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Accretion and jets in a low-luminosity AGN: the nucleus of NGC 1052
Larsson, J.; Falocco, S.; Nandi, S.
Aims: We aim to determine the properties of the central region of NGC 1052 using X-ray and radio data. NGC 1052 (z = 0.005) has been investigated for decades in different energy bands and shows radio lobes and a low-luminosity active galactic nucleus.
Methods: We used X-ray images from Chandra and radio images from Very Large Array to ex…
Testing the Keplerian disk hypothesis using x-ray reflection spectroscopy
Tripathi, Ashutosh; Zhou, Biao; Abdikamalov, Askar B. +3 more
The Novikov-Thorne model is the standard framework for the description of geometrically thin and optically thick accretion disks around black holes and is widely used to study the electromagnetic spectra of accreting black holes. One of the assumptions of the model is that the particles of the gas move on nearly geodesic circular orbits on the equ…
Reflection Features in the X-Ray Spectrum of Fairall 9 and Implications for Tests of General Relativity
Abdikamalov, Askar B.; Ayzenberg, Dimitry; Bambi, Cosimo +2 more
X-ray reflection spectroscopy is potentially a powerful tool to probe the spacetime geometry around astrophysical black holes and test general relativity in the strong field regime. However, precision tests of general relativity are only possible if we employ the correct astrophysical model and if we can limit the systematic uncertainties. It is t…
Influence of landslides on the erosion of slopes on comet 9P/Tempel 1: Laboratory experiments and numerical simulations
Czechowski, Leszek; Kossacki, Konrad J.; Skóra, Grzegorz
Observations of Comet 9P/Tempel 1 indicate that the boundary of the thick, fluid-like deposit had retreated by up to 50 m during one orbital period (Veverka et al., 2013; Thomas et al., 2013). According to Kossaki (2015), sublimation of buried ice may be responsible for the observed effect, but only if the dust has very high thermal conductivity. …
On Venus' cloud top chemistry, convective activity and topography: A perspective from HST
Bertaux, Jean-Loup; Marcq, Emmanuel; Limaye, Sanjay +3 more
Hubble Space Telescope Imaging Spectrograph (HST/STIS) observations were obtained on 3 dates in December 2010 and January 2011 recording the cloud top properties over Aphrodite Terra and a low elevation region downwind of Aphrodite through LSTs extending from 7 to 11 a.m. From these data we trace the cloud top sulfur-oxide chemistry and UV albedo …
Atmospheric Characterization and Further Orbital Modeling of κ Andromeda b
Currie, Thayne; De Rosa, Robert J.; Kwon, Jungmi +19 more
We present κ Andromeda b’s photometry and astrometry taken with Subaru/SCExAO+HiCIAO and Keck/NIRC2, combined with recently published SCExAO/CHARIS low-resolution spectroscopy and published thermal infrared photometry to further constrain the companion’s atmospheric properties and orbit. The Y/Y-K colors of κ And b are redder than field dwarfs, co…
PHAT XX. AGB Stars and Other Cool Giants in M31 Star Clusters
Dolphin, Andrew E.; Skillman, Evan D.; Williams, Benjamin F. +20 more
The presence of asymptotic giant branch (AGB) stars in clusters provides key constraints for stellar models, as has been demonstrated with historical data from the Magellanic Clouds. In this work, we look for candidate AGB stars in M31 star clusters from the Panchromatic Hubble Andromeda Treasury survey. Our photometric criteria selects stars brig…
Atacama Compact Array observations of the pulsar-wind nebula of SNR 0540-69.3
Lundqvist, P.; Olofsson, G.; Zyuzin, D. A. +6 more
We present observations of the pulsar-wind nebula (PWN) region of SNR 0540-69.3. The observations were made with the Atacama Compact Array (ACA) in Bands 4 and 6. We also add radio observations from the Australia Compact Array at 3 cm. For 1.449-233.50 GHz, we obtain a synchrotron spectrum $F_{\nu } \propto \nu ^{-\alpha _{\nu }}$ , with the spect…
Comprehensive Characterization of Solar Eruptions with Remote and In-Situ Observations, and Modeling: The Major Solar Events on 4 November 2015
Veronig, Astrid M.; Nitta, Nariaki V.; Dresing, Nina +12 more
Solar energetic particles (SEPs) are an important product of solar activity. They are connected to solar active regions and flares, coronal mass ejections (CMEs), EUV waves, shocks, Type II and III radio emissions, and X-ray bursts. These phenomena are major probes of the partition of energy in solar eruptions, as well as for the organization, dyn…
SALT revisits DY Cen: a rapidly evolving strontium-rich single helium star
Rao, N. Kameswara; Lambert, David L.; Jeffery, C. Simon
The hydrogen-deficient star DY Cen has been reported as an R CrB-type variable, an extreme helium star (with some hydrogen), and as a single-lined spectroscopic binary. It has been associated with a dramatic change in visual brightness and colour corresponding to a change in effective temperature ( Teff) of some 20 000 K in the last cen…