Search Publications
A Helicity-Based Method to Infer the CME Magnetic Field Magnitude in Sun and Geospace: Generalization and Extension to Sun-Like and M-Dwarf Stars and Implications for Exoplanet Habitability
Patsourakos, S.; Georgoulis, M. K.
Patsourakos et al. (Astrophys. J.817, 14, 2016) and Patsourakos and Georgoulis (Astron. Astrophys.595, A121, 2016) introduced a method to infer the axial magnetic field in flux-rope coronal mass ejections (CMEs) in the solar corona and farther away in the interplanetary medium. The method, based on the conservation principle of magnetic helicity, …
NuSTAR and Swift Observations of the Ultraluminous X-Ray Source IC 342 X-1 in 2016: Witnessing Spectral Evolution
Fabrika, S.; Shidatsu, M.; Ueda, Y.
We report on an X-ray observing campaign of the ultraluminous X-ray source IC 342 X-1 with NuSTAR and Swift in 2016 October, in which we captured the very moment when the source showed spectral variation. The Swift/XRT spectrum obtained in October 9-11 has a power-law shape and is consistent with those observed in the coordinated XMM-Newton and Nu…
Peering Through the Dust. II. XMM-Newton Observations of Two Additional FIRST-2MASS Red Quasars
Piconcelli, Enrico; Lacy, Mark; LaMassa, Stephanie +2 more
We obtained XMM-Newton observations of two highly luminous dust-reddened quasars, F2M1113+1244 and F2M1656+3821, that appear to be in the early, transitional phase predicted by merger-driven models of quasar/galaxy co-evolution. These sources have been well studied at optical through mid-infrared wavelengths and are growing relatively rapidly, wit…
Time-series Spectroscopy of the Oscillating Algol-type Binary AB Cas
Koo, Jae-Rim; Lee, Chung-Uk; Kim, Seung-Lee +4 more
This study presents the high-resolution spectra of the eclipsing binary AB Cas with a δ Sct-type pulsating component, which were obtained using the Bohyunsan Optical Echelle Spectrograph in Korea. In this paper, the radial velocities for the primary and secondary stars were measured from a total of 27 spectra made during two nights in 2015 October…
Hydrogen in diffuse molecular clouds in the Milky Way. Atomic column densities and molecular fraction along prominent lines of sight
Menten, K. M.; Gerin, M.; Wyrowski, F. +6 more
Context. Recent submillimeter and far-infrared wavelength observations of absorption in the rotational ground-state lines of various simple molecules against distant Galactic continuum sources have opened the possibility of studying the chemistry of diffuse molecular clouds throughout the Milky Way. In order to calculate abundances, the column den…
Morphological Properties of the Crab Nebula: A Detailed Multiwavelength Study Based on New VLA, HST, Chandra, and XMM-Newton Images
Talavera, A.; Pavlov, G. G.; Kargaltsev, O. +3 more
We present a detailed analysis of the morphological properties of the Crab Nebula across the electromagnetic spectrum based on new and previous high-quality data from radio to X-rays. In the radio range we obtained an image of the entire nebula at 3 GHz with subarcsecond angular resolution using the VLA (NRAO) and an image at 100 GHz of the centra…
XMM-Newton spectroscopy of the accreting magnetar candidate 4U0114+65
Torrejón, J. M.; Postnov, K.; Oskinova, L. +3 more
Aims: 4U0114+65 is one of the slowest known X-ray pulsars. We present an analysis of a pointed observation by the XMM-Newton X-ray telescope in order to study the nature of the X-ray pulsations and the accretion process, and to diagnose the physical properties of the donor's stellar wind.
Methods: We analysed the energy-resolved light cu…
Small electron acceleration episodes in the solar corona
James, Tomin; Subramanian, Prasad; Kontar, Eduard P.
We study the energetics of non-thermal electrons produced in small acceleration episodes in the solar corona. We carried out an extensive survey spanning 2004-2015 and shortlisted six impulsive electron events detected at 1 au that were not associated with large solar flares (GOES soft X-ray class > C1) or with coronal mass ejections. Each of t…
Constraining cosmological ultralarge scale structure using numerical relativity
Peiris, Hiranya V.; Braden, Jonathan; Johnson, Matthew C. +1 more
Cosmic inflation, a period of accelerated expansion in the early universe, can give rise to large amplitude ultralarge scale inhomogeneities on distance scales comparable to or larger than the observable universe. The cosmic microwave background (CMB) anisotropy on the largest angular scales is sensitive to such inhomogeneities and can be used to …
Improved Diffuse Foreground Subtraction with the ILC Method: CMB Map and Angular Power Spectrum Using Planck and WMAP Observations
Aluri, Pavan K.; Souradeep, Tarun; Saha, Rajib +2 more
We report an improved technique for diffuse foreground minimization from Cosmic Microwave Background (CMB) maps using a new multiphase iterative harmonic space internal-linear-combination (HILC) approach. Our method nullifies a foreground leakage that was present in the old and usual iterative HILC method. In phase 1 of the multiphase technique, w…