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Constraining models of activity on comet 67P/Churyumov-Gerasimenko with Rosetta trajectory, rotation, and water production measurements
Jorda, L.; Kührt, E.; Mottola, S. +11 more
Aims: We use four observational data sets, mainly from the Rosetta mission, to constrain the activity pattern of the nucleus of comet 67P/Churyumov-Gerasimenko (67P).
Methods: We developed a numerical model that computes the production rate and non-gravitational acceleration of the nucleus of comet 67P as a function of time, taking into …
Fluctuation of the background sky in the Hubble Extremely Deep Field (XDF) and its origin
Matsumoto, Toshio; Tsumura, Kohji
We performed a fluctuation analysis of the Hubble Extremely Deep Field (XDF) at four optical wavelength bands and found large fluctuations that are significantly brighter than those expected for ordinary galaxies. Good cross-correlations with flat spectra are found down to {0{^''.}2}, indicating the existence of a spatial structure even…
Plasma properties of suprathermal electrons near comet 67P/Churyumov-Gerasimenko with Rosetta
Henri, P.; Goldstein, R.; Galand, M. +6 more
Context. The Rosetta spacecraft escorted comet 67P/Churyumov-Gerasimenko from 2014 to September 2016. The mission provided in situ observations of the cometary plasma during different phases of the cometary activity, which enabled us to better understand its evolution as a function of heliocentric distance.
Aims: In this study, different elec…
Speckle Observations and Orbits of Multiple Stars
Torres, Guillermo; Latham, David W.; Tokovinin, Andrei +2 more
We report results of speckle-interferometric monitoring of visual hierarchical systems using the newly commissioned instrument NN-EXPLORE Exoplanet and Stellar Speckle Imager at the 3.5 m WIYN telescope. During one year, 390 measurements of 129 resolved subsystems were made, while some targets were unresolved. Using our astrometry and archival dat…
Constraining the Johannsen deformation parameter ɛ3 with black hole x-ray data
Tripathi, Ashutosh; Abdikamalov, Askar B.; Ayzenberg, Dimitry +2 more
We extend our previous work on tests of the Kerr black hole hypothesis using x-ray reflection spectroscopy and we infer observational constraints on the Johannsen deformation parameter ɛ3 . We analyze a NuSTAR observation of the stellar-mass black hole in GS 1354-645, Suzaku data of the supermassive black holes in Ark 564, 1H0419-577, a…
Where Do Quasar Hosts Lie with Respect to the Size-Mass Relation of Galaxies?
Kartaltepe, Jeyhan S.; Treu, Tommaso; Schramm, Malte +8 more
The evolution of the galaxy size-mass relation has been a puzzle for over a decade. High-redshift galaxies are significantly more compact than galaxies observed today at an equivalent mass, but how much of this apparent growth is driven by progenitor bias, minor mergers, secular processes, or feedback from active galactic nuclei (AGNs) is unclear.…
Infrared K-band Photometry of Field RR Lyrae Variable Stars
Layden, Andrew C.; Chaboyer, Brian; Tiede, Glenn P. +2 more
We present multi-epoch infrared photometry in the K s -band for 74 bright RR Lyrae variable stars tied directly to the Two-Micron All-Sky Survey (2MASS) photometric system. We systematize additional K-band photometry from the literature to the 2MASS system and combine it to obtain photometry for 146 RR Lyrae stars on a consistent, mode…
Nitrogen abundance in the X-ray halos of clusters and groups of galaxies
Gu, Liyi; Mao, Junjie; Kaastra, Jelle S. +6 more
Context. Chemical abundances in the X-ray halos (also known as the intracluster medium, ICM) of clusters and groups of galaxies can be measured via prominent emission line features in their X-ray spectra. Elemental abundances are footprints of time-integrated yields of various stellar populations that have left their specific abundance patterns pr…
A compilation of known QSOs for the Gaia mission
Liao, Shi-Long; Qi, Zhao-Xiang; Guo, Su-Fen +1 more
Quasars are essential for astrometry in the sense that they are spatially stationary because of their large distance from the Sun. The European Space Agency (ESA) astrometric satellite Gaia is scanning the whole sky with unprecedented accuracy up to the level of a few µas. However, Gaia’s two-fields-of-view-observation strategy may introduce…
Interstellar dust in the solar system: model versus in situ spacecraft data
Altobelli, Nicolas; Krüger, Harald; Grün, Eberhard +3 more
Context. In the early 1990s, contemporary interstellar dust penetrating deep into the heliosphere was identified with the in situ dust detector on board the Ulysses spacecraft. Later on, interstellar dust was also identified in the data sets measured with dust instruments on board Galileo, Cassini, and Helios. Ulysses monitored the interstellar du…