Search Publications
High-resolution Reddening Map in the Direction of the Stellar System Terzan 5
Dalessandro, Emanuele; Mucciarelli, Alessio; Ferraro, Francesco R. +7 more
We have used optical images acquired with the Hubble Space Telescope to construct the first high-resolution extinction map in the direction of Terzan 5, a peculiar stellar system in the inner bulge of our Galaxy. The map has a spatial resolution of 8'' × 8'', over a total field of view of 200'' × 200''. The absorption clouds show a patchy structur…
On the Weak-wind Problem in Massive Stars: X-Ray Spectra Reveal a Massive Hot Wind in µ Columbae
Hamaguchi, Kenji; Huenemoerder, David P.; Ignace, Richard +4 more
µ Columbae is a prototypical weak-wind O star for which we have obtained a high-resolution X-ray spectrum with the Chandra LETG/ACIS instrument and a low-resolution spectrum with Suzaku. This allows us, for the first time, to investigate the role of X-rays on the wind structure in a bona fide weak-wind system and to determine whether there a…
The Size Evolution of Passive Galaxies: Observations from the Wide-Field Camera 3 Early Release Science Program
Holtzman, J. A.; O'Connell, R. W.; Walker, A. R. +28 more
We present the size evolution of passively evolving galaxies at z ~ 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z >~ 1.5. We identify 30 galaxies in…
Herschel Observations of Interstellar Chloronium
Menten, Karl M.; Nagy, Zsófia; Neufeld, David A. +21 more
Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have observed para-chloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight lines to the bright submillimeter continuum sources Sgr A (+50 km s-1<…
Broadband Spectroscopy Using Two Suzaku Observations of the HMXB GX 301-2
Rothschild, Richard E.; Fürst, Felix; Pottschmidt, Katja +5 more
We present the analysis of two Suzaku observations of GX 301-2 at two orbital phases after the periastron passage. Variations in the column density of the line-of-sight absorber are observed, consistent with accretion from a clumpy wind. In addition to a cyclotron resonance scattering feature (CRSF), multiple fluorescence emission lines were detec…
Magnetic Fields of an Active Region Filament from Full Stokes Analysis of Si I 1082.7 nm and He I 1083.0 nm
Liu, Y.; Lagg, A.; Solanki, S. +1 more
Vector magnetic fields of an active region filament in the photosphere and upper chromosphere are obtained from spectro-polarimetric observations recorded with the Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope. We apply Milne-Eddington inversions on full Stokes vectors of the photospheric Si I 1082.7 nm and the upper …
Measuring Microlensing Using Spectra of Multiply Lensed Quasars
Muñoz, J. A.; Mediavilla, E.; Motta, V. +1 more
We report on a program of spectroscopic observations of gravitationally lensed QSOs with multiple images. We seek to establish whether microlensing is occurring in each QSO image using only single-epoch observations. We calculate flux ratios for the cores of emission lines in image pairs to set a baseline for no microlensing. The offset of the con…
Velocity and Magnetic Transients Driven by the X2.2 White-light Flare of 2011 February 15 in NOAA 11158
Maurya, R. A.; Ambastha, A.; Vemareddy, P.
The first X-class flare of the current solar cycle 24 occurred in Active Region NOAA 11158 during its central meridian passage on 2011 February 15. This two-ribbon white-light flare was observed by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. During the peak phase of the flare, we detected magnetic and Dopple…
A 30 AU Radius CO Gas Hole in the Disk around the Herbig Ae Star Oph IRS 48
van Dishoeck, E. F.; Pontoppidan, K. M.; Herczeg, G. J. +1 more
The physical processes leading to the disappearance of disks around young stars are not well understood. A subclass of transitional disks, the so-called cold disks with large inner dust holes, provides a crucial laboratory for studying disk dissipation processes. IRS 48 has a 30 AU radius hole previously measured from dust continuum imaging at 18.…
The Coronal Source of Extreme-ultraviolet Line Profile Asymmetries in Solar Active Region Outflows
Warren, Harry P.; Brooks, David H.
High-resolution spectra from the Hinode EUV Imaging Spectrometer have revealed that coronal spectral line profiles are sometimes asymmetric, with a faint enhancement in the blue wing on the order of 100 km s-1. These asymmetries could be important since they may be subtle yet diagnostically useful signatures of coronal heating or solar …