Fluorescent Line Emission Research Articles

The exosphere of Mars can be tracked by a high-spectral resolution telescope, such as the Line Emission Mapper

Abstract Mars provides our local analogue for unmagnetized terrestrial planets and is thus key to understanding the habitability of exoplanets. The lack of a global magnetic field means that the atmosphere interacts directly with the solar wind, causing significant loss of the atmosphere. While in situ measurements provide a wealth of detailed local information, they are limited in deriving the global picture. In contrast, remote X-ray observations can provide important global instantaneous coverage over multiple seasons and sampling different solar wind. Previous XMM-Newton observations have detected significant flux via the solar wind charge exchange emission (SWCX) mechanism from an extended planetary halo, and from atmospheric fluorescence. In contrast, Chandra observations only detected a low-luminosity disk and a faint halo. It is postulated that these observational differences are due to transient solar wind with increased heavy ion fractions. Here, we present simulated spectra for the proposed NASA mission Line Emission Mapper, of both halo and disk regions, under quiet and transient solar wind. We show that even under moderate solar wind conditions, both SWCX and fluorescence emission lines are readily detected above the background, providing new insights into the loss of planetary atmospheres and the molecular composition of less well-characterised atmospheric abundances.

The chemical composition of CO-rich comet C/2023 H2 (Lemmon)

We report on the composition of comet C/2023 H2 (Lemmon) (hereafter C/2023 H2) as measured with CRIRES$^+$ at VLT/ESO, under the Director Discretionary Time program: 2112.C-5015. We observed C/2023 H2 between November 24 and 27, 2023, after perihelion and during its close approach to Earth. We used three settings sampling the spectral region from approx 2.5 to 5 mu m, to search for fluorescence emission lines of H$_2$O, HCN, C$_2$H$_2$, NH$_3$, C$_2$H$_6$, H$_2$CO, CH$_3$OH, CH$_4$, and CO. C/2023 H2 spectra are dominated by signatures from hyper-volatile species, namely CO, C$_2$H$_6$, and CH$_4$, while it is particularly difficult to identify lines from less volatile species such as water or methanol. When compared to other comets, C/2023 H2 has an overall typical-to-enriched composition, with CO showing one of the highest infrared values reported so far in Solar System comets within 2 au from the Sun. In this respect, C/2023 H2 shares many similarities with C/2013 R1 (Lovejoy), C/2009 P1 (Garrad), and C/1999 T1 (McNaught-Hartley), although still being rather unique. Results from the analysis of optical spectra (approx 300 to 650 nm) obtained on November 16, 2023, using the Intermediate Dispersion Spectrograph at the Isaac Newton Telescopes are consistent with the infrared ones. Assuming that the composition of C/2023 H2 is original, this comet most likely formed in a region of the disc where CO was particularly enriched, or it could have been captured from other planetary systems forming in the Sun's birth cluster. Similarities with a few other comets suggest the existence of a sub-class of CO-enriched comets, which may be currently under-sampled. Alternatively, water sublimation may have been ineffective due to the presence of a thick dust mantle covering the nucleus surface.

Giant Quantum Electrodynamic Effects on Single SiV Color Centers in Nanosized Diamonds.

Understanding and mastering quantum electrodynamics phenomena is essential to the development of quantum nanophotonics applications. While tailoring of the local vacuum field has been widely used to tune the luminescence rate and directionality of a quantum emitter, its impact on their transition energies is barely investigated and exploited. Fluorescent defects in nanosized diamonds constitute an attractive nanophotonic platform to investigate the Lamb shift of an emitter embedded in a dielectric nanostructure with high refractive index. Using spectral and time-resolved optical spectroscopy of single SiV defects, we unveil blue shifts (up to 80 meV) of their emission lines, which are interpreted from model calculations as giant Lamb shifts. Moreover, evidence for a positive correlation between their fluorescence decay rates and emission line widths is observed, as a signature of modifications not only of the photonic local density of states but also of the phononic one, as the nanodiamond size is decreased. Correlative light-electron microscopy of single SiVs and their host nanodiamonds further supports these findings. These results make nanodiamond-SiVs promising as optically driven spin qubits and quantum light sources tunable through nanoscale tailoring of vacuum-field fluctuations.

Fluorescent Fe K line emission of γ Cas stars

Context. γ Cas stars are early-type Be stars that exhibit an unusually hard and bright thermal X-ray emission. One of the proposed scenarios to explain these properties postulates the existence of a neutron star companion in the propeller stage, during which the magnetosphere of a rapidly rotating neutron star repels infalling material. Aims. To test this model, we examined the fluorescent Fe Kα emission line at ~6.4keV in the X-ray spectra of γ Cas stars, which offers a powerful diagnostic of both the primary source of hard X-rays and the reprocessing material. Methods. We computed synthetic line profiles of the fluorescent Fe Kα emission line in the framework of the propelling neutron star scenario. Two reservoirs of material contribute to the fluorescence in this case: the Be circumstellar decretion disk and a shell of cool material that surrounds the shell of X-ray-emitting plasma around the putative propelling neutron star. Results. We analysed the synthetic line profiles and expected equivalent widths of the lines for three well-studied γ Cas stars. The predicted line strengths fall short of the observed values by at least an order of magnitude. Pushing the model parameters to reproduce the observed line strengths led to column densities towards the primary X-ray source that exceed the observationally determined values by typically a factor of 20, and would further imply a higher X-ray luminosity than observed. Conclusions. The strengths of the observed Fe Kα fluorescent emission lines in γ Cas stars are inconsistent with the expected properties of a propeller scenario as proposed in the literature.

Incorporation of realistic intrinsic profiles for the Fe Kα and Fe Kβ emission lines in X-ray reprocessor models

ABSTRACT The Fe Kα fluorescent emission line from neutral matter is widely used as a diagnostic tool in X-ray spectroscopy for many astrophysical X-ray sources. The line properties can potentially be used to constrain the geometry, column density, and kinematics of the material in which the line is formed. The intrinsic width and the shape of the intrinsic line profile has been neglected thus far, because it is much smaller than the instrumental broadening in all space-based X-ray detectors before Hitomi. However, the instrumental broadening of X-ray microcalorimeters is comparable to the intrinsic line width. We have performed new calculations based on Monte Carlo simulations of the MYTORUS X-ray reprocessor spectral-fitting model that utilize parametrizations of historical high-precision laboratory measurements of the intrinsic profiles of the Fe Kα and Fe Kβ lines. A publicly available table is provided that can seamlessly replace the existing Fe Kα and Fe Kβ line spectrum in the MYTORUS model. The new table can also be used in a standalone mode (without the MYTORUS model) in order to derive empirical velocity widths, if the line-emitting matter is Compton thin. Neglecting to account for the intrinsic profiles of the Fe Kα and Fe Kβ lines can result in a significant overestimate of the velocity broadening, if the true velocity broadening is less than ${\sim} 2000 \ \rm km \ s^{-1}$. Residual artefacts may also appear in observed line profiles in data with a high signal-to-noise ratio.

One dimensional temperature measurements by resonantly ionized photoemission thermometry of molecular nitrogen

This paper presents an extensive parameter study of a non-intrusive and non-seeded laser diagnostic method for measuring one dimensional (1D) rotational temperature of molecular nitrogen (N2) at 165 - 450 K. Compared to previous efforts using molecular oxygen, here resonantly ionized and photoelectron induced fluorescence of molecular nitrogen for thermometry (N2 RIPT) was demonstrated. The RIPT signal is generated by directly probing various rotational levels within the rovibrational absorption band of N2, corresponding to the 3-photon transition of N2 (X1Σ g +,v=0→b1Π u ,v′=6) near 285 nm, without involving collisional effects of molecular oxygen and nitrogen. The photoionized N2 produces strong first negative band of N2+ (B2Σ u +−X2Σ g +) near 390 nm, 420 nm, and 425 nm. Boltzmann analyses of various discrete fluorescence emission lines yield rotational temperatures of molecular nitrogen. By empirically choosing multiple rotational levels within the absorption band, non-scanning thermometry can be accurately achieved for molecular nitrogen. It is demonstrated that the N2 RIPT technique can measure 1D temperature profile up to ∼5 cm in length within a pure N2 environment. Multiple wavelengths are thoroughly analyzed and listed that are accurate for RIPT for various temperature ranges.

Moving Corona and the Line Profile of the Relativistic Broad Iron Emission Line

Iron fluorescence emission lines from X-ray binaries and active galactic nuclei are important diagnostic tools for studying the physical processes near the event horizon of both the stellar-mass black holes in X-ray binaries and the supermassive black holes in active galactic nuclei. In this work, we investigate the line profile of the relativistic broad iron lines from the cool accretion disk of a black hole due to the asymmetric illumination of a moving corona, which moves away from the disk with a relativistic velocity. Both the off-axis location and the radial velocity of the moving corona are considered. Our results clearly show that the illumination and the line profile are dependent on the position and velocity of the corona, since the disk region below the corona receives more flux, which is the most important factor affecting the line profiles. As expected, if the corona is close to the receding part of the rotating disk, the red peak is enhanced, while the blue peak is weakened in the broad line profile, and the central energy of the emission line is low. Conversely, if the corona is close to the approaching part of the disk, the blue peak is strong and the central energy of the emission line is high, even higher than the intrinsic energy of the emission line. Due to the beaming effect of the moving corona, the corona with high velocity illuminates the outer region of the disk, which leads to the red peak disappearing and there being only one blue peak in the profile of the emission line.

Calcium element quantification model using a portable X-ray fluorescence unit

A methodology is proposed to achieve an effective quantification of the element Calcium in soil samples, using a portable X-ray Fluorescence (pXRF) equipment. The protocol began by preparing two ideal matrices using an increasing mass, measured on an analytical balance, of Calcium and Sodium Nitrate as binder. It is the Gravimetric technique. In both samples the fluorescent emission line of the element Calcium was calibrated using an standard reference material 1400 boneash.The validation of ideal samples of the element Calcium using the XRF technique with respect to AAS as an experimental standard, using linear correlation methods, to estimate from statistical inference the real concentration of the analyte, allowed us to appreciate that both approaches remain above the standard curve provided by AAS, with a value of 1.8 and 1.68, respectively. Which means that the tendency to evaluate Calcium samples by XRF are overestimated with respect to the curve provided by AAS. Since the last correlation coefficient is very close to 1.0 and its statistical inference equation is precisely known, the authors of this work propose to apply quantification protocol to real sediment samples.•A methodology is proposed to achieve an effective quantification of the element Calcium in soil samples, using a portable X-ray Fluorescence (pXRF) equipment•The validation of ideal samples of the element Calcium using the XRF technique with respect to AAS as an experimental standard, using linear correlation methods•This work pretend to resolve another weakness by the portable system and is that the number of accounts provided by conventional XRF are not consistent with a% w/w of analyte.

Observing the onset of the accretion wake in Vela X-1

High-mass X-ray binaries (HMXBs) offer a unique opportunity to investigate accretion onto compact objects and the wind structure in massive stars. A key source for such studies is the bright neutron star HMXB Vela X-1 whose convenient physical and orbital parameters facilitate analyses and in particular enable studies of the wind structure in HMXBs. Here, we analyse simultaneous XMM-Newton and NuSTAR observations at ϕorb ≈ 0.36–0.52 and perform time-resolved spectral analysis down to the pulse period of the neutron star based on our previous NuSTAR-only results. For the first time, we are able to trace the onset of the wakes in a broad 0.5–78 keV range with a high-time resolution of ~283 s and compare our results with theoretical predictions. We observe a clear rise in the absorption column density of the stellar wind NH,1 starting at orbital phase ~0.44, corresponding to the wake structure entering our line of sight towards the neutron star, together with local extrema throughout the observation, which are possibly associated with clumps or other structures in the wind. Periods of high absorption reveal the presence of multiple fluorescent emission lines of highly ionised species, mainly in the soft-X-ray band between 0.5 and 4 keV, indicating photoionisation of the wind.

Peering into the central region of a nano-quasar: XMM–Newton and Chandra views of the CH Cyg symbiotic system

ABSTRACT We present the analysis of archival XMM–Newton and Chandra observations of CH Cyg, one of the most studied symbiotic stars (SySts). The combination of the high-resolution XMM–Newton RGS and Chandra HETG X-ray spectra allowed us to obtain reliable estimates of the chemical abundances and to corroborate the presence of multitemperature X-ray-emitting gas. Spectral fitting of the medium-resolution XMM–Newton MOS (MOS1+MOS2) spectrum required the use of an additional component not seen in previous studies in order to fit the 2.0–4.0 keV energy range. Detailed spectral modelling of the XMM–Newton MOS data suggests the presence of a reflection component, very similar to that found in active galactic nuclei. The reflection component is very likely produced by an ionized disc (the accretion disc around the white dwarf) and naturally explains the presence of the fluorescent Fe emission line at 6.4 keV while also contributing to the soft and medium energy ranges. The variability of the global X-ray properties of CH Cyg are discussed as well as the variation of the three Fe lines around the 6–7 keV energy range. We conclude that reflection components are needed to model the hard X-ray emission and may be present in most β/δ-type SySt.

Extended Hard X-Ray Emission in Highly Obscured AGNs

Kiloparsec-scale hard (>3 keV) X-ray continuum and fluorescent Fe Kα line emission has been recently discovered in nearby Compton-thick (CT) active galactic nuclei (AGNs), which opens new opportunities to improve AGN torus modeling and investigate how the central supermassive black hole interacts with and impacts the host galaxy. Following a pilot Chandra survey of nearby CT AGNs, we present in this paper the results of Chandra spatial analysis of five uniformly selected non-CT but still heavily obscured AGNs to investigate the extended hard X-ray emission by measuring the excess emission counts, excess fractions, and physical scales. Three of these AGNs show extended emission in the 3.0–7.0 keV band detected at >3σ above the Chandra point-spread function with total excess fractions ranging from ∼8% to 20%. The extent of the hard emission ranges from at least ∼250 pc to 1.1 kpc in radius. We compare these new sources with CT AGNs and find that CT AGNs appear to be more extended in the hard band than the non-CT AGNs. Similar to CT AGNs, the amounts of extended hard X-ray emission relative to the total emission of these obscured AGNs are not negligible. Together with other AGNs detected with extended hard X-ray emission in the literature, we further explore potential correlations between the extended hard X-ray component and AGN parameters. We also discuss the implications for torus modeling and AGN feedback. Considering potential contributions from X-ray binaries (XRBs) to the extended emission, we do not see strong XRB contamination in the overall sample.

NGC 4388: a test case for relativistic disc reflection and Fe K fluorescence features

ABSTRACT We present a new analysis of the Suzaku X-ray spectrum of the Compton-thin Seyfert 2 galaxy NGC 4388. The spectrum above ∼2 keV can be described by a remarkably simple and rather mundane model, consisting of a uniform, neutral spherical distribution of matter, with a radial column density of $2.58\pm 0.02 \times 10^{23} \ \rm cm^{-2}$, and an Fe abundance of $1.102^{+0.024}_{-0.021}$ relative to solar. The model does not require any phenomenological adjustments to self-consistently account for the low-energy extinction, the Fe Kα and Fe Kβ fluorescent emission lines, the Fe K edge, and the Compton-scattered continuum from the obscuring material. The spherical geometry is not a unique description, however, and the self-consistent, solar abundance MYTORUS model, applied with toroidal and non-toroidal geometries, gives equally good descriptions of the data. In all cases, the key features of the spectrum are so tightly locked together that for a wide range of parameters, a relativistic disc-reflection component contributes no more than $\sim 2{{\ \rm per\ cent}}$ to the net spectrum in the 2–20 keV band. We show that the commonly invoked explanations for weak X-ray reflection features, namely a truncated and/or very highly ionized disc, do not work for NGC 4388. If relativistically broadened Fe Kα lines and reflection are ubiquitous in Seyfert 1 galaxies, they should also be ubiquitous in Compton-thin Seyfert 2 galaxies. The case of NGC 4388 shows the need for similar studies of more Compton-thin AGN to ascertain whether this is true.

High-sensitive XANES analysis at Ce L2-edge for Ce in bauxites using transition-edge sensors: Implications for Ti-rich geological samples

Accurate determination of cerium (Ce) valence state is important for interpreting the Ce anomaly in geological archives for (paleo)redox reconstruction. However, the routine application of Ce L3-edge X-ray absorption near-edge structure (XANES) spectroscopy for detecting trace Ce in geological samples can often be restricted by coexisting titanium (Ti) due to the proximity of their fluorescence emission lines. Therefore, the signal-to-noise ratio of Ce L3-edge XANES spectra may not be sufficiently high for high-quality spectroscopic analysis. This study introduces a semi-quantitative approach appropriate for Ti-rich, Ce-dilute geological materials by synchrotron-based X-ray measurement at the Ce L2-edge. First, the results confirm that Ce L2-edge XANES spectra are able to avoid overlapping Ti Kβ emissions and provide more reliable information on the Ce valence state in Ti-rich materials relative to L3-edge XANES. Moreover, the application of transition-edge sensor (TES) could reach the higher sensitivity with better energy resolution than conventional silicon drift detector (SDD) to detect fluorescence X-ray (Ce Lβ1). The investigation on bauxites developed from the Columbia River Basalts shows that combining Ce L2-edge XANES and TES allows for resolving weak Ce fluorescence lines at the L2-edge from Ti-rich, Ce-dilute samples (Ti/Ce mass ratio up to ∼6000, tens of ppm Ce). The outcome emphasizes the practical possibility of investigating Ce redox state in Ti-rich geological samples.

HST UV Spectroscopy of the Planet-hosting T Tauri Star PDS 70

We summarize Hubble Space Telescope (HST) UV observations of the weak-lined T Tauri star (wTTS) PDS 70 obtained with the Space Telescope Imaging Spectrograph. These observations provide the first far-UV (FUV) and near-UV (NUV) spectra of PDS 70. Ground-based observations have so far revealed two formative giant planets orbiting in a wide gap in its circumstellar disk. Both the star and young planets are thought to still be accreting. The HST spectra provide new insight into physical conditions in the star’s outer atmosphere and circumstellar environment. The spectra are dominated by chromospheric and transition-region emission lines with maximum formation temperatures log T = 4.5–5.2 K. Stellar continuum emission is present in the NUV but we find no significant FUV continuum, as could arise from accretion shocks. Several fluorescent FUV H2 emission lines are present, a surprising result since H2 lines are usually undetected in wTTS. The H2 lines likely originate in irradiated circumstellar gas that could serve as a reservoir for the star’s waning accretion. A previously established correlation between C iv line luminosity and accretion rate yields , consistent with previous estimates. Atacama Large Millimeter/submillimeter Array disk gas models imply strong absorption of stellar X-ray and UV (XUV) radiation near the star, effectively shielding the planets. Inner disk gas is exposed to ongoing photoevaporation by XUV radiation and the disk is nearing the end of its expected lifetime, making PDS 70 an important example of a young planet-hosting star in the late stage of accretion.

X-ray confirmation of the intermediate polar IGR J16547-1916

Using X-ray observations from the NuSTAR and Swift satellites, we present temporal and spectral properties of an intermediate polar (IP) IGR J16547-1916. A persistent X-ray period at ∼546 s confirming the optical spin period obtained from previous observations is detected. The detection of a strong X-ray spin pulse reinforces the classification of this system as an intermediate polar. The lack of orbital or side-band periodicities in the X-rays implies that the system is accreting predominantly via a disk. A variable covering absorber appears to be responsible for the spin pulsations in the low energy range. In the high energy band, the pulsations are likely due to the self occultation of tall shocks above the white dwarf surface. The observed double-humped X-ray spin pulse profile indicates two-pole accretion geometry with tall accretion regions in short rotating IP IGR J16547-1916. We present the variation of the spin pulse profile over an orbital phase to account for the effects of orbital motion on the spin pulsation. X-ray spectra obtained from the contemporaneous observations of Swift and NuSTAR in the 0.5–78.0 keV energy band are modeled with a maximum temperature of 31 keV and a blackbody temperature of 64 eV, along with a common column density of 1.8 × 1023 cm−2 and a power-law index of −0.22 for the covering fraction. An additional Gaussian component and a reflection component are needed to account for a fluorescent emission line at 6.4 keV and the occurrence of X-ray reflection in the system. We also present the spin phase-resolved spectral variations of IGR J16547-1916 in the 0.5–78.0 keV energy band and find dependencies in the X-ray spectral parameters during the rotation of the white dwarf.

Saturation and optical pumping effects in the fluorescence that follows the excitation of the D2 transition in atomic rubidium

In this article we study saturation effects in the fluorescence spectra at the D2 transition in 87Rb excited by two counter-propagating laser beams of the same frequency. The effects appear as dips in the Doppler broadened fluorescence emission lines at the atomic transitions and in all but one of the cross-over resonances. The 5SF=1→5P3/2F=0, 1 cross-over presents a strong dependence in the laser intensity. For low intensities it appears as a weak dip, but at higher laser intensities an increase in fluorescence is clearly present. A rate equation calculation which includes the velocity profile is used to interpret the experimental data. For the 5SF=2→5P3/2F=1, 2 and 3 manifold, a five level model that takes into account the hyperfine structure of both initial and final states is in good agreement with the experiment. For the 5SF=1→5P3/2F=0, 1 and 2 manifold, it is necessary to include the magnetic sublevel structure of all hyperfine levels involved. The calculation also shows that the onset of this magnetic pumping effect occurs near the 5S→5P3/2 saturation intensity. In both cases the comparison between theory and experiment allowed a direct determination of the ratio of the laser intensity to the atomic saturation intensity.

AstroSat observations of eclipsing high mass X-ray binary pulsar OAO 1657-415

We present the results obtained from analysis of two AstroSat observations of the high mass X-ray binary pulsar OAO 1657-415. The observations covered 0.681–0.818 and 0.808–0.968 phases of the $$\sim $$ 10.4 day orbital period of the system, in March and July 2019, respectively. Despite being outside the eclipsing regime, the power density spectrum from the first observation lacks any signature of pulsation or quasi-periodic oscillations. However, during July observation, X-ray pulsations at a period of 37.0375 s were clearly detected in the light curves. The pulse profiles from the second observation consist of a broad single peak with a dip-like structure in the middle across the observed energy range. We explored evolution of the pulse profile in narrow time and energy segments. We detected pulsations in the light curves obtained from 0.808–0.92 orbital phase range, which is absent in the remaining part of the observation. The spectrum of OAO 1657-415 can be described by an absorbed power-law model along with an iron fluorescent emission line and a blackbody component for out-of-eclipse phase of the observation. Our findings are discussed in the frame of stellar wind accretion and accretion wake at late orbital phases of the binary.

Tidal Disruption Events

The concept of stars being tidally ripped apart and consumed by a massive black hole (MBH) lurking in the center of a galaxy first captivated theorists in the late 1970s. The observational evidence for these rare but illuminating phenomena for probing otherwise dormant MBHs first emerged in archival searches of the soft X-ray ROSAT All-Sky Survey in the 1990s, but has recently accelerated with the increasing survey power in the optical time domain, with tidal disruption events (TDEs) now regarded as a class of optical nuclear transients with distinct spectroscopic features. Multiwavelength observations of TDEs have revealed panchromatic emission, probing a wide range of scales, from the innermost regions of the accretion flow to the surrounding circumnuclear medium. I review the current census of 56 TDEs reported in the literature, and their observed properties can be summarized as follows: ▪ The optical light curves follow a power-law decline from peak that scales with the inferred central black hole mass as expected for the fallback rate of the stellar debris, but the rise time does not. ▪ The UV-optical and soft X-ray thermal emission come from different spatial scales, and their intensity ratio has a large dynamic range and is highly variable, providing important clues as to what is powering the two components. ▪ They can be grouped into three spectral classes, and those with Bowen fluorescence line emission show a preference for a hotter and more compact line-emitting region, whereas those with only Heii emission lines are the rarest class.

Long-term X-ray variability of the symbiotic system RT Cru based on Chandra spectroscopy

ABSTRACT RT Cru belongs to the rare class of hard X-ray emitting symbiotics, whose origin is not yet fully understood. In this work, we have conducted a detailed spectroscopic analysis of X-ray emission from RT Cru based on observations taken by the Chandra Observatory using the Low Energy Transmission Grating (LETG) on the High-Resolution Camera Spectrometer (HRC-S) in 2015 and the High Energy Transmission Grating (HETG) on the Advanced CCD Imaging Spectrometer S-array (ACIS-S) in 2005. Our thermal plasma modelling of the time-averaged HRC-S/LETG spectrum suggests a mean temperature of kT ∼ 1.3 keV, whereas kT ∼ 9.6 keV according to the time-averaged ACIS-S/HETG. The soft thermal plasma emission component (∼1.3 keV) found in the HRC-S is heavily obscured by dense materials (>5 × 1023 cm−2). The aperiodic variability seen in its light curves could be due to changes in either absorbing material covering the hard X-ray source or intrinsic emission mechanism in the inner layers of the accretion disc. To understand the variability, we extracted the spectra in the ‘low/hard’ and ‘high/soft’ spectral states, which indicated higher plasma temperatures in the low/hard states of both the ACIS-S and HRC-S. The source also has a fluorescent iron emission line at 6.4 keV, likely emitted from reflection off an accretion disc or dense absorber, which was twice as bright in the HRC-S epoch compared to the ACIS-S. The soft thermal component identified in the HRC-S might be an indication of a jet that deserves further evaluations using high-resolution imaging observations.

Bent crystal Laue analyser combined with total reflection fluorescence X-ray absorption fine structure (BCLA + TRF-XAFS) and its application to surface studies.

A bent crystal Laue analyser (BCLA) is an X-ray energy analyser used for fluorescence X-ray absorption fine-structure (XAFS) spectroscopy to separate the fluorescence X-ray emission line of a target atom from the elastic scattering X-rays and other fluorescence emission lines. Here, the feasibility of the BCLA for total reflection fluorescence XAFS (TRF-XAFS), which has a long X-ray footprint on the substrate surface owing to grazing incidence, was tested. The focal line of the BCLA was adjusted on the X-ray footprint and the XAFS signal for one monolayer of Pt deposited on a 60 nm Au film with high sensitivity was obtained. Although range-extended XAFS was expected by the rejection of Au fluorescence arising from the Au substrate, a small glitch was found in the Au L3 edge because of the sudden change of the complex refraction index of the Au substrate at the Au edge. This abnormal spectrum feature can be removed by reflectivity correction using Au foil absorption data. BCLA combined with TRF-XAFS spectroscopy (BCLA + TRF-XAFS) is a new technique for the in situ surface analysis of highly dispersed systems even in the presence of a liquid overlayer.