Analysis of Galactic late-type O dwarfs: more constraints on the weak wind problem (2009)
Marcolino, W. L. F., Martins, F., Hillier, D. J., Lanz, T., Escolano, C.
We have investigated the stellar and wind properties of a sample of five late-type O dwarfs in order to address the weak wind problem. A grid of TLUSTY models was used to obtain the stellar...
Properties of WNh stars in the Small Magellanic Cloud: evidence for homogeneous evolution (2008)
Martins, F., Hillier, D. J., Bouret, J. C., Depagne, E., Foellmi, C., Marchenko, S., ...
We derive the physical properties of three WNh stars in the SMC to constrain stellar evolution beyond the main sequence at low metallicity and to investigate the metallicity dependence of the...
Zsargo, J., Hillier, D. J., Lanz, T., Leutenegger, M. A., Cohen, D.
We have studied superionization and X-ray line formation in the spectra of Zeta Pup using our new stellar atmosphere code (XCMFGEN) that can be used to simultaneously analyze optical, UV, and X-ray...
D. J. Hillier, F. Paresce, R. Lenzen
Direct measurement of the size and shape of the present-day stellar wind of η Carinae ⋆
NLTE Model of NGC 6543's Central Star and its Relation with the Surrounding Planetary Nebula (2008)
Georgiev, L. N., Peimbert, M., Hillier, D. J., Richer, M. G., Arrieta, A., Peimbert, A.
We analyze the chemical composition of the central star of the planetary nebula NGC 6543 based upon a detailed NLTE model of its stellar wind. The logarithmic abundances by number are H=12.00,...
The most massive stars in the Arches cluster (2008)
Martins, F., Hillier, D. J., Paumard, T., Eisenhauer, F., Ott, T., Genzel, R.
Massive stars in the galactic center (2008)
Martins, F., Hillier, D. J., Genzel, R., Eisenhauer, F., Ott, T., Gillessen, S., ...
Zsargo, J., Hillier, D. J., Georgiev, L. N.
We calculate the hydrogen and helium ionization in B[e] envelopes and explore their dependence on mass-loss and effective temperature. We also present simulated observations of the Halpha emission...
The periodicity of the eta Carinae events (2007)
Damineli, A., Corcoran, M. F., Hillier, D. J., Stahl, O., Levenhagen, R. S., Leister, N. V., ...
Extensive spectral observations of eta Carinae over the last cycle, and particularly around the 2003.5 low excitation event, have been obtained. The variability of both narrow and broad lines, when...
A multispectral view of the periodic events in eta Carinae (2007)
Damineli, A., Hillier, D. J., Corcoran, M. F., Stahl, O., Groh, J. H., Arias, J., ...
A full description of the 5.5-yr low excitation events in Eta Carinae is presented. We show that they are not as simple and brief as previously thought, but a combination of two components. The...
The interstellar and intrinsic polarizations of EZ CMa (2007)
T. J. Harries, I. D. Howarth, D. J. Hillier
We present multi-epoch, intermediate-dispersion linear spectropolarimetry of the pathological Wolf-Rayet star EZ CMa. The continuum polarization shows long-term quasi-periodic variations, both in...
Tailored Analyses of the WN8 Stars WR40 and WR16 (2007)
Herald Hillier And, J. E. Herald, D. J. Hillier
We present the results of tailored spectral analyses of two WN8 Wolf-Rayet stars: WR40 (HD 96548) and WR16 (HD 86161). These analyses were carried out utilizing line blanketed non-LTE model...
A spectropolarimetric survey of northern-hemisphere Wolf-Rayet stars (2007)
Harries Hillier And, T. J. Harries, D. J. Hillier, I. D. Howarth
We present a homogeneous, high-signal-to-noise spectropolarimetric survey of 16 northern-hemisphere Wolf-Rayet (WR) stars. A reduction in polarization at emissionline wavelengths -- the `line...
G. Koenigsberger, J. E. Herald, D. J. Hillier
A tailored analysis of the WN8 star WR 40
P. A. Crowther, Laurent Drissen, D. J. Hillier
HST/STIS spectroscopy of V1-- a recently discovered LBV in the extragalactic giant H ii region NGC 2363-- is analysed using a sophisticated non-LTE, line blanketed atmospheric code. Complementary...
Ejected Nebulae as Probe of Wolf-Rayet Lyman Continua (2007)
A. Pasquali, P. A. Crowther, W. Schmutz, D. J. Hillier
Abstract. We present the first results from our analysis of WR model atmospheres in the UV domain. Specifically, we test the model atmospheres derived for WR124 and WR18 from the Hillier & Miller...
A. Pasquali, M. Clampin, A. Nota, D. J. Hillier, O. L. Lupie
Abstract. We have taken advantage of the high spatial resolution attainable with the HST to map the linear polarization in the V band across the nebulosity surrounding Eta Car. There are several new...
The most massive stars in the Arches cluster (2007)
Martins, F., Hillier, D. J., Paumard, T., Eisenhauer, F., Ott, T., Genzel, R.
We study a sample composed of 28 of the brightest stars in the Arches cluster. We analyze K-band spectra obtained with the integral field spectrograph SINFONI on the VLT. Atmosphere models computed...
Stellar and wind properties of massive stars in the central parsec of the Galaxy (2007)
Martins, F., Genzel, R., Hillier, D. J., Eisenhauer, F., Paumard, T., Gillessen, S., ...
We study the stellar and wind properties of massive stars in the central cluster of the Galaxy. We use non-LTE atmosphere models including winds and line-blanketing to fit their H and K band spectra...
LBVs and the nature of the S Dor cycles: the case of AG Carinae (2007)
Groh, J. H., Damineli, A., Hillier, D. J.
We present the results of a detailed spectroscopic analysis of 20 years of observations of AG Carinae using the radiative transfer code CMFGEN. Among the conclusions of this work, we highlight the...
Eta Carinae across the 2003.5 minimum: Spectroscopic Evidence for Massive Binary Interactions (2007)
Nielsen, K. E., Corcoran, M. F., Gull, T. R., Hillier, D. J., Hamaguchi, K., Ivarsson, S., ...
We have analyzed high spatial, moderate spectral resolution observations of Eta Carinae obtained with the STIS from 1998.0 to 2004.3. The spectra show prominent P-Cygni lines in H I, Fe II and He I...
Stellar and wind properties of massive stars in the central parsec of the galaxy (2007)
Martins, F., Genzel, R., Hillier, D. J., Eisenhauer, F., Paumard, T., Gillessen, S., ...
Clumping in O-type Supergiants (2007)
Lanz, T., Hillier, D. J., Foellmi, C.
We have analyzed the spectra of seven Galactic O4 supergiants, with the NLTE wind code CMFGEN. For all stars, we have found that clumped wind models match well lines from different species spanning a...
Tracking the Clumping in OB Stars from UV to radio (2007)
Najarro, F., Puls, Joachim, Herrero, A., Hanson, M. M., Martín-Pintado, J., Hillier, D. J.
We review different line and continua diagnostics from the UV to radio, which can be utilized to simultaneously constrain the clumping structure throughout the stellar wind of massive OB stars.
Mass-loss rate and clumping in LBV stars : the impact of time-dependent effects (2007)
Groh, J. H., Hillier, D. J., Damineli, A.
This paper outlines a newly-developed method to include the effects of time variability in the radiative transfer code CMFGEN. It is shown that the flow timescale is often large compared to the...
On the influence of clumping on O and Wolf-Rayet spectra (2007)
Overwhelming observational and theoretical evidence suggests that the winds of massive stars are highly clumped. We briefly discuss the influence of clumping on model diagnostics and the difficulties...
Moffat, Anthony F. J., Hillier, D. J., Hamann, Wolf-Rainer, Owocki, S. P.
Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007
Moffat, Anthony F. J., Hillier, D. J., Hamann, Wolf-Rainer, Owocki, S. P.
Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007
On the influence of clumping on O and Wolf-Rayet spectra (2007)
Overwhelming observational and theoretical evidence suggests that the winds of massive stars are highly clumped. We briefly discuss the influence of clumping on model diagnostics and the difficulties...
Mass-loss rate and clumping in LBV stars : the impact of time-dependent effects (2007)
Groh, J. H., Hillier, D. J., Damineli, A.
This paper outlines a newly-developed method to include the effects of time variability in the radiative transfer code CMFGEN. It is shown that the flow timescale is often large compared to the...
Tracking the Clumping in OB Stars from UV to radio (2007)
Najarro, F., Puls, Joachim, Herrero, A., Hanson, M. M., Martín-Pintado, J., Hillier, D. J.
We review different line and continua diagnostics from the UV to radio, which can be utilized to simultaneously constrain the clumping structure throughout the stellar wind of massive OB stars.
Clumping in O-type Supergiants (2007)
Lanz, T., Hillier, D. J., Foellmi, C.
We have analyzed the spectra of seven Galactic O4 supergiants, with the NLTE wind code CMFGEN. For all stars, we have found that clumped wind models match well lines from different species spanning a...
Investor confusion and similarly identified securities (2007)
Davies, J.R., Hillier, D.J., Thamm, J.
This paper extends the analysis of Rashes (2001) to examine the co-movement of prices for a sample of UK equity securities with similar ticker symbols and names. In contrast to Rashes (2001), we find...
Detailed Far-UV to Optical Analysis of Four [WR] Stars (2006)
Marcolino, W. L. F., Hillier, D. J., De Araujo, F. X., Pereira, C. B.
We present far-UV to optical analyses of four hydrogen deficient central stars of planetary nebulae: BD+303639, NGC 40, NGC 5315 and NGC 6905. Using the radiative transfer code CMFGEN, we determined...
On the sensitivity of HeI singlet lines to the FeIV model atom in O stars (2006)
Najarro, F., Hillier, D. J., Puls, J., Lanz, T., Martins, F.
Recent calculations and analyses of O star spectra have revealed discrepancies between theory and observations, and between different theoretical calculations, for the strength of optical HeI singlet...
On the sensitivity of He I singlet lines to the Fe IV model atom in O stars (2006)
Najarro, F., Hillier, D. J., Puls, J., Lanz, T., Martins, F.
An analysis of changes in board structure during corporate governance reforms (2006)
This study examines the evolution of company board structure during a period of corporate governance reform. Using data over a time period following the publication of the Cadbury Report (1992) we...
An analysis of changes in board structure during corporate governance reforms (2006)
This study examines the evolution of company board structure during a period of corporate governance reform. Using data over a time period following the publication of the Cadbury Report (1992) we...
An analysis of changes in board structure during corporate governance reforms (2006)
This study examines the evolution of company board structure during a period of corporate governance reform. Using data over a time period following the publication of the Cadbury Report (1992) we...
AG Carinae: a Luminous Blue Variable with a high rotational velocity (2005)
Groh, J. H., Hillier, D. J., Damineli, A.
We report the detection of broad absorptions due to Si IV 4088-4116 A in the Luminous Blue Variable (LBV) AG Carinae during its last hot phase (2001-2003). Our NLTE spectral analysis, with the...
Zsargo, J., Hillier, D. J., Georgiev, L. N.
We present a new radiative transfer code for axi-symmetric stellar atmospheres and compare test results against 1D and 2D models with and without velocity fields. The code uses the short...
An examination of linear factor models in country equity asset allocation strategies (2005)
We examine the out of sample performance of country equity asset allocation strategies between January 1985 and February 2000 that use conditional versions of international asset pricing models to...
An examination of linear factor models in country equity asset allocation strategies (2005)
We examine the out of sample performance of country equity asset allocation strategies between January 1985 and February 2000 that use conditional versions of international asset pricing models to...
An examination of linear factor models in country equity asset allocation strategies (2005)
We examine the out of sample performance of country equity asset allocation strategies between January 1985 and February 2000 that use conditional versions of international asset pricing models to...
On the He II Emission In Eta Carinae and the Origin of Its Spectroscopic Events (2005)
Martin, J. C., Davidson, K., Humphreys, R. M., Hillier, D. J., Ishibashi, K.
We describe and analyze Hubble Space Telescope (HST) observations of transient emission near 4680 {\AA} in Eta Car, reported earlier by Steiner & Damineli (2004). If, as seems probable, this is He II...
A new calibration of stellar parameters of Galactic O stars (2005)
Martins, F., Schaerer, D., Hillier, D. J.
We present new calibrations of stellar parameters of O stars at solar metallicity taking non-LTE, wind, and line-blanketing effects into account. Gravities and absolute visual magnitudes are derived...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D.J., Leinert, Ch., ...
The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D.J., Leinert, Ch., ...
The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D. J., Leinert, Ch., ...
The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D.J., Leinert, Ch., ...
The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D.J., Leinert, C., ...
O stars with weak winds: the galactic case (2005)
Martins, F., Schaerer, D., Hillier, D. J., Meynadier, F., Heydari-Malayeri, M., Walborn, N. R.
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Leinert, Ch., Hillier, D. J.
The core of the nebula surrounding Eta Carinae was observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to spatially and spectrally isolate the warm dusty...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D. J., Leinert, Ch., ...
The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D.J., Leinert, C., ...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Leinert, C., Hillier, D.J.
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D.J., Leinert, C., ...
The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty...
The sub-arcsecond dusty environment of Eta Carinae (2005)
Chesneau, O., Min, M., Herbst, T., Hillier, D.J., Leinert, Ch., ...
The core of the nebula surrounding Eta Carinae has been observed with the VLT Adaptive Optics system NACO and with the interferometer VLTI/MIDI to constrain spatially and spectrally the warm dusty...
Equity issuance, CEO turnover and corporate governance (2005)
McColgan, P., Hillier, D.J., Linn, S.C.
There is substantial evidence on the effect of external market discipline on chief executive turnover decisions in poorly performing companies. In this study we present evidence on the role of...
Ownership Structure, Managerial Behaviour and Corporate Value (2005)
McColgan, P., Davies, J.R., Hillier, D.J.
The nonlinear relationship between corporate value and managerial ownership is well documented. This has been attributed to the onset of managerial entrenchment, which results in a decrease of...
Equity issuance, CEO turnover and corporate governance (2005)
McColgan, P., Hillier, D.J., Linn, S.C.
There is substantial evidence on the effect of external market discipline on chief executive turnover decisions in poorly performing companies. In this study we present evidence on the role of...
Equity issuance, CEO turnover and corporate governance (2005)
McColgan, P., Hillier, D.J., Linn, S.C.
There is substantial evidence on the effect of external market discipline on chief executive turnover decisions in poorly performing companies. In this study we present evidence on the role of...
We have analyzed the far-UV spectrum of two Galactic O4 stars, the O4If+ supergiant HD190429A and the O4V((f)) dwarf HD96715, using archival FUSE and IUE data. We have conducted a quantitative...
Zsargo, J., Hillier, D. J., Georgiev, L. N.
We discuss work toward developing a 2.5D non-LTE radiative transfer code. Our code uses the short characteristic method with modifications to handle realistic 3D wind velocities. We also designed...
A Change in the Physical State of $\eta$ Carinae? (2004)
Davidson, K., Martin, J. C., Humphreys, R. M., Ishibashi, K., Gull, T. R., Stahl, O., ...
During $\eta$ Car's spectroscopic event in mid-2003, the stellar wind's bright H$\alpha$ and H$\beta$ emission lines temporarily had a distinctive shape unlike that reported on any previous occasion,...
Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula (2004)
Corcoran, M. F., Hamaguchi, K., Gull, T., Davidson, K., Petre, R., Hillier, D. J., ...
We report the first detection of X-ray emission associated with the Homunculus Nebula which surrounds the supermassive star Eta Carinae. The emission is characterized by a temperature in excess of...
Evans, C. J., Crowther, P. A., Fullerton, A. W., Hillier, D. J.
We present quantitative studies of 8 late O and early B-type supergiants in the Magellanic Clouds using far-ultraviolet FUSE, ultraviolet IUE/HST and optical VLT-UVES spectroscopy. Temperatures,...
Puzzling wind properties of young massive stars in SMC-N81 (2004)
Martins, F., Schaerer, D., Hillier, D. J., Heydari-Malayeri, M.
We present a quantitative study of the stellar and wind properties of massive stars in the compact star forming region SMC-N81. Non-LTE spherically extended atmosphere models including...
Direct measurement of the size and shape of the present-day stellar wind of Eta Carinae (2003)
Van Boekel, R., Kervella, P., Schoeller, M., Herbst, T., Brandner, W., ...
We present new high angular resolution observations at near-IR wavelengths of the core of the Luminous Blue Variable Eta Carinae, using NAOS-CONICA at the VLT and VINCI at the VLT Interferometer...
Quantitative Spectroscopy of O Stars at Low Metallicity. O Dwarfs in NGC 346 (2003)
Lanz, T., Hillier, D. J., Heap, S. R., Hubeny, I., Lennon, D. J., ...
We present the results of a detailed UV and optical spectral analysis of the properties of 6 dwarf O-type stars in the SMC H II region NGC 346. Stellar parameters, chemical abundances, and wind...
The HST Treasury Project on Eta Carinae (2003)
Davidson, K., Ishibashi, K., Gull, T. R., Martin, J. C., Humphreys, R. M., Damineli, A., ...
This program is valuable for a broad range of stellar and nebularastrophysics, as well as data processing techniques and instrumentcharacteristics. While observing this objects mysterious...
Direct measurement of the size and shape of the present-day stellar wind of eta Carinae (2003)
Kervella, P., Scholler, M., Herbst, T., Brandner, W., Koter, A. De, ...
Direct measurement of the size and shape of the present-day stellar wind of Eta Carinae (2003)
Van Boekel, R., Kervella, P., Schöller, M., Herbst, T., Brandner, W., De Koter, A., ...
We present new high angular resolution observations at near-IR wavelengths of the core of the Luminous Blue Variable eta Carinae, using NAOS-CONICA at the VLT and VINCI at the VLT Interferometer...
Crowther, P. A., Hillier, D. J., Evans, C. J., Fullerton, A. W., De Marco, O., Willis, A. J.
We have undertaken quantitative analysis of four LMC and SMC O4--9.7 extreme supergiants using far-ultraviolet FUSE, ultraviolet IUE/HSTand optical VLT UVES spectroscopy. Extended, non-LTE model...
Kurosawa, R., Hillier, D. J., Pittard, J. M.
A newly developed 3-D Monte Carlo model is used, in conjunction with a multi-line non-LTE radiative transfer model, to determine the mass-loss rate of the Wolf-Rayet (W-R) star in the massive binary...
On the effective temperature scale of O stars (2001)
Martins, F., Schaerer, D., Hillier, D. J.
We rediscuss the temperature of O dwarfs based on new non-LTE line blanketed atmosphere models including stellar winds computed with the CMFGEN code of Hillier & Miller (1998). Compared to the latest...
An examination of resampled portfolio efficiency (2001)
We examined the out-of-sample performance of using resampled portfolio efficiency, an approach proposed in 1998, in international asset allocation strategies for the period January 1983 to May 2000....
An examination of resampled portfolio efficiency (2001)
We examined the out-of-sample performance of using resampled portfolio efficiency, an approach proposed in 1998, in international asset allocation strategies for the period January 1983 to May 2000....
An examination of resampled portfolio efficiency (2001)
We examined the out-of-sample performance of using resampled portfolio efficiency, an approach proposed in 1998, in international asset allocation strategies for the period January 1983 to May 2000....
Tree-Structured Grid Model of Line and Polarization Variability from Massive Binaries (2001)
We have developed a 3-D Monte Carlo radiative transfer model which computes line and continuum polarization variability for a binary system with an optically thick non-axisymmetric envelope. This...
Physical parameters of erupting Luminous Blue Variables: NGC 2363-V1 caught in the act (2000)
Drissen, L., Crowther, P. A., Smith, L. J., Robert, C., Hillier, D. J.
A quantitative study of the Luminous Blue Variable NGC 2363-V1 in the Magellanic galaxy NGC 2366 (D = 3.44 Mpc) is presented, based on ultraviolet and optical HST/STIS spectroscopy. Contemporary...
Far-UV FUSE spectroscopy of the OVI resonance doublet in Sand2 (WO) (2000)
Crowther, Paul A., Fullerton, A. W., Hillier, D. J., Brownsberger, K., Dessart, L., Willis, A. J., ...
We present Far-Ultraviolet Spectroscopic Explorer (FUSE) spectroscopy of Sand 2, a LMC WO-type Wolf-Rayet star, revealing the OVI resonance P Cygni doublet at 1032-38A. These data are combined with...
The gamma Velorum binary system. II. WR stellar parameters and the photon loss mechanism (2000)
De Marco, Orsola, Schmutz, W., Crowther, P. A., Hillier, D. J., Dessart, L., De Koter, A., ...
In this paper we derive stellar parameters for the Wolf-Rayet star in the gamma Velorum binary system (WR11), from a detailed non-LTE model of its optical and infrared spectra. Compared to the study...
The gamma Velorum binary system (2000)
Marco, O. De, Schmutz, W., Crowther, P.A., Hillier, D.J., Dessart, L., Koter, A. De, ...
Wolf-Rayet nebulae as tracers of stellar ionizing fluxes: I. M1-67 (1999)
Crowther, P. A., Pasquali, A., De Marco, O., Schmutz, W., Hillier, D. J., De Koter, A.
We use WR124 (WN8h) and its associated nebula M1-67, to test theoretical non-LTE models for Wolf-Rayet (WR) stars. Lyman continuum ionizing flux distributions derived from a stellar analysis of...
Wolf-Rayet nebulae as tracers of stellar ionizing fluxes: I. M1-67 (1999)
Crowther, P.A., Pasquali, A., De Marco, O., Schmutz, W., Hillier, D.J., Koter, A. De
Ionized outflows of hot stars (1998)
Najarro, F., Kudritzki, R.P., Hillier, D.J., Voors, R.H.M., Morris, P.W., ...