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Nakamura K.,NAOJ
RESCEU Symposium on General Relativity and Gravitation, JGRG 22 | Year: 2012

We have summarized three problems in the nth-order extension of our general relativistic gauge-invariant perturbation theory. Problems that we pointed out are as follows: 1. Group properties of general diffeomorphisms; 2. Decomposition conjecture for linear metric perturbations; 3. Construction of nth-order gauge-invariant variables. Of course, the higher-order perturbation theory requires tough calculations to develop. However, we mainly focus on the essential problems in our formulation, i.e., the construction of gauge-invariant variables. I am now trying to show the extendibility of our construction of gauge-invariant variables to nth-order perturbations by induction.

Nishizawa A.,Kyoto University | Hayama K.,NAOJ
RESCEU Symposium on General Relativity and Gravitation, JGRG 22 | Year: 2012

• Search for graviton mass and polarization enable us to perform model-independent test of gravity and to constrain alternative theory of gravity. • We considered massive GWB and showed that if GWB is detected, advanced-detector network can search for graviton mass in the range. 6.7 × 1(-15 eV ≤ mg ≤ 2.0 × 10-13 eV Notel: If the correlation signal is a mixture of 3 pol. modes, we can robustly separate these mode with a detector network as shown in [AN et al., PRD 79, 082002 (2009); PRD 81, 104043 (2010) Note2: If we take the Fisher matrix for λ(f) into account, detectable mass range would broaden. Note3: It'd be interesting to consider space-based detectors and pulsar timing, which can constrain different mass range.

Sekii T.,NAOJ | Appourchaux T.,University Paris - Sud | Fleck B.,NASA | Turck-Chieze S.,CEA Saclay Nuclear Research Center
Space Science Reviews | Year: 2015

Future space-mission concepts currently discussed in the helioseismology community are reviewed. One popular idea is to observe the Sun from high latitudes, to explore the polar regions as well as to probe the deep interior using stereoscopic techniques, by combining observations from high latitudes with observations from within the ecliptic plane. Another idea is to stay within the ecliptic plane but still aim for stereoscopic helioseismology for deep layers. A new instrument and a novel mission concept for studying the solar core regions are also discussed. © 2015, Springer Science+Business Media Dordrecht.

Nyman L.-A.,JAO | Andreani P.,ESO | Hibbard J.,NRAO | Okumura S.K.,NAOJ
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

The ALMA (Atacama Large Millimeter/submillimeter Array) project is an international collaboration between Europe, East Asia and North America in cooperation with the Republic of Chile. The ALMA Array Operations Site (AOS) is located at Chajnantor, a plateau at an altitude of 5000 m in the Atacama desert in Chile, and the ALMA Operations Support Facility (OSF) is located near the AOS at an altitude of 2900 m. ALMA will consist of an array of 66 antennas, with baselines up to 16 km and state-of-the-art receivers that cover all the atmospheric windows up to 1 THz. An important component of ALMA is the compact array of twelwe 7-m and four 12-m antennas (the Atacama Compact Array, ACA), which will greatly enhance ALMA's ability to image extended sources. Construction of ALMA started in 2003 and will be completed in 2013. Commissioning started in January 2010 and Early Science Operations is expected to start during the second half of 2011. ALMA science operations is provided by the Joint ALMA Observatory (JAO) in Chile, and the three ALMA Regional Centers (ARCs) located in each ALMA region - Europe, North America and East Asia. ALMA observations will take place 24h per day, interrupted by maintenance periods, and will be done in service observing mode with flexible (dynamic) scheduling. The observations are executed in the form of scheduling blocks (SBs), each of which contains all information necessary to schedule and execute the observations. The default output to the astronomer will be pipeline-reduced images calibrated according to the calibration plan. The JAO is responsible for the data product quality. All science and calibration raw data are captured and archived in the ALMA archive, a distributed system with nodes at the OSF, the Santiago central office and the ARCs. Observation preparation will follow a Phase 1/Phase 2 process. During Phase 1, observation proposals will be created using software tools provided by the JAO and submitted for scientific and technical review. Approved Phase 1 proposals will be admitted to Phase 2 where all observations will be specified as SBs using software tools provided by the JAO. User support will be done at the ARCs through a helpdesk system as well as face-to-face support. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Currie T.,NAOJ | Muto T.,Tokyo University of the Arts | Kudo T.,NAOJ | Honda M.,Kanagawa University | And 24 more authors.
Astrophysical Journal Letters | Year: 2014

We report the first independent, second epoch (re-)detection of a directly imaged protoplanet candidate. Using L′ high-contrast imaging of HD 100546 taken with the Near-Infrared Coronagraph and Imager on Gemini South, we recover "HD 100546 b" with a position and brightness consistent with the original Very Large Telescope/NAos-COnica detection from Quanz et al., although data obtained after 2013 will be required to decisively demonstrate common proper motion. HD 100546 b may be spatially resolved, up to ≈12-13 AU in diameter, and is embedded in a finger of thermal IR-bright, polarized emission extending inward to at least 0″.3. Standard hot-start models imply a mass of ≈15 MJ. However, if HD 100546 b is newly formed or made visible by a circumplanetary disk, both of which are plausible, its mass is significantly lower (e.g., 1-7 MJ). Additionally, we discover a thermal IR-bright disk feature, possibly a spiral density wave, at roughly the same angular separation as HD 100546 b but 90° away. Our interpretation of this feature as a spiral arm is not decisive, but modeling analyses using spiral density wave theory implies a wave launching point exterior to ≈0″.45 embedded within the visible disk structure: plausibly evidence for a second, hitherto unseen, wide-separation planet.With one confirmed protoplanet candidate and evidence for one to two others, HD 100546 is an important evolutionary precursor to intermediate-mass stars with multiple super-Jovian planets at moderate/wide separations like HR 8799. © 2014. The American Astronomical Society. All rights reserved.

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