XRISM Reveals Complex Ionization and Velocity Structures in the GX 340+0 X-Ray Binary

Broad relativistic iron lines from neutron star X-ray binaries are important probes of the inner accretion disk. The X-ray reflection features can be weakened due to strong magnetic fields or very low iron abundances such as is possible in X-ray binaries with low mass, first generation stars as companions. Here we investigate the reality of the broad iron line detected earlier from the neutron star low mass X-ray binary 4U~1820--30 with a degenerate helium dwarf companion. We perform a comprehensive, systematic broadband spectral study of the atoll source using \suzaku{} and simultaneous \nustar{} \& \swift{} observations. We have used different continuum models involving accretion disk emission, thermal blackbody and thermal Comptonization of either disk or blackbody photons. The \suzaku{} data show positive and negative residuals in the region of iron K band. These features are well described by two absorption edges at $7.67\pm0.14\kev$ and $6.93\pm0.07\kev$ or partial covering photoionized absorption or by blurred reflection. Though, the simultaneous \swift{} and \nustar{} data do not clearly reveal the emission or absorption features, the data are consistent with the presence of either absorption or emission features. Thus, the absorption based models provide an alternative to the broad iron line or reflection model. The absorption features may arise in winds from the inner accretion disk. The broadband spectra appear to disfavour continuum models in which the blackbody emission from the neutron star surface provides the seed photons for thermal Comptonization. Our results suggest emission from a thin accretion disk ($kT_{disk} \sim 1\kev$), Comptonization of disk photons in a boundary layer most likely covering a large fraction of the neutron star surface and innermost parts of the accretion disk, and blackbody emission ($kT_{bb} \sim 2\kev$) from the polar regions.

We have obtained spectra of the thermal emission from Mars in the 5.4–10.5 μm wavelength domain at a resolving power of about 60 from the Kuiper Airborne Observatory. Spectra were obtained for several large spots on Mars, whose ground temperatures and air masses through the Martian atmosphere differed significantly. These data were taken at two times during the flight. By taking the ratio of the spectral flux from one spot to that of a second spot, we obtained results that were independent of uncertainties in the instrument's spectral response and the transmission of the Earth's atmosphere. These data, as well as spectral fluxes of single spots based using the star α Tau as a calibration standard, show a number of emission and absorption features. They are present in sets of spectra taken at two different times. Some of the absorption features are due to gaseous CO2 in the Martian atmosphere. The remainder of the absorption and emission features are due to minerals present in the airborne dust and on the surface. Comparison of the strength of features seen at similar times, but with three different air masses and ground temperatures, suggests that the emission features arise primarily from surface emissivity spectral variations and that the absorption features arise from components of the atmosphere. Based on comparisons of the observed features with laboratory data for a broad ensemble of minerals, spectra of other solar system bodies, and relevant compositional information about Mars, we have made the following tentative identifications of the observed features. Emission features at 7.8 and 9.7 μm are attributed to surface silicates; an emission feature at 6.1 μm is attributed to a molecular water component of the surface material; an absorption band at 8.7 μm as well as possibly one at 9.8 μm is ascribed to sulfate or bisulfate anions, probably located in a distorted crystalline site; and an absorption band at 6.7 μm is attributed to carbonate or bicarbonate anions located in a distorted crystalline site, although we cannot totally rule out a nitrate origin for this feature. We have simulated these spectra with radiative transfer programs for the atmosphere and surface. These simulations indicate that the sulfate‐ and carbonate‐bearing minerals are contained in the same particles of the airborne dust as the dominant silicate minerals, that the dust optical depth was about 0.6 at a reference wavelength of 0.3 μm over the area of the observed spots, and that sulfates and carbonates constitute about 10–15% and 1–3% by volume of the airborne dust, respectively. These results imply that minerals formed by weathering processes represent major reservoirs of volatile species on current Mars.

Context. The He I λ0830 Å line is a high excitation line which allows us to probe the material in the innermost regions of protostellar disks, and to trace both accreting and outflowing material simultaneously. Aims. We use X-shooter observations of a sample of 107 young stars in the Lupus (1–3 Myr) and Upper Scorpius (5–10 Myr) star-forming regions to search for correlations between the line properties, as well as the disk inclination and accretion luminosity. Methods. We identified eight distinct profile types in the sample. We fitted Gaussian curves to the absorption and/or emission features in the line to measure the maximum velocities traced in absorption, the full-width half-maximum (FWHM) of the line features, and the Gaussian area of the features. Results. We compare the proportion of each profile type in our sample to previous studies in Taurus. We find significant variations between Taurus and Lupus in the proportion of P Cygni and inverse P Cygni profiles, and between Lupus and Upper Scorpius in the number of emission-only and combination profile types. We examine the emission-only profiles in our sample individually and find that most sources (nine out of 12) with emission-only profiles are associated with known jets. When examining the absorption features, we find that the blue-shifted absorption features appear less blue-shifted at disk inclinations close to edge-on, which is in line with past works, but no such trend with inclination is observed in the sources with only red-shifted features. Additionally, we do not see a strong correlation between the FWHM and inclination. Higher accretion rates were observed in sources with strong blue-shifted features which, along with the changes in the proportions of each profile type observed in the two regions, indicates that younger sources may drive stronger jets or winds. Conclusions. Overall, we observe variations in the proportion of each He I λ10830 Å profile type and in the line properties which indicates an evolution of accretion and ejection signatures over time, and with source properties. These results confirm past works and models of the He I λ10830 Å line, but for a larger sample and for multiple star-forming regions. This work highlights the power of the He I λ0830 Å line as a probe of the gas in the innermost regions of the disk.

Supersoft X-ray sources (SSSs) are white dwarf (WD) binaries that radiate almost entirely below ∼1 keV. Their X-ray spectra are often complex when viewed with the X-ray grating spectrometers, where numerous emission and absorption features are intermingled and hard to separate. The absorption features are mostly from the WD atmosphere, for which radiative transfer models have been constructed. The emission features are from the corona surrounding the WD atmosphere, in which incident emission from the WD surface is reprocessed. Modeling the corona requires different solvers and assumptions for the radiative transfer, which has yet to be achieved. We chose CAL87, an SSS in the Large Magellanic Cloud, which exhibits emission-dominated spectra from the corona, as the WD atmosphere emission is assumed to be completely blocked by the accretion disk. We constructed a radiative transfer model for the corona using two radiative transfer codes: xstar for a one-dimensional two-stream solver and MONACO for a three-dimensional Monte Carlo solver. We identified their differences and limitations in comparison to the spectra taken with the Reflection Grating Spectrometer on board the XMM-Newton satellite. We finally obtained a sufficiently good spectral model of CAL87 based on the radiative transfer of the corona plus an additional collisionally ionized plasma. In the coming X-ray microcalorimeter era, it will be required to interpret spectra based on radiative transfer in a wider range of sources than what is presented here.

We present a reanalysis of the ROSAT PSPC data within the central 100 kpc of M87 to search for intrinsic oxygen absorption similar to that recently measured in several galaxies and groups. Since M87 is the brightest nearby galaxy or cluster possessing an average temperature (~2 keV) within the PSPC bandpass, it is the ideal target for this study. Using a spatial-spectral deprojection analysis we find the strongest evidence to date for intrinsic oxygen absorption in the hot gas of a galaxy, group, or cluster. Single-phase plasma models modified by intervening Galactic absorption cannot fit the 0.2-2.2 keV PSPC data as they underpredict the 0.2-0.4 keV region and overpredict the 0.5-0.8 keV region where the emission and absorption residuals are obvious upon visual inspection of the spectral fits. These absorption and emission features are significant out to the largest radii investigated. Since the excess emission between 0.2-0.4 keV rules out intrinsic absorption from cold gas or dust, the most reasonable model for the excess emission and absorption features is warm, collisionally ionized gas with a temperature of ~106 K. Simple multiphase models (cooling flow, two phases) modified by both intervening Galactic absorption and by a single oxygen edge provide good fits and yield temperatures and Fe abundances of the hot gas that agree with previous determinations by ASCA and SAX. The multiphase models of M87 inferred from the PSPC can account for the excess EUV emission observed with EUVE and the excess X-ray absorption inferred from Einstein and ASCA data above 0.5 keV. This evidence for a multiphase warm+hot interstellar medium in M87 essentially confirms the original detection by Canizares et al. within the central ~2' using the Einstein FPCS. Although the total mass of the warm gas implied by the oxygen absorption is consistent with the matter deposited by a cooling flow, the suppression of the mass deposition rate and the distortion of the X-ray isophotes in the region where the radio emission is most pronounced suggest some feedback effect from the active galactic nucleus on the cooling gas.

We present 0.8-5.2 μm spectroscopy of the compact source at the base of a variable nebula (McNeil's Nebula Object) in the Lynds 1630 dark cloud that went into outburst in late 2003. The spectrum of this object reveals an extremely red continuum, CO bands at 2.3-2.5 μm in emission, a deep 3.1 μm ice absorption feature, and a solid-state CO absorption feature at 4.7 μm. In addition, emission lines of H, Ca II, Mg I, and Na I are present. The Paschen lines exhibit P Cygni profiles, as do two lines of He I, although the emission features are very weak in the latter. The Brackett lines, however, are seen to be purely in emission. The P Cygni profiles clearly indicate that mass outflow is occurring in a wind with a velocity of ~400 km s-1. The H line ratios do not yield consistent estimates of the reddening, nor do they agree with the extinction estimated from the ice feature (AV ~ 11). We propose that these lines are optically thick and are produced in a dense, ionized wind. The near-infrared spectrum does not appear similar to any known FUor or EXor object. However, all evidence suggests that McNeil's Nebula Object is a heavily embedded low-mass Class I protostar, surrounded by a disk, whose brightening is due to a recent accretion event.

We have measured the excess IR emission from carbon mira and SR variable stars from IRAS LRS spectra. The 8-22μm excess is defined as the ratio of flux above a 2500K energy distribution fit to the LRS spectrum at about 8μm. The carbon star LRS spectra show both emission and absorption features, which are incorporated into our 8-22pm excess. The most prominent feature in carbon stars is the 11.2μm SiC dust emission feature extending from 10μm to 13.8 μm. We observe another emission feature of unknown origin which peaks between 8.4-8.7μm. The SiC emission feature is occasionally blended on the red side by an absorption feature (attributed to gaseous HCN + C2H2) which extends from about 12-16μm. Many of the spectra appear to turn down at the 8μm end due (?) to an HCN + C2H2 absorption feature located at 7.1μm. Carbon stars do not generally show as large an excess as the M mira variables do. The figure below shows our measured excesses for both carbon miras and carbon semi-regular variables. There appears to be little correlation of excess with period, however the mira variables show about twice the range of variation of excess that the semi-regular variables do. We find little correlation between our measured 8-22μm excess and the excesses of Jura (Ap. J., 303, 327, 1986) based on the ratio of 12μm flux to 2μm flux. Our data do support hi s conclusion that longer period variable stars show larger average excesses, but this is only true for mira variables in our analysis.

We studied the absorption features of CO lines against the continuum originating from the heated dust in the obscuring tori around active galactic nuclei (AGNs). We investigated the formation of absorption lines corresponding to the CO rotational transitions using three-dimensional non-LTE line transfer simulations considering the dust thermal emission. As in Papers I–III of this series, we performed post-processed radiative transfer calculations using the “radiation-driven fountain model” (Wada et al. 2016), which yields a geometrically thick obscuring structure around the nucleus. This model is consistent with the spectral energy distribution of the nearest type-2 Seyfert galaxy, the Circinus galaxy. We found that the continuum-subtracted channel maps of J = 4−3 and higher transitions show absorption regions along the disk midplane for an edge-on viewing angle. The spectra consist of multiple absorption and emission features, reflecting the internal inhomogeneous and turbulent structure of the torus. The deepest absorption feature is caused by the gas on the near side of the torus between r = 10 and 15 pc, which is located in front of the AGN-heated dust inside r ≃ 5 pc. We also found that a spatial resolution of 0.5–1.0 pc is necessary to resolve the absorption features. Moreover, the inclination angle must be close to the edge-on angle (i.e., ≳85°) to observe the absorption features. The findings of the present study imply that combining our radiation-hydrodynamic model with high-resolution observations of CO (7–6) by ALMA can provide new information about the internal structure of the molecular tori in nearby AGNs.

We have reduced and analyzed the Infrared Space Observatory (ISO) Short-Wavelength Spectrometer (SWS) spectra of 29 infrared carbon stars with a silicon carbide feature at 11.30 mum, 17 of which have not been previously published. Absorption or emission features of C-2, HCN, C2H2, C-3 and silicon carbide (SiC) have been identified in all 17 unpublished carbon stars. In addition, two unidentified absorption features at 3.50 and 3.65 mum are listed for the first time in this paper. We classify these 29 carbon stars into groups A, B, C and D according to the shapes of their spectral energy distribution, and this classification seems to show an evolutionary sequence of carbon stars with an SiC feature. Moreover we have found the following results for the different groups: on average, the relative integrated flux of the 3.05 mum C2H2+HCN absorption feature increases gradually from group A to B and C; that of the 5.20 mum C-3 absorption feature becomes gradually weaker from group A to B and C; that of the 11.30 mum SiC emission feature increases gradually from group A to B and C but weakens in group D; and in contrast, that of the 13.70 mum C2H2 absorption feature weakens gradually from group A to B and C but becomes stronger in group D. We suggest that the evolution of the IR spectra of carbon stars along the sequence A to D is a result of the following phenomena: as the near-IR black-body temperature (T-nir) decreases, the circumstellar envelope becomes thicker; also the effective temperature (T-eff) of the photosphere of the central star decreases gradually and the C/O ratio increases from A to B.

Iron emission and absorption features from nine X-ray binaries are compared with a model that predicts characteristics of iron K-shell features corresponding to different viewing angles for the accretion disk. In this model, emission and absorption features arise from an accretion disk corona whose structure is computed under the assumptions of ionization, thermal, and hydrostatic balance of gas illuminated by the central continuum source. Hence the equivalent widths of the emission and absorption features are predicted without the introduction of any free parameters to control the physical conditions in the disk corona. Our data/model comparison suggests an explanation for the equivalent widths of the iron K-alpha emission and the depth of the absorption edge in terms of (1) the angle of inclination between the observer's line of sight and the plane of the accretion disk and (2) the shape of the incident source spectrum.

Orbital-phase-resolved infrared spectra of Cygnus X-3 in outburst and quiescence, including tomographic analysis, are presented. We confirm the phasing of broad He II and N V lines in quiescence, such that maximum blueshift corresponds to the X-ray minimum at Φ = 0.00 ± 0.04. In outburst, double-peaked He I structures show a similar phasing with two significant differences: (1) although varying in relative strength, there is continuous line emission in blue and red peaks around the orbit; and (2) an absorption component, ~ of an orbit out of phase with the emission features, is discerned. Doppler tomograms of the double-peaked profiles are consistent with a disk-wind geometry, rotating at velocities of 1000 km s-1. Regrettably, the tomography algorithm will produce a similar ring structure from alternative line sources if contaminated by overlying P Cygni profiles. This is certainly the case in the strong 2.0587 μm He I line, leading to an ambiguous solution for the nature of double-peaked emission. The absorption feature, detected of an orbit out of phase with the emission features, is consistent with an origin in the He star wind and yields for the first time a plausible radial velocity curve for the system. We directly derive the mass function of the system, 0.027 M☉. If we assume a neutron star accretor and adopt a high orbital inclination, i > 60°, we obtain a mass range for the He star of 5 M☉ MWR 11 M☉. Alternatively, if the compact object is a black hole, we estimate MBH 10 M☉. We discuss the implications of these masses for the nature and size of the binary system.

OurSwiftmonitoring program triggered two jointXMM-Newton,NuSTAR, and HST observations on 11 and 21 December 2016 targeting NGC 3783 because its soft X-ray continuum was heavily obscured. Consequently, emission features, including the O VIIradiative recombination continuum, stand out above the diminished continuum. We focus on the photoionized emission features in the December 2016 Reflection Grating Spectrometer (RGS) spectra, and compare them to the time-averaged RGS spectrum obtained in 2000–2001 when the continuum was unobscured. A two-phase photoionized plasma is required to account for the narrow emission features. These narrow emission features are weakly varying between 2000–2001 and December 2016. We also find a statistically significant broad emission component in the time-averaged RGS spectrum in 2000–2001. This broad emission component is significantly weaker in December 2016, suggesting that the obscurer is farther away than the X-ray broad-line region. In addition, by analyzing the archival high-resolution X-ray spectra, we find that nine photoionized absorption components with different ionization parameters and kinematics are required for the warm absorber in X-rays.

view Abstract Citations (63) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS 10 Micron Spectroscopy of Young Stars in the rho Ophiuchi Cloud Hanner, M. S. ; Brooke, T. Y. ; Tokunaga, A. T. Abstract Spectra in the 10 micrometer region were obtained of 14 young stars associated with the central core of the rho Oph dark cloud complex. Silicate dust emission and absorption features can be fairly well reproduced with simple models using the emissivity of the silicates in the Orion Trapezium region, believed to be typical of molecular cloud dust. A spectrum of the Trapezium star theta1 Ori D was obtained to define the emissivity more precisely. The emissivity of silicate dust around the late-type giant Mu Cep does not improve the fits to the absorption features and provides a poorer match to the emission features. None of the sources display a strong 11.2 micrometer peak like that seen in comet Halley and attributed to crystalline olivine. A broad weak feature near 11.2 micrometer, possibly related to the comet feature, may be present in the emission spectrum of the Herbig Ae star HD 150193. Absorption features toward two of the objects are narrower than would be expected from Trapezium-like silicates, suggesting differences in the composition of the silicates. The relation between the silicate extinction band depth and H2O ice band depths is determined for the deeply embedded objects. One late-type object, Elias 14, clearly shows the 11.25 micrometer aromatic hydrocarbon emission feature, possibly excited by the nearby B star, HD 147889, though the latter does not exhibit the feature. Publication: The Astrophysical Journal Pub Date: January 1995 DOI: 10.1086/175069 Bibcode: 1995ApJ...438..250H Keywords: Absorption Spectra; Emission Spectra; Infrared Astronomy; Infrared Spectra; Ophiuchi Clouds; Pre-Main Sequence Stars; Astronomical Spectroscopy; Silicates; Stellar Envelopes; Astronomy; INFRARED: STARS; ISM: INDIVIDUAL NAME: RHO OPHIUCHI; STARS: CIRCUMSTELLAR MATTER; STARS: PRE--MAIN-SEQUENCE full text sources ADS | data products SIMBAD (17)

Ultraviolet and X-ray observations show evidence of outflowing gas around many active galactic nuclei. Some of these outflows may be driven off gas infalling towards the central black hole. We perform radiative transfer calculations to compute the gas ionization state and X-ray spectra for two- and three-dimensional (3D) hydrodynamical simulations of this outflow-from-inflow scenario. By comparison with observations, our results can be used to test the theoretical models and guide future numerical simulations. We predict both absorption and emission features, most of which are formed in a polar funnel of outflowing gas. This outflow causes strong absorption for observer orientation angles of < 35 degrees. Particularly in 3D, the strength of this absorption varies significantly for different lines-of-sight owing to the fragmentary structure of the gas flow. Although infalling material occupies a large fraction of the simulation volume, we do not find that it imprints strong absorption features since the ionization state is very high. Thus, an absence of observed inflow absorption features does not exclude the models. The main spectroscopic consequence of the infalling gas is a scattered continuum component that partially re-fills the absorption features caused by the outflowing polar funnel. Fluorescence and scattering in the outflow is predicted to give rise to several emission features for all observer orientations. For the hydrodynamical simulations considered we find both ionization states and column densities for the outflowing gas that are too high to be quantitatively consistent with well-observed X-ray absorption systems. Nevertheless, our results are qualitatively encouraging and further exploration of the model parameter space is warranted. (Abridged.)

We present an atlas of very high resolution ( R ~ 50000) H α line profiles of 63 pre-main sequence stars, divided among 43 T Tauri stars, 18 Herbig Ae/Be stars, and 2 FU Orionis objects. H α emission is the most common and prominent spectroscopic feature of pre-main sequence stars, and although it is optically very thick it is still the most frequently modelled emission line in young stars. In T Tauri stars the principal models involve magnetically driven winds, and more recently the role of infalling magnetospheric material has been explored. For Herbig Ae/Be stars a variety of models have been proposed, current emphasis is directed towards obscuration by clumpy circumstellar disk structures. In order to provide constraints on such models, we have made a statistical analysis of the 63 high resolution profiles. We here ignore the considerable variability of the H α emission, which is discussed in detail in a second paper. Most of our observed lines show complex profiles due to an interplay between emission and absorption features, and we suggest a two-dimensional classification scheme to describe these line profiles, based on the relative height of a secondary peak to the primary peak, as well as whether the absorption is blue- or red-shifted. Among T Tauri stars, 25% have symmetric profiles, 49% have blueshifted absorption dips, and 5% have P Cygni profiles; the remaining 21% show a variety of redshifted absorptions. For Herbig Ae/Be stars symmetric lines are quite rare (11%), indeed almost all of these stars have deep and prominent central absorptions. We have measured the extent of the line wings for all of our stars at the I max /40 level, and find that almost all have very extended wings, with typical extents of ± 350 km/s, but in high spectra the wings can be traced to lower intensities, and velocities as high as ± 900 km/s have been observed. Pronounced asymmetries of these extended wings are found for many stars, suggesting the possibility that the highest velocity material could be non-uniformly distributed. The equivalent widths of the H α emission in our sample of stars span two orders of magnitude, with a distribution that increases with decreasing equivalent width.