Results 61 to 70 of about 165 (125)

Accurate Astrometry of 22 Southern Hemisphere Radio Sources [PDF]

The Astronomical Journal, 2004
Milliarcsecond-accurate radio positions for 22 southern hemisphere extragalactic sources are reported. These positions are derived from Mark III very long baseline interferometry observations made between 2003 February and 2003 August. The results presented here supplement an ongoing project to increase the sky density of southern hemisphere sources in
Alan L. Fey, Roopesh Ojha, David L. Jauncey, Kenneth J. Johnston, John E. Reynolds, James E. J. Lovell, Anastasios K. Tzioumis, Jonathan F. H. Quick, George D. Nicolson, Simon P. Ellingsen, Peter M. McCulloch, Yasuhiro Koyama   +11 more
openaire   +1 more source

Synthesis Imaging with a Lunar Orbit Array. III. Augmented Lagrangian Multiplier Imaging Using Gradient Descent Optimization (AMIGO)

The Astrophysical Journal Supplement Series
Ground-based radio observations below 30 MHz are severely limited by ionospheric interference and radio-frequency interference from Earth. A lunar-orbiting radio interferometer mission, the Discovering the Sky at the Longest wavelengths (DSL, also known ...
Meng Zhou, Furen Deng, Yidong Xu, Xuelei Chen   +3 more
doaj   +1 more source

JWST imaging of the closest globular clusters—I. Possible infrared excess among white dwarfs in NGC 6397

Astronomische Nachrichten, Volume 345, Issue 6-7, July-August 2024.
Abstract We present James Webb Space Telescope observations of the globular cluster NGC 6397 and use them to extend to infrared wavelengths the characterization of the cluster's entire white dwarf (WD) cooling sequence (CS). The data allows us to probe fundamental astrophysical WD properties and to search for evidence in their colors for (or against ...
L. R. Bedin, D. Nardiello, M. Salaris, M. Libralato, P. Bergeron, A. J. Burgasser, D. Apai, M. Griggio, M. Scalco, J. Anderson, R. Gerasimov, A. Bellini   +11 more
wiley   +1 more source

Ultra-precise astrometry with the next generation of radio instruments

, 2022
We are at the cusp of a generational shift in the power of radio interferometers, with both the SKA and ngVLA planning for exciting new and powerful instruments. These will be used in conjunction with other radio telescopes to provide VLBI with an order of magnitude greater sensitivity.
Dodson, Richard, Rioja, Maria
openaire   +2 more sources

Not So Fast: A New Catalog of Meteor Persistent Trains

Journal of Geophysical Research: Space Physics, Volume 129, Issue 7, July 2024.
Abstract This paper presents the results of a nearly 2‐year long campaign to detect and analyze meteor persistent trains (PTs)—self‐emitting phenomena which can linger up to an hour after their parent meteor. The modern understanding of PTs has been primarily developed from the Leonid storms at the turn of the century; our goal was to assess the ...
L. E. Cordonnier, K. S. Obenberger, J. M. Holmes, G. B. Taylor, D. Vida   +4 more
wiley   +1 more source

Synthesis Imaging with a Lunar Orbit Array. II. Impacts of Instrument-induced Phase Errors

The Astronomical Journal
A lunar orbit interferometer array suffers from a number of systematics. Beyond systematics induced by the imaging algorithm itself and thermal noise considered in F.
Meng Zhou, Furen Deng, Yidong Xu, Li Zhou, Xuelei Chen   +4 more
doaj   +1 more source

The fireball of November 24, 1970, as the most probable source of the Ischgl meteorite

Meteoritics &Planetary Science, Volume 59, Issue 7, Page 1658-1691, July 2024.
Abstract The discovery of the Ischgl meteorite unfolded in a captivating manner. In June 1976, a pristine meteorite stone weighing approximately 1 kg, fully covered with a fresh black fusion crust, was collected on a mountain road in the high‐altitude Alpine environment.
Maria Gritsevich, Jarmo Moilanen, Jaakko Visuri, Matthias M. M. Meier, Colin Maden, Jürgen Oberst, Dieter Heinlein, Joachim Flohrer, Alberto J. Castro‐Tirado, Jorge Delgado‐García, Christian Koeberl, Ludovic Ferrière, Franz Brandstätter, Pavel P. Povinec, Ivan Sýkora, Florian Schweidler   +15 more
wiley   +1 more source

Infrared-radio-follow-up observations for detection of the magnetic radio emission of extra solar planets: a new window to detect exoplanets

Frontiers in Astronomy and Space Sciences
There are several methods for indirectly detecting exoplanets, such as transit, radial velocity, astrometry, and the conventional gravitational microlensing approach.
Fatemeh Bagheri, Fatemeh Bagheri, Ramon E. Lopez, Amir Shahmoradi, Amir Shahmoradi   +4 more
doaj   +1 more source

Cross‐Polarization Gain Calibration of Linearly Polarized VLBI Antennas by Observations of 4C 39.25

Radio Science, Volume 59, Issue 4, April 2024.
Abstract Radio telescopes with dual linearly polarized feeds regularly participate in Very Long Baseline Interferometry. One example is the VLBI Global Observing System (VGOS), which is employed for high‐precision geodesy and astrometry. In order to achieve the maximum signal‐to‐noise ratio, the visibilities of all four polarization products are ...
F. Jaron, I. Martí‐Vidal, M. Schartner, J. González‐García, E. Albentosa‐Ruiz, S. Bernhart, J. Böhm, J. Gruber, S. Modiri, A. Nothnagel, V. Pérez‐Díez, T. Savolainen, B. Soja, E. Varenius, M. H. Xu   +14 more
wiley   +1 more source

Serial MultiView: An Efficient Approach to Mitigating Atmospheric Spatial-structure Errors for Very-long-baseline-interferometry Astrometry

The Astronomical Journal
Atmospheric propagation errors are a main constraint on the accuracy of very-long-baseline-interferometry astrometry. For relative astrometry, differential techniques can mitigate these errors, but their effectiveness diminishes with decreasing elevation
Jingdong Zhang, Bo Zhang, Shuangjing Xu, Maria J. Rioja, Richard Dodson, Xiaofeng Mai, Oleg Titov   +6 more
doaj   +1 more source