Search Publications
Permitted Oxygen Abundances and the Temperature Scale of Metal-poor Turnoff Stars
Meléndez, Jorge; Shchukina, Nataliya G.; Vasiljeva, Irina E. +1 more
We use high-quality VLT/UVES published data of the permitted O I triplet and Fe II lines to determine oxygen and iron abundances in unevolved (dwarfs, turnoff, subgiants) metal-poor halo stars. The calculations have been performed both in LTE and non-LTE (NLTE), employing effective temperatures obtained with the new infrared flux method (IRFM) tem…
Large-Scale Zonal Flows Near the Solar Surface
Thompson, M. J.; Howe, R.; Komm, R. +5 more
Migrating bands of weak, zonal flow, associated with the activity bands in the solar cycle, have been observed at the solar surface for some time. More recently, these flows have been probed deep within the convection zone using global helioseismology and examined in more detail close to the surface with the techniques of local helioseismology. We…
Masses of Astrometrically Discovered and Imaged Binaries: G78-28AB and GJ 231.1BC
Ireland, Michael J.; Martinache, Frantz; Lloyd, James P. +5 more
The Stellar Planet Survey (STEPS) is an ongoing astrometric search for giant planets and brown dwarfs around a sample of ~30 M dwarfs. We have discovered several low-mass companions by measuring the motion of our target stars relative to their reference frames. The highest mass discovery thus far is G78-28B, a companion to the M dwarf G78-28A. The…
The infrared Hourglass cluster in M8*†
Maíz Apellániz, J.; Barbá, R. H.; Rubio, M. +2 more
A detailed study of the Hourglass nebula in the M8 star-forming region is presented. The study is mainly based on recent subarcsec-resolution JHKs images taken at Las Campanas Observatory and complemented with archival Hubble Space Telescope (HST) images and long-slit spectroscopy retrieved from the European Southern Observatory Archive…
3D spectroscopy with VLT/GIRAFFE. II. Are luminous compact galaxies merger remnants?
Östlin, G.; Flores, H.; Hammer, F. +2 more
Luminous Compact Galaxies (LCGs) are enigmatic sources in many aspects. They can reach the luminosity of the Milky Way within a radius of only a few kpc. They also represent one of the most rapidly evolving populations of galaxies since they represent up to 1/5 of the luminous galaxies at redshift z= 0.7, while being almost absent in the local Uni…
How extreme are the Wolf-Rayet clusters in NGC3125?*
Crowther, P. A.; Hadfield, L. J.
We reinvestigate the massive stellar content of the irregular dwarf galaxy NGC3125 (Tol 3) using Very Large Telescope (VLT)/FORS1 imaging and spectroscopy, plus archival VLT/ISAAC, Hubble Space Telescope (HST)/FOC and HST/STIS data sets. FORS1 narrow-band imaging confirms that the NGC3125-A and -B knots represent the primary sites of Wolf-Rayet (W…
Two years of INTEGRAL monitoring of the soft gamma-ray repeater SGR 1806-20: from quiescence to frenzy
Hurley, K.; Sunyaev, R.; Götz, D. +16 more
SGR 1806-20 has been observed for more than 2 years with the INTEGRAL satellite. In this period the source went from a quiescent state into a very active one culminating in a giant flare on December 27, 2004. Here we report on the properties of all the short bursts detected with INTEGRAL before the giant flare. We derive their number-intensity dis…
Deep Chandra and Multicolor HST Follow-up of the Jets in Two Powerful Radio Quasars
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +5 more
We present deep (70-80 ks) Chandra and multicolor HST ACS images of two jets hosted by the powerful quasars 1136-135 and 1150+497, together with new radio observations. The sources have an FR II morphology and were selected from our previous X-ray and optical jet survey for detailed follow-up aimed at obtaining better constraints on the jet multiw…
A statistical comparison of solar wind sources of moderate and intense geomagnetic storms at solar minimum and maximum
Liemohn, Michael W.; Thomsen, Michelle F.; Weygand, James M. +3 more
Superposed epoch analyses of 549 storms are performed to make a comparison of solar wind features of geomagnetic storm events at solar minimum (July 1974 to June 1977; July 1984 to June 1987; July 1994 to June 1997) and solar maximum (January 1979 to December 1981; January 1989 to December 1991; July 1999 to June 2002). In this study, geomagnetic …
Large-scale source regions of earth-directed coronal mass ejections
Zhang, J.; Wang, J. X.; Zhou, G. P.
Based on SOHO/MDI, EIT, Yohkoh/SXT, Hα, and other relevant observations, we analyzed all the earth-directed halo coronal mass ejections (CMEs) in the interval from Mar. 1997 to Dec. 2003. A total of 288 earth-directed CMEs were studied and their associated surface activity events identified. Unlike the previous studies that often attributed a surf…