Search Publications
Observations of Upward Propagating Waves in the Transition Region and Corona above Sunspots
Fu, Hui; Li, Bo; Xia, Lidong +2 more
We present observations of persistent oscillations of some bright features in the upper-chromosphere/transition region above sunspots taken by IRIS SJ 1400 Å and upward propagating quasi-periodic disturbances along coronal loops rooted in the same region taken by the AIA 171 Å passband. The oscillations of the features are cyclic oscillatory motio…
EPIC 203868608: A Low-mass Quadruple Star System in the Upper Scorpius OB Association
Albrecht, Simon; Hillenbrand, Lynne A.; Mawet, Dimitri +3 more
Young multiple star systems provide excellent testing grounds for theories of star formation and evolution. EPIC 203868608 was previously studied as a triple star system in the Upper Scorpius OB association, but the followup Keck NIRC2/HIRES/NIRSPAO observations reported here reveal its quadruple nature. We find that the system consists of a doubl…
Kinematics of Stars from the TGAS (Gaia DR1) Catalogue
Tsvetkov, A. S.; Vityazev, V. V.; Popov, A. V. +3 more
Based on the stellar proper motions of the TGAS (Gaia DR1) catalogue, we have analyzed the velocity field of main-sequence stars and red giants from the TGAS catalogue with heliocentric distances up to 1.5 kpc. We have obtained four variants of kinematic parameters corresponding to different methods of calculating the distances from the parallaxes…
Modelling of integrated-light spectra from the optical to the near-infrared: the globular cluster G280 in M31
Larsen, S. S.; Pugliese, G.; Brodie, J. P.
Context. In previous papers, we introduced our method for measuring chemical abundances from integrated-light spectra of globular clusters and applied it to a variety of extragalactic star clusters. Our work so far, however, has concentrated primarily on the optical range 4200 Å -6200 Å.
Aims: Here we extend our analysis technique to the infr…
Survival function analysis of planet size distribution with Gaia Data Release 2 updates
Vanderburg, Andrew; Zeng, Li; Sasselov, Dimitar D. +1 more
Applying the survival function analysis to the planet radius distribution of the Kepler confirmed/candidate planets, we have identified two natural divisions of planet radius at 4 Earth radii (R⊕) and 10 R⊕. These divisions place constraints on planet formation and interior structure model. The division at 4 R⊕ sep…
Periodic optical variability and debris accretion in white dwarfs: a test for a causal connection*
Maoz, Dan; Loeb, Abraham; Hallakoun, Na'ama +9 more
Recent Kepler photometry has revealed that about half of white dwarfs (WDs) have periodic, low-level (∼10-4 - 10-3), optical variations. Hubble Space Telescope (HST) ultraviolet spectroscopy has shown that up to about one half of WDs are actively accreting rocky planetary debris, as evidenced by the presence of photospheric m…
Pre-discovery transits of the exoplanets WASP-18b and WASP-33b from Hipparcos
McDonald, I.; Kerins, E.
We recover transits of WASP-18b and WASP-33b from Hipparcos (1989-1993) photometry. Marginal detections of HAT-P-56b and HAT-P-2b may be also present in the data. New ephemerides are fitted to WASP-18b and WASP-33b. A tentative (∼1.3σ) orbital decay is measured for WASP-18b, but the implied tidal quality factor (Q΄ ∼ 5 × 105)…
Evolution of the Solar Wind Speed with Heliocentric Distance and Solar Cycle. Surprises from Ulysses and Unexpectedness from Observations of the Solar Corona
Malova, H. V.; Zelenyi, L. M.; Bemporad, A. +5 more
An extensive analysis of Ulysses observations of the solar wind speed V from 1990 to 2008 is undertaken. It is shown that the evolution of V with heliocentric distance r depends substantially on both the heliolatitude and the solar activity cycle. Deviations from the predicted Parker's profile of V(r) are so considerable that cannot be explained b…
A distance estimate to the Cygnus Loop based on the distances to two stars located within the remnant
Neustadt, Jack M. M.; Milisavljevic, Dan; Fesen, Robert A. +1 more
Underlying nearly every quantitative discussion of the Cygnus Loop supernova remnant is uncertainty about its distance. Here, we present optical images and spectra of nebulosities around two stars whose mass-loss material appears to have interacted with the remnant's expanding shock front and thus can be used to estimate the Cygnus Loop's distance…
Imaging Stellar Radio Photospheres with the Next Generation Very Large Array
White, S. M.; Carilli, C. L.; Butler, B. +2 more
We perform simulations of the capabilities of the next generation Very Large Array to image stellar radio photospheres. For very large (in angle) stars, such as red supergiants within a few hundred parsecs, good imaging fidelity results can be obtained on radio photospheric structures at 38 GHz employing standard techniques, such as disk model fit…