Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020+4320: Recently Restarted Jet Activity?

This paper reports very-long-baseline interferometry observations of the radio-loud broad absorption line (BAL) quasar J1020+4320 at 1.7, 2.3, 6.7, and 8.4 GHz using the Japanese VLBI network (JVN) and European VLBI network (EVN). The radio morphology is compact with a size of ~10 pc. The convex radio spectrum is stable over the last decade; an observed peak frequency of 3.2 GHz is equivalent to 9.5 GHz in the rest frame, suggesting an age of the order of ~100 years as a radio source, according to an observed correlation between linear size and peak frequency of compact steep spectrum (CSS) and giga-hertz peaked spectrum (GPS) radio sources. A low-frequency radio excess suggests relic of past jet activity. J1020+4320 may be one of the quasars with recurrent and short-lived jet activity during a BAL-outflowing phase.Comment: 7 pages, 2 figures, 2 tables, accepted for publication in PAS

VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars

We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey (SDSS) Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network (JVN). We aimed at selecting BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 10^5 K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four inverted-spectrum sources, which are interpreted as Doppler-beamed, pole-on-viewed relativistic jet sources or young radio sources: single edge-on geometry cannot describe all BAL quasars. We discuss the implications of the OCTAVE observations for investigations for the orientation and evolutionary stage of BAL quasars.Comment: 10 pages, no figure, 3 tables, accepted for publication in PAS

Mapping Observations of 6.7 GHz Methanol Masers with Japanese VLBI Network

We have observed 13 methanol maser sources associated with massive star-forming regions; W3(OH), Mon R2, S 255, W 33A, IRAS 18151-1208, G 24.78+0.08, G 29.95-0.02, IRAS 18556+0136, W 48, OH 43.8-0.1, ON 1, Cep A and NGC 7538 at 6.7 GHz using the Japanese VLBI Network (JVN). Twelve of the thirteen sources were detected at our longest baseline of $\sim$50 M$\lambda$, and their images are presented. Seven of them are the first VLBI images at 6.7 GHz. This high detection rate and the small fringe spacing of $\sim$4 milli-arcsecond suggest that most of the methanol maser sources have compact structure. Given this compactness as well as the known properties of long-life and small internal-motion, this methanol maser line is suitable for astrometry with VLBI.Comment: 15 pages, 13 figures, accepted for publication in PAS

A prospective compound screening contest identified broader inhibitors for Sirtuin 1

Potential inhibitors of a target biomolecule, NAD-dependent deacetylase Sirtuin 1, were identified by a contest-based approach, in which participants were asked to propose a prioritized list of 400 compounds from a designated compound library containing 2.5 million compounds using in silico methods and scoring. Our aim was to identify target enzyme inhibitors and to benchmark computer-aided drug discovery methods under the same experimental conditions. Collecting compound lists derived from various methods is advantageous for aggregating compounds with structurally diversified properties compared with the use of a single method. The inhibitory action on Sirtuin 1 of approximately half of the proposed compounds was experimentally accessed. Ultimately, seven structurally diverse compounds were identified

Observational Study of the Water Maser Burst in the Orion-KL Region

In December 1997 we discovered the enormous outburst of the water maser source in the nearest massive star forming region Orion-KL. The intensity of the burst maser shows nearly exponential increase up to a few 10 6 Jy and lasted for a year. Though the water maser burst in the Orion-KL region was also reported in 20 years ago, the monitoring observations of the previous maser burst were only obtained by single-dish radio telescopes, thus the spatial distribution and time variation were unknown and the amplification mechanisms of the water maser burst are still unclear. In order to investigate the time variation of the spatial distribution of the burst region, we conducted a series of VLBI monitoring observations, especially onset of the burst and enormous increasing period of the burst, toward the region using Japanese domestic VLBI network called J-Net. We determined the absolute position of the burst maser feature by the fringe-rate mapping method with 1 arcsec accuracy. The position of the burst maser feature is about 4000 AU southwest of IRc2 and compared with the previous results of the burst occurred in the Orion-KL 20 years ago, we found the burst occurred repeatedly in the same region. The apparent shifts in the peak velocity and line narrowing in the initial stage of the amplification have been reported in observations of the previous maser bursts. Our total power spectra obtained with Kashima 34-m telescope showed apparent shift in the peak velocity and narrowing of the burst line, too. However, no shift in the peak velocity nor narrowing was detected in our VLBI cross-power spectra of the burst maser feature ( V LSR～7.68 km/s , ΔV ～0.38 km/s ). 　The　absence of the narrowing required that the burst maser must be saturated and must be caused by the beaming but not by the intensity variation of the input source. The apparent phenomena are well explained by the varying weight of the burst feature among other largely stationary features. From the spatial distribution, the burst feature is about 5 AU in size and is elongated in the northwest-southeast direction. We found a clear velocity gradient in the velocity channel components (spots) of the masers. Redder spots were located in the northwest and bluer spots are located in the southeast of the burst feature. Comparison of the spatial distribution of our multi-epoch VLBI observations revealed that most of the maser spots in the burst feature show apparent movements relative to the 7.6km/s burst spot. In the region of the vicinity of the burst feature, there are five maser features with LSR velocity within a few km/s around the velocity of the burst feature (7.3 km/s) aligned linearly in the northwest-southeast direction with spatial extension of 200 AU from the burst feature. Two of the maser features in the linear structure are very similar to those observed in the quiescent period. It is most likely that they are the same maser features. These results indicate that the beaming in the two overlapping masing regions caused a mechanism of the enormous amplification, and this is consistent with the interacting maser model. It seems therefore natural to seek for a possible relationship between linear structure of the burst region in 100 AU scale and a mechanism, which causes the maser burst. Based on the interacting maser model, in order to explain the overlapping of two maser features along our line of sight, we consider a possibility of the model that assumes the 100 AU scale northwest -southeast structure as an edge-on view of a large rotating disk. Some features could be explained. However, the velocity difference among the linear aligned features is difficult to explain. It seems to be consider the structure as another possibility that the overlapping of two maser features is caused by a compact maser source and a steady large-scale flow such as the shocked layer may be formed by the high velocity flow from the source I which shows a characteristic bend in this region