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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…
Simultaneous Ultraviolet and X-Ray Observations of the Seyfert Galaxy NGC 4151. II. Physical Conditions in the UV Absorbers
Gull, T. R.; Kriss, G. A.; Turner, T. J. +8 more
We present a detailed analysis, including photoionization modeling, of the intrinsic absorption in the Seyfert 1 galaxy NGC 4151 using ultraviolet (UV) spectra from the Hubble Space Telescope Space Telescope Imaging Spectrograph and the Far Ultraviolet Spectrographic Explorer obtained 2002 May as part of a set of contemporaneous observations that …
Electron oscillations in the induced martian magnetosphere
Coates, A. J.; Kallio, E.; Fedorov, A. +42 more
The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment flown on the Mars Express (MEX) spacecraft includes the Electron Spectrometer (ELS) as part of its complement. The ELS instrument measures the differential electron flux spectrum in a 128-level logarithmic energy sweep within a time period of 4 s. The orbital path of MEX trave…
First ENA observations at Mars: ENA emissions from the martian upper atmosphere
Coates, A. J.; Kallio, E.; Fedorov, A. +44 more
The neutral particle detector (NPD) on board Mars Express has observed energetic neutral atoms (ENAs) from a broad region on the dayside of the martian upper atmosphere. We show one such example for which the observation was conducted at an altitude of 570 km, just above the induced magnetosphere boundary (IMB). The time of flight spectra of these…