U Sco 2010 outburst: observational evidence of an underlying ONeMg white dwarf

U-band study of the accretion properties in the sigma Ori star-forming region

Ubiquitous High Speed Transition Region and Coronal Upflows in the Quiet Sun

Ubiquitous quiet-Sun jets

Ubiquitous rotating network magnetic fields and EUV cyclones in the quiet Sun

UBV Photometry of the Post-AGB Star IRAS 22272+5435=V354 Lac in 1990-2008

UBV(RI)_C photometry of the open clusters Be 15, Be 80, and NGC 2192

UBVI CCD Photometry of the Open Cluster NGC 4609 and Hogg 15

UBVRI observations of the flickering of RS Ophiuchi at Quiescence

UBVRI Photometric Standard Stars Around the Celestial Equator: Updates and Additions

UCAC3 Proper Motion Survey. I. Discovery of New Proper Motion Stars in UCAC3 with 0.40 "/yr > mu >= 0.18 "/yr between Declinations -90 deg and -47 deg

UCAC3 Proper Motion Survey. II. Discovery Of New Proper Motion Stars In UCAC3 With 0.40" yr^-1 > mu >= 0.18" yr^-1 Between Declinations -47 deg and 00 deg

UKIDSS detections of cool brown dwarfs - proper motions of 14 known $>$T5 dwarfs and discovery of three new T5.5-T6 dwarfs

ULAS J141623.94+134836.3: a Blue T Dwarf Companion to a Blue L Dwarf

Ultra-bright optical transients are linked with type Ic supernovae

Ultra-low Amplitude Variables in the LMC -- Classical Cepheids, Pop. II Cepheids, RV Tau Stars and Binary Variables

Ultra-soft sources as supernova type Ia progenitors

Ultracool Dwarf Science from Widefield Multi-Epoch Surveys

Ultracool Field Brown Dwarf Candidates Selected at 4.5 microns

Ultraviolet and extreme-ultraviolet line ratio diagnostics for O IV