Search Publications
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…
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…
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…
A comparative analysis of the active galactic nucleus and star formation characteristics of broad- and narrow-line Seyfert 1 galaxies
Stalin, C. S.; Mountrichas, G.; Sagar, R. +4 more
We report here our comparative analysis of the active galactic nucleus (AGN) and star formation (SF) characteristics of a sample of narrow-line Seyfert 1 (NLS1) and broad-line Seyfert 1 (BLS1) galaxies. Our sample consisted of 373 BLS1 and 240 NLS1 galaxies and spanned the redshift 0.02 < z < 0.8. The broad-band spectral energy distribution,…
The time-variable ultraviolet sky: Active galactic nuclei, stars, and white dwarfs
Bühler, R.; Schliwinski, J.
Here, we present the first catalog of Ultraviolet time-VAriable sources (1UVA). We describe a new analysis pipeline called VAriable Source Clustering Analysis (VASCA). We applied this pipeline to 10 yr of data from the Galaxy Evolution Explorer (GALEX) satellite. We analyzed a sky area 302 deg2, and detected 4,202 time-variable ultravio…
Connecting integrated red giant branch mass loss from asteroseismology and globular clusters
Miglio, A.; Brogaard, K.; Willett, E. +2 more
Context. Asteroseismic investigations of solar-like oscillations in giant stars enable the derivation of their masses and radii. For mono-age mono-metallicity populations of stars, this allows the integrated red giant branch (RGB) mass loss to be estimated by comparing the median mass of the low-luminosity RGB stars to that of the helium-core-burn…
X-ray observations of Blueberry galaxies
Zezas, A.; Petrucci, P. -O.; Boorman, P. G. +7 more
Context. Compact star-forming galaxies were dominant galaxy types in the early Universe. Blueberry galaxies (BBs) represent their local analogues, being very compact and having intense star formation. Aims. Motivated by high X-ray emission recently found in other analogical dwarf galaxies, called Green Peas, we probed the X-ray properties of BBs t…
Thermal and magnetic field structure of near-equatorial coronal holes
Hegde, M.; Hiremath, K. M.
Context. Coronal holes are low-density and unipolar magnetic field structures in the solar corona that trigger geomagnetic disturbances on the Earth. Hence, it is important to understand the genesis and evolutionary behavior of these coronal activity features during their passage across the solar disk.
Aims: We study the day-to-day latitudina…
Solar internetwork magnetic fields: Statistical comparison between observations and MHD simulations
Borrero, J. M.; Ebert, E.; Milić, I.
Context. Although the magnetic fields in the quiet Sun account for the majority of the magnetic energy in the solar photosphere, inferring their exact spatial distribution, origin, and evolution poses an important challenge because the signals lie at the limit of today's instrumental precision. This severely hinders and biases our interpretations,…