Search Publications
TYC 8606-2025-1: a mild barium star surrounded by the ejecta of a very late thermal pulse
Fossati, L.; Gvaramadze, V. V.; Grebel, E. K. +4 more
We report the discovery of a spiral-like nebula with the Wide-field Infrared Survey Explorer and the results of optical spectroscopy of its associated star TYC 8606-2025-1 with the Southern African Large Telescope. We find that TYC 8606-2025-1 is a G8 III star of ≈ 3 M_{⊙ }, showing a carbon depletion by a factor of 2 and a nitrogen enhancement by…
Spatial Variation of the Chemical Properties of Massive Star-forming Clumps
Zhou, Jianjun; Esimbek, Jarken; He, Yuxin +4 more
We selected 90 massive star-forming clumps with strong N2H+(1-0), HCO+(1-0), HCN(1-0), and HNC(1-0) emission from the Millimetre Astronomy Legacy Team 90 GHz survey. We obtained Herschel data for all 90 sources and NRAO VLA Sky Survey data for 51 of them. We convolved and regridded all images to the same resolution…
Murchison Widefield Array and XMM-Newton observations of the Galactic supernova remnant G5.9+3.1
Haberl, F.; Callingham, J. R.; Filipović, M. D. +27 more
Aims: In this paper we discuss the radio continuum and X-ray properties of the so-far poorly studied Galactic supernova remnant (SNR) G5.9 + 3.1.
Methods: We present the radio spectral energy distribution (SED) of the Galactic SNR G5.9 + 3.1 obtained with the Murchison Widefield Array (MWA). Combining these new observations with the surv…
A classifier to detect elusive astronomical objects through photometry
Vig, S.; Ghosh, S. K.; Bhavana, D. +1 more
The application of machine learning principles in the photometric search of elusive astronomical objects has been a less-explored frontier of research. Here, we have used three methods, the neural network and two variants of k-nearest neighbour, to identify brown dwarf candidates using the photometric colours of known brown dwarfs. We initially ch…
Galactic foreground of gamma-ray bursts from AKARI Far-Infrared Surveyor
Doi, Yasuo; Onishi, Toshikazu; Zahorecz, Sarolta +8 more
We demonstrate the use of the AKARI FIS All-Sky Survey maps in the study of extragalactic objects. A quick but reliable estimate of the Galactic foreground is essential for extragalactic research in general. We explored the galactic foreground and calculated hydrogen column densities using AKARI FIS and other recent all-sky survey data, and compar…
Development of a 3-D Plasmapause Model With a Back-Propagation Neural Network
He, Fei; Lei, Jiuhou; Zhang, Xiao-Xin +2 more
Several empirical models have been previously developed to study the characteristics of the global plasmasphere. A three-dimensional solar wind-driven global dynamic plasmapause model was developed in this study using a back-propagation neural network based on multisatellite measurements. Our database contains 37,859 plasmapause crossing events fr…
Link between trees of fragmenting granules and deep downflows in MHD simulation
Malherbe, J. M.; Roudier, T.; Frank, Z. +1 more
Context. Trees of fragmenting granules (TFG) and associated flows are suspected to play a major role in the formation of the network in the quiet Sun. We investigate the counterparts, in terms of dynamics, of surface structures detectable by high resolution observations in deeper layers up to 15 Mm, which are only available from numerical simulati…
Equatorial Magnetosonic Waves Observed by Cluster Satellites: The Chirikov Resonance Overlap Criterion
Aryan, Homayon; Walker, Simon N.; Balikhin, Michael A. +1 more
Magnetosonic waves play an important role on the overall dynamics of relativistic radiation belt electrons. Numerical codes modeling the evolution of the radiation belts often account for wave-particle interaction with magnetosonic waves. The diffusion coefficients incorporated in these codes are generally estimated based on the results of statist…
Analysis of Field-Aligned Currents in the High-Altitude Nightside Auroral Region: Cluster Observation
Shin, Youra; Lee, Ensang; Lee, Jae-Jin
In this paper we present analysis of current density when the Cluster spacecraft pass the nightside auroral region at about 4-5 RE from the center of Earth. The analysis is made when the inter-spacecraft separation is within 200 km, which allows all four spacecraft to be situated inside the same current sheet. On 22 February 2002, two field-aligne…
Surveying the Bright Stars by Optical Interferometry. II. A Volume-limited Multiplicity Survey of Main-sequence F Stars
Hutter, D. J.; Tycner, C.; Zavala, R. T. +3 more
We present the results of a multiplicity survey for a volume-limited sample of 29 main-sequence F0-G0 stars within 17 pc conducted with the Navy Precision Optical Interferometer (NPOI). Four companions were detected in previously known binary systems. The results for these stars show good agreement with previously published orbits. For one of thes…