Search Publications

Fip Enhancement by Alfvén Ionization

Fletcher, L.; Potts, H. E.; Diver, D. A.

Alfvén ionization is offered as a possible mechanism underlying the enhanced population of low first ionization potential (FIP) species in the solar corona. In this process, the photospheric flow impinging on the magnetic structure of a coronal flux tube collides with, and displaces, ions in the magnetised plasma within the flux tube. This leads t…

High resolution observations of continuum radiation

Gurnett, D. A.; Pickett, J. S.; Santolik, O. +1 more

The Polar spacecraft has identified near-source regions of continuum emission in the plasmapause and outer plasmasphere. As in the case of kilometric continuum (KC), near-source regions of continuum emission often display a high resolution fine structure of closely spaced bands of emission. The separation of the bands is much less than the local g…

Cluster observations of magnetospheric substorm behavior in the near- and mid-tail region

McPherron, R. L.; Dunlop, M. W.; Baker, D. N.

The Cluster constellation of spacecraft has returned substantial new data on particle and field variations in the near- and mid-magnetotail regions of Earth's magnetosphere. Using the Research with Adaptive Particle Imaging Detectors (RAPID) system onboard the four Cluster vehicles, we have identified substorm-related energetic ( E > 20 keV) el…

The Impact of Sunspots on the Interpretation of Coronal Observations of the O VI Doublet

Morgan, H.; Habbal, S. Rifai

Due to their high intensity of emission in the O VI λλ1031.9 and 1037.6 lines, even small sunspots on the solar disk can strongly influence the intensity of the radiative scattering component of O VI lines in the corona. Observations of O VI disk spectra show a λ1032/λ1038 line intensity ratio of >2.6 in a sunspot, compared to quiet-disk values…

Hubble Space Telescope STIS Spectroscopy of the Lyα Emission Line in the Central Dominant Galaxies in A426, A1795, and A2597: Constraints on Clouds in the Intracluster Medium

Koekemoer, Anton M.; Baum, Stefi A.; Mack, Jennifer +2 more

We report on HST STIS spectra of the Lyα emission in the central dominant galaxies in three rich clusters of galaxies. We find evidence for a population of clouds in the intracluster medium. We detect 10 Lyα absorption systems toward the nucleus of NGC 1275 with columns of N(HI)~10¹²-10¹⁴ cm^-2. These columns would …

A Spectroscopic and Photometric Study of NGC 2685, the Prototype Polar-Ring Galaxy

Moiseev, A. V.; Burenkov, A. N.; Hagen-Thorn, V. A. +3 more

We present and analyze spectroscopic and photometric observations for NGC 2685, the prototype polar-ring galaxy. The spectroscopic data were acquired using the 6 m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences with the UAGS spectrograph and a scanning Fabry-Perot interferometer, while the photometric analysi…

A Chandra Observation of the Diffuse Emission Centered on the Low-Mass X-Ray Binary 4U 1755-33

McClintock, Jeffrey E.; Miller, Jon M.; Murray, Stephen S. +1 more

We present an analysis of a Chandra observation of the field surrounding the low-mass X-ray binary 4U 1755-33, which has been in quiescence since 1996. In 2003, Angelini & White reported the appearance of a narrow 7'-long jetlike feature centered on the position of 4U 1755-33 using the XMM-Newton telescope. Although the source and jet are not …

Heliospheric energetic neutral atoms as a means to determine the anomalous cosmic ray spectrum at the termination shock

Hsieh, K. C.; Hilchenbach, M.; Czechowski, A.

We demonstrate the possibility of deriving the anomalous cosmic ray (ACR) spectrum at the solar wind termination shock and the strength of the shock using energetic neutral H and He atoms (ENA) measurements at 1 AU. Assuming that the energetic neutral atoms detected by CELIAS/HSTOF on board SOHO are of ACR origin, we consider χ² fits to…

New beta Cephei and SPB Stars Discovered in Hipparcos Photometry

Molenda-Zakowicz, J.; Polubek, G.

We discuss 34 stars for which we detected new frequencies in Hipparcos Hp magnitudes. 13 of these stars are variables discovered in this paper. For 20 stars, we derive log T_eff and log g from Stromgren or Geneva photometry.

We classify one new beta Cep star, HIP 88352, two new beta Cep suspects, HIP 54753 and 88123, four new SPBs, HIP 1030, …

Erratum: The XMM Large-Scale Structure survey: an initial sample of galaxy groups and clusters to a redshift z < 0.6

Altieri, B.; Valtchanov, I.; Pierre, M. +14 more

We present X-ray and optical spectroscopic observations of twelve galaxy groups and clusters identified within the XMM Large-Scale Structure (LSS) survey. Groups and clusters are selected as extended X-ray sources from a 3.5 deg2 XMM image mosaic above a flux limit 8e-15 ergs/s/cm2 in the [0.5-2] keV energy band. Deep BVRI images and multi-object …