Iron Line Equivalent Width Research Articles

Changes in the distribution of circum-binary material around the HMXB GX 301-2 during a rapid spin-up episode of the neutron star

ABSTRACT Some accretion-powered X-ray pulsars with supergiant companion stars undergo occasional rapid spin-up episodes that last for weeks to a few months. We explore the changes in the accretion environment of the pulsar GX 301-2 during its latest 80 days long spin-up episode in 2019 when the spin frequency of the pulsar increased by ∼2 per cent over two orbits of the binary. By performing time-resolved spectroscopy with the MAXI/GSC spectra of the source, we estimated the equivalent hydrogen column density and equivalent width of the iron fluorescence line during the spin-up episode, and compared them with the long-term average values estimated by orbital-phase-resolved spectroscopy. The measured absorption column density during the spin-up episode is about twice that of an average orbit, while the equivalent width of the iron line is less than half of an average orbit. Though the spin-up episode started immediately after a pre-periastron flare and lasted for the two consecutive orbits of the binary, the associated enhancement in luminosity started a few days after the pre-periastron flare and lasted only during the first orbit, and some enhancement was seen again during the pre-periastron passage of the second orbit. The absorption column density and iron line equivalent width vary throughout the spin-up episode and are distinct from an average orbit. These observations indicate a significant change in the accretion and reprocessing environment in GX 301-2 during the spin-up episode and may hold important clues for the phenomenon in this source and several other sources with supergiant companions.

Chandra Observations of Excess Fe Kα Line Emission in Galaxies with High Star Formation Rates: X-Ray Reflection on Galaxy Scales?

Abstract In active galactic nuclei (AGNs), fluorescent Fe Kα (iron) line emission is generally interpreted as originating from obscuring material around a supermassive black hole on the scale of a few parsecs. However, recent Chandra studies indicate the existence of iron line emission extending to kiloparsec scales in the host galaxy. The connection between iron line emission and large-scale material can be spatially resolved directly only in nearby galaxies, but could be inferred in more distant AGNs by a connection between line emission and star-forming gas and dust that is more extended than the parsec-scale torus. Here we present the results from a stacking analysis and X-ray spectral fitting performed on sources in the Chandra Deep Field South (CDFS) 7 Ms observations. From the deep stacked spectra, we select sources with stellar mass at 0.5 < z < 2, obtaining 25 sources with high-infrared (IR) luminosity (star formation rate, SFRFIR ≥ 17 M ☉ yr−1) and 32 sources below this threshold. We find that the equivalent width (EW) of the iron line EW(Fe) is a factor of three higher with 3σ significance for high-IR luminosity measured from Herschel observations, indicating a connection between iron line emission and star-forming material on galaxy scales. We show that there is no significant dependence of the EW(Fe) on M * or X-ray luminosity, suggesting that the reflection of AGN X-ray emission over large scales in their host galaxies may be widespread.

A receding torus model for the Iwasawa–Taniguchi effect for Compton-thick AGN

Recently, Boorman et al. (2018) reported on the discovery of the Iwasawa-Taniguchi (I-T) effect (a.k.a. X-ray Baldwin effect) for Compton-thick AGN. They measured a decrease of the 6.4 keV iron line equivalent width with the 12mu luminosity, assumed as a proxy for the intrinsic X-ray luminosity, which in Compton-thick AGN is not directly observable. One of the most popular explanations of the classic I-T effect is the so-called receding torus model, i.e. the decrease of the covering factor of the molecular `torus' with X-ray luminosity. In this paper we show that an I-T effect for Compton-thick AGN is indeed expected in the receding torus model, assuming that the torus is funnelling the primary X-ray luminosity which is then scattered in a `hot mirror'. We found that the observed relation is well reproduced provided that the typical column density of the `hot mirror' is about 7.5x10^{22} cm^{-2}.

Suzaku observation of the eclipsing high mass X-ray binary pulsar XTE J1855-026

We report results from analysis performed on an eclipsing supergiant high mass X-ray binary pulsar XTE J1855-026 observed with the X-ray Imaging Spectrometer (XIS) on-board Suzaku Observatory in April 2015. Suzaku observed this source for a total effective exposure of $$\sim $$ 87 ks just before an eclipse. Pulsations are clearly observed and the pulse profiles of XTE J1855-026 did not show significant energy dependence during this observation consistent with previous reports. The time averaged energy spectrum of XTE J1855-026 in the 1.0–10.5 keV energy range can be well fitted with a partial covering power law model modified with interstellar absorption along with a black-body component for soft excess and a gaussian for iron fluorescence line emision. The hardness ratio evolution during this observation indicated significant absorption of soft X-rays in some segments of the observation. For better understanding of the reason behind this, we performed time-resolved spectroscopy in the 2.5–10.5 keV energy band which revealed significant variations in the spectral parameters, especially the hydrogen column density and iron line equivalent width with flux. The correlated variations in the spectral parameters indicate towards the presence of clumps in the stellar wind of the companion star accounting for the absorption of low energy X-rays in some time segments.

Phase-resolved spectroscopy of low-frequency quasi-periodic oscillations in GRS 1915+105

X-ray radiation from black hole binary (BHB) systems regularly displays quasi-periodic oscillations (QPOs). In principle, a number of suggested physical mechanisms can reproduce their power spectral properties, thus more powerful diagnostics which preserve phase are required to discern between different models. In this paper, we first find for two Rossi X-ray Timing Explorer observations of the BHB GRS 1915+105 that the QPO has a well-defined average waveform. That is, the phase difference and amplitude ratios between the first two harmonics vary tightly around a well-defined mean. This enables us to reconstruct QPO waveforms in each energy channel, in order to constrain QPO phase-resolved spectra. We fit these phase-resolved spectra across 16 phases with a model including Comptonization and reflection (Gaussian and smeared edge components) to find strong spectral pivoting and a modulation in the iron line equivalent width. The latter indicates the observed reflection fraction is changing throughout the QPO cycle. This points to a geometric QPO origin, although we note that the data presented here do not entirely rule out an alternative interpretation of variable disc ionization state. We also see tentative hints of modulations in the iron line centroid and width which, although not statistically significant, could result from a non-azimuthally symmetric QPO mechanism.

Suzaku Observation of the Supergiant Fast X-Ray Transient AX J1841.0−0536

We observed the supergiant fast X-ray transient AX J1841.0$-$ 0536 with Suzaku in 2011 March. Many short flares with time-scales of a few hundred seconds and a large flare with a peak flux (1.0–10 keV) of $ \gtrsim$ 2 $ \times$ 10$ ^{-10}$ erg s$ ^{-1}$ cm$ ^{-2}$ were detected. The broad-band (1.0–40 keV) spectrum was fitted with a cut-off power-law continuum plus a K$ \alpha$ line from a neutral iron absorbed by partial covering gas. In addition, a broad absorption feature was found in a high-energy band. The photon index of the power-law is 1.01 $ \pm$ 0.12 in a low-luminosity state, and decreases (becomes hard) with increasing luminosity. On the other hand, the absorption column density and the iron line equivalent width are nearly constant. The covering fraction does not vary significantly, except for the full coverage epoch at the end of the large flare. We thus propose that the X-ray emission is due to subsequent in-falls of many small blobs.

X-RAY SPECTROSCOPY OF THE HIGH-MASS X-RAY BINARY PULSAR CENTAURUS X-3 OVER ITS BINARY ORBIT

We present a comprehensive spectral analysis of the high mass X-ray binary (HMXB) pulsar Centaurus X-3 with the Suzaku observatory covering nearly one orbital period. The light curve shows the presence of extended dips which are rarely seen in HMXBs. These dips are seen up to as high as ~40 keV. The pulsar spectra during the eclipse, out-of-eclipse, and dips are found to be well described by a partial covering power-law model with high energy cut-off and three Gaussian functions for 6.4 keV, 6.7 keV, and 6.97 keV iron emission lines. The dips in the light curve can be explained by the presence of an additional absorption component with high column density and covering fraction, the values of which are not significant during the rest of the orbital phases. The iron line parameters during the dips and eclipse are significantly different compared to those during the rest of the observation. During the dips, the iron line intensities are found to be lesser by a factor of 2--3 with significant increase in the line equivalent widths. However, the continuum flux at the corresponding orbital phase is estimated to be lesser by more than an order of magnitude. Similarities in the changes in the iron line flux and equivalent widths during the dips and eclipse segments suggests the dipping activity in Cen X-3 is caused by obscuration of the neutron star by dense matter, probably structures in the outer region of the accretion disk, as in case of dipping low mass X-ray binaries.

Variations in the X-ray eclipse transitions of Cen X-3

We report here an investigation of the X-ray eclipse transitions of the high mass X-ray binary pulsar Cen X-3 in different intensity states. The long term light curve of Cen X-3 obtained with RXTE-ASM spanning more than 5000d shows strong aperiodic flux variations with low and high states. We have investigated the eclipse transitions of Cen X-3 in different intensity states with data obtained from pointed observations with the more sensitive instruments onboard ASCA, BeppoSAX, XMM-Newton, Chandra and RXTE. We found a very clear trend of sharp eclipse transitions in the high state and longer transitions in the low state. This is a confirmation of this feature first observed with the RXTE-ASM but now observed with much better clarity. From the light curves obtained from several missions, it is seen that the eclipse egress in the low state starts earlier by an orbital phase of 0.02 compared to the eclipse egress in the high state indicating that the observed X-rays originate from a much larger region. We have also performed spectral analysis of the post-eclipse part of each observation. From BeppoSAX observations, the out-of-eclipse X-ray flux is found to differ by a factor of ∼26 during the high and low intensity states while the eclipse count rates differ by a factor of only ∼ 4.7. This indicates that in the low state, there is an additional scattering medium which scatters some of the source photons towards the observer even when the neutron star is completely eclipsed. We could also resolve the three iron line components using XMM-Newton observation in the low state. By comparing the iron line equivalent width during the high and low states, it is seen that the width of the iron line is relatively large during the low state which supports the fact that significant reprocessing and scattering of X-rays takes place in the low state.

Seyfert galaxies in the local Universe (z ≤0.1): the average X-ray spectrum as seen byBeppoSAX

The BeppoSAX archive is currently the largest reservoir of high sensitivity simultaneous soft and hard-X ray data of Seyfert galaxies. From this database all the Seyfert galaxies (105 objects of which 43 are type I and 62 are type II) with redshift lower than 0.1 have been selected and analyzed in a homogeneous way. Taking advantage of the broad-band coverage of the BeppoSAX MECS and PDS instruments (~2-100 keV), the X-ray data so collected allow us to infer the average spectral properties of nearby Seyfert galaxies included in the original sample and, most notably the photon index (Γ ~ 1.8), the high-energy cut-off (Ec ~ 290 keV), and the relative amount of reflection (R ~ 1.0). The data collected have been used to test some basic assumptions of the unified scheme for active galactic nuclei. The distributions of the isotropic indicators used here (photon index, relative amount of reflection, high-energy cut-off and narrow FeKα energy centroid) are similar in type I and type II objects while the absorbing column and the iron line equivalent width significantly differ between the two classes of active galactic nuclei with type II objects displaying larger columns (NH ~ 3.71022 and 6.11023 cm-2 for type I and II objects respectively) and equivalent width (EW ~ 220 and 690 eV for type I and II sources respectively). Confirming previous results, the narrow FeKα line is consistent, in Seyfert 2, with being produced in the same matter responsible for the observed obscuration. These results support the basic picture of the unified model. Moreover, the presence of a X-ray Baldwin effect in Seyfert 1 has been measured using the 20-100 keV luminosity . Finally, the possible presence of a correlation between the photon index and the amount of reflection is confirmed thus indicating thermal Comptonization as the most likely origin of the high energy emission for the active galactic nuclei included in the original sample.

Broadband X‐Ray Spectroscopy of A0535+262 withSuzaku

The transient X-ray binary pulsar A0535+262 was observed with Suzaku on 2005 September 14 when the source was in the declining phase of the August-September minor outburst. The ~103 s X-ray pulse profile was strongly energy dependent, a double peaked profile at soft X-ray energy band (<3 keV) and a single peaked smooth profile at hard X-rays. The width of the primary dip is found to be increasing with energy. The broad-band energy spectrum of the pulsar is well described with a Negative and Positive power-law with EXponential (NPEX) continuum model along with a blackbody component for soft excess. A weak iron K_alpha emission line with an equivalent width ~25 eV was detected in the source spectrum. The blackbody component is found to be pulsating over the pulse phase implying the accretion column and/or the inner edge of the accretion disk may be the possible emission site of the soft excess in A0535+262. The higher value of the column density is believed to be the cause of the secondary dip at the soft X-ray energy band. The iron line equivalent width is found to be constant (within errors) over the pulse phase. However, a sinusoidal type of flux variation of iron emission line, in phase with the hard X-ray flux suggests that the inner accretion disk is the possible emission region of the iron fluorescence line.

Possible X‐Ray Diagnostic for Jet/Disk Dominance in Type 1 AGNs

Using Rossi X-Ray Timing Explorer Seyfert 1 and 1.2 data spanning 9 years, we study correlations between X-ray spectral features. The sample consists of 350 time-resolved spectra from 12 Seyfert 1 and 1.2 galaxies. Each spectrum is fitted to a model with an intrinsic power-law X-ray spectrum produced close to the central black hole that is reprocessed and absorbed by material around the black hole. To test the robustness of our results, we performed Monte Carlo simulations of the spectral sample. We find a complex relationship between the iron line equivalent width (EW) and the underlying power-law index (?). The data reveal a correlation between ? and EW, which turns over at ? 2, but finds a weak anticorrelation for steeper photon indices. We propose that this relationship is driven by dilution of a disk spectrum (which includes the narrow iron line) by a beamed jet component and hence could be used as a diagnostic of jet dominance. In addition, our sample shows a strong correlation between R and ?, but we find that it is likely the result of modeling degeneracies. We also see the X-ray Baldwin effect (an anticorrelation between the 2-10 keV X-ray luminosity and EW) for the sample as a whole, but not for the individual galaxies and galaxy types.

Swift and Suzaku Observations of the X-Ray Afterglow from the GRB 060105

Results are presented of early X-ray afterglow observations of GRB 060105 by Swift and Suzaku. The bright, long gamma-ray burst GRB 060105 triggered the Swift Burst Alert Telescope at 06:49:28 on 2006 January 5 ($T_0$). The Suzaku team commenced a pre-planned target of opportunity observation at 19 ks (5.3 hr) after the Swift trigger. The X-ray flux faded during observations from $6.8 \times 10^{-9} \,\mathrm{erg} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2}$ (at $T_0 + 87 \,\mathrm{s}$ with the Swift/XRT) to $1.5 \times 10^{-13} \,\mathrm{erg} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2}$ [at $T_0 + 94 \hbox{}{--} 101 \,\mathrm{ks}$ with the Suzaku X-ray Imaging Spectrometer (XIS)] in the 2–10 keV energy band. Following prompt emission and successive very steep decay, a shallow decay was observed from $T_0 + 187 \,\mathrm{s}$ to $T_0 + 1287 \,\mathrm{s}$. After an observation gap during $T_0 + (1.5 \hbox{}{--} 3) \;\mathrm{ks}$, an extremely early steep decay was observed in $T_0 + (4 \hbox{}{--} 30) \;\mathrm{ks}$. The lightcurve flattened again at $T_0 + 30 \,\mathrm{ks}$, and another steep decay followed from $T_0 + 50 \,\mathrm{ks}$ to the end of observations. Both steep decays exhibited decay indices of 2.3–2.4. This very early break, if it is a jet break, is the earliest case among X-ray afterglow observations, suggesting a very narrow jet whose opening angle is well below $1^\circ$. The unique Suzaku/XIS data allow us to set very tight upper limits on line emission or absorption in this GRB. For the reported pseudo-redshift of $z = 4.0 \pm 1.3$ the upper limit on the iron line equivalent width is 50 eV.

The XMM-Newton/INTEGRAL monitoring campaign of IGR J16318-4848

IGR J16318-4848 is the prototype and one of the more extreme examples of the new class of highly obscured Galactic X-ray sources discovered by INTEGRAL. A monitoring campaign on this source has been carried out by XMM-Newton and INTEGRAL, consisting in three simultaneous observations performed in February, March and August 2004. The long-term variability of the Compton-thick absorption and emission line complexes will be used to probe the properties of the circumstellar matter. A detailed timing and spectral analysis of the three observations is performed, along with the reanalysis of the XMM-Newton observation performed in February 2003. The results are compared with predictions from numerical radiative transfer simulations to derive the parameters of the circumstellar matter. Despite the large flux dynamic range observed (almost a factor 3 between observations performed a few months apart), the source remained bright (suggesting it is a persistent source) and Compton-thick (NH >1.2x10^24 cm-2). Large Equivalent Width (EW) emission lines from Fe Kalpha, Fe Kbeta and Ni Kalpha were present in all spectra. The addition of a Fe Kalpha Compton Shoulder improves the fits, especially in the 2004 observations. Sporadic occurrences of rapid X-ray flux risings were observed in three of the four observations. The Fe Kalpha light curve followed the continuum almost instantaneously, suggesting that the emission lines are produced by illumination of small-scale optically-thick matter around the high-energy continuum source. Using the iron line EW and Compton Shoulder as diagnostic of the geometry of the matter, we suggest that the obscuring matter is in a flattened configuration seen almost edge-on.

BeppoSAXView of Radio‐loud Active Galactic Nuclei

A systematic analysis of a large sample of radio-loud Active Galactic Nuclei available in the BeppoSAX public archive has been performed. The sample includes 3 Narrow Line Radio Galaxies (NLRG), 10 Broad Line Radio Galaxies (BLRG), 6 Steep Spectrum Radio Quasars (SSRQ), and 16 Flat Spectrum Radio Quasars (FSRQ). According to the unified models, these classes correspond to objects with increasing viewing angles. As expected, the presence of a non-thermal beamed component emerges clearly in FSRQ. This class shows in fact a featureless continuum (with the exception of 3C273), and a significantly flatter average spectral slope. On the contrary, traces of a non-thermal Doppler enhanced radiation are elusive in the other classes. We find that the iron line equivalent widths (EW) are generally weaker in radio- loud AGN than in Seyfert 1 galaxies, and confirm the presence of an X-ray Baldwin effect, i.e. a decrease of EW with the 2--10 keV luminosity (L) from Seyferts to BLRG and quasars. Since the EW--L anti-correlation is present also in radio-quiet AGN alone, this effect cannot be ascribed entirely to a strongly beamed jet component. Possible alternative interpretations are explored.

XMM-Newton observation of the bright Seyfert 1 galaxy, MCG+8-11-11

We report on the XMM-Newton observation of the bright Seyfert 1 galaxy, MCG+8-11-11. Data from the EPIC/p-n camera, the Reflection Gratings Spectrometers (RGS) and the Optical Monitor (OM) have been analyzed. The p-n spectrum is well fitted by a power law, a spectrally unresolved Fe Kalpha line, a Compton reflection component (whose large value, when compared to the iron line equivalent width, suggests iron underabundance), and absorption by warm material. Absorption lines are apparent in the RGS spectra, but their identification is uncertain and would require large matter velocities. The UV fluxes measured by the OM are well above the extrapolation of the X-ray spectrum, indicating the presence of a UV bump.

A changing inner radius in the accretion disc of Q0056–363?

Q0056-363 is the most powerful X-ray quasar known to exhibit a broad, likely relativistic iron line (Porquet & Reeves 2003, A&A, 408, 119). It has been observed twice by XMM–Newton, three and half years apart (July 2000 and December 2003). In the second observation, the UV and soft X-ray fluxes were fainter, the hard X-ray power law flatter, and the iron line equivalent width (EW) smaller than in the 2000 observation. These variations can all be explained, at least qualitatively, if the disc is truncated in the second observation. We report also on the possible detection of a transient, redshifted iron absorption line during the 2003 observation.

A light bending model for the X-ray temporal and spectral properties of accreting black holes

Some of the X-ray temporal and spectral properties of accreting black holes represent a challenge for current theoretical models. In particular, uncorrelated variability between direct continuum and reflection components (including the iron line, if present) has been reported in many cases. Here, we explore a light bending model in which we assume a primary source of X-rays located close to a central, maximally rotating Kerr black hole and illuminating both the observer at infinity and the accretion disc. We show that, due to strong light bending, the observed flux can vary by more than one order of magnitude as the height of the primary source above the accretion disc varies, even if its intrinsic luminosity is constant. We identify three different regimes in which the reflection-dominated component (and the iron line) is correlated, anticorrelated or almost independent with respect to the direct continuum. These regimes correspond to low, high and intermediate flux states of the X-ray source. As a general rule, the reflection component varies with much smaller amplitude than the continuum. X-ray observations of the Seyfert galaxy MCG-6-30-15 and of the Galactic black hole candidate XTE Jl 650-500 reveal that a series of predictions of our model is actually observed; the consistent behaviour of the iron line flux and equivalent width with respect to the direct continuum, as well as the increase of the relative strength of disc reflection as the flux drops, all match very well our predictions. The iron line profile is predicted to be narrower in high flux states and broader in (reflection-dominated) low flux states, in fairly good agreement with observations of the best-studied case of MCG-6-30-15. Observations of some other narrow-line Seyfert 1 galaxies (e.g. NGC 4051) also seem to support our model, which may explain what are otherwise puzzling characteristics of some sources. We also show that beaming along the equatorial plane can enhance the re-emission of narrow reflection features from distant material during low flux states providing a possible contribution to the observed X-ray Baldwin effect.

BeppoSAX observations of Mrk 841 and Mrk 335

We present and discuss BeppoSAX observations of Mrk 841 and Mrk 335, two Seyfert 1 galaxies in which previous observations have established the presence of soft excesses. We conrm the soft excess in both sources, even if for Mrk 841 a warm absorber provides a t almost as good as the one with a true excess. As far as the hard X-ray continuum is concerned, a Comptonization model provides a t as good as a power law and a physically sound solution for Mrk 841. For Mrk 335, the Comptonization model gives a result which is somewhat better on statistical ground, but rather problematic on physical ground. The most interesting results regard the reprocessing components. For Mrk 841 we nd a very large reflection continuum but an almost normal iron line equivalent width even if, within the errors, a solution in which both components are a factor2 larger than expected for an accretion disc is still marginally acceptable. If this is the case, an anisotropy of the primary emission seems the best explanation. On the contrary, in Mrk 335 we nd a very large iron line EW but a reflection component not accordingly large. In this case, the best solution seems to be in terms of reflection from an ionized disc.

The effects of a Comptonizing corona on the appearance of the reflection components in accreting black hole spectra

We discuss the effects of a Comptonizing corona on the appearance of the reflection components, and in particular of the reflection hump, in the X-ray spectra of accreting black holes. Indeed, in the framework of a thermal corona model, we expect that some (or even all, depending on the coronal covering factor) of the reflection features should cross the hot plasma, and thus suffer Compton scattering, before being observed. We have studied in detail the dependence of these effects on the physical (i.e. temperature and optical depth) and geometrical (i.e. inclination angle) parameters of the corona, concentrating on the slab geometry. Owing to the smoothing and shifting towards high energies of the Comptonized reflection hump, the main effects on the emerging spectra appear above 100 keV. We have also investigated the importance of such effects on the interpretation of the results obtained with the standard fitting procedures. We found that fitting Comptonization models, taking into account Comptonized reflection, by the usual cut-off power law + unComptonized reflection model may lead to an underestimation of the reflection normalization and an overestimation of the high-energy cut-off. We discuss and illustrate the importance of these effects by analysing recent observational results, such as those of the galaxy NGC 4258. We also find that the Comptonizing corona can produce and/or emphasize correlations between the reflection feature characteristics (like the iron line equivalent width or the covering fraction) and the X-ray spectral index, similar to those recently reported in the literature. We also underline the importance of these effects when dealing with accurate spectral fitting of the X-ray background.

GingaObservations of Hercules X‐1: Spectrum Dependence on 35 Day Phase

Her X-1 was observed with good coverage and good sensitivity over a wide range of 35 day phase with the Ginga LAC in 1988 and 1989. Although several small sections have been previously studied, the spectra from this full set of observations have not been analyzed previously. Main high, short high, and low state spectra all require a two component continuum (absorbed and unabsorbed). Dips and eclipses were identified and the behavior of spectral parameters outside these events is studied. Excluding dips/eclipses, the iron line energy is 6.60 keV (whereas during dips/eclipses, it drops to 6.4 keV); the column density of the absorbed component is NH 1024.0cm-2; and the power-law index is α 0.95. The iron line intensity is well correlated with the total continuum intensity, indicating that reprocessing is important at all times and that a major source of the iron line is the accretion column during main high. The iron line equivalent width (EW) varies between main high, short high, and low states, with mean values for each state of 0.48 keV, 0.66 keV, and 1.37 keV, respectively. The ratio of absorbed continuum to unabsorbed continuum, R, also varies with 35 day phase, and EW is correlated with R. The behaviors of absorbed and unabsorbed continuum normalizations, EW and R are consistent with the accretion-column inner-disk model of Scott, Leahy, & Wilson.