Search Publications
A Retrograde Spin of the Black Hole in MAXI J1659-152
Méndez, Mariano; Vadawale, Santosh; Rout, Sandeep K.
We present the results of spectral analysis of the galactic black hole binary MAXI J1659-152 in the rising phase of the outburst that lasted for about 65 days starting on 2010 September 25. The presence of a broad Fe line, verified by Monte Carlo simulations, and coverage of a wide energy band by utilizing the combined spectral capabilities of XMM…
On Measuring Divergence for Magnetic Field Modeling
Leka, K. D.; Barnes, G.; Wheatland, M. S. +2 more
A physical magnetic field has a divergence of zero. Numerical error in constructing a model field and computing the divergence, however, introduces a finite divergence into these calculations. A popular metric for measuring divergence is the average fractional flux $\left\langle | {f}_{i}| \right\rangle $ . We show that $\left\langle | {f}_{i}| \r…
Determining quasar orientation
Yong, Suk Yee; Bate, Nicholas F.; Webster, Rachel L. +3 more
Since the discovery of active galactic nuclei (AGN) and their subclasses, a unification scheme of AGN has been long sought. Orientation-based unified models predict that some of the diversity within AGN subclasses can be explained by the different viewing angles of the observer. Several orientation categorizations have been suggested, but a widely…
X-raying molecular clouds with a short flare: probing statistics of gas density and velocity fields
Sunyaev, R.; Churazov, E.; Federrath, C. +3 more
We take advantage of a set of molecular cloud simulations to demonstrate a possibility to uncover statistical properties of the gas density and velocity fields using reflected emission of a short (with duration much less than the cloud's light-crossing time) X-ray flare. Such a situation is relevant for the Central Molecular Zone (CMZ) of our Gala…
Ultraviolet Line Identifications and Spectral Formation Near Max Light in Type Ia Supernova 2011fe
Baron, E.; Wang, Lifan; Branch, David +4 more
We present ultraviolet line identifications of near maximum-light Hubble Space Telescope observations of SN 2011fe using synthetic spectra generated from both SYNOW and PHOENIX. We find the spectrum to be dominated by blends of iron group elements Fe, Co, and Ni (as expected due to heavy line blanketing by these elements in the UV) and for the fir…
The dynamics of rings around Centaurs and Trans-Neptunian objects
Sicardy, Bruno; Leiva, Rodrigo; Roques, Françoise +4 more
Since 2013, dense and narrow rings are known around the small Centaur object Chariklo and the dwarf planet Haumea. Dense material has also been detected around the Centaur Chiron, although its nature is debated. This is the first time ever that rings are observed elsewhere than around the giant planets, suggesting that those features are more comm…
MHD Modeling of the Background Solar Wind in the Inner Heliosphere From 0.1 to 5.5 AU: Comparison With In Situ Observations
Wang, C.; Li, H.; Guo, X. C. +4 more
The accurate prediction of solar wind conditions in the interplanetary space is crucial in the context of both scientific research and technical applications. In this study, we simulate the solar wind throughout the heliosphere from 0.1 to 5.5 astronomical units (AU) with our improved heliospheric magnetohydrodynamics (MHD) model during the time p…
A blazar as the likely counterpart to 4FGL J0647.7-4418 instead of a gamma-ray binary
Corbet, Robin H. D.; Luque-Escamilla, Pedro L.; Martí, Josep +3 more
The persistent gamma-ray source 4FGL J0647.7-4418 is tentatively associated in the latest Fermi catalogue with the subdwarf O-type X-ray binary HD 49798. However, an active galactic nucleus (AGN) candidate is also mentioned as an alternative identification in updated versions of the catalogue accompanying paper. If the first association were corre…
Multiwavelength Photometry and Progenitor Analysis of the Nova V906 Car
Law, Nicholas M.; Blagorodnova, Nadejda; Kupfer, Thomas +12 more
We present optical and infrared photometry of the classical nova V906 Car, also known as Nova Car 2018 and ASASSN-18fv, which was discovered by the All-Sky Automated Survey for SuperNovae (ASAS-SN) on 2018 March 16.32 UT (MJD 58193.0). The nova reached its maximum on MJD 58222.56 at Vmax = 5.84 ± 0.09 mag, and had decline times of ${t}_…
Short-Term X-ray Variability during Different Activity Phases of Blazars S5 0716+714 and PKS 2155-304
Pal, Main; Kushwaha, Pankaj
We explored the statistical properties of short-term X-ray variability using long-exposure XMM-Newton data during high X-ray variability phases of blazars S5 0716+714 and PKS 2155-304. In general, the hardness ratio shows correlated variations with the source flux state (count rate), but in a few cases, mainly the bright phases, the trend is compl…