Search Publications
A Detailed Morpho-kinematic Model of the Eskimo, NGC 2392: A Unifying View with the Cat's Eye and Saturn Planetary Nebulae
López, J. A.; Steffen, W.; García-Díaz, Ma. T. +1 more
The three-dimensional and kinematic structure of the Eskimo nebula, NGC 2392, has been notoriously difficult to interpret in detail given its complex morphology, multiple kinematic components and its nearly pole-on orientation along the line of sight. We present a comprehensive, spatially resolved, high-resolution, long-slit spectroscopic mapping …
The Long-term X-Ray Variability of Broad Absorption Line Quasars
Bauer, F. E.; Brandt, W. N.; Garmire, G. P. +2 more
We analyze the long-term (rest-frame 3-30 yr) X-ray variability of 11 broad absorption line (BAL) quasars, mainly to constrain the variation properties of the X-ray absorbing shielding gas that is thought to play a critical role in BAL wind launching. Our BAL quasar sample has coverage with multiple X-ray observatories including Chandra, XMM-Newto…
A Multi-epoch Timing and Spectral Study of the Ultraluminous X-Ray NGC 5408 X-1 with XMM-Newton
Pasham, Dheeraj R.; Strohmayer, Tod E.
We present results of new XMM-Newton observations of the ultraluminous X-ray source (ULX) NGC 5408 X-1, one of the few ULXs to show quasi-periodic oscillations (QPOs). We detect QPOs in each of four new (≈100 ks) pointings, expanding the range of frequencies observed from 10 to 40 mHz. We compare our results with the timing and spectral correlatio…
Contribution of the Accretion Disk, Hot Corona, and Obscuring Torus to the Luminosity of Seyfert Galaxies: INTEGRAL and Spitzer Observations
Sunyaev, R.; Krivonos, R.; Revnivtsev, M. +12 more
We estimate the relative contributions of the supermassive black hole (SMBH) accretion disk, corona, and obscuring torus to the bolometric luminosity of Seyfert galaxies, using Spitzer mid-infrared (MIR) observations of a complete sample of 68 nearby active galactic nuclei (AGNs) from the INTEGRAL all-sky hard X-ray (HX) survey. This is the first …
Why is the Solar Constant Not a Constant?
Yang, L. H.; Li, K. J.; Xu, J. C. +4 more
In order to probe the mechanism of variations of the solar constant on the inter-solar-cycle scale, the total solar irradiance (TSI; the so-called solar constant) in the time interval of 1978 November 7 to 2010 September 20 is decomposed into three components through empirical mode decomposition and time-frequency analyses. The first component is …
Turbulent Convection Model in the Overshooting Region. I. Effects of the Convective Mixing in the Solar Overshooting Region
Li, Y.; Zhang, Q. S.
The overshooting in the framework of the turbulent convection model is investigated in the solar overshooting region. The overshooting mixing is treated as a diffusive process. It is found that the sound speed profile can be improved to be in good agreement with helioseismic inversions. The bump in the sound speed differences between solar models …
Pervasive Linear Polarization Signals in the Quiet Sun
Bellot Rubio, L. R.; Orozco Suárez, D.
This paper investigates the distribution of linear polarization signals in the quiet-Sun internetwork using ultra-deep spectropolarimetric data. We reduce the noise of the observations as much as is feasible by adding single-slit measurements of the Zeeman-sensitive Fe I 630 nm lines taken by the Hinode spectropolarimeter. The integrated Stokes sp…
A New Sample of Candidate Intermediate-mass Black Holes Selected by X-Ray Variability
Awaki, Hisamitsu; Terashima, Yuichi; Kamizasa, Naoya
We present the results of X-ray variability and spectral analysis of a sample of 15 new candidates for active galactic nuclei with relatively low-mass black holes (BHs). They are selected from the Second XMM-Newton Serendipitous Source Catalogue based on strong variability quantified by normalized excess variances. Their BH masses are estimated to…
The ACS LCID Project. VII. The Blue Stragglers Population in the Isolated dSph Galaxies Cetus and Tucana
Hidalgo, S. L.; Mayer, L.; Stetson, P. B. +8 more
We present the first investigation of the Blue Straggler star (BSS) population in two isolated dwarf spheroidal galaxies of the Local Group, Cetus and Tucana. Deep Hubble Space Telescope/Advanced Camera for Surveys photometry allowed us to identify samples of 940 and 1214 candidates, respectively. The analysis of the star formation histories of th…
Discovery of Two Supernovae in the Nuclear Regions of the Luminous Infrared Galaxy IC 883
Colina, L.; Kankare, E.; Efstathiou, A. +10 more
We report the discovery of two consecutive supernovae (SNe), 2010cu and 2011hi, located at 0farcs37 (180 pc) and 0farcs79 (380 pc) projected distance, respectively, from the center of the K-band nucleus of the luminous infrared galaxy (LIRG) IC 883. The SNe were discovered in an ongoing near-infrared K-band search for core-collapse SNe in such gal…