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Observational Problems in Extragalactic Astronomy [PDF]
Highlights of Astronomy, 1992 AbstractA large number of observations have accumulated which represent baffling mysteries from the standpoint of current astronomy. A sample of the most crucial of these cases is reviewed and updated. Evidence has slowly built up to the point where often each individual object is a formidable challenge to conventional theory. But, most importantly, it
openaire +1 more source
A Comparative Study of VTEC Estimates Derived From S/X VLBI and VGOS Observations
Space Weather, Volume 23, Issue 12, December 2025.Abstract The ionosphere, which strongly varies in time and space, is one of the largest error sources for microwave measurements, if not accounted for accurately. Especially for single‐frequency observations, precise ionospheric models are needed to correct for the ionospheric delays. This study explores the utility of Very Long Baseline Interferometry
Arno Rüegg +2 more
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HEAD IN THE STARS, FEET ON THE GROUND: Scale and Astronomy Initiatives in Southern Africa
Cultural Anthropology, Volume 40, Issue 4, Page 571-596, November 2025.ABSTRACT This article explores the evolution of radio astronomy in South Africa and Madagascar, focusing on how “scale” functions as both a way of understanding the world and marking differences in existence. In outer space research, the ground is crucial but often overlooked.
HANNA NIEBER, DAVIDE CHINIGÒ
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Deep Space Network Radio Science and Ground‐Based Planetary Radar in the Next Decade
Radio Science, Volume 60, Issue 7, July 2025.Abstract The Deep Space Network (DSN) has been a core operational element of NASA's crewed and robotic exploration of the Solar System since the early 1960s. The primary role of the DSN has been to acquire telemetry and navigation data, but over the years, its radiometric and radar capabilities have expanded to form a system for obtaining unique ...
R. S. Park +13 more
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On the Age Distribution of Classical Cepheids in the Galaxy
Astronomische Nachrichten, Volume 346, Issue 5, June 2025.ABSTRACT We revisit the problem of the positive correlation between age and Galactocentric distance seen in Galactic Classical Cepheids, which at first sight may seem counter‐intuitive in the context of inside‐out galaxy formation. To explain it, we use the Besançon Galaxy Model and a simulation of star particles in the Galactic disc coupled with ...
Friedrich Anders +5 more
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Astronomische Nachrichten, Volume 346, Issue 3-4, March-May 2025.ABSTRACT The discovery of radio‐quiet, x‐ray thermally emitting isolated neutron stars (XINSs) in the ROSAT All‐Sky Survey revealed a previously overlooked component of the neutron star population. Advancements in x‐ray instrumentation and the availability of deep, wide‐area optical surveys now enable us to explore XINSs at fainter x‐ray fluxes and ...
Adriana Mancini Pires +11 more
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SLICE: Combining strong lensing and X-ray data of AC 114
Astronomy & AstrophysicsAC 114 is a historically significant galaxy cluster, being one of the first strong lensing clusters detected from the ground in the early 1990s, prior to the launch of the Hubble Space Telescope (HST).
Limousin Marceau +16 more
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Beyond Accretion Limits: The Rise of Pulsating Gems
Astronomische Nachrichten, Volume 346, Issue 1, January 2025.ABSTRACT The discovery of several ultraluminous X‐ray sources exhibiting fast and rapidly evolving X‐ray pulsations unequivocally associates these sources with accreting neutron stars orbiting relatively massive companion stars (> 8M ⊙$$ {}_{\odot } $$).
Gian Luca Israel +26 more
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Modeling the Emission and Polarization Properties of Pulsating Ultraluminous X‐Ray Sources
Astronomische Nachrichten, Volume 346, Issue 1, January 2025.ABSTRACT Pulsating Ultraluminous X‐ray Sources (PULXs) are a class of extragalactic sources with high X‐ray luminosity, in excess of 1039$$ {10}^{39} $$ erg s−1$$ {\mathrm{s}}^{-1} $$, and showing pulsations that associate them with neutron stars accreting at a super‐Eddington rate.
S. Conforti +6 more
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The Astrophysical Journal LettersCataclysmic variables can experience short optical brightenings, which are commonly attributed to phenomena such as dwarf novae outbursts, micronovae, donor flares, or magnetic gating bursts.
Krystian Iłkiewicz +7 more
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