Search Publications
Highly variable AGN from the XMM-Newton slew survey
Read, A. M.; Esquej, P.; Miniutti, G. +4 more
Aims: We investigate the properties of a variability-selected complete sample of active galactic nuclei (AGN) in order to identify the mechanisms which cause large amplitude X-ray variability on timescales of years.
Methods: A complete sample of 24 sources was constructed, from AGN which changed their soft X-ray luminosity by more than o…
A Hard X-Ray Study of the Normal Star-forming Galaxy M83 with NuSTAR
Argo, M. K.; Krivonos, R.; Wik, D. R. +19 more
We present the results from sensitive, multi-epoch NuSTAR observations of the late-type star-forming galaxy M83 (d = 4.6 Mpc). This is the first investigation to spatially resolve the hard (E\gt 10 keV) X-ray emission of this galaxy. The nuclear region and ∼20 off-nuclear point sources, including a previously discovered ultraluminous X-ray source,…
Helical Motions of Fine-structure Prominence Threads Observed by Hinode and IRIS
Liu, Wei; Tsuneta, Saku; Okamoto, Takenori J.
Fine-structure dynamics in solar prominences holds critical clues to understanding their physical nature of significant space-weather implications. We report evidence of rotational motions of horizontal helical threads in two active-region prominences observed by the Hinode and/or Interface Region Imaging Spectrograph satellites at high resolution…
Ceres: Sulfur deposits and graphitized carbon
Vilas, Faith; Li, Jian-Yang; Hendrix, Amanda R.
We report new results from observations of the dwarf planet Ceres using the Hubble Space Telescope in the spectral range 1160-5700 Å. Comparisons between Ceres' UV-visible spectra and laboratory measurements indicate that both sulfur species and graphitized carbon are important on Ceres' surface. We find a latitudinal gradient in UV absorption, wi…
The awakening of the γ-ray narrow-line Seyfert 1 galaxy PKS 1502+036
Pearson, T. J.; Giroletti, M.; Readhead, A. C. S. +7 more
After a long low-activity period, a γ-ray flare from the narrow-line Seyfert 1 PKS 1502+036 (z = 0.4089) was detected by the Large Area Telescope (LAT) on board Fermi in 2015. On 2015 December 20, the source reached a daily peak flux, in the 0.1-300 GeV band, of (93 ± 19) × 10-8 ph cm-2 s-1, attaining a flux of (23…
A Comparison of Global Magnetic Field Skeletons and Active-Region Upflows
Culhane, J. L.; Brooks, D. H.; Harra, L. K. +2 more
Plasma upflows have been detected in active regions using Doppler velocity maps. The origin and nature of these upflows is not well known with many of their characteristics determined from the examination of single events. In particular, some studies suggest these upflows occur along open field lines and, hence, are linked to sources of the solar …
Observational effects of a running Planck mass
Huang, Zhiqi
We consider observational effects of a running effective Planck mass in the scalar-tensor gravity theory. At the background level, an increasing effective Planck mass allows a larger Hubble constant H0, which is more compatible with the local direct measurements. At the perturbative level, for cosmic microwave background (CMB) anisotrop…
Spheroidal and ellipsoidal harmonic expansions of the gravitational potential of small Solar System bodies. Case study: Comet 67P/Churyumov-Gerasimenko
Reimond, Stefan; Baur, Oliver
Gravitational features are a fundamental source of information to learn more about the interior structure and composition of planets, moons, asteroids, and comets. Gravitational field modeling typically approximates the target body with a sphere, leading to a representation in spherical harmonics. However, small celestial bodies are often irregula…
Astrometry with MCAO: HST-GeMS proper motions in the globular cluster NGC 6681
Massari, D.; Stetson, P. B.; Bono, G. +7 more
Aims: For the first time the astrometric capabilities of the Gemini Multi-Conjugate Adaptive Optics System (GeMS) facility at the Gemini South Adaptive Optics Imager (GSAOI) camera on Gemini-South are tested to quantify the accuracy in determining stellar proper motions in the Galactic globular cluster NGC 6681.
Methods: Proper motions f…
On the distance to the North Polar Spur and the local CO-H2 factor
Casandjian, J. M.; Kuntz, K. D.; Lallement, R. +4 more
Aims: Most models identify the X-ray bright North Polar Spur (NPS) with a hot interstellar (IS) bubble in the Sco-Cen star-forming region at ≃130 pc. An opposite view considers the NPS as a distant structure associated with Galactic nuclear outflows. Constraints on the NPS distance can be obtained by comparing the foreground IS gas column inf…