arXiv subjects

Dirk Grupe

Publications and source records attributed to Dirk Grupe.

At least 55 records · Page 3Linked to original sources

arXiv2013

The Burst Cluster: Dark Matter in a Cluster Merger Associated with the Short Gamma Ray Burst, GRB 050509B

We have identified a merging galaxy cluster with evidence of two distinct sub-clusters. The X-ray and optical data suggest that the subclusters are moving away from each other after closest approach. This cluster merger was discovered from observations of the well localized short-duration gamma-ray burst (GRB), GRB 050509B. The Swift/Burst Alert Telescope (BAT) source position is coincident with a cluster of galaxies ZwCl 1234.0+02916. The subsequent Swift/X-Ray Telescope (XRT) localization of the X-ray afterglow found the GRB coincident with 2MASX J12361286+2858580, a giant red elliptical galaxy in the cluster. Deep multi-epoch optical images were obtained to constrain the evolution of the GRB afterglow, including a 27480s exposure in the F814W band with Hubble Space Telescope Advanced Camera for Surveys (ACS), among the deepest imaging ever obtained towards a known galaxy cluster in a single passband. We perform a weak gravitational lensing analysis, including mapping the total mass distribution of the merger system. Combined with Chandra X-ray Observatory and Swift/XRT observations, we investigate the dynamical state of the merger to probe the nature of the dark matter component. Our weak gravitational lensing measurements reveal a separation of the X-ray centroid of the western subcluster from the center of the mass and galaxy light distributions, similar to that of the famous "Bullet cluster". We conclude that the "Burst cluster" is another candidate merger system for determining the nature of dark matter and for studying the environment of short GRBs. We discuss connections between the cluster dynamical state and/or matter composition and compact object mergers, the leading model for the origin of short GRBs. Finally, we present results from a weak lensing survey based on archival Very Large Telescope (VLT) images in the areas of 5 other short GRBs.

astro-ph.CO↗

arXiv2012

Multiwavelength Variations of 3C 454.3 during the November 2010 to January 2011 Outburst

We present multiwavelength data of the blazar 3C 454.3 obtained during an extremely bright outburst from November 2010 through January 2011. These include flux density measurements with the Herschel Space Observatory at five submillimeter-wave and far-infrared bands, the Fermi Large Area Telescope at gamma-ray energies, Swift at X-ray, ultraviolet (UV), and optical frequencies, and the Submillimeter Array at 1.3 mm. From this dataset, we form a series of 52 spectral energy distributions (SEDs) spanning nearly two months that are unprecedented in time coverage and breadth of frequency. Discrete correlation anlaysis of the millimeter, far-infrared, and gamma-ray light curves show that the variations were essentially simultaneous, indicative of co-spatiality of the emission, at these wavebands. In contrast, differences in short-term fluctuations at various wavelengths imply the presence of inhomegeneities in physical conditions across the source. We locate the site of the outburst in the parsec-scale core, whose flux density as measured on 7 mm Very Long Baseline Array images increased by 70 percent during the first five weeks of the outburst. Based on these considerations and guided by the SEDs, we propose a model in which turbulent plasma crosses a conical standing shock in the parsec-scale region of the jet. Here, the high-energy emission in the model is produced by inverse Compton scattering of seed photons supplied by either nonthermal radiation from a Mach disk, thermal emission from hot dust, or (for X-rays) synchrotron radiation from plasma that crosses the standing shock. For the two dates on which we fitted the model SED to the data, the model corresponds very well to the observations at all bands except at X-ray energies, where the spectrum is flatter than observed.

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arXiv2012

Supermassive black holes, pseudobulges, and the narrow-line Seyfert 1 galaxies

We present HST/ACS observations of ten galaxies that host narrow-line Seyfert 1 (NLS1) nuclei, believed to contain relatively smaller mass black holes accreting at high Eddington ratios. We deconvolve each ACS image into a nuclear point source (AGN), a bulge, and a disk, and fitted the bulge with a Sersic profile and the disk with an exponential profile. We find that at least five galaxies can be classified as having pseudobulges. All ten galaxies lie below the \mbh--L$_{bulge}$ relation, confirming earlier results. Their locus is similar to that occupied by pseudobulges. This leads us to conclude that the growth of BHs in NLS1s is governed by secular processes rather than merger-driven. Active galaxies in pseudobulges point to an alternative track of black hole--galaxy co-evolution. Because of the intrinsic scatter in black hole mass--bulge properties scaling relations caused by a combination of factors such as the galaxy morphology, orientation, and redshift evolution, application of scaling relations to determine BH masses may not be as straightforward as has been hoped.

astro-ph.CO↗

arXiv2012

A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift

We have compiled a catalog of optically-selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both UVOT and XRT observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ~60% which rises to ~85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about 0.3 dex to the quasar luminosity. We re-visit the alpha_ox-L_uv relation by selecting a clean sample with only type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared to studies that use non-simultaneous UV/optical and X-ray data. We only found a weak correlation between L/L_Edd and alpha_uv. We do not find significant correlations between alpha_x and alpha_ox, alpha_ox and alpha_uv, and alpha_x and Log L(0.3-10 keV). The correlations between alpha_uv and alpha_x, alpha_ox and alpha_x, alpha_ox and alpha_uv, L/L_Edd and alpha_x, and L/L_Edd and alpha_ox are stronger amongst low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state.

astro-ph.CO↗

arXiv2012

Correlation Analysis of a Large Sample of Narrow-Line Seyfert 1 Galaxies: Linking Central Engine and Host Properties

We present a statistical study of a large, homogeneously analyzed sample of narrow-line Seyfert 1 (NLS1) galaxies, accompanied by a comparison sample of broad-line Seyfert 1 (BLS1) galaxies. Optical emission-line and continuum properties are subjected to correlation analyses, in order to identify the main drivers of active galactic nuclei (AGN) correlation space, and of NLS1 galaxies in particular. For the first time, we have established the density of the narrow-line region as a key parameter in Eigenvector 1 space, as important as the Eddington ratio L/Ledd. This is important because it links the properties of the central engine with the properties of the host galaxy; i.e., the interstellar medium (ISM). We also confirm previously found correlations involving the line width of Hbeta, and the strength of the FeII and [OIII]5007 emission lines, and we confirm the important role played by L/Ledd in driving the properties of NLS1 galaxies. A spatial correlation analysis shows that large-scale environments of the BLS1 and NLS1 galaxies of our sample are similar. If mergers are rare in our sample, accretion-driven winds on the one hand, or bar-driven inflows on the other hand, may account for the strong dependence of Eigenvector 1 on ISM density.

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arXiv2011

Discovery of an Ultrasoft X-ray Transient Source in the 2XMM Catalog: a Tidal Disruption Event Candidate

We have discovered an ultrasoft X-ray transient source, 2XMMi J184725.1-631724, which was detected serendipitously in two XMM-Newton observations in the direction of the center of the galaxy IC 4765-f01-1504 at a redshift of 0.0353. These two observations were separated by 211 days, with the 0.2-10 keV absorbed flux increasing by a factor of about 9. Their spectra are best described by a model dominated by a thermal disk or a single-temperature blackbody component (contributing >80% of the flux) plus a weak power-law component. The thermal emission has a temperature of a few tens of eV, and the weak power-law component has a photon index of ~3.5. Similar to the black hole X-ray binaries in the thermal state, our source exhibits an accretion disk whose luminosity appears to follow the $L\propto T^4$ relation. This would indicate that the black hole mass is about 10^5-10^6 M_sun using the best-fitting inner disk radius. Both XMM-Newton observations show variability of about 21% on timescales of hours, which can be explained as due to fast variations in the mass accretion rate. The source was not detected by ROSAT in an observation in 1992, indicating a variability factor of >64 over longer timescales. The source was not detected again in X-rays in a Swift observation in 2011 February, implying a flux decrease by a factor of >12 since the last XMM-Newton observation. The transient nature, in addition to the extreme softness of the X-ray spectra and the inactivity of the galaxy implied by the lack of strong optical emission lines, makes it a candidate tidal disruption event. If this is the case, the first XMM-Newton observation would have been in the rising phase, and the second one in the decay phase.

astro-ph.HE↗

arXiv2011

Statistical Analysis of an AGN sample with Simultaneous UV and X-ray Observations with Swift

I report on the statistical analysis of a sample of about 100 AGN with simultaneous UV and X-ray observations with Swift. I found clear correlations between the X-ray spectral slope alpha-X, the UV slope alpha-UV, and the optical-to-x-ray spectral slope alpha-ox with the Eddington ratio L/Ledd. I also report on the bolometric corrections for L(0.2-2.0 keV) and L(5100A). A major aspect of the statistical analysis is multi-variate analysis statistical tools such as the Principal Component Analysis (PCA) and cluster analysis. This analysis shows that the main driver of the AGN properties in this sample is the Eddington ratio L/Ledd. Although separating Seyfert 1s into NLS1s and BLS1s is a good classification, with the 2000 km/s cutoff line it is still arbitrary. A better classification scheme may be to separate AGN into low and highL/Ledd AGN as suggested from the cluster analysis.

astro-ph.CO↗

arXiv2011

NGC 2207/IC 2163: A Grazing Encounter with Large Scale Shocks

Radio continuum, Spitzer infrared, optical and XMM-Newton X-ray and UVM2 observations are used to study large-scale shock fronts, young star complexes, and the galactic nuclei in the interacting galaxies NGC 2207/IC 2163. There are two types of large-scale shock fronts in this galaxy pair. The shock front along the rim of the ocular oval in IC 2163 has produced vigorous star formation in a dusty environment. In the outer part of the companion side of NGC 2207, a large-scale front attributed to disk or halo scraping is particularly bright in the radio continuum but not in any tracers of recent star formation or in X-rays. This radio continuum front may be mainly in the halo on the back side of NGC 2207 between the two galaxies. Values of the flux density ratio S(8 um)/S(6 cm) of kpc-sized, Spitzer IRAC star-forming clumps in NGC 2207/IC 2163 are compared with those of giant H II regions in M81. We find evidence that in 2001 a radio supernova was present in the core of feature i, a mini-starburst on an outer arm of NGC 2207. X-ray emission is detected from the NGC 2207 nucleus and from nine discrete sources, one of which corresponds to SN 1999ec, and another may be a radio supernova or a background quasar. The X-ray luminosity and X-ray spectrum of the NGC 2207 nucleus suggests it is a highly absorbed, low luminosity AGN.

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arXiv2010

The Simultaneous Optical-to-X-ray Spectral Energy Distribution of Soft X-ray Selected AGN observed by Swift

We report Swift observations of a sample of 92 bright soft X-ray selected active galactic nuclei (AGN). This sample represents the largest number of AGN observed to study the spectral energy distribution (SED) of AGN with simultaneous optical/UV and X-ray data. The principal motivation of this study is to understand the SEDs of AGN in the optical/UV to X-ray regime and to provide bolometric corrections which are important in determining the Eddington ratio L/Ledd. In particular, we rigorously explore the dependence of the UV-EUV contribution to the bolometric correction on the assumed EUV spectral shape. We find strong correlations of the spectral slopes alpha-x and alpha-UV with L/Ledd. Although Narrow-Line Seyfert 1 galaxies (NLS1s) have steeper alpha-x and higher L/Ledd than Broad-Line Seyfert 1 galaxies (BLS1s), their optical/UV to X-ray spectral slopes alpha-ox and optical/UV slopes alpha-UV are very similar. The mean SED of NLS1s shows that in general this type of AGN appears to be fainter in the UV and at hard X-ray energies than BLS1s. We find a strong correlation between alpha-x and alpha-UV for AGN with X-ray spectral slopes alpha-x<1.6. For AGN with steeper X-ray spectra, both this relation and the relation between alpha-x and L/Ledd break down. At alpha-x$\approx$1.6, L/Ledd reaches unity. We note an offset in the alpha-UV - L/Ledd relation between NLS1s and BLS1s. We argue that alpha-UV is a good estimator of L/Ledd and suggest that alpha-UV can be used to estimate L/Ledd in high-redshift QSOs. Although NLS1s appear to be highly variable in X-rays they only vary marginally in the UV.

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arXiv2010

Late-time detections of the X-ray afterglow of GRB 060729 with Chandra - the latest detections ever of an X-ray afterglow

We report on 5 Chandra observations of the X-ray afterglow of the Gamma-Ray Burst GRB 060729 performed between 2007 March and 2008 May. In all five observations the afterglow is clearly detected. The last Chandra pointing was performed on 2008-May-04, 642 days after the burst - the latest detection of a GRB X-ray afterglow ever. A reanalysis of the Swift XRT light curve together with the three detections by Chandra in 2007 reveals a break at about 1.0 Ms after the burst with a slight steepening of the decay slope from alpha = 1.32 to 1.61. This break coincides with a significant hardening of the X-ray spectrum, consistent with a cooling break in the wind medium scenario, in which the cooling frequency of the afterglow crosses the X-ray band. The last two Chandra observations in 2007 December and 2008 May provide evidence for another break at about one year after the burst. If interpreted as a jet break, this late-time break implies a jet half opening angle of about 14 degrees for a wind medium. Alternatively, this final break may have a spectral origin, in which case no jet break has been observed and the half-opening angle of the jet of GRB 060729 must be larger than about 15 degrees for a wind medium. We compare the X-ray afterglow of GRB 060729 in a wind environment with other bright X-ray afterglows, in particular GRBs 061121 and 080319B, and discuss why the X-ray afterglow of GRB 060729 is such an exceptionally long-lasting event.

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arXiv2010

Suzaku Monitoring of the Iron K Emission Line in the Type 1 AGN NGC 5548

We present 7 sequential weekly observations of NGC 5548 conducted in 2007 with the \textit{Suzaku} X-ray Imaging Spectrometer (XIS) in the 0.2-12 keV band and Hard X-ray Detector (HXD) in 10-600 keV band. The iron K$α$ line is well detected in all seven observations and K$β$ line is also detected in four observations. In this paper, we investigate the origin of the Fe K lines using both the width of the line and the reverberation mapping method. With the co-added XIS and HXD spectra, we identify Fe K$α$ and K$β$ line at 6.396$_{-0.007}^{+0.009}$ keV and 7.08$_{-0.05}^{+0.05}$ keV, respectively. The width of line obtained from the co-added spectra is 38$_{-18}^{+16}$ eV ($\textrm{FWHM}=4200_{-2000}^{+1800}$ km/s) which corresponds to a radius of 20$_{-10}^{+50}$ light days, for the virial production of $1.220\times10^7$ M$_{\odot}$ in NCG 5548. To quantitatively investigate the origin of the narrow Fe line by the reverberation mapping method, we compare the observed light curves of Fe K$α$ line with the predicted ones, which are obtained by convolving the continuum light curve with the transfer functions in a thin shell and an inclined disk. The best-fit result is given by the disk case with $i=30^\circ$ which is better than a fit to a constant flux of the Fe K line at the 92.7% level (F-test). We find that the emitting radius obtained from the light curve is 25-37 light days, which is consistent with the radius derived from the Fe K line width. Combining the results of the line width and variation, the most likely site for the origin of the narrow iron lines is 20-40 light days away from the central engine, though other possibilities are not completely ruled out. (abridged)

astro-ph.HE↗

arXiv2009

Emergence of a Broad-Absorption-Line Outflow in the Narrow-line Seyfert 1 Galaxy WPVS 007

We report results from a 2003 FUSE observation, and reanalysis of a 1996 HST observation of the unusual X-ray transient Narrow-line Seyfert 1 galaxy WPVS 007. The HST FOS spectrum revealed mini-BALs with V_max ~ 900 km s^-1 and FWHM ~ 550 km s^-1. The FUSE spectrum showed that an additional BAL outflow with V_max ~ 6000 km s^-1 and FWHM ~ 3400 km s^-1 had appeared. WPVS 007 is a low-luminosity object in which such a high velocity outflow is not expected; therefore, it is an outlier on the M_V/V_max relationship. Template spectral fitting yielded apparent ionic columns, and a Cloudy analysis showed that the presence of PV requires a high ionization parameter log(U) >= 0 and high column density log(N_H) >= 23 assuming solar abundances and a nominal SED for low-luminosity NLS1s with alpha_ox=-1.28. A recent long Swift observation revealed the first hard X-ray detection and an intrinsic (unabsorbed) alpha_ox ~ -1.9$. Using this SED in our analysis yielded lower column density constraints (log(N_H) >= 22.2 for Z=1, or log(N_H) >= 21.6 if Z=5). The X-ray weak continuum, combined with X-ray absorption consistent with the UV lines, provides the best explanation for the observed Swift X-ray spectrum. The large column densities and velocities implied by the UV data in any of these scenarios could be problematic for radiative acceleration. We also point out that since the observed PV absorption can be explained by lower total column densities using an intrinsically X-ray weak spectrum, we might expect to find PV absorption preferentially more often (or stronger) in quasars that are intrinsically X-ray weak.

astro-ph.CO↗

arXiv2009

GRB 060605: multi-wavelength analysis of the first GRB observed using integral field spectroscopy

The long and relatively faint gamma-ray burst GRB 060605 detected by \emph{Swift}/BAT lasted about 20 sec. Its afterglow could be observed with \emph{Swift}/XRT for nearly 1 day, while \emph{Swift}/UVOT could detect the afterglow during the first 6 hours after the event. Here, we report on integral field spectroscopy of its afterglow performed with PMAS/PPak mounted at the Calar Alto 3.5 m telescope. In addition, we report on a detailed analysis of XRT and UVOT data and on the results of deep late-time VLT observations that reveal the GRB host galaxy. We find that the burst occurred at a redshift of $z$=3.773, possibly associated with a faint, $R_C=26.4 \pm 0.3$ host. Based on the optical and X-ray data, we deduce information on the SED of the afterglow, the position of the cooling frequency in the SED, the nature of the circumburst environment, its collimation factor, and its energetics. We find that the GRB fireball was expanding into a constant-density medium and that the explosion was collimated with a narrow half-opening angle of about 2.4 degrees. The initial Lorentz factor of the fireball was about 250; however, its beaming-corrected energy release in the gamma-ray band was comparably low. The optical, X-ray afterglow, on the other hand, was rather luminous. Finally, we find that the data are consistent within the error bars with an achromatic evolution of the afterglow during the suspected jet break time at about 0.27 days after the burst.

astro-ph↗

arXiv2009

Black Hole Masses of Intermediate-Redshift Quasars: Near Infrared Spectroscopy

We present near-infrared spectra of ten luminous, intermediate redshift quasars observed with SofI at the NTT of ESO/La Silla. With these rest-frame optical spectra we probe the Hb -[OIII] emission line region. Using the standard scaling relation involving the width of the Hb line and the continuum luminosity, we measure black hole masses in the range of ~2x10^9 to 10^10 Msol. We also used SDSS spectra to probe MgII2798 and CIV1549 emission lines and used these for black hole mass measurements as well. The massive black holes we observe could not have grown by simple radiatively efficient accretion at the observed accretion rate starting from seeds of up to thousand solar masses. About 10% of the observed black hole mass must have been accumulated by earlier merger events and radiatively inefficient accretion. Radiatively efficient accretion would further grow these BHs to masses of several 10^9 Msol in 2 to 3 e-folding times i.e. in several 10^8yrs. The Hb-based Eddington luminosity ratios are in the range of ~0.2 to ~0.7, with an average of (Lbol/Ledd) = 0.39+-0.05. The Lbol/Ledd ratio distribution follows a log-normal distribution which is consistent with prior studies of quasars with comparable luminosity. The Lbol/Ledd ratio distribution of less luminous quasars tend to be shifted to lower Eddington ratios. We also find that the gas metallicity of the broad-line region is ~3Z/Zsol, using NIII]/OIII] and NV/CIV emission line ratios. We find no correlation of the gas metallicity with the optical FeII emission line strength.

astro-ph.CO↗

arXiv2008

First detection of hard X-ray photons in the soft X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007: The X-ray photon distribution observed by Swift

We report on the first detection of hard X-ray photons (E>2.5 keV) in the X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007 which was the AGN with the softest X-ray spectrum during the ROSAT All-Sky Survey. The AGN is clearly detected at a level of about 2 x 10^{-17} W m^{-2} in the observed 0.3-10.0 keV band by Swift in a 50 ks observation in 2007 September. For the first time since the ROSAT All-Sky Survey observation in 1990 it was possible to derive an X-ray photon distribution by adding together all Swift observations that have been performed so far (85.5 ks in total). This photon distribution is consistent with an X-ray spectrum of an AGN with a partial covering absorber with a column density in the order of ~ 1 x 10^{23} cm^{-2} and a covering fraction of about 90%. A comparison with the 2002 Chandra data suggests that WPVS 007 has become brighter by a factor of about 4. The Swift data also suggest that the absorber which is causing the current low-state may have started to disappear. This disappearance is indicated by a significant change in the hardness ratio from a very soft X-ray state during the 2005 October to 2007 January observations to a rather hard X-ray state in the 2007 September observations. In the UV, WPVS 007 seems to become fainter by up to 0.5 mag over the last two years. The optical to X-ray spectral slope derived from the spectral energy distribution is alpha-ox=2.5 which classifies WPVS 007 as an X-ray weak AGN. After correcting for reddening and X-ray absorption, alpha-ox becomes 1.9 and the luminosity in the Big-Blue-Bump is log LBBB=37.7 [W], which translates into an Eddington ratio L/LEdd ~ 1.0.

astro-ph↗

arXiv2008

XMM-Newton observations of the Narrow-Line Seyfert 1 galaxy Mrk 335 in an historical low X-ray flux state

We report the discovery of strong soft X-ray emission lines and a hard continuum above 2 keV in the Narrow-Line Seyfert 1 galaxy Mrk 335 during an extremely low X-ray flux state. Mrk 335 was observed for 22 ks by XMM-Newton in July 2007 as a Target of Opportunity to examine it in its X-ray low-flux state, which was discovered with Swift. Long-term light curves suggest that this is the lowest flux state this AGN has ever been seen in. However, Mrk 335 is still sufficiently bright that its X-ray properties can be studied in detail. The X-ray continuum spectrum is very complex and requires several components to model. Statistically, partial covering and blurred reflection models work well. We confirm the presence of a strong narrow Fe line at 6.4 keV. High-resolution spectroscopy with the XMM-RGS reveals strong, soft X-ray emission lines not detected in previous, higher signal-to-noise, XMM-Newton observations, such as: highly ionized Fe lines, O VII, Ne IX and Mg XI lines. The optical/UV fluxes are similar to those previously measured with Swift. Optical spectroscopy taken in 2007 September do not show any changes to optical spectra obtained 8 years earlier.

astro-ph↗

arXiv2007

Discovery of the Narrow-Line Seyfert 1 galaxy Mkn 335 in an historical low X-ray flux state

We report the discovery of the Narrow-Line Seyfert 1 galaxy Mkn 335 in an extremely low X-ray state. A comparison of Swift observations obtained in May and June/July 2007 with all previous X-ray observations between 1971 to 2006 show the AGN to have diminished in flux by a factor of more than 30, the lowest X-ray flux Mkn 335 has ever been observed in. The Swift observations show an extremely hard X-ray spectrum at energies above 2 keV. Possible interpretations include partial covering absorption or X-ray reflection from the disk. In this letter we consider the partial covering interpretation. The Swift observations can be well fit by a strong partial covering absorber with varying absorption column density N_H= 1-4 x 10^{23} cm-2 and a covering fraction f_c=0.9 - 1. When corrected for intrinsic absorption, the X-ray flux of Mkn 335 varies by only factors of 4-6. In the UV Mkn 335 shows variability in the order of 0.2 mag. We discuss the similarity of Mkn 335 with the highly variable NLS1 WPVS007, and speculate about a possible link between NLS1 galaxies and broad-absorption line quasars.

astro-ph↗

arXiv2007

Revisiting the Black Hole Masses of Soft X-ray-Selected Active Galactic Nuclei

In our previous work, using luminosity and the H-beta FWHM as surrogates for black hole mass (M_BH), we compared the black hole masses of narrow-line Seyfert 1 galaxies (NLS1s) and broad-line Seyfert 1 galaxies (BLS1s) in a sample of soft X-ray-selected active galactic nuclei. We found that the distributions of black hole masses in the two populations are statistically different. Recent work shows that the second moment of the H-beta emission line (the line dispersion) is a better estimator of black hole mass than FWHM. To test whether changing the width measure affects our results, we calculate line dispersion-based black hole masses for our sample. We find that using the line dispersion rather than the FWHM as a measure of the gas velocity shifts NLS1 and BLS1 virial product distributions closer together, but they remain distinct. On the M_BH-sigma plane, we find that using the line dispersion leaves NLS1s below the M_BH-sigma relation, but to a less significant degree than when FWHM is used to calculate black hole masses (the [OIII] 5007A FWHM is used as a surrogate for the bulge stellar velocity dispersion). The level of significance of our findings is such that we cannot draw firm conclusions on the location of the two samples on the M_BH-sigma plane. We are still left with two alternative scenarios: either (1) NLS1s lie below the M_BH-sigma relation indicating that their black hole masses are growing, or (2) NLS1s lie on the M_BH-sigma relation, so they preferentially reside in smaller mass, less luminous galaxies; the present data do not allow us to choose one over the other. More trustworthy stellar velocity dispersions and accurate black hole mass measurements are required for a firmer statement about the locus of NLS1s on the M_BH-sigma plane.

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