Search Publications
Spatial Variation in Temperature and Density in the IC 63 PDR from H2 Spectroscopy
Karoly, Janik; Soam, Archana; Andersson, B. -G. +2 more
We have measured the gas temperature in the IC 63 photodissociation region (PDR) using the S(1) and S(5) pure rotation lines of molecular hydrogen with SOFIA/EXES. We divide the PDR into three regions for analysis based on the illumination from γ Cas: sunny, ridge, and shady. Constructing rotation diagrams for the different regions, we obtain temp…
Constraining Soft and Hard X-Ray Irradiation in Ultraluminous X-Ray Sources
Feng, Hua; Qiu, Yanli
Most ultraluminous X-ray sources (ULXs) are argued to be powered by supercritical accretion onto compact objects. One of the key questions regarding these objects is whether or not the hard X-rays are geometrically beamed toward the symmetric axis. We propose testing the scenario using disk irradiation to see how much the outer accretion disk sees…
SDSS J1059+4251, a Highly Magnified z 2.8 Star-forming Galaxy: ESI Observations of the Rest-frame UV Spectrum
Pettini, Max; Erb, Dawn K.; James, Bethan L. +3 more
Detailed analyses of high-redshift galaxies are challenging because these galaxies are faint, but this difficulty can be overcome with gravitational lensing, in which the magnification of the flux enables spectroscopy with a high signal-to-noise ratio (S/N). We present the rest-frame ultraviolet (UV) Keck Echellette Spectrograph and Imager (ESI) s…
The Complex Nature of Magnetic Element Transport in the Quiet Sun: The Multiscaling Character
Consolini, Giuseppe; Giannattasio, Fabio
In recent studies the dynamic properties of small-scale magnetic fields (magnetic elements [MEs]) in the quiet Sun were used to investigate peculiar features of turbulent convection and get insights on the characteristic spatial and temporal scales of evolution of magnetic fields, from granular to supergranular. The aim of this work is to extend p…
Thermophysical Characterization of Cyclic Frost Formation in the Subsurface and Nominal Water Activity on Comets: Case Study of 67P/Churyumov-Gerasimenko
Shi, Xian; Hu, Xuanyu
We use a generic thermophysical model to study in detail the formation of water-ice frost in the near-surface layers of comet 67P/Churyumov-Gerasimenko. We show that nightly frost formation is a common phenomenon. In particular, while abrupt landscapes may be conducive to frost formation, they are not a requisite condition. We show that the proces…
Sustaining Star Formation in the Galactic Star Cluster M 36?
Chen, Wen Ping; Gao, Yu; Sun, Yan +3 more
We present comprehensive characterization of the Galactic open cluster M 36. Some 200 member candidates, with an estimated contamination rate of ∼8%, have been identified on the basis of proper motion and parallax measured by the Gaia DR2. The cluster has a proper motion grouping around ( ${\mu }_{\alpha }\cos \delta =-0.15\pm 0.01$ <!-- -->…
Dynamics of Sunspot Shock Waves in the Chromosphere and Transition Region
Kayshap, Pradeep; Tripathi, Durgesh; Jelínek, P.
We study the dynamics of shock waves observed in the umbra of a sunspot using the spectroscopic observations from the Interface Region Imaging Spectrograph. The presence of a shock significantly deforms the shape of the spectral lines of Mg II, C II, and Si IV. We found that C II 1335.71 Å and Si IV 1393.75 Å show double-peaked profiles that chang…
Shocks and Molecules in Diffuse Interstellar Cloud Pairs
Heiles, Carl; Reach, William T.
The diffuse interstellar medium (ISM) is dynamic, and its chemistry and evolution are determined by shock fronts as well as photodissociation. Shocks are implied by the supersonic motions and velocity dispersion, often statistically called "turbulence". We compare models of magnetohydrodynamic (MHD) shocks, with speeds typical of cloud motions thr…
Physical Characteristics of Unstructured Coronal Clouds
Golub, L.; Hahn, M.; Savin, D. W. +2 more
Active regions in the inner solar corona, when observed in X-ray emission, consist of bright, hot loops surrounded by unstructured clouds. The emission from the clouds extends to a height of ≈4-5 × 104 km at temperatures of ≈2-3 MK. These "hot clouds" are variable, but persist for many days and do not appear to connect directly to the a…
Characterization of HD 206893 B from Near- to Thermal-infrared
Lee, Eve J.; Gao, Peter; Beichman, Charles +9 more
HD 206893 B is a brown-dwarf companion orbiting inside the debris disk of its host star. We detect the brown dwarf in the Ms band using the Keck/NIRC2 instrument and vortex coronagraph. We measure its magnitude to be ${Ms}={12.97}_{-0.11}^{0.10}$ . It is at an angular separation of 0"22 ± 0"03, and a position angle of 39.6° ± 5.4° east of north. U…