Search Publications
Spectral irradiance variations: comparison between observations and the SATIRE model on solar rotation time scales
Solanki, S. K.; Krivova, N. A.; Kopp, G. +2 more
Aims: We test the reliability of the observed and calculated spectral irradiance variations between 200 and 1600 nm over a time span of three solar rotations in 2004.
Methods: We compare our model calculations to spectral irradiance observations taken with SORCE/SIM, SoHO/VIRGO, and UARS/SUSIM. The calculations assume LTE and are based on the …
GRB 070201: A Possible Soft Gamma-Ray Repeater in M31
Cenko, S. B.; Stiele, H.; Pietsch, W. +13 more
GRB 070201 was a bright, short-duration, hard-spectrum gamma-ray burst detected by the Interplanetary Network. Its error quadrilateral, which has an area of 0.124 deg2, intersects some prominent spiral arms of the nearby M31 (Andromeda) galaxy. Given the properties of this GRB, along with the fact that LIGO data argue against a compact …
A Multi-Epoch HST Study of the Herbig-Haro Flow from XZ Tauri
Krist, John E.; Hester, J. Jeff; Stapelfeldt, Karl R. +3 more
We present nine epochs of Hubble Space Telescope optical imaging of the bipolar outflow from the pre-main-sequence binary XZ Tauri. Our data monitor the system from 1995 to 2005 and include emission line images of the flow. The northern lobe appears to be a succession of bubbles, the outermost of which expanded ballistically from 1995 to 1999 but …
The Late Stellar Assembly of Massive Cluster Galaxies via Major Merging
Tran, Kim-Vy H.; Moustakas, John; Gonzalez, Anthony H. +3 more
We present multiwavelength observations of the brightest galaxies in four X-ray-luminous groups at z ~ 0.37 that will merge to form a cluster comparable in mass to Coma. Ordered by increasing stellar mass, the four brightest group galaxies (BGGs) present a time sequence where BGG-1, 2, and 3 are in merging systems and BGG-4 is a massive remnant (M…
Evidence of magnetic field wrapping around penumbral filaments
Solanki, S. K.; Lites, B. W.; Borrero, J. M.
We employ high-spatial resolution spectropolarimetric observations from the Solar Optical Telescope on-board the Hinode spacecraft to investigate the fine structure of the penumbral magnetic fields. The Stokes vector of two neutral iron lines at 630 nm is inverted at every spatial pixel to retrieve the depth-dependence of the magnetic field vector…
Suzaku Wide-Band Observations of SN1006
Petre, Rob; Fukazawa, Yasushi; Kokubun, Motohide +17 more
We report on the wide-band spectra of SN1006, as observed by Suzaku. Thermal and nonthermal emissions were successfully resolved thanks to the excellent spectral response of Suzaku's X-ray CCD XIS. The nonthermal emission could not be reproduced by a simple power-law model, but needed a roll-off at 5.7 × 1016Hz = 0.23keV. The roll-off f…
Keck spectroscopy of the faint dwarf elliptical galaxy population in the Perseus Cluster core: mixed stellar populations and a flat luminosity function
Conselice, Christopher J.; Penny, Samantha J.
We present the result of a photometric and Keck low-resolution imaging spectrometer (LRIS) spectroscopic study of dwarf galaxies in the core of the Perseus Cluster, down to a magnitude of MB = -12.5. Spectra were obtained for 23 dwarf-galaxy candidates, from which we measure radial velocities and stellar population characteristics from …
The Off-Disk Thermal Structure of a Polar Coronal Hole
Landi, Enrico
The thermal structure of the coronal portion of coronal holes is a key factor in the modeling of the source regions and acceleration mechanisms of the fast solar wind. Studies aimed at this region are best carried out on observations outside the disk, where the chromosphere and transition region are not included in the line of sight. In the past, …
Stratification of Sunspot Umbral Dots from Inversion of Stokes Profiles Recorded by Hinode
Solanki, S. K.; Lagg, A.; Riethmüller, T. L.
This work aims to constrain the physical nature of umbral dots (UDs) using high-resolution spectropolarimetry. Full Stokes spectra recorded by the spectropolarimeter on Hinode of 51 UDs in a sunspot close to the disk center are analyzed. The height dependence of the temperature, magnetic field vector, and line-of-sight velocity across each UD is o…
The X-ray cycle in the solar-type star HD 81809. XMM-Newton observations and implications for the coronal structure
Schmitt, J. H. M. M.; Orlando, S.; Hall, J. +3 more
Context: The 11-yr cycle is the best known manifestation of the Sun's activity. While chromospheric cycles have been studied in a number of solar-like stars, very little is known about how these are reflected in the cyclical behavior of the coronal X-ray emission in stars other than the Sun.
Aims: Our long-term XMM-Newton program of long-term …