Search Publications
The Emission of Cygnus X-1: Observations with INTEGRAL SPI from 20 keV to 2 MeV
Malzac, J.; Jourdain, E.; Roques, J. P.
We report on Cyg X-1 observations performed by the SPI telescope on board the INTEGRAL mission and distributed over more than 6 years. We investigate the variability of the intensity and spectral shape of this peculiar source in the hard X-ray domain, and more particularly up to the MeV region. We first study the total averaged spectrum which pres…
Suzaku Observations of 4U 1957+11: Potentially the Most Rapidly Spinning Black Hole in (the Halo of) the Galaxy
Pottschmidt, Katja; Wilms, Jörn; Nowak, Michael A. +3 more
We present three Suzaku observations of the black hole candidate 4U 1957+11 (V1408 Aql)—a source that exhibits some of the simplest and cleanest examples of soft, disk-dominated spectra. 4U 1957+11 also presents among the highest peak temperatures found from disk-dominated spectra. Such temperatures may be associated with rapid black hole spin. Th…
Numerical Modeling of the Initiation of Coronal Mass Ejections in Active Region NOAA 9415
Poedts, S.; Zuccarello, F. P.; Meliani, Z.
Coronal mass ejections (CMEs) and solar flares are the main drivers of weather in space. Understanding how these events occur and what conditions might lead to eruptive events is of crucial importance for up to date and reliable space weather forecasting. The aim of this paper is to present a numerical magnetohydrodynamic (MHD) data-inspired model…
Study of Single-lobed Circular Polarization Profiles in the Quiet Sun
Sainz Dalda, A.; Martínez-Sykora, J.; Title, A. +1 more
The existence of asymmetries in the circular polarization (Stokes V) profiles emerging from the solar photosphere has been known since the 1970s. These profiles require the presence of a velocity gradient along the line of sight (LOS), possibly associated with gradients of magnetic field strength, inclination, and/or azimuth. We have focused our s…
Hydrogen Fluoride in High-mass Star-forming Regions
Ceccarelli, C.; Lis, D. C.; Phillips, T. G. +5 more
Hydrogen fluoride (HF) has been established to be an excellent tracer of molecular hydrogen in diffuse clouds. In denser environments, however, the HF abundance has been shown to be approximately two orders of magnitude lower. We present Herschel/HIFI observations of HF J = 1-0 toward two high-mass star formation sites, NGC 6334 I and AFGL 2591. I…
The Close T Tauri Binary System V4046 Sgr: Rotationally Modulated X-Ray Emission from Accretion Shocks
Donati, J. -F.; Audard, M.; Güdel, M. +11 more
We report initial results from a quasi-simultaneous X-ray/optical observing campaign targeting V4046 Sgr, a close, synchronous-rotating classical T Tauri star (CTTS) binary in which both components are actively accreting. V4046 Sgr is a strong X-ray source, with the X-rays mainly arising from high-density (n e~ 1011-1012…
Newly Discovered Global Temperature Structures in the Quiet Sun at Solar Minimum
Landi, Enrico; Gombosi, Tamas I.; Frazin, Richard A. +3 more
Magnetic loops are building blocks of the closed-field corona. While active region loops are readily seen in images taken at EUV and X-ray wavelengths, quiet-Sun (QS) loops are seldom identifiable and are therefore difficult to study on an individual basis. The first analysis of solar minimum (Carrington Rotation 2077) QS coronal loops utilizing a…
The Distance to M101 Hosting Type Ia Supernova 2011fe Based on the Tip of the Red Giant Branch
Lee, Myung Gyoon; Jang, In Sung
We present a new determination of the distance to M101, host of the Type Ia supernova (SN Ia) 2011fe, based on the tip of the red giant branch (TRGB) method. Our determination is based on Hubble Space Telescope archival F555W and F814W images of nine fields within the galaxy. Color-magnitude diagrams of arm-free regions in all fields show a promin…
Evidence of Photoevaporation and Spatial Variation of Grain Sizes in the Orion 114-426 Protoplanetary Disk
Ricci, L.; Miotello, Anna; Robberto, Massimo +1 more
Deep Hubble Space Telescope broadband images taken with Advanced Camera for Surveys (ACS) and WFPC2 of the giant (~1000 AU diameter) dark silhouette proplyd 114-426 in the Orion Nebula show that this system is tilted, asymmetric, warped, and photoevaporated. The exquisite angular resolution of ACS allows us to map the distribution of dust grains a…
Secular Changes in Eta Carinae's Wind 1998-2011
Walter, Frederick M.; Humphreys, Roberta M.; Davidson, Kris +4 more
Stellar wind-emission features in the spectrum of eta Carinae have decreased by factors of 1.5-3 relative to the continuum within the last 10 years. We investigate a large data set from several instruments (STIS, GMOS, UVES) obtained between 1998 and 2011 and analyze the progression of spectral changes in direct view of the star, in the reflected …