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Bubbles and Knots in the Kinematical Structure of the Bipolar Planetary Nebula NGC 2818
Vázquez, Roberto
High-resolution Hubble Space Telescope archive imaging and high-dispersion spectroscopy are used to study the complex morphological and kinematical structure of the planetary nebula, NGC 2818. We analyze narrowband Hα, [O III], [N II], [S II], and He II images, addressing important morphological features. Ground-based long-slit echelle spectra wer…
On the Polarimetric Signature of Emerging Magnetic Loops in the Quiet Sun
Viticchié, B.
The abundance of Stokes V profiles dominated by one lobe at the locations of emergence of Ω-shaped magnetic loops is evaluated. The emergence events were found in Hinode Solar Optical Telescope/spectro-polarimeter time sequences of quiet-Sun regions. Such a study has the aim of confirming a prediction based on the basic geometrical and physical pr…
Revisiting Algorithms for Generating Surrogate Time Series
Papadakis, I. E.; Brinkmann, W.; Gliozzi, M. +1 more
The method of surrogates is one of the key concepts of nonlinear data analysis. Here, we demonstrate that commonly used algorithms for generating surrogates often fail to generate truly linear time series. Rather, they create surrogate realizations with Fourier phase correlations leading to nondetections of nonlinearities. We argue that reliable s…
Optical identification of six hard X-ray sources from the INTEGRAL and SWIFT all-sky surveys
Bikmaev, I. F.; Lutovinov, A. A.; Revnivtsev, M. G. +1 more
We present results of optical identifications of six hard X-ray sources from the INTEGRAL and Swift all-sky surveys (IGR J03249+4041, SWIFT J1449.5+8602, SWIFT J1542.0-1410, IGR J17009+3559, IGR J18151-1052, IGR J18538-0102). Our optical observations were performed in 2009-2011 with the 6-m BTA telescope (Special Astrophysical Observatory, Nizhnii…
Searching for γ-Ray Blazar Candidates among the Unidentified INTEGRAL Sources
Tosti, G.; Massaro, F.; Paggi, A. +1 more
The identification of low-energy counterparts for γ-ray sources is one of the biggest challenges in modern γ-ray astronomy. Recently, we developed and successfully applied a new association method to recognize γ-ray blazar candidates that could be possible counterparts for the unidentified γ-ray sources above 100 MeV in the second Fermi Large Area…
The Herschel Filament: A Signature of the Environmental Drivers of Galaxy Evolution during the Assembly of Massive Clusters at z = 0.9
Egami, E.; Yee, H. K. C.; Gladders, M. +11 more
We have discovered a 2.5 Mpc (projected) long filament of infrared-bright galaxies connecting two of the three ~5 × 1014 M ⊙ clusters making up the RCS 2319+00 supercluster at z = 0.9. The filament is revealed in a deep Herschel Spectral and Photometric Imaging REceiver (SPIRE) map that shows 250-500 µm emission associa…
Measuring the Geometry of the Universe from Weak Gravitational Lensing behind Galaxy Groups in the HST COSMOS Survey
Koekemoer, Anton M.; Ellis, Richard; Leauthaud, Alexie +12 more
Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the l…
Subsurface Flows in and Around Active Regions with Rotating and Non-rotating Sunspots
Hill, F.; González Hernández, I.; Komm, R. W. +2 more
The temporal variation of the horizontal velocity in sub-surface layers beneath three different types of active region is studied using the technique of ring diagrams. In this study, we select active regions (ARs) 10923, 10930, 10935 from three consecutive Carrington rotations: AR 10930 contains a fast-rotating sunspot in a strong emerging active …
XMM-Newton Observation of the Very Old Pulsar J0108-1431
Manchester, R. N.; Pavlov, G. G.; Shannon, R. M. +3 more
We report on an X-ray observation of the 166 Myr old radio pulsar J0108-1431 with XMM-Newton. The X-ray spectrum can be described by a power-law model with a relatively steep photon index Γ ≈ 3 or by a combination of thermal and non-thermal components, e.g., a power-law component with fixed photon index Γ = 2 plus a blackbody component with a temp…
In the whirlpool's coils: tracing substructure from combined optical/X-ray data in the galaxy cluster A1300
Finoguenov, A.; Böhringer, H.; Ziparo, F. +3 more
Structure formation is thought to act via hierarchical mergers and accretion of smaller systems driven by gravity, with dark matter dominating the gravitational field. Combining X-ray and optical imaging and spectroscopy provides a powerful approach to the study of the cluster dynamics and mass assembly history. The ROSAT-ESO Flux Limited X-ray (R…