We present a concept for an X-ray imaging system with a high angular resolution and moderate sensitivity. In this concept, a two-dimensional detector, i.e., an imager, is put at a slightly out-of-focus position of the focusing mirror, rather than …
Weak gravitational lensing is a powerful probe of the large-scale cosmic matter distribution. Wide-field galaxy surveys allow us to generate the so-called weak lensing maps, but actual observations suffer from noise due to imperfect measurement of …
Recent developments in compact object astrophysics, especially the discovery of merging neutron stars by LIGO, the imaging of the black hole in M87 by the Event Horizon Telescope, and high- precision astrometry of the Galactic Center at close to the …
We present an overview of a deep transient survey of the COSMOS field with the Subaru Hyper Suprime-Cam (HSC). The survey was performed for the 1.77 deg ultra-deep layer and 5.78 deg deep layer in the Subaru Strategic Program over 6- and 4-month …
When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon …
The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength …
We present the calibration and reduction of Event Horizon Telescope (EHT) $1.3$ mm radio wavelength observations of the supermassive black hole candidate at the center of the radio galaxy M87 and the quasar 3C 279, taken during the 2017 April 5--11 …
We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at $1.3$ mm wavelength. These images show a prominent ring with a diameter of $\sim 40$ $\mu$as, consistent with the size and shape of the lensed …
The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at $1.3$ mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. …