Search Publications
The Incidence of Active Galactic Nuclei in Pure Disk Galaxies: The Spitzer View
Abel, N. P.; Böker, T.; Satyapal, S. +3 more
Using the Spitzer telescope, we have conducted a high-resolution spectroscopic study of 18 bulgeless (Hubble type of Sd or Sdm) galaxies that show no definitive signatures of nuclear activity in their optical spectra. This is the first systematic mid-infrared (MIR) search for weak or hidden active galactic nuclei (AGNs) in a statistically signific…
Prominence Formation Associated with an Emerging Helical Flux Rope
Shibata, Kazunari; Tsuneta, Saku; Shimizu, Toshifumi +12 more
The formation and evolution process and magnetic configuration of solar prominences remain unclear. In order to study the formation process of prominences, we examine continuous observations of a prominence in NOAA AR 10953 with the Solar Optical Telescope on the Hinode satellite. As reported in our previous Letter, we find a signature suggesting …
The ACS LCID Project. I. Short-Period Variables in the Isolated Dwarf Spheroidal Galaxies Cetus and Tucana
Skillman, Evan D.; Cole, Andrew A.; Tolstoy, Eline +9 more
We present the first study of the variable star populations in the isolated dwarf spheroidal galaxies (dSphs) Cetus and Tucana. Based on Hubble Space Telescope images obtained with the Advanced Camera for Surveys in the F475W and F814W bands, we identified 180 and 371 variables in Cetus and Tucana, respectively. The vast majority are RR Lyrae star…
Quantitative Examination of Supra-arcade Downflows in Eruptive Solar Flares
Savage, Sabrina L.; McKenzie, D. E.
Downward motions above post-coronal mass ejection flare arcades are an unanticipated discovery of the Yohkoh mission, and have subsequently been detected with TRACE, SOHO/LASCO, SOHO/SUMER, and Hinode/XRT. These supra-arcade downflows are interpreted as outflows from magnetic reconnection, consistent with a three-dimensional generalization of the …
The Evolution of Early- and Late-type Galaxies in the Cosmic Evolution Survey up to z ≈ 1.2
Bender, Ralf; Drory, Niv; Pannella, Maurilio +6 more
The Cosmic Evolution Survey (COSMOS) allows for the first time a highly significant census of environments and structures up to redshift 1, as well as a full morphological description of the galaxy population. In this paper we present a study aimed to constrain the evolution, in the redshift range 0.2 < z < 1.2, of the mass content of differ…
Strong Bursts from the Anomalous X-Ray Pulsar 1E 1547.0-5408 Observed with the INTEGRAL/SPI Anti-Coincidence Shield
Tiengo, A.; Götz, D.; Mereghetti, S. +9 more
In 2009 January, multiple short bursts of soft gamma rays were detected from the direction of the anomalous X-ray pulsar 1E 1547.0-5408 by different satellites. Here we report on the observations obtained with the Anti Coincidence Shield (ACS) of the SPI instrument on INTEGRAL during the period with the strongest bursting activity. More than 200 b…
Spectral States and Evolution of Ultraluminous X-Ray Sources
Feng, Hua; Kaaret, Philip
We examined spectral evolution in ultraluminous X-ray sources (ULXs) with apparent luminosities of about 1040 erg s-1. Based on new results in this paper, and those reported in the literature, two common spectral behaviors were found. Some ULXs in starburst galaxies have varying luminosity (L) but remain in the hard state wit…
Chandra Localizations and Spectra of Integral Sources in the Galactic Plane: The Cycle 9 Sample
Kaaret, Philip; Walter, Roland; Tomsick, John A. +2 more
We report on 0.3-10 keV X-ray observations by the Chandra X-ray Observatory of the fields of 22 sources that were discovered as hard X-ray (20-100 keV) sources by the International Gamma-Ray Astrophysics Satellite ("IGR" sources). The observations were made during Chandra's 9th observing cycle, and their purpose is to localize the sources and to m…
Testing the E peak-E iso Relation for GRBs Detected by Swift and Suzaku-WAM
Sakamoto, T.; Yamauchi, M.; Yamaoka, K. +12 more
One of the most prominent, yet controversial associations derived from the ensemble of prompt-phase observations of gamma-ray bursts (GRBs) is the apparent correlation in the source frame between the peak energy (E peak) of the νF(ν) spectrum and the isotropic radiated energy, E iso. Since most GRBs have E peak abo…
The Relation Between EIT Waves and Coronal Mass Ejections
Chen, P. F.
More and more evidence indicates that "EIT waves" are strongly related to coronal mass ejections (CMEs). However, it is still not clear how the two phenomena are related to each other. We investigate a CME event on 1997 September 9, which was well observed by both the EUV Imaging Telescope (EIT) and the high-cadence Mark-III K-Coronameter at Mauna…