- 标题
- 摘要
- 关键词
- 实验方案
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An Upper Limit on Nickel Overabundance in the Supercritical Accretion Disk Wind of SS 433 from X-ray Spectroscopy
摘要： We analyze a long (with a total exposure time of 120 ks) X-ray observation of the unique Galactic microquasar SS 433 carried out by the XMM-Newton space observatory with the goal of searching for the fluorescent line of neutral (or weakly ionized) nickel at energy 7.5 keV. We consider two models for the formation of fluorescent lines in the spectrum of SS 433: (1) through the reflection of radiation from a putative central X-ray source off the optically thick neutral gas of the supercritical disk 'funnel' walls; and (2) due to the scattering of the radiation coming from the hottest parts of the jets in the optically thin wind of the system. We show that for these two cases the flux of the Ni I Kα fluorescent line is expected to be 0.45 of the flux of the Fe I Kα fluorescent line at 6.4 keV for the relative nickel overabundance ZNi/Z = 10 observed in the jets of SS 433. For the continuum model without the absorption edge of neutral iron, we have found an upper limit on the flux of the narrow Ni I Kα fluorescent line of 0.9 × 10?5 phot s?1 cm?2 (90% confidence level). In the continuum model with the absorption edge we have determined an upper limit on the flux of the Ni I Kα line at the level of 2.5 × 10?5 phot s?1 cm?2. At the same time, the flux of the fluorescent iron line has been measured to be 9.9+1.2?1.1 × 10?5 phot s?1 cm?2. This result implies that the nickel overabundance in the accretion disk wind should be at least a factor of 1.5 times smaller than the corresponding nickel overabundance observed in the jets of SS 433.
关键词： neutron stars,SS 433,black holes,accretion,jets
更新于2025-09-23 15:23:52
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NuSTAR observations of Mrk 766: distinguishing reflection from absorption
摘要： We present two new NuSTAR observations of the narrow-line Seyfert 1 (NLS1) galaxy Mrk 766 and give constraints on the two scenarios previously proposed to explain its spectrum and that of other NLS1s: relativistic reflection and partial covering. The NuSTAR spectra show a strong hard (>15 keV) X-ray excess, while simultaneous soft X-ray coverage of one of the observations provided by XMM–Newton constrains the ionized absorption in the source. The pure reflection model requires a black hole of high spin (a > 0.92) viewed at a moderate inclination (i = 46+1?4°). The pure partial covering model requires extreme parameters: the cut-off of the primary continuum is very low (22+7?5 keV) in one observation and the intrinsic X-ray emission must provide a large fraction (75 per cent) of the bolometric luminosity. Allowing a hybrid model with both partial covering and reflection provides more reasonable absorption parameters and relaxes the constraints on reflection parameters. The fractional variability reduces around the iron K band and at high energies including the Compton hump, suggesting that the reflected emission is less variable than the continuum.
关键词： accretion, accretion discs,galaxies: individual: Mrk 766,galaxies: Seyfert,black hole physics
更新于2025-09-23 15:22:29
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ESO-H <i>α</i> 574 and Par-Lup 3-4 jets: Exploring the spectral, kinematical, and physical properties
摘要： In this paper a comprehensive analysis of VLT/X-Shooter observations of two jet systems, namely ESO-Hα 574 a K8 classical T Tauri star and Par-Lup 3-4 a very low mass (0.13 M☉) M5 star, is presented. Both stars are known to have near-edge on accretion disks. A summary of these first X-shooter observations of jets was given in a 2011 letter. The new results outlined here include flux tables of identified emission lines, information on the morphology, kinematics and physical conditions of both jets and, updated estimates of ?out/?acc. Asymmetries in the ESO-Hα 574 flow are investigated while the Par-Lup 3-4 jet is much more symmetric. The density, temperature, and therefore origin of the gas traced by the Balmer lines are investigated from the Balmer decrements and results suggest an origin in a jet for ESO-Hα 574 while for Par-Lup 3-4 the temperature and density are consistent with an accretion flow. ?acc is estimated from the luminosity of various accretion tracers. For both targets, new luminosity relationships and a re-evaluation of the effect of reddening and grey extinction (due to the edge-on disks) allows for substantial improvements on previous estimates of ?acc. It is found that log(?acc) = ?9.15 ± 0.45 M☉ yr?1 and ?9.30 ± 0.27 M☉ yr?1 for ESO-Hα 574 and Par-Lup 3-4 respectively. Additionally, the physical conditions in the jets (electron density, electron temperature, and ionisation) are probed using various line ratios and compared with previous determinations from iron lines. The results are combined with the luminosity of the [SII]λ6731 line to derive ?out through a calculation of the gas emissivity based on a 5-level atom model. As this method for deriving ?out comes from an exact calculation based on the jet parameters (measured directly from the spectra) rather than as was done previously from an approximate formula based on the value of the critical density at an assumed unknown temperature, values of ?out are far more accurate. Overall the accuracy of earlier measurements of ?out/?acc is refined and ?out/?acc = 0.5 (+1.0)(?0.2) and 0.3 (+0.6)(?0.1) for the ESO-Hα 574 red and blue jets, respectively, and 0.05 (+0.10)(?0.02) for both the Par-Lup 3-4 red and blue jets. While the value for the total (two-sided) ?out/?acc in ESO-Hα 574 lies outside the range predicted by magneto-centrifugal jet launching models, the errors are large and the effects of veiling and scattering on extinction measurements, and therefore the estimate of ?acc, should also be considered. ESO-Hα 574 is an excellent case study for understanding the impact of an edge-on accretion disk on the observed stellar emission. The improvements in the derivation of ?out/?acc means that this ratio for Par-Lup 3-4 now lies within the range predicted by leading models, as compared to earlier measurements for very low mass stars. Par-Lup 3-4 is one of a small number of brown dwarfs and very low mass stars which launch jets. Therefore, this result is important in the context of understanding how ?out/?acc and, thus, jet launching mechanisms for the lowest mass jet driving sources, compare to the case of the well-studied low mass stars.
关键词： ISM: jets and outflows,line: identification,accretion, accretion disks,stars: formation
更新于2025-09-23 15:22:29
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Optical and <i>J, K</i> -photometry of the quiescent black hole X-ray nova A0620?00 in the passive and active states
摘要： In 2015–2016, the X-ray nova A0620?00 in quiescence was observed in the passive state, according to the terminology of Cantrell et al., and in less than 230 d it transited into the active state. The system mean luminosity increased by 0.20 mag in the optical and by 0.25 and 0.30 mag in J and K infrared bands, respectively, while the orbital light curves changed drastically, and the ?ickering amplitude more than doubled. The mean light-curve analysis performed in the context of two models argued that the interaction region where the gas stream reaches the disc is responsible for these effects. The growth of this region’s luminosity in the active state implies the increase of the mass transfer rate via the L1 point, likely due to non-stationary processes in the donor star atmosphere. The non-stellar spectrum Fλ in the observed range λλ6400–22 000 ? obeys a power law of λα where α = ?(2.13 ± 0.1) in the passive state and α = ?(1.85 ± 0.1) in the active, while the absolute mean square ?ickering amplitude behaves like (cid:4)F?(λ) ～ λ?2.36 in both states of activity.
关键词： X-rays: individual: 1A 0620?00,X-rays: binaries,accretion discs,techniques: photometric,starspots,radiation mechanisms: non-thermal,accretion
更新于2025-09-23 15:22:29
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OBSERVATIONS OF THE LENSED QUASAR Q2237+0305 WITH CANARICAM AT GTC
摘要： We present new mid-IR observations of the quadruply lensed quasar Q2237+0305 taken with CanariCam on the Gran Telescopio Canarias. Mid-IR emission by hot dust, unlike the optical and near-IR emission from the accretion disk, is unaffected by the interstellar medium (extinction/scattering) or stellar microlensing. We compare these “true” ratios to the (stellar) microlensed ?ux ratios observed in the optical/near-IR to constrain the structure of the quasar accretion disk. We ?nd a half-light radius of R1/2 = 3.4^{+0.3}_{-0.3} lt-day at λ_rest = 1736 ? and an exponent for the temperature pro?le p = 0.79 ± 0.55 for a standard thin-disk model. If we assume that the differences in the mid-IR ?ux ratios measured over the years are due to microlensing variability, we ?nd a lower limit for the size of the mid-IR-emitting region of R1/2 > 200 lt-day. We also test for the presence of substructure/satellites by comparing the observed mid-IR ?ux ratios with those predicted from smooth lens models. We can explain the differences if the surface density fraction in satellites near the lensed images is α = 0.046^{+0.033}_{-0.019} for a singular isothermal ellipsoid plus external shear mass model or α = 0.013^{+0.008}_{-0.008} for a mass model combining ellipsoidal NFW and de Vaucouleurs pro?les in an external shear.
关键词： gravitational lensing: micro,dark matter,accretion, accretion disks,quasars: individual (Q2237+0305)
更新于2025-09-23 15:22:29
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The power of infrared AGN selection in mergers: a theoretical study
摘要： The role of galaxy mergers in fuelling active galactic nuclei (AGNs) is still debated, owing partly to selection effects inherent to studies of the merger/AGN connection. In particular, luminous AGNs are often obscured in late-stage mergers. Mid-infrared (IR) colour selection of dust-enshrouded AGN with, e.g. the Wide-field Infrared Survey Explorer (WISE) has uncovered large new populations of obscured AGN. However, this method is sensitive mainly to AGN that dominate emission from the host. To understand how selection biases affect mid-IR studies of the merger/AGN connection, we simulate the evolution of AGN throughout galaxy mergers. Although mid-IR colours closely trace luminous, obscured AGN, we show that nearly half of merger-triggered AGNs are missed with common mid-IR selection criteria, even in late-stage, gas-rich major mergers. At z (cid:2) 0.5, where merger signatures and dual nuclei can most easily be detected, we find that a more lenient W1 ? W2 > 0.5 cut greatly improves completeness without significantly decreasing reliability. Extreme nuclear starbursts are briefly able to mimic this AGN signature, but this is largely irrelevant in mergers, where such starbursts are accompanied by AGN. We propose a two-colour cut that yields high completeness and reliability even in starbursting systems. Further, we show that mid-IR colour selection very effectively identifies dual AGN hosts, with the highest fraction at the smallest separations (<3 kpc). Thus, many merger hosts of mid-IR AGN should contain unresolved dual AGN; these are ideal targets for high-resolution follow-up, particularly with the James Webb Space Telescope.
关键词： galaxies: interactions,infrared: galaxies,accretion,accretion discs,galaxies: active,black hole physics
更新于2025-09-23 15:21:21
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X-Ray, UV, and Radio Timing Observations of the Radio Galaxy 3C 120
摘要： We report the results of monitoring of the radio galaxy 3C?120 with the Neil Gehrels Swift Observatory, Very Long Baseline Array, and Mets?hovi Radio Observatory. The UV-optical continuum spectrum and R-band polarization can be explained by a superposition of an inverted-spectrum source with a synchrotron component containing a disordered magnetic ?eld. The UV-optical and X-ray light curves include dips and ?ares, while several superluminal knots appear in the parsec-scale jet. The recovery time of the second dip was longer at UV-optical wavelengths, in con?ict with a model in which the inner accretion disk (AD) is disrupted during a dip and then re?lled from outer to inner radii. We favor an alternative scenario in which occasional polar alignments of the magnetic ?eld in the disk and corona cause the ?ux dips and formation of shocks in the jet. Similar to observations of Seyfert galaxies, intra-band time lags of ?ux variations are longer than predicted by the standard AD model. This suggests that scattering or some other reprocessing occurs. The 37 GHz light curve is well-correlated with the optical-UV variations, with a ～20 day delay. A radio ?are in the jet occurred in a superluminal knot 0.14 milliarcseconds downstream of the 43 GHz “core,” which places the site of the preceding X-ray/UV/optical ?are within the core 0.5–1.3?pc from the black hole. The inverted UV-optical ?are spectrum can be explained by a nearly monoenergetic electron distribution with energy similar to the minimum energy inferred in the TeV γ-ray emitting regions of some BL?Lacertae objects.
关键词： ultraviolet: galaxies,accretion,galaxies: individual (3C 120),galaxies: active,accretion disks,X-rays: galaxies,radio continuum: galaxies
更新于2025-09-23 15:21:21
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Exploring inside-out Doppler tomography: non-magnetic cataclysmic variables
摘要： Context.Doppler tomography is a technique that has revolutionised the interpretation of the phase-resolved spectroscopic observations of interacting binary systems. Aims. We present the results of our investigation of reversing the velocity axis to create an inside-out Doppler coordinate framework with the intent to expose overly compacted and enhance washed out emission details in the standard Doppler framework. Methods. The inside-out tomogram is constructed independently of the standard tomogram by directly projecting phase-resolved spectra onto an inside-out velocity coordinate frame. For the inside-out framework, the zero-velocity origin is transposed to the outer circumference and the maximum velocities to the origin of the velocity space. We test the technique on a simulated system and two real systems with easily identi?able features, namely the accretion disc and bright spot in WZ Sge, and spiral shocks in IP Peg. Results. Our tests show that there is a redistribution of the relative brightness of emission components throughout the tomograms, i.e., where the standard framework tends to concentrate and enhance lower velocity features towards the origin, the inside-out velocity framework tends to concentrate and enhance higher velocity features towards the origin. Conversely, the standard framework disperses and smears the higher velocities farther away from the origin whereas the inside-out framework disperses and smears the lower velocities. In addition, the projection of the accretion disc in velocity space now appears correctly orientated with the inner edge close to the maximum velocity origin and its outer edge closer to the zero-velocity outer circumference. Furthermore, the gas stream and secondary star are projected on the outside of the disc with the bright spot of the stream-disc impact region on the disc’s outer edge in the inside-out velocity space. Conclusions. We conclude that inside-out Doppler tomography complements the already powerful tomographic techniques in the analysis of spectroscopic emissions from interacting binary systems.
关键词： binaries: close,novae,accretion disks,cataclysmic variables,techniques: spectroscopic,accretion
更新于2025-09-23 15:21:21
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Detection of a 23.6 min periodic modulation in the optical counterpart of 3XMMJ051034.6–670353
摘要： We present high speed optical photometric observations made using the NTT and ULTRACAM of the optical counterpart of 3XMMJ051034.6–670353, which was recently identi?ed as an X-ray source showing a modulation on a period of 23.6 min. Although the optical counterpart is faint (g = 21.4), we ?nd that the u(cid:48)g(cid:48)r(cid:48) light curves show a periodic modulation on a period which is consistent with the X-ray period. We also obtained three low resolution spectra of 3XMMJ051034.6–670353 using the Gemini South Telescope and GMOS. There is no evidence for strong emission lines in the optical spectrum of 3XMMJ051034.6–670353. We compare and contrast the optical and X-ray observations of 3XMMJ051034.6–670353 with the ultra compact binaries HM Cnc and V407 Vul. We ?nd we can identify a distribution of binary masses in which stable direct impact accretion can occur.
关键词： novae,X-rays: stars,cataclysmic variables,accretion,binaries: close,accretion disks
更新于2025-09-23 15:21:01
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A physical model of the broad-band continuum of AGN and its implications for the UV/X relation and optical variability
摘要： We develop a new spectral model for the broad-band spectral energy distribution (SED) of active galactic nuclei (AGN). This includes an outer standard disc, an inner warm Comptonizing region to produce the soft X-ray excess and a hot corona. We tie these together energetically by assuming Novikov–Thorne emissivity, and use this to de?ne a size scale for the hard X-ray corona as equal to the radius where the remaining accretion energy down to the black hole can power the observed X-ray emission. We test this on three AGN with well-de?ned SEDs as well as on larger samples to show that the average hard X-ray luminosity is always approximately a few per cent of the Eddington luminosity across a large range of Eddington ratio. As a consequence, the radial size scale required for gravity to power the X-ray corona has to decrease with increasing Eddington fraction. For the ?rst time, we hardwire this into the spectral models, and set the hard X-ray spectral index self-consistently from the ratio of the hard X-ray luminosity to intercepted seed photon luminosity from the disc. This matches the observed correlation of steeper spectral index with increasing Eddington ratio, as well as reproducing the observed tight UV/X relation of quasars. We also include the reprocessed emission produced by the hot inner ?ow illuminating the warm Comptonization and standard disc regions and show that this predicts a decreasing amount of optical variability with increasing Eddington ratio as observed, though additional processes may also be required to explain the observed optical variability.
关键词： galaxies: Seyfert,accretion,black hole physics,accretion discs
更新于2025-09-23 15:21:01