Search Publications
Using Polar Faculae to Determine the Sun's High-latitude Rotation Rate. I. Techniques and Initial Measurements
Sheeley, Neil R.
This paper describes a new way of determining the high-latitude solar rotation rate statistically from simultaneous observations of many polar faculae. In this experiment, I extracted frames from a movie made previously from flat-fielded images obtained in the 6767 Å continuum during 1997–1998 February and used those frames to construct spacetime …
Dynamical Mass of the Ophiuchus Intermediate-mass Stellar System S1 with DYNAMO-VLBA
Dupuy, Trent J.; Rodríguez, Luis F.; Loinard, Laurent +8 more
We report dynamical mass measurements of the individual stars in the most luminous and massive stellar member of the nearby Ophiuchus star-forming region, the young tight binary system S1. We combine 28 archival data sets with seven recent proprietary Very Long Baseline Array (VLBA) observations obtained as part of the Dynamical Masses of Young St…
Large Eruptive and Confined Flares in Relation to the Solar Active Region Evolution
Liu, Yu; Wang, Huaning; Rao, Changhui +5 more
Solar active regions (ARs) provide the required magnetic energy and the topology configuration for flares. Apart from conventional static magnetic parameters, the evolution of AR magnetic flux systems should have nonnegligible effects on magnetic energy store and the trigger mechanism of eruptions, which would promote the prediction for the flare …
Coupling between magnetic reconnection, energy release, and particle acceleration in the X17.2 2003 October 28 solar flare
Veronig, Astrid M.; Hinterreiter, Jürgen; Fleishman, Gregory D. +3 more
Context. The 2003 October 28 (X17.2) eruptive flare was a unique event. The coronal electric field and the π-decay γ-ray emission flux displayed the highest values ever inferred for solar flares.
Aims: Our aim is to reveal physical links between the magnetic reconnection process, energy release, and acceleration of electrons and ions to high …
Spectral analysis of three hot subdwarf stars: EC 11481-2303, Feige 110, and PG 0909+276. A critical oscillator-strength evaluation for iron-group elements
Rauch, T.; Werner, K.; Landstorfer, A.
Context. For the precise spectral analysis of hot stars, advanced stellar-atmosphere models that consider deviations from the local thermodynamic equilibrium are mandatory. This requires accurate atomic data to calculate all transition rates and occupation numbers for atomic levels in the considered model atoms, not only for a few prominent lines …
The double low-mass white dwarf eclipsing binary system J2102-4145 and its possible evolution
Dhillon, V. S.; Marsh, T. R.; Littlefair, S. P. +7 more
In recent years, about 150 low-mass white dwarfs (WDs), typically with masses below 0.4 M⊙, have been discovered. The majority of these low-mass WDs are observed in binary systems as they cannot be formed through single-star evolution within Hubble time. In this work, we present a comprehensive analysis of the double low-mass WD eclipsi…
The Plasma β in Quiet Sun Regions: Multi-instrument View
Veronig, Astrid; Podladchikova, Tatiana; Gömöry, Peter +4 more
A joint campaign of several spaceborne and ground-based observatories, such as the GREGOR solar telescope, the Extreme-ultraviolet Imaging Spectrometer (EIS), and the Interface Region Imaging Spectrograph (Hinode Observing Plan 381, 2019 October 11–22) was conducted to investigate the plasma β in quiet Sun regions. In this work, we focus on 2019 O…
Searching for redshifted 2.2 MeV neutron-capture lines from accreting neutron stars: Theoretical X-ray luminosity requirements and INTEGRAL/SPI observations
Tsygankov, S.; Santangelo, A.; Ducci, L. +2 more
Accreting neutron stars (NSs) are expected to emit a redshifted 2.2 MeV line due to the capture of neutrons produced through the spallation processes of 4He and heavier ions in their atmospheres. Detecting this emission would offer an independent method for constraining the equation of state of NSs and provide valuable insights into nuc…
LAMOST J040901.83+329355.6 - a new Galactic star with Wolf-Rayet characteristics in the transitional stage from post-asymptotic giant branch to central star of a planetary nebula
Karpov, Sergey; Maryeva, Olga; Moiseev, Alexei +2 more
The similarity in physical conditions in the winds of low-mass post-asymptotic giant branch stars and evolved massive stars leads to the appearance of an interesting phenomenon of spectral mimicry. Because of this, the discovery of every new star with a Wolf-Rayet (WR) spectrum requires a special study of its evolutionary status before it can be i…
eROSITA detection of a cloud obscuration event in the Seyfert AGN EC 04570-5206
Schramm, Malte; Gromadzki, Mariusz; Buckley, David A. H. +13 more
Context. Recent years have seen broad observational support for the presence of a clumpy component within the circumnuclear gas around supermassive black holes (SMBHs). In the X-ray band, individual clouds can manifest themselves when they transit the line of sight to the X-ray corona, temporarily obscuring the X-ray continuum and thereby indicati…