Search Publications
MCMC Inversion of Stokes Profiles
Sun, Leilei; Xu, Zhi; Li, Hao +1 more
Stokes inversion techniques, based on the analysis of the polarization in spectral lines, are the most powerful tools to obtain the information about the magnetic and thermodynamic quantities in the solar atmosphere. In this paper, we present a Milne-Eddington inversion code based on Bayesian inference, which is implemented with the Markov chain M…
Formation and Eruption of Sigmoidal Structure from a Weak Field Region of NOAA 11942
Ravindra, B.; Doddamani, V. H.; Vemareddy, P. +1 more
Using observations from the Solar Dynamics Observatory, we studied an interesting example of a sigmoid formation and eruption from small-scale flux-canceling regions of active region (AR) 11942. Through an analysis of Helioseismic and Magnetic Imager and Atmospheric Imaging Assembly observations we infer that initially the AR is compact and bipola…
Observations of the Ultra-compact X-Ray Binary 4U 1543-624 in Outburst with NICER, INTEGRAL, Swift, and ATCA
Altamirano, D.; Fabian, A. C.; Miller, J. M. +17 more
We report on X-ray and radio observations of the ultra-compact X-ray binary 4U 1543-624 taken in August 2017 during an enhanced accretion episode. We obtained Neutron Star Interior Composition Explorer (NICER) monitoring of the source over a ∼10 day period during which target-of-opportunity observations were also conducted with Swift, INTErnationa…
A Study of the 20 day Superorbital Modulation in the High-mass X-Ray Binary IGR J16493-4348
Fürst, Felix; Pottschmidt, Katja; Corbet, Robin H. D. +4 more
We report on Nuclear Spectroscopic Telescope Array (NuSTAR), Neil Gehrels Swift Observatory (Swift) X-ray Telescope (XRT), and Swift Burst Alert Telescope (BAT) observations of IGR J16493-4348, a wind-fed supergiant X-ray binary showing significant superorbital variability. From a discrete Fourier transform of the BAT light curve, we refine its su…
Hot Plasma in a Quiescent Solar Active Region as Measured by RHESSI, XRT, and AIA
Krucker, Säm; Ishikawa, Shin-nosuke
This paper investigates a quiescent (nonflaring) active region observed on 2010 July 13 in extreme ultraviolet (EUV), soft X-ray (SXR), and hard X-rays to search for a hot component that is speculated to be a key signature of coronal heating. We use a combination of Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) imaging and long-dur…
Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei
Neuhäuser, R.; Chen, W. P.; Mugrauer, M. +30 more
UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting sporadic occultation of stellar light by circumstellar dust. GM Cephei is such a UXor in the young (∼4 Myr) open cluster Trumpler 37, showing prominent infrared excess, emission-line spectra, and flare activity. Our photometric monitoring (2008-2018) detects (1) an ∼3.43 day per…
Auroral Beads at Saturn and the Driving Mechanism: Cassini Proximal Orbits
Roussos, E.; Badman, S. V.; Bonfond, B. +9 more
During the Grand Finale Phase of Cassini, the Ultraviolet Imaging Spectrograph on board the spacecraft detected repeated detached small-scale auroral structures. We describe these structures as auroral beads, a term introduced in the terrestrial aurora. Those on DOY 232 2017 are observed to extend over a large range of local times, i.e., from 20 L…
Eclipsing Binaries in the Open Cluster Ruprecht 147. II. Epic 219568666
Torres, Guillermo; Vanderburg, Andrew; Beichman, Charles A. +7 more
We report our spectroscopic monitoring of the detached, grazing, and slightly eccentric 12 day double-lined eclipsing binary EPIC 219568666 in the old nearby open cluster Ruprecht 147. This is the second eclipsing system to be analyzed in this cluster, following our earlier study of EPIC 219394517. Our analysis of the radial velocities combined wi…
Chandra, MDM, Swift, and NuSTAR Observations Confirming the SFXT Nature of AX J1949.8+2534
Halpern, Jules P.; Hare, Jeremy; Rahoui, Farid +3 more
AX J1949.8+2534 is a candidate supergiant fast X-ray transient (SFXT) observed in outburst by the International Gamma-ray Astrophysics Laboratory (IGR J19498+2534). We report on the results of six Neil Gehrels Swift-XRT, one Chandra, and one Nuclear Spectroscopic Telescope Array observation of the source. We find evidence of rapid X-ray variabilit…
Lyα Observations of High Radial Velocity Low-mass Stars Ross 1044 and Ross 825
Shkolnik, Evgenya L.; Schneider, Adam C.; Barman, Travis S. +1 more
The discovery of habitable zone (HZ) planets around low-mass stars has highlighted the need for a comprehensive understanding of the radiation environments in which such planets reside. Of particular importance is knowledge of the far-ultraviolet (FUV) radiation, as low-mass stars are typically much more active than solar-type stars and the proxim…