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Quasars are high-luminosity active galactic nuclei believed to be powered by accretion of interstellar matter onto a super-massive black hole (SMBH) therein. Most of the observed energy is released in an accretion disk of inspiralling gas surrounding the SMBH. An enormous amount of fueling material is expected to be transported inwards. However, basic questions remain unanswered as to whether and how the accretion disks are supplied with external gas, since no disk-feeding inflow has hitherto been observed clearly. Here we report the discovery of highly redshifted broad absorption lines arising from neutral hydrogen and helium atoms in a small sample of quasars. Their absorption troughs show a broad range of Doppler velocities from zero extending continuously inward up to as high as $\sim 5,000$ km s$^{-1}$. We thus see through streams of cold gas moving with a radially inward velocity component that spans an immense gradient---a result of gravitational acceleration by the central SMBH. Extensive photo-ionization modeling for the archetypical object SDSS J103516.20+142200.6 indicates the inflowing gas to be dense, thick and moderately ionized, with a characteristic distance to the SMBH of $\sim 1,000$ gravitational radii, possibly overlapping or close to the outer accretion disk. Our results present the first compelling evidence for the long-sought inflow directly feeding quasars' accretion disks with external materials, likely originating from the dusty torus at a parsec scale. Our approach provides a new tool to probe the bulk of the so far elusive fueling inflows in quasars. Their studies may help address some of the fundamental questions concerning accretion physics, the onset and sustainment of quasar activity, and the SMBH growth at centers of most galaxies. more...

Transiting extrasolar planets (exoplanets), especially those orbiting bright stars, are desired for study of the diversity of planetary compositions, internal structures and atmospheres beyond our solar system. Dome A at Antarctica is a promising site for planetary transit surveys, where the continuous darkness and the large clear-sky fraction in the winter months greatly enhance the detection efficiency. The Chinese Small Telescope ARray and the Antarctic Survey Telescopes are the first facilities that have been operated at Dome A for use in exoplanet surveys. To increase the sky coverage, a low-temperature-resistant wide-field robotic telescope, named the bright star survey telescope (BSST), has been developed to join the ongoing planetary transit survey in Antarctica. The BSST has an aperture size of 300 mm and is equipped with a large-frame 4k x 4k CCD camera to receive starlight from a 3.degrees 4 x 3.degrees 4 field of view. The BSST was operated at Lijiang observatory in April and May 2015 for a test run. Photometric precision of 3.5 mmag was achieved for stars with V similar to 11 mag using 75 s exposures. The transiting events of two Jupiter-size exoplanets, HAT-P-3b and HAT-P-12b, were observed on May 10 and May 20, 2015, respectively. more...

We report a clear detection of He I*lambda lambda 2946, 3189, and 3889 broad absorption line (BAL) in the low-ionization BAL (LoBAL) quasar SDSS J144842.45+042403.1. We also detected new BALs, including Ly alpha, C II, and Si IV, as well as optical emission lines, such as H alpha, H beta, and [O III]. Using photoionization simulations, we constrained the physical conditions of the outflow to a hydrogen column density of N-H approximate to 10(21.3) cm(-2), an ionization parameter of U approximate to 10(-1.4), and a hydrogen number density of n(H) approximate to 10(3.6) cm(-3), and located its radial distance at r(abs) similar to 1.52 kpc from the central engine. The photoionization model predicts the presence of a Lyman limit system with H I column density of N-H (I) similar to 3.0 x 10(17)-1.2 x 10(18) cm(-2), which is confirmed by the GALEX photometry. Interestingly, we found that the [O III] emission line doublet has an outflow component at a large blueshift of v similar to 1700 km s(-1) and a width of FWHM similar to 5000 km s(-1). Assuming that we are witnessing the same outflow in both emission and absorption lines, we estimate the global covering fraction of the emission line outflow to be similar to 4%, its mass-loss rate to be similar to 70 M(circle dot)yr(-1) and its kinetic luminosity to be similar to 3.2 x 10(44) erg s(-1). SDSS J1448 +0424 is a representative example of a significant fraction of LoBAL quasars, which deserves further studies to understand the connection between the growth of supermassive black holes and the evolution of their host galaxies. more...

Using newly released data from the Wide-field Infrared Survey Explorer, we report the discovery of rapid infrared variability in three radio-loud narrow-line Seyfert 1 galaxies (NLS1s) selected from the 23 sources in the sample of Yuan et al. (2008). J0849+5108 and J0948+0022 clearly show intraday variability, while J1505+0326 has a longer measurable time scale within 180 days. Their variability amplitudes, corrected for measurement errors, are $\sim 0.1-0.2$ mag. The detection of intraday variability restricts the size of the infrared-emitting region to $\sim 10^{-3}$ pc, significantly smaller than the scale of the torus but consistent with the base of a jet. The three variable sources are exceptionally radio-loud, have the highest radio brightness temperature among the whole sample, and all show detected $\gamma$-ray emission in Fermi/LAT observations. Their spectral energy distributions resemble those of low-energy-peaked blazars, with a synchrotron peak around infrared wavelengths. This result strongly confirms the view that at least some radio-loud NLS1s are blazars with a relativistic jet close to our line of sight. The beamed synchrotron emission from the jet contributes significantly to and probably dominates the spectra in the infrared and even optical bands., Comment: To appear in The Astrophysical Journal Letters more...