Search Publications
Oxygen abundances in metal-poor subgiants as determined from [O I], O I and OH lines
Gustafsson, B.; Asplund, M.; Nissen, P. E. +2 more
The debate on the oxygen abundances of metal-poor stars has its origin in contradictory results obtained using different abundance indicators. To achieve a better understanding of the problem we have acquired high quality spectra with the Ultraviolet and Visual Echelle Spectrograph at VLT, with a signal-to-noise of the order of 100 in the near ult…
The timing of relativistic proton acceleration in the 20 January 2005 flare
Simnett, G. M.
Understanding the energy budget in large solar flares requires a good knowledge of how and where the energetic charged particles are accelerated. If they are mainly accelerated by a Coronal Mass Ejection (CME)-driven shock, then they do not have to derive their energy from the flare region. Conversely, if the CME does not accelerate the particles,…
Heliospheric magnetic field polarity inversions driven by radial velocity field structures
Landi, Simone; Hellinger, Petr; Velli, Marco
Magnetic field polarity inversions embedded in the predominantly unipolar fast solar wind have been observed by the Ulysses spacecraft at high latitudes. Such reversals have the nature of folded back field lines which we suggest are generated by the interaction of standard large amplitude, low frequency, Alfvénic turbulence with velocity shears in…
Tracing Galaxy Assembly: Tadpole Galaxies in the Hubble Ultra Deep Field
Ryan, R. E.; Hathi, N. P.; Jansen, R. A. +3 more
In the Hubble Ultra Deep Field (HUDF) an abundance of galaxies is seen with a knot at one end plus an extended tail, resembling a tadpole. These ``tadpole galaxies'' appear dynamically unrelaxed-presumably in an early merging stage-where tidal interactions likely created the distorted knot-plus-tail morphology. Here we systematically select tadpol…
Ultraviolet-to-Far-Infrared Properties of Local Star-forming Galaxies
Giavalisco, M.; Leitherer, C.; Armus, L. +5 more
We present the results of a multiwavelength study of nearby galaxies aimed at understanding the relation between the ultraviolet and far-infrared emission in star-forming galaxies. The data set comprises new ultraviolet (from HST STIS), ground-based Hα, and radio continuum observations, together with archival infrared data (from IRAS and ISO). The…
The Star Formation Histories of the Bulge and Disk of M31 from Resolved Stars in the Near-Infrared
Massey, Philip; Olsen, Knut A. G.; Blum, Robert D. +4 more
We discuss H and K observations of three fields in the bulge and disk of M31 obtained with the ALTAIR adaptive optics system and NIRI instrument on Gemini North. These are the highest resolution and deepest near-infrared observations obtained to date of the inner regions of M31 and demonstrate the promise of ground-based adaptive optics for studyi…
Outflows from young objects observed with the ISO-LWS. I. Fine structure lines [O I] 63 µm, [O I] 145 µm and [C II] 157 µm
Liseau, R.; Justtanont, K.; Tielens, A. G. G. M.
Far infrared fine structure line data from the ISO archive have been extracted for several hundred YSOs and their outflows, including molecular (CO) outflows, optical jets and Herbig-Haro (HH) objects. Given the importance of these lines to astrophysics, their excitation and transfer ought to be investigated in detail and, at this stage, the relia…
Low-resolution VLT spectroscopy of GRBs 991216, 011211 and 021211
Piro, L.; Pian, E.; Palazzi, E. +16 more
We present low-resolution VLT spectroscopy of the afterglow of the gamma-ray bursts (GRBs) 991216, 011211 and 021211. Our spectrum of GRB 991216 is the only optical spectrum for this afterglow. It shows two probable absorption systems at z=0.80 and z=1.02, where the highest redshift most likely reflects the distance to the host galaxy. A third sys…
Infrared and Optical Observations of GRB 030115 and its Extremely Red Host Galaxy: Implications for Dark Bursts
Mobasher, Bahram; Garnavich, Peter; Tanvir, Nial +24 more
We present near-infrared (NIR) and optical observations of the afterglow of GRB 030115. Discovered in an infrared search at Kitt Peak 5 hr after the burst trigger, this afterglow is the faintest ever observed in the R band at such an early epoch and exhibits very red colors, with R-K~6. The optical magnitude of the afterglow of GRB 030115 is faint…
Energetic Particle Observations
Simnett, G. M.; Lario, D.; Klecker, B. +14 more
The characteristics of solar energetic particles (SEP) as observed in interplanetary space provide fundamental information about the origin of these particles, and the acceleration and propagation processes at the Sun and in interplanetary space. Furthermore, energetic particles provide information on the development and structure of coronal mass …