Search Publications
ISO spectroscopy of disks around Herbig Ae/Be stars
van den Ancker, M. E.; Acke, B.
We have investigated the infrared spectra of all 46 Herbig Ae/Be stars for which spectroscopic data are available in the ISO data archive. Our quantitative analysis of these spectra focuses on the emission bands at 3.3, 6.2, ``7.7'', 8.6 and 11.2 micron, linked to polycyclic aromatic hydrocarbons (PAHs), the nanodiamond-related features at 3.4 and…
Discovery of a Transient Magnetar: XTE J1810-197
Safi-Harb, Samar; Hurley, Kevin; Kouveliotou, Chryssa +10 more
We report the discovery of a new X-ray pulsar, XTE J1810-197, that was serendipitously discovered on 2003 July 15 by the Rossi X- Ray Timing Explorer (RXTE) while observing the soft gamma repeater SGR 1806-20. The pulsar has a 5.54 s spin period, a soft X-ray spectrum (with a photon index of ~4), and is detectable in earlier RXTE observations back…
Resistive Emergence of Undulatory Flux Tubes
Aulanier, G.; Schmieder, B.; Pariat, E. +3 more
During its 2000 January flight, the Flare Genesis Experiment observed the gradual emergence of a bipolar active region, by recording a series of high-resolution photospheric vector magnetograms and images in the blue wing of the Hα line. Previous analyses of these data revealed the occurrence of many small-scale, transient Hα brightenings identifi…
Resolution of the MACHO-LMC-5 Puzzle: The Jerk-Parallax Microlens Degeneracy
Gould, Andrew
By extending the constant-acceleration analysis of Smith, Mao, & Paczyński to include jerk, I show that microlens parallax measurements are subject to a four-fold discrete degeneracy. The new degeneracy is characterized by a projected velocity vj=-(3/4)cscβec(cos2ψsin2βec+sin2ψ)3/2v⊕, wher…
Interstellar Carbon in Translucent Sight Lines
Sofia, Ulysses J.; Meyer, David M.; Lauroesch, James T. +1 more
We report interstellar C II column densities or upper limits determined from weak absorption of the 2325.4029 Å intersystem transition observed in six translucent sight lines (AV>~1) with the Space Telescope Imaging Spectrograph (STIS). The sight lines sample a wide range of interstellar characteristics, including total to selective …
The Effect of Metallicity on Cepheid-based Distances
Ferrarese, Laura; Saha, Abhijit; Sakai, Shoko +1 more
We have used the Wide Field Planetary Camera 2 on board the Hubble Space Telescope to obtain V and I images of seven nearby galaxies. For each, we have measured a distance using the tip of the red giant branch (TRGB) method. By comparing the TRGB distances with published Cepheid distances, we investigate the metallicity dependence of the Cepheid p…
The local surface density of disc matter mapped by Hipparcos
Flynn, Chris; Holmberg, Johan
We determine the surface density of matter in the disc of the Galaxy at the solar position using K giant stars. The local space density and luminosity function of the giants is determined using parallaxes from the Hipparcos satellite; for more distant giants, observed in a cone at the South Galactic Pole, distances are determined using intermediat…
On the nature of EIT waves, EUV dimmings and their link to CMEs
Zhukov, A. N.; Auchère, F.
EIT waves and extreme-ultraviolet (EUV) dimmings attract particular attention as they frequently accompany Coronal Mass Ejections (CMEs). We present several examples of EIT waves and EUV dimmings with particular morphologies previously unreported in the literature. We report for the first time an EIT wave in the Fe XV (284 Å) bandpass of the SOHO/…
Evidence for a New Elliptical-Galaxy Paradigm: Sérsic and Core Galaxies
Graham, Alister W.; Trujillo, I.; Asensio Ramos, A. +1 more
We fitted the surface-brightness profiles of 21 elliptical galaxies using both the Sérsic function and a new empirical model that combines an inner power law with an outer Sérsic function. The profiles are combinations of deconvolved Hubble Space Telescope (HST) profiles from the literature and ellipse fits to the full WFPC2 mosaic images and thus…
Grids of model spectra for WN stars, ready for use
Hamann, W. -R.; Gräfener, G.
Grids of model atmospheres for Wolf-Rayet stars of the nitrogen sequence (WN subclass) are presented. The calculations account for the expansion of the atmosphere, non-LTE, clumping, and line blanketing from iron-group elements. Observed spectra of single Galactic WN stars can in general be reproduced consistently by this generation of models. The…