Search Publications
NICMOS Polarimetry of "Polar-scattered" Seyfert 1 Galaxies
Alexander, D. M.; Batcheldor, D.; Young, S. +5 more
The nuclei of Seyfert 1 galaxies exhibit a range of optical polarization characteristics that can be understood in terms of two scattering regions producing orthogonal polarizations: an extended polar scattering region (PSR) and a compact equatorial scattering region (ESR), located within the circum-nuclear torus. Here we present NICMOS 2.0 µ…
New Constraints on the Origin of the Short-term Cyclical Variability of the Wolf-Rayet Star WR 46
Talavera, A.; Pollock, A. M. T.; Hénault-Brunet, V. +3 more
The Wolf-Rayet star WR 46 is known to exhibit a very complex variability pattern on relatively short timescales of a few hours. Periodic but intermittent radial velocity shifts of optical lines as well as multiple photometric periods have been found in the past. Non-radial pulsations, rapid rotational modulation, or the presence of a putative low-…
The Solar Decimetric Spike Burst of 2006 December 6: Possible Evidence for Field-aligned Potential Drops in Post-eruption Loops
White, S. M.; Balasubramaniam, K. S.; Cliver, E. W.
A 1.4 GHz solar radio burst associated with a 3B/X6 eruptive flare on 2006 December 6 had the highest peak flux density (~106 sfu) of any event yet recorded at this frequency. The decimetric event characteristics during the brightest emission phase (numerous intense, short-lived, narrow-band bursts that overlapped to form a continuous s…
Discovery of a Candidate Quiescent Low-mass X-Ray Binary in the Globular Cluster NGC 6553
Pavlov, George G.; Guillot, Sebastien; Zavlin, Vyacheslav E. +2 more
This paper reports the search for quiescent low-mass X-ray binaries (qLMXBs) in the globular cluster (GC) NGC 6553 using an XMM-Newton observation designed specifically for that purpose. We spectrally identify one candidate qLMXB in the core of the cluster, based on the consistency of the spectrum with a neutron star H-atmosphere model at the dist…
A Deep Chandra View of the NGC 404 Central Engine
Dalcanton, J. J.; Skillman, E. D.; Weisz, D. R. +7 more
We present the results of a 100 ks Chandra observation of the NGC 404 nuclear region. The long exposure and excellent spatial resolution of Chandra have enabled us to critically examine the nuclear environment of NGC 404, which is known to host a nuclear star cluster and potentially an intermediate-mass black hole (IMBH; on the order of a few time…
Multi-fluid Model of a Streamer at Solar Minimum and Comparison with Observations
Giordano, Silvio; Ofman, Leon; Abbo, Lucia
We present the results of a time-dependent 2.5-dimensional three-fluid magnetohydrodynamic model of the coronal streamer belt, which is compared with the slow solar wind plasma parameters obtained in the extended corona by the UV spectroscopic data from the Ultraviolet Coronagraph Spectrometer (UVCS) on board SOHO during the past minimum of solar …
Structure and Dynamics of the 2009 July 22 Eclipse White-light Corona
Rušin, V.; Saniga, M.; Pasachoff, J. M. +2 more
The white-light corona (WLC) during the total solar eclipse of 2009 July 22 was observed by several teams in the Moon's shadow stretching from India and China across the Pacific Ocean with its many isolated islands. We present a comparison of the WLC as observed by eclipse teams located in China (Shanghai region) and on the Enewetak Atoll in the M…
Supersonic Downflows at the Umbra-Penumbra Boundary of Sunspots
Venkatakrishnan, P.; Mathew, Shibu K.; Louis, Rohan E. +1 more
High-resolution spectropolarimetric observations of three sunspots taken with Hinode demonstrate the existence of supersonic downflows at or close to the umbra-penumbra boundary which have not been reported before. These downflows are confined to large patches, usually encompassing bright penumbral filaments, and have lifetimes of more than 14 hr.…
Long-term Radiative Behavior Of SGR 1900+14
Kouveliotou, Chryssa; Göǧüş, Ersin; Güver, Tolga +2 more
The prolific magnetar SGR 1900+14 showed two outbursts in the last decade and has been closely monitored in the X-rays to track the changes in its radiative properties. We use archival Chandra and XMM-Newton observations of SGR 1900+14 to construct a history of its spectrum and persistent X-ray flux spanning a period of about seven years. We show …
Spectral Energy Distribution of z >~ 1 Type Ia Supernova Hosts in GOODS: Constraints on Evolutionary Delay and the Initial Mass Function
Chary, R. R.; Thomson, M. G.
We identify a sample of 22 host galaxies of Type Ia Supernovae (SNe Ia) at redshifts 0.95 < z < 1.8 discovered in the Hubble Space Telescope (HST) observations of the Great Observatories Origins Deep Survey (GOODS) fields. We measure the photometry of the hosts in Spitzer Space Telescope and ground-based imaging of the GOODS fields to provid…