Search Publications
Intergalactic HeII absorption towards QSO 1157+3143
Reimers, D.; Hagen, H. -J.; Jakobsen, P. +3 more
We report the discovery of a further line of sight allowing detection of He II Lyα absorption by the intergalactic medium. A HST/STIS survey of 32 bright z ∼ 3 quasars selected from the Hamburg Quasar Surveys yielded one detection toward QSO 1157+3143 (z ∼ 3, B ≃ 17). A 10 orbit follow-up spectrum reveals a UV spectrum significantly suppressed by …
Identification of 8 INTEGRAL hard X-ray sources with Chandra
Sunyaev, R.; Revnivtsev, M.; Sazonov, S. +2 more
We report the results of identification of 8 hard X-ray sources discovered by the INTEGRAL observatory during the ongoing all-sky survey. These sources have been observed by Chandra. In 6 cases a bright X-ray source was found within the INTEGRAL localization region, which permitted to unambiguously identify 5 of the objects with nearby galaxies, i…
The Araucaria Project: The Effect of Blending on the Cepheid Distance to NGC 300 from Advanced Camera for Surveys Images
Bresolin, Fabio; Kudritzki, Rolf-Peter; Gieren, Wolfgang +1 more
We have used the Advanced Camera for Surveys aboard the Hubble Space Telescope (HST) to obtain F435W, F555W, and F814W single-epoch images of six fields in the spiral galaxy NGC 300. Taking advantage of the superb spatial resolution of these images, we have tested the effect that blending of the Cepheid variables studied from the ground with close…
Hubble Space Telescope NICMOS Imaging of W3 IRS 5: A Trapezium in the Making?
Megeath, S. T.; Wilson, T. L.; Corbin, M. R.
We present Hubble Space Telescope NICMOS imaging of W3 IRS 5, a binary high-mass protostar. In addition to the two protostars, NICMOS images taken in the F222M and F160W filters show three new 2.22 µm sources with very red colors; these sources fall within a region 5600 AU in diameter and are coincident with an ~100 Msolar, dense …
Variation of the full Sun hydrogen Lyman profiles through solar cycle 23
Vial, J. -C.; Wilhelm, K.; Curdt, W. +3 more
The hydrogen Lyman (Lyα, 121.267 nm and Lyβ, 102.572 nm) lines are important contributors to the solar extreme ultra violet (EUV) flux which illuminates the upper Earth’s atmosphere. From high resolution spectral observations performed with the solar ultraviolet measurement of emitted radiations (SUMER) spectrometer on the Solar and Heliospheric O…
Rotation periods for stars of the TW Hydrae association: the evidence for two spatially and rotationally distinct pre-main-sequence populations
Lawson, Warrick A.; Crause, Lisa A.
We have conducted a photometric study of late-type members of the TW Hydrae association (TWA) and measured the rotation periods for 16 stars in 12 systems. For TWA stars listed by Webb et al. and Sterzik et al. (TWA 1-13 led by TW Hya = TWA 1) we find a median period of 4.7 d. However, for stars that we measured in the TWA 14-19 group identified b…
Energy deposition of pickup ions and heating of Titan's atmosphere
Johnson, R. E.; Michael, M.
The deposition of energy, escape of atomic and molecular nitrogen and heating of the upper atmosphere of Titan are studied using a Direct Simulation Monte Carlo method. It is found that the globally averaged flux of deflected magnetospheric atomic nitrogen ions and molecular pickup ions deposit more energy in Titan's upper atmosphere than solar ra…
Ring Analysis of Solar Subsurface Flows and Their Relation to Surface Magnetic Activity
Howe, R.; Komm, R.; Hill, F. +3 more
We measure the horizontal flows in the outer 2% of the Sun by analyzing 14 consecutive Carrington rotations of Global Oscillation Network Group (GONG) Doppler images and two of Michelson Doppler Imager (MDI) Dynamics Program data with the ring-diagram technique. The zonal and meridional flows show no variation with activity at low to medium activi…
A High Angular Resolution Search for the Progenitor of the Type Ic Supernova 2004gt
Cenko, S. B.; Kulkarni, S. R.; Matthews, K. +6 more
We report the results of a high spatial resolution search for the progenitor of Type Ic supernova SN 2004gt, using the newly commissioned Keck laser guide star adaptive optics (LGSAO) system along with archival Hubble Space Telescope data. This is the deepest search yet performed for the progenitor of any Type Ib/c event in a wide wavelength range…
Magnetic Fields from SOHO MDI Converted to the Mount Wilson 150 Foot Solar Tower Scale
Ulrich, Roger K.; Tran, Tham; Bertello, Luca +1 more
In order to permit the construction of long-duration time series dependent on the Sun's magnetic field, this paper presents a detailed cross-correlation between sets of simultaneous magnetograms from the Mount Wilson Observatory (MWO) and the Michelson Doppler Imager (MDI) aboard the SOHO spacecraft. The MWO 150 foot (45.72 m) solar tower telescop…