Search Publications
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 …
Jet Rotation Investigated in the Near-ultraviolet with the Hubble Space Telescope Imaging Spectrograph
Bacciotti, Francesca; Coffey, Deirdre; Eislöffel, Jochen +2 more
We present results of the second phase of our near-ultraviolet investigation into protostellar jet rotation using the Hubble Space Telescope Imaging Spectrograph. We obtain long-slit spectra at the base of five T Tauri jets to determine if there is a difference in radial velocity between the jet borders which may be interpreted as a rotation signa…
Prior Flaring as a Complement to Free Magnetic Energy for Forecasting Solar Eruptions
Moore, Ronald L.; Falconer, David A.; Barghouty, Abdulnasser F. +1 more
From a large database of (1) 40,000 SOHO/MDI line-of-sight magnetograms covering the passage of 1300 sunspot active regions across the 30° radius central disk of the Sun, (2) a proxy of each active region's free magnetic energy measured from each of the active region's central-disk-passage magnetograms, and (3) each active region's full-disk-passa…
Rebirth of X-Ray Emission from the Born-again Planetary Nebula A30
Steffen, M.; Gruendl, R. A.; Hamann, W. -R. +8 more
The planetary nebula A30 is believed to have undergone a very late thermal pulse resulting in the ejection of knots of hydrogen-poor material. Using multi-epoch Hubble Space Telescope images, we have detected the angular expansion of these knots and derived an age of 850+280 - 150 yr. To investigate the spectral and spatial p…
The Cold Shoulder: Emission Measure Distributions of Active Region Cores
Schmelz, J. T.; Pathak, S.
The coronal heating mechanism for active region core loops is difficult to determine because these loops are often not resolved and cannot be studied individually. Rather, we concentrate on the "inter-moss" areas between loop footpoints. We use observations from the Hinode EUV Imaging Spectrometer and the X-Ray Telescope to calculate the emission …
Superorbital Modulation of X-Ray Emission from Gamma-Ray Binary LSI +61 303
Lutovinov, A.; Molkov, S.; Chernyakova, M. +3 more
We report the discovery of a systematic constant time lag between the X-ray and radio flares of the gamma-ray binary LSI +61 303, persistent over a long, multi-year timescale. Using the data from the monitoring of the system by RXTE we show that the orbital phase of X-ray flares from the source varies from phi X ~= 0.35 to phi X <…