Rolf P. Kudritzki

Metallicity in the Galactic Center: The Quintuplet cluster (2008)

Najarro, Francisco, Figer, Don F., Hillier, D. John, Geballe, T. R., Kudritzki, Rolf P.

We present a measurement of metallicity in the Galactic center Quintuplet Cluster made using quantitative spectral analysis of two Luminous Blue Variables (LBVs). The analysis employs line-blanketed...

Radial Velocities of Stars in the Galactic Center (2008)

Zhu, Qingfeng, Kudritzki, Rolf P., Figer, Donald F., Najarro, Francisco, Merritt, David

We present results from K band slit scan observations of a ~20''x20'' region of the Galactic center (GC) in two separate epochs more than five years apart. The high resolution (R>=14,000)...

The Arches Cluster Mass Function (2006)

Kim, Sungsoo S., Figer, Donald F., Kudritzki, Rolf P., Najarro, F.

We have analyzed H and K_s-band images of the Arches cluster obtained using the NIRC2 instrument on Keck with the laser guide star adaptive optics (LGS AO) system. With the help of the LGS AO system,...

Discovery of an Extraordinarily Massive Cluster of Red Supergiants (2006)

Figer, Donald F., MacKenty, John, Robberto, Massimo, Smith, Kester, Najarro, Francisco, Kudritzki, Rolf P., ...

We report the discovery of an extraordinarily massive young cluster of stars in the Galaxy, having an inferred total initial cluster mass comparable to the most massive young clusters in the Galaxy....

High spectral resolution observations of the massive stars in the galactic center (2006)

Tanner, Angelle, Figer, Donald F., Najarro, Fransisco, Kudritzki, Rolf P., Gilmore, Diane, Morris, Mark, ...

High Spectral Resolution Observations of the Massive Stars in the Galactic Center (2005)

Tanner, Angelle, Figer, Donald F., Najarro, Paco, Kudritzki, Rolf P., Gilmore, Diane, Morris, Mark, ...

We present high-resolution near-infrared spectra, obtained with the NIRSPEC spectrograph on the W. M. Keck II Telescope, of a collection of hot, massive stars within the central 25 arcseconds of the...

The Physical Properties and Effective Temperature Scale of O-type Stars as a Function of Metallicity. II. Analysis of 20 More Magellanic Cloud Stars, and Results from the Complete Sample (2005)

Massey, Philip, Puls, Joachim, Pauldrach, A. W. A., Bresolin, Fabio, Kudritzki, Rolf P., Simon, Theodore

We analyze the optical and UV spectra of an additional sample of 20 Magellanic Cloud O stars, and draw conclusions from the complete sample of 40 stars. We find (1) The SMC O3-7 dwarfs are about 4000...

Massive Stars in the SGR 1806-20 Cluster (2005)

Figer, Donald F., Najarro, Francisco, Geballe, T. R., Blum, R. D., Kudritzki, Rolf P.

We report the discovery of additional hot and massive stars in the cluster surrounding the soft gamma repeater SGR 1806-20, based upon UKIRT and Keck near-infrared spectroscopy. Of the newly...

Metallicity in the Galactic Center: The Arches cluster (2004)

Najarro, Francisco, Figer, Donald F., Hillier, D. John, Kudritzki, Rolf P.

We present a quantitative spectral analysis of five very massive stars in the Arches cluster, located near the Galactic center, to determine stellar parameters, stellar wind properties and, most...

The Double-Lined Spectrum of LBV 1806-20 (2004)

Figer, Donald F., Najarro, Francisco, Kudritzki, Rolf P.

Despite much theoretical and observational progress, there is no known firm upper limit to the masses of stars. Our understanding of the interplay between the immense radiation pressure produced by...

The Physical Properties and Effective Temperature Scale of O-type Stars as a Function of Metallicity. I. A Sample of 20 Stars in the Magellanic Clouds (2004)

Massey, Philip, Bresolin, Fabio, Kudritzki, Rolf P., Puls, Joachim, Pauldrach, A. W. A.

We have obtained HST and ground-based observations of a sample of 20 O-type stars in the LMC and SMC, including six of the hottest massive stars known (subtypes O2-3) in the R136 cluster. In general,...

A new extragalactic distance determination method using the flux-weighted gravity of late B and early A supergiants (2002)

Kudritzki, Rolf P., Bresolin, Fabio, Przybilla, Norbert

Stellar evolution calculations predict the flux-weighted gravity g/Teff^4 and absolute bolometric magnitude of blue supergiants to be strongly correlated. We use medium resolution multi-object...

Line-driven winds, ionizing fluxes and UV-spectra of hot stars at extremely low metallicity. I. Very massive O-stars (2002)

Kudritzki, Rolf P.

Wind models of very massive stars with metallicities in a range from 1E-4 to 1.0 solar are calculated using a new treatment of radiation driven winds with depth dependent radiative force multipliers...

An ionizing UV background dominated by massive stars (2000)

Haehnelt, Martin G., Madau, Piero, Kudritzki, Rolf P., Haardt, Francesco

We discuss implications of a stellar-dominated UV background at high redshifts. The composite spectrum of 29 LBGs evaluated by Steidel etal (2000) at =3.4 can be well fit by a stellar population with...

Generic Spectrum and Ionization Efficiency of a Heavy Initial Mass Function for the First Stars (2000)

Bromm, Volker, Kudritzki, Rolf P., Loeb, Abraham

We calculate the generic spectral signature of an early population of massive stars at high redshifts. For metal-free stars in the mass range of 100-1000 solar masses, we find that the combined...