Search Publications
Hubble Space Telescope Spectral Observations Near the He II Lyα Break: Implications for He II Reionization
Anderson, Scott F.; Schneider, Donald P.; York, Donald G. +4 more
Quasars that allow the study of intergalactic medium (IGM) He II are very rare, since they must be at high redshift along sightlines free of substantial hydrogen absorption, but recent work has dramatically expanded the number of such quasars known. We analyze two dozen higher-redshift (z = 3.1-3.9) low-resolution He II quasar spectra from the Hub…
Is There a Black Hole in NGC 4382?
Gebhardt, Karl; Kormendy, John; Lauer, Tod R. +5 more
We present Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph observations of the galaxy NGC 4382 (M85) and axisymmetric models of the galaxy to determine mass-to-light ratio (Upsilon V ) and central black hole mass (M BH). We find Upsilon V = 3.74 ± 0.1 M sun/L sun and M …
A Magnetohydrodynamic Model of the 2006 December 13 Eruptive Flare
Fan, Y.
We present a three-dimensional magnetohydrodynamic simulation that qualitatively models the coronal magnetic field evolution associated with the eruptive flare that occurred on 2006 December 13 in the emerging δ-sunspot region NOAA 10930 observed by the Hinode satellite. The simulation is set up to drive the emergence of an east-west-oriented magn…
Identification of Three New Protoplanetary Nebulae Exhibiting the Unidentified Feature at 21 µm
Hora, Joseph L.; Fazio, Giovanni; Trigilio, Corrado +3 more
Among its great findings, the Infrared Astronomical Satellite mission showed the existence of an unidentified mid-IR feature around 21 µm. Since its discovery, this feature has been detected in all C-rich protoplanetary nebulae (PPNe) of intermediate spectral type (F-G) and—weakly—in a few PNe and asymptotic giant branch (AGB) stars, but the…
Initiation and Early Development of the 2008 April 26 Coronal Mass Ejection
Pick, M.; Auchère, F.; Démoulin, P. +3 more
We present a detailed study of a coronal mass ejection (CME) with high temporal cadence observations in radio and extreme-ultraviolet (EUV). The radio observations combine imaging of the low corona with radio spectra in the outer corona and interplanetary space. The EUV observations combine the three points of view of the STEREO and SOHO spacecraf…
Mid-infrared Period-luminosity Relations of RR Lyrae Stars Derived from the WISE Preliminary Data Release
Bloom, Joshua S.; Richards, Joseph W.; Butler, Nathaniel R. +1 more
Interstellar dust presents a significant challenge to extending parallax-determined distances of optically observed pulsational variables to larger volumes. Distance ladder work at mid-infrared wavebands, where dust effects are negligible and metallicity correlations are minimized, has been largely focused on few-epoch Cepheid studies. Here we pre…
Testing Photometric Diagnostics for the Dynamical State and Possible Intermediate-mass Black Hole Presence in Globular Clusters
Baumgardt, Holger; Noyola, Eva
Surface photometry is a necessary tool to establish the dynamical state of star clusters. We produce realistic HST-like images from N-body models of star clusters with and without central intermediate-mass black holes (IMBHs) in order to measure their surface brightness profiles. The models contain ~600,000 individual stars, black holes of various…
Reverberation Mapping of the Intermediate-mass Nuclear Black Hole in SDSS J114008.71+030711.4
Kaspi, Shai; Kollatschny, Wolfram; Behar, Ehud +2 more
We present the results of a reverberation mapping (RM) campaign on the black hole (BH) associated with the active galactic nucleus (AGN) in SDSS J114008.71+030711.4 (hereafter GH08). This object is selected from a sample of 19 candidate intermediate-mass BHs (M BH < 106 M sun) found by Greene & Ho in the Slo…
The TeV Binary HESS J0632+057 in the Low and High X-Ray State
Rea, Nanda; Torres, Diego F.
We report on a 40 ks Chandra observation of the TeV emitting high-mass X-ray binary HESS J0632+057 performed in 2011 February during a high state of X-ray and TeV activity. We have used the ACIS-S camera in continuous clocking mode to search for a possible X-ray pulsar in this system. Furthermore, we compare the emission of the source during this …
The Faintest Radio Source Yet: Expanded Very Large Array Observations of the Gravitational Lens SDSS J1004+4112
Jackson, N.
We present new radio observations of the large-separation gravitationally lensed quasar SDSS J1004+4112, taken in a total of 6 hr of observations with the Expanded Very Large Array. The maps reach a thermal noise level of approximately 4 µJy. We detect four of the five lensed images at the 15-35 µJy level, representing a source of intr…