-rays from flares pass through gas denser than the gas along the line of sight of the quiescent corona. In a different scenario, a contribution from scattered soft photons to the primary coronal emission could mimic a shallower NH in the quiescent spectrum. In the spectrum of the full NuSTAR exposure, we detect hard X-ray emission in the band ≈20 − 80 keV which is in excess with respect to the thermal emission and that is significant at a level of ≥2σ. We speculate that the hard X-ray emission could be due to a population of energetic electrons accelerated by the magnetic field along the accretion streams. These particles, along with X-ray photons with E > 7.11 keV, could be responsible for pumping up the Fe fluorescence when hitting cold Fe in the circumstellar disk.

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X-Ray Emissions from Solar Flares and from Celestial Sources

Publications of the Astronomical Society of Australia ◽

10.1017/s132335800001002x ◽

1967 ◽

Vol 1 (1) ◽

pp. 4-5 ◽

Cited By ~ 1

Author(s):

T. A. Chubb

Keyword(s):

Solar Flares ◽

Thermal Emission ◽

High Energy ◽

Geiger Counter ◽

X Rays ◽

Large Measure ◽

X Ray ◽

Ion Chamber

One of the interesting questions in solar X-ray astronomy is the question as to whether the hard X-ray emission which occurs during major solar flares is a thermal or nonthermal phenomenon. The evidence for non-thermal emission has been based in large measure on a balloon-borne experiment by Peterson and Winckler, which constituted the first detection of high energy flare X-rays. In the Peterson-Winckler experiment, the incident solar X-rays were measured by both an ion chamber and a Geiger counter photometer, and from the ratio of responses, the hardness character of the incident X-rays was reduced. It was concluded that the observed result could have been explained in terms of the sudden non-thermal production of a group of electrons with energy of the order of 500 kilovolts.

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Observational limits on the X-ray emission from the bubble nebula surrounding Ho IX X-1

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2022 ◽

2019 ◽

Vol 488 (4) ◽

pp. 4614-4622 ◽

Cited By ~ 2

Author(s):

Rajath Sathyaprakash ◽

Timothy P Roberts ◽

Magdalena M Siwek

Keyword(s):

Strong Evidence ◽

Thermal Emission ◽

High Energy ◽

Accretion Disc ◽

Spatial Extent ◽

X Rays ◽

Radio Observations ◽

High Energy Astrophysics ◽

Photometric Analysis ◽

X Ray

ABSTRACT Optical and radio observations of shock-ionized bubble nebulae surrounding ultraluminous X-ray sources (ULXs) suggest that they are powered by jets or supercritical outflows presumably launched from the ULX accretion disc. Recent simulations of these systems have shown that the shocked wind can emit thermal X-rays with estimated luminosities ≲1036 erg s−1. In this work, we investigated whether it is possible to detect and spatially resolve the X-ray emission from these systems using archival Chandra observations of the ULX Holmberg IX X-1 (Ho IX X-1). This source is an ideal target to study for two reasons: it is surrounded by an optical bubble nebula with a large spatial extent (∼400 pc) that can easily be resolved with Chandra. Further, it has a hard X-ray continuum that is easily distinguishable from the expected soft thermal emission from the nebula. However, a spectral and photometric analysis on stacked Chandra observations of the source reveals that there is no strong evidence for an X-ray bubble associated with it, to a limiting luminosity of ∼2 × 1036 erg s−1. The detection of such X-ray nebulae may be possible with future X-ray missions such as Advanced Telescope for High ENergy Astrophysics(ATHENA), which would provide useful constraints on the kinematics of the outflow. Finally, our observations also emphasize that the nebular emission does not contribute significantly to the residuals in the X-ray spectrum of the source, which are more likely to be linked to processes localized to the ULX.

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High-Energy Continuum Variability in Active Galactic Nuclei

Symposium - International Astronomical Union ◽

10.1017/s0074180900174893 ◽

1994 ◽

Vol 159 ◽

pp. 113-122

Author(s):

Rick Edelson

Keyword(s):

Accretion Disk ◽

Thermal Emission ◽

High Energy ◽

Thermal Source ◽

X Rays ◽

Optical Monitoring ◽

Bl Lac Objects ◽

X Ray ◽

Bl Lac ◽

Bl Lacs

CGRO and IUE observations suggest that the strong, aperiodic variability seen in the Exosat long-look observations of AGN extends over a much wider energy band. Some BL Lac objects (but no Seyfert 1 galaxies) have shown X-ray variations which were so rapid that they violate the assumptions of isotropy inherent in the Eddington limit. In the ultraviolet, Seyfert 1s as a class show an anti-correlation between the variability amplitude and luminosity, while BL Lacs show a positive correlation. Furthermore, Seyfert 1s show strong flux-correlated spectral variability, while BL Lacs show little or none. All of this suggests that the high-energy continua of BL Lacs are beamed towards us, while the ultraviolet continua of Seyfert 1s are emitted isotropically.The November 1991 multi-waveband monitoring of the BL Lac PKS 2155−304 showed strong correlated variability, with the soft X-rays leading the ultraviolet by a few hours, and no measurable lag between the ultraviolet and optical down to a limit of ≲ 1.5 hr. This indicates that the X-rays from this BL Lac are not produced by Compton upscattering, and that the ultraviolet does not come directly from a thermal source such as an accretion disk. This also strongly constrains the relativistic jet model, suggesting that all of the radiation is produced in a flattened region like a shock front.Low temporal resolution ultraviolet/optical monitoring of the Seyfert 1 NGC 5548 in 1989 yielded a strong correlation with no measurable lag to a limit of ≲4 days, casting some doubt on the standard model of thermal emission from an accretion disk in Seyfert 1s. Upcoming X-ray/ultraviolet/optical monitoring of the Seyfert 1 NGC 4151 in December 1993 will have much faster sampling, to permit a strong test of both this model and the competing reprocessing model.

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The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117777 ◽

1985 ◽

Vol 43 ◽

pp. 154-157

Author(s):

A.J. Tousimis

Keyword(s):

Ion Beam ◽

Depth Resolution ◽

Sample Surface ◽

High Energy ◽

X Rays ◽

X Ray ◽

Electrons And Ions ◽

Spatial Depth ◽

Minimum Surface Area ◽

Physical Principles

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

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A multi-length-scale USAXS/SAXS facility: 10–50 keV small-angle X-ray scattering instrument

Journal of Applied Crystallography ◽

10.1107/s0021889813021900 ◽

2013 ◽

Vol 46 (5) ◽

pp. 1508-1512 ◽

Cited By ~ 11

Author(s):

Byron Freelon ◽

Kamlesh Suthar ◽

Jan Ilavsky

Keyword(s):

Small Angle ◽

Soft Matter ◽

High Energy ◽

X Rays ◽

X Ray ◽

X Ray Scattering ◽

Wide Range ◽

And Performance ◽

New Facility ◽

Ray Scattering

Coupling small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS) provides a powerful system of techniques for determining the structural organization of nanostructured materials that exhibit a wide range of characteristic length scales. A new facility that combines high-energy (HE) SAXS and USAXS has been developed at the Advanced Photon Source (APS). The application of X-rays across a range of energies, from 10 to 50 keV, offers opportunities to probe structural behavior at the nano- and microscale. An X-ray setup that can characterize both soft matter or hard matter and high-Zsamples in the solid or solution forms is described. Recent upgrades to the Sector 15ID beamline allow an extension of the X-ray energy range and improved beam intensity. The function and performance of the dedicated USAXS/HE-SAXS ChemMatCARS-APS facility is described.

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1/4 Ke V Diffuse Background and the Local Interstellar Medium

International Astronomical Union Colloquium ◽

10.1017/s0252921100024362 ◽

1989 ◽

Vol 120 ◽

pp. 536-536

Author(s):

S.L. Snowden

Keyword(s):

Interstellar Medium ◽

Filling Factor ◽

Thermal Emission ◽

Mean Free Path ◽

Physical Parameters ◽

X Rays ◽

Local Interstellar Medium ◽

X Ray ◽

Diffuse Background ◽

X Ray Background

The 1/4 keV diffuse X-ray background (SXRB) is discussed in relation to the local interstellar medium (LISM). The most likely source for these soft X-rays is thermal emission from a hot diffuse plasma. The existence of a non-zero flux from all directions and the short ISM mean free path of these X-rays (1020HI cm-2), coupled with ISM pressure constraints, imply that the plasma has a local component and that it must, at least locally (nearest hundred parsecs), have a large filling factor. Our understanding of the geometry and physical parameters of the LISM is therefore directly tied to our understanding of the SXRB.

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A high-energy triple-axis X-ray diffractometer for the study of the structure of bulk crystals

Journal of Applied Crystallography ◽

10.1107/s0021889804023805 ◽

2004 ◽

Vol 37 (6) ◽

pp. 901-910 ◽

Cited By ~ 6

Author(s):

C. Seitz ◽

M. Weisser ◽

M. Gomm ◽

R. Hock ◽

A. Magerl

Keyword(s):

High Energy ◽

X Rays ◽

Bulk Crystals ◽

X Ray Diffraction ◽

X Ray ◽

Peak Intensity ◽

High Penetration ◽

Massive Sample ◽

Laue Geometry ◽

The Ideal

A triple-axis diffractometer for high-energy X-ray diffraction is described. A 450 kV/4.5 kW stationary tungsten X-ray tube serves as the X-ray source. Normally, 220 reflections of thermally annealed Czochralski Si are employed for the monochromator and analyser. Their integrated reflectivity is about ten times higher than the ideal crystal value. With the same material as the sample, and working with the WKα line at 60 keV in symmetric Laue geometry for all axes, the full width at half-maximum (FWHM) values for the longitudinal and transversal resolution are 2.5 × 10−3and 1.1 × 10−4for ΔQ/Q, respectively, and the peak intensity for a non-dispersive setting is 3000 counts s−1. In particular, for a double-axis mode, an energy well above 100 keV from theBremsstrahlungspectrum can be used readily. High-energy X-rays are distinguished by a high penetration power and materials of several centimetre thickness can be analysed. The feasibility of performing experiments with massive sample environments is demonstrated.

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Testing the disk-corona interplay in radiatively-efficient broad-line AGN

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935874 ◽

2019 ◽

Vol 628 ◽

pp. A135 ◽

Cited By ~ 6

Author(s):

R. Arcodia ◽

A. Merloni ◽

K. Nandra ◽

G. Ponti

Keyword(s):

Accretion Disk ◽

Reference Sample ◽

Selection Effect ◽

Galactic Nuclei ◽

Theoretical Explanation ◽

X Rays ◽

Broad Line ◽

Coronal Emission ◽

X Ray ◽

Intrinsic Scatter

The correlation observed between monochromatic X-ray and UV luminosities in radiatively-efficient active galactic nuclei (AGN) lacks a clear theoretical explanation despite being used for many applications. Such a correlation, with its small intrinsic scatter and its slope that is smaller than unity in log space, represents the compelling evidence that a mechanism regulating the energetic interaction between the accretion disk and the X-ray corona must be in place. This ensures that going from fainter to brighter sources the coronal emission increases less than the disk emission. We discuss here a self-consistently coupled disk-corona model that can identify this regulating mechanism in terms of modified viscosity prescriptions in the accretion disk. The model predicts a lower fraction of accretion power dissipated in the corona for higher accretion states. We then present a quantitative observational test of the model using a reference sample of broad-line AGN and modeling the disk-corona emission for each source in the LX − LUV plane. We used the slope, normalization, and scatter of the observed relation to constrain the parameters of the theoretical model. For non-spinning black holes and static coronae, we find that the accretion prescriptions that match the observed slope of the LX − LUV relation produce X-rays that are too weak with respect to the normalization of the observed relation. Instead, considering moderately-outflowing Comptonizing coronae and/or a more realistic high-spinning black hole population significantly relax the tension between the strength of the observed and modeled X-ray emission, while also predicting very low intrinsic scatter in the LX − LUV relation. In particular, this latter scenario traces a known selection effect of flux-limited samples that preferentially select high-spinning, hence brighter, sources.

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X-ray spectra and light curves of cooling novae and a nova like

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3012 ◽

2020 ◽

Vol 499 (2) ◽

pp. 3006-3018

Author(s):

Bangzheng Sun ◽

Marina Orio ◽

Andrej Dobrotka ◽

Gerardo Juan Manuel Luna ◽

Sergey Shugarov ◽

...

Keyword(s):

Light Curve ◽

Accretion Rate ◽

High Energy ◽

Gravitational Energy ◽

Light Curves ◽

Clear Correlation ◽

X Rays ◽

High State ◽

X Ray ◽

Low X

ABSTRACT We present X-ray observations of novae V2491 Cyg and KT Eri about 9 yr post-outburst of the dwarf nova and post-nova candidate EY Cyg, and of a VY Scl variable. The first three objects were observed with XMM–Newton, KT Eri also with the Chandra ACIS-S camera, V794 Aql with the Chandra ACIS-S camera and High Energy Transmission Gratings. The two recent novae, similar in outburst amplitude and light curve, appear very different at quiescence. Assuming half of the gravitational energy is irradiated in X-rays, V2491 Cyg is accreting at $\dot{m}=1.4\times 10^{-9}{\!-\!}10^{-8}\,{\rm M}_\odot \,{\rm yr}^{-1}$, while for KT Eri, $\dot{m}\lt 2\times 10^{-10}{\rm M}_\odot \,{\rm yr}$. V2491 Cyg shows signatures of a magnetized WD, specifically of an intermediate polar. A periodicity of 39 min, detected in outburst, was still measured and is likely due to WD rotation. EY Cyg is accreting at $\dot{m}\sim 1.8\times 10^{-11}{\rm M}_\odot \,{\rm yr}^{-1}$, one magnitude lower than KT Eri, consistently with its U Gem outburst behaviour and its quiescent UV flux. The X-rays are modulated with the orbital period, despite the system’s low inclination, probably due to the X-ray flux of the secondary. A period of 81 min is also detected, suggesting that it may also be an intermediate polar. V794 Aql had low X-ray luminosity during an optically high state, about the same level as in a recent optically low state. Thus, we find no clear correlation between optical and X-ray luminosity: the accretion rate seems unstable and variable. The very hard X-ray spectrum indicates a massive WD.

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