Search Publications
He II λ4686 Emission from the Massive Binary System in η Car: Constraints to the Orbital Elements and the Nature of the Periodic Minima
Gull, T. R.; Corcoran, M. F.; Madura, T. I. +27 more
Eta Carinae (η Car) is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He II λ4686 line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of t…
The X-ray spectral evolution of the ultraluminous X-ray source Holmberg IX X-1
Done, Chris; Roberts, Timothy P.; Luangtip, Wasutep
We present a new analysis of X-ray spectra of the archetypal ultraluminous X-ray source (ULX) Holmberg IX X-1 obtained by the Swift, XMM-Newton and NuSTAR observatories. This ULX is a persistent source, with a typical luminosity of ∼1040 erg s-1, that varied by a factor of 4-5 over eight years. We find that its spectra tend t…
The Solar Internetwork. II. Flux Appearance and Disappearance Rates
Gošić, M.; Bellot Rubio, L. R.; Katsukawa, Y. +2 more
Small-scale internetwork magnetic fields are important ingredients of the quiet Sun. In this paper we analyze how they appear and disappear on the solar surface. Using high resolution Hinode magnetograms, we follow the evolution of individual magnetic elements in the interior of two supergranular cells at the disk center. From up to 38 hr of conti…
The origin of UV-optical variability in AGN and test of disc models: XMM-Newton and ground-based observations of NGC 4395
Gandhi, P.; Netzer, H.; Peterson, B. M. +12 more
The origin of short timescale (weeks/months) variability of AGN, whether due to intrinsic disc variations or reprocessing of X-ray emission by a surrounding accretion disc, has been a puzzle for many years. However recently a number of observational programmes, particularly of NGC 5548 with Swift, have shown that the UV/optical variations lag behi…
Detailed homogeneous abundance studies of 14 Galactic s-process enriched post-AGB stars: In search of lead (Pb)
Van Winckel, H.; Kamath, D.; Karakas, A. I. +4 more
Context. This paper is part of a larger project in which we systematically study the chemical abundances of Galactic and extragalactic post-asymptotic giant branch (post-AGB) stars. The goal at large is to provide improved observational constraints to the models of the complex interplay between the AGB s-process nucleosynthesis and the associated …
Radial Profile of the 3.5 keV Line Out to R200 in the Perseus Cluster
Boyarsky, Alexey; Ruchayskiy, Oleg; Bulbul, Esra +10 more
The recent discovery of the unidentified emission line at 3.5 keV in galaxies and clusters has attracted great interest from the community. As the origin of the line remains uncertain, we study the surface brightness distribution of the line in the Perseus cluster since that information can be used to identify its origin. We examine the flux distr…
An EMHD soliton model for small-scale magnetic holes in magnetospheric plasmas
Pu, Zu-Yin; Xiao, Chi-Jie; Fu, Sui-Yan +6 more
Small-scale magnetic holes (SSMHs) in the magnetosphere plasma sheet are investigated in this paper. A developed electron magnetohydrodynamics (EMHD) soliton model is proposed as a new approach to SSMHs formation. The Biermann battery effect is taken into account in resolving the magnetic evolution equation with a slow-mode solution in the weak no…
Forecasting performance of CMB experiments in the presence of complex foreground contaminations
Errard, Josquin; Stompor, Radek; Poletti, Davide
We present a new, semianalytic framework for estimating the level of residuals present in cosmic microwave background (CMB) maps derived from multifrequency CMB data and forecasting their impact on cosmological parameters. The data are assumed to contain non-negligible signals of astrophysical and/or Galactic origin, which we clean using a paramet…
Statistical analysis of suprathermal electron drivers at 67P/Churyumov-Gerasimenko
Frahm, R. A.; Eriksson, A.; Henri, P. +16 more
We use observations from the Ion and Electron Sensor (IES) on board the Rosetta spacecraft to study the relationship between the cometary suprathermal electrons and the drivers that affect their density and temperature. We fit the IES electron observations with the summation of two kappa distributions, which we characterize as a dense and warm pop…
Toward a Tomographic Analysis of the Cross-Correlation between Planck CMB Lensing and H-ATLAS Galaxies
Baccigalupi, C.; Bielewicz, P.; Danese, L. +10 more
We present an improved and extended analysis of the cross-correlation between the map of the cosmic microwave background (CMB) lensing potential derived from the Planck mission data and the high-redshift galaxies detected by the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in the photometric redshift range {z}{{ph}}≥slan…