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We report the discovery, from the HI Parkes All-Sky Survey (HIPASS), of an isolated cloud of neutral hydrogen which we believe to be extragalactic. The HI mass of the cloud (HIPASS J1712-64) is very low, 1.7 x 10^7 Msun, using an estimated distance of ~3.2 Mpc. Most significantly, we have found no optical companion to this object to very faint limits (mu(B)~ 27 mag arcsec^-2). HIPASS J1712-64 appears to be a binary system similar to, but much less massive than, HI 1225+01 (the Virgo HI Cloud) and has a size of at least 15 kpc. The mean velocity dispersion, measured with the Australia Telescope Compact Array (ATCA), is only 4 km/s for the main component and because of the weak or non-existent star-formation, possibly reflects the thermal linewidth (T<2000 K) rather than bulk motion or turbulence. The peak column density for HIPASS J1712-64, from the combined Parkes and ATCA data, is only 3.5 x 10^19 cm^-2, which is estimated to be a factor of two below the critical threshold for star formation. Apart from its significantly higher velocity, the properties of HIPASS J1712-64 are similar to the recently recognised class of Compact High Velocity Clouds. We therefore consider the evidence for a Local Group or Galactic origin, although a more plausible alternative is that HIPASS J1712-64 was ejected from the interacting Magellanic Cloud/Galaxy system at perigalacticon ~ 2 x 10^8 yr ago.
We report the detection of an HI counterpart to the extended, far-ultraviolet-emitting tail associated with the asymptotic giant branch star Mira (o Ceti). Using the Nancay Radio Telescope (NRT), we have detected emission as far as 88 north of the st
An isolated HI cloud with peculiar properties has recently been discovered by Dedes, Dedes, & Kalberla (2008, A&A, 491, L45) with the 300-m Arecibo telescope, and subsequently imaged with the VLA. It has an angular size of ~6, and the HI emission has
We present ZTF20aajnksq (AT2020blt), a fast-fading ($Delta r=2.4$ mag in $Delta t=1.3$ days) red ($g-rapprox0.6$ mag) and luminous ($M_{1626}=-25.9$) optical transient at $z=2.9$ discovered by the Zwicky Transient Facility (ZTF). AT2020blt shares sev
Multiwavelength studies of the seven identified X-ray dim isolated neutron stars (XDINSs) offer a unique opportunity to investigate their surface thermal and magnetic structure and the matter-radiation interaction in presence of strong gravitational
We perform a $z$-band survey for an optical counterpart of a binary neutron star coalescence GW170817 with Subaru/Hyper Suprime-Cam. Our untargeted transient search covers $23.6$ deg$^2$ corresponding to the $56.6%$ credible region of GW170817 and re