Search Publications
Refinement of Global Coronal and Interplanetary Magnetic Field Extrapolations Constrained by Remote-sensing and In Situ Observations at the Solar Minimum
Feng, Li; Gan, Weiqun; Shi, Guanglu +2 more
Solar magnetic fields are closely related to various physical phenomena on the Sun, which can be extrapolated with different models from photospheric magnetograms. However, the open flux problem (OFP), the underestimation of the magnetic field derived from the extrapolated model, is still unsolved. To minimize the impact of the OFP, we propose thr…
Solar Chromospheric Heating by Magnetohydrodynamic Waves: Dependence on the Inclination of the Magnetic Field
Shimizu, Toshifumi; Koyama, Mayu
A proposed mechanism for solar chromospheric heating is magnetohydrodynamic waves propagating upward along magnetic field lines and dissipating their energy in the chromosphere. In particular, compressible magnetoacoustic waves may contribute to the heating. Theoretically, the components below the cutoff frequency cannot propagate into the chromos…
NGC 7314: X-Ray Study of the Evolving Accretion Properties
Chang, Hsiang-Kuang; Chatterjee, Debjit; Jana, Arghajit +1 more
We present a comprehensive analysis of the timing and spectral properties of NGC 7314, a Seyfert 1.9 galaxy, using X-ray observations from XMM-Newton, NuSTAR, and RXTE/proportional counter array (PCA). The timing analysis reveals significant variability across different energy bands, with fractional variability values consistent with previous stud…
Evolution of the Ratio of Mg II Intensities during Solar Flares
Tripathi, Durgesh; Roy, Soumya
The Mg II k and h line intensity ratios can be used to probe the characteristics of the plasma in the solar atmosphere. In this study, using the observations recorded by the Interface Region Imaging Spectrometer, we study the variation of the Mg II k and h intensity ratio for three flares belonging to X-class, M-class, and C-class, throughout thei…
The Chemical Puzzle of Weak G-Band Stars: A Comprehensive Study of HD 54627, HD 105783, HD 198718, and HD 201557
Pereira, C. B.; Quispe-Huaynasi, F.; Holanda, N. +2 more
Weak G-band stars (WGBs) are a unique class of objects characterized by weak CH molecular lines in the Fraunhofer G band, indicative of a deficiency in 12C. This peculiar spectral feature is often accompanied by significant enrichments in N and, occasionally, Li and Na abundances. Despite their rarity and recent discoveries of new WGB c…
Formation of a Magnetic Cloud from the Merging of Two Successive Coronal Mass Ejections
Wang, Rui; Liu, Ying D.; Hu, Huidong +2 more
On 2022 March 28 two successive coronal mass ejections (CMEs) were observed by multiple spacecraft and resulted in a magnetic cloud (MC) at 1 au. We investigate the propagation and interaction properties of the two CMEs correlated with the MC using coordinated multipoint remote sensing and in situ observations from Solar Orbiter, STEREO-A, Solar a…
Tracing the Propagation of Shocks in the Equatorial Ring of SN 1987A over Decades with the Hubble Space Telescope
Fransson, Claes; Larsson, Josefin; Tegkelidis, Christos
The nearby SN 1987A offers a unique opportunity to investigate the complex shock interaction between the ejecta and circumstellar medium. We track the evolution of the optical hot spots within the equatorial ring (ER) by analyzing 33 Hubble Space Telescope imaging observations between 1994 and 2022. By fitting the ER with an elliptical model, we d…
Witt's Hyperbola Is Both Predicted and Observed to Pass Close to the Lensing Galaxies in Quadruple Quasars
Schechter, Paul L.; Luhtaru, Richard
When a rectangular hyperbola is constructed from the image positions of a quadruply lensed quasar, as proposed by Witt, it passes very close to the lensing galaxy. The median measured perpendicular offset between the observed light center of the lens and Witt's hyperbola is 0.″013 for a sample for 39 systems lensed by a relatively isolated galaxy.…
Deriving the Interaction Point between a Coronal Mass Ejection and High-speed Stream: A Case Study
Dumbović, Mateja; Temmer, Manuela; Remeshan, Akshay Kumar
We analyze the interaction between an interplanetary coronal mass ejection (ICME) detected in situ at the L1 Lagrange point on 2016 October 12 with a trailing high-speed stream (HSS). We aim to estimate the region in the interplanetary (IP) space where the interaction happened/started using a combined observational-modeling approach. We use minimu…
The Black Hole Mass and Photometric Components of NGC 4826
Gebhardt, Karl; Kormendy, John; Lauer, Tod R. +6 more
We present infrared photometry and Hubble Space Telescope imaging and spectroscopy of the Sab galaxy NGC 4826. Schwarzschild dynamical modeling is used to measure its central black hole mass M. Photometric decomposition is used to enable a comparison of M to published scaling relations between black hole masses and properties of host bulges. This …