Search Publications
Orbital eccentricities as indicators of stellar populations. A kinematical analysis of the local disc from Gaia DR2 catalogue
Cubarsi, R.; Stojanović, M.; Ninković, S.
Aims: Based on a local sample from Gaia DR2 catalogue composed of 74 339 stars, we are able to derive more accurate kinematic statistics defining the local stellar populations and classify the stars in terms of their planar and vertical orbital eccentricities.
Methods: Firstly, we carried out a kinematical characterisation of stellar pop…
Optical counterparts of ULXs in two dwarf galaxies: NGC 4861 and NGC 4449
Ozdogan Ela, M.; Akyuz, A.; Aksaker, N. +7 more
We present the results of a search for optical candidates of ultraluminous X-ray sources (ULXs) in two dwarf galaxies, NGC 4861 and NGC 4449, using Hubble Space Telescope (HST) archival data. With precise astrometry, we confirm that NGC 4861 X1 is associated with an H II complex and we conclude that NGC 4861 X2 resides in a young star group of mas…
The destruction of the cometary nucleus - The case of 73P/Schwassmann-Wachmann
Wesołowski, M.
The paper presents an analysis of the actual brightness change of comet 73P/Schwassmann-Wachmann, which took place in 1995. The consequence of a cometary outburst is the destruction of a fragment of its surface. This causes the emission of comet material from both the surface and from exposed subsurface layers. Therefore, the calculations take int…
Partitioning the Galactic halo with Gaussian Mixture Models
Zhao, Gang; Zhao, Jing-Kun; Liang, Xi-Long +1 more
The Galactic halo is supposed to form from merging with nearby dwarf galaxies. In order to probe different components of the Galactic halo, we have applied the Gaussian Mixture Models method to a selected sample of metal poor stars with [Fe/H] < -0.7 dex in the APOGEE DR16 catalogue based on four-parameters, metallicity, [Mg/Fe] ratio and spati…
Evidence for Cold Plasma in Planetary Nebulae From Radio Observations With the LOw Frequency ARray (LOFAR)
White, Glenn J.; Haverkorn, Marijke; Shimwell, Timothy +6 more
We present observations of planetary nebulae with the LOw Frequency ARray (LOFAR) between 120 and 168 MHz. The images show thermal free-free emission from the nebular shells. We have determined the electron temperatures for spatially resolved, optically thick nebulae. These temperatures are 20%-60% lower than those estimated from collisionally exc…
On the unified view of extragalactic sources based on their broadband emission properties
Iyida, E. U.; Eya, I. O.; Odo, F. C.
Our understanding of the unification of jetted active galactic nuclei (AGNs) has advanced greatly as the size of extragalactic sources increased. In this paper, based on the large sample of radio sources, we compiled 680 blazars (279 flat spectrum radio quasars (FSRQs) and 401 BL Lacertae (BL Lacs)) from the 3FGL sample and 64 Seyfert galaxies (3 …
A Gemini-NIFS view of the merger remnant NGC 34
Pastoriza, M. G.; Storchi-Bergmann, T.; Ricci, T. V. +8 more
The merger remnant NGC 34 is a local luminous infrared galaxy (LIRG) hosting a nuclear starburst and a hard X-ray source associated with a putative, obscured Seyfert 2 nucleus. In this work, we use adaptive optics assisted near-infrared (NIR) integral field unit observations of this galaxy to map the distribution and kinematics of the ionized and …
The sharpest ultraviolet view of the star formation in an extreme environment of the nearest Jellyfish Galaxy IC 3418
Hota, Ananda; Devaraj, Ashish; Pradhan, Ananta C. +11 more
We present the far ultraviolet (FUV) imaging of the nearest Jellyfish or Fireball galaxy IC3418/VCC 1217, in the Virgo cluster of galaxies, using Ultraviolet Imaging Telescope (UVIT) onboard the AstroSat satellite. The young star formation observed here in the 17 kpc long turbulent wake of IC3418, due to ram pressure stripping of cold gas surround…
Solar EUV-Enhancement and Thermospheric Disturbances
Briand, C.; Doerksen, K.; Deleflie, F.
The increase of energetic electromagnetic flux during solar flares and particle precipitation during geomagnetic activity are among the most important sources of neutral density disturbances to the Earth's thermosphere. However, disentangling the role of X and EUV radiation during solar flares is difficult due to the rarity of sufficiently isolate…
Mapping Milky Way Halo Substructure Using Stars in the Extended Blue Tail of the Horizontal Branch
Newberg, Heidi Jo; Gryncewicz, Robert; Martin, Charles +2 more
Although blue horizontal branch (BHB) stars are commonly used to trace halo substructure, the stars bluer than (g - r) < -0.3 are ignored owing to the difficulty in determining their absolute magnitudes. The blue extension of the horizontal branch (HBX) includes BHB tail stars and extreme horizontal branch (EHB) stars. We present a method for i…