ABSTRACT We report the discovery of a planet by the microlensing method, OGLE-2012-BLG-0724Lb. Although the duration of the planetary signal for this event was one of the shortest seen for a ...planetary event, the anomaly was well covered thanks to high-cadence observations taken by the survey groups OGLE and MOA. By analyzing the light curve, this planetary system is found to have a mass ratio q = ( 1.58 0.15 ) × 10 − 3 . By conducting a Bayesian analysis, we estimate that the host star is an M dwarf with a mass of M L = 0.29 − 0.16 + 0.33 M ☉ located at D L = 6.7 − 1.2 + 1.1 kpc away from the Earth and the companion's mass is m P = 0.47 − 0.26 + 0.54 M Jup . The projected planet-host separation is a = 1.6 − 0.3 + 0.4 AU . Because the lens-source relative proper motion is relatively high, future high-resolution images would detect the lens host star and determine the lens properties uniquely. This system is likely a Saturn-mass exoplanet around an M dwarf, and such systems are commonly detected by gravitational microlensing. This adds another example of a possible pileup of sub-Jupiters ( 0.2 < m P / M Jup < 1 ) in contrast to a lack of Jupiters ( ∼ 1 - 2 M Jup ) around M dwarfs, supporting the prediction by core accretion models that Jupiter-mass or more massive planets are unlikely to form around M dwarfs.
We report the discovery and the analysis of the planetary microlensing event, OGLE-2013-BLG-1761. There are some degenerate solutions in this event because the planetary anomaly is only sparsely ...sampled. However, the detailed light-curve analysis ruled out all stellar binary models and shows the lens to be a planetary system. There is the so-called close/wide degeneracy in the solutions with the planet/host mass ratio of q ∼ (7.0 2.0) × 10−3 and q ∼ (8.1 2.6) × 10−3 with the projected separation in Einstein radius units of s = 0.95 (close) and s = 1.18 (wide), respectively. The microlens parallax effect is not detected, but the finite source effect is detected. Our Bayesian analysis indicates that the lens system is located away from us and the host star is an M/K dwarf with a mass of orbited by a super-Jupiter mass planet with a mass of at the projected separation of . The preference of the large lens distance in the Bayesian analysis is due to the relatively large observed source star radius. The distance and other physical parameters may be constrained by the future high-resolution imaging by large ground telescopes or HST. If the estimated lens distance is correct, then this planet provides another sample for testing the claimed deficit of planets in the Galactic bulge.
Coronagraphic imaging for the Herbig Ae star, HD 142527, was performed using the Coronagraphic Imager with Adaptive Optics (CIAO) on the 8.2 m Subaru Telescope. The images were obtained in the H2O ...ice filter ( lambda = 3.08 is a subset of m) using adaptive optics (AO), and in the L' band without AO. Combining these data with previous observational results in the H and K bands, we derived the spectra of the scattered light from the circumstellar disk around HD 142527 and detected an H2O ice absorption feature in the spectra. This result can be explained by the presence of silicate and H2O ice grains of ~1 is a subset of m in size, according to the prediction model by Inoue et al. This grain size is consistent with previous observational study by Fukagawa et al. and Fujiwara et al. The present result demonstrates that high-resolution imaging of disk-scattered light in the ice band is useful for detecting H2O ice grain distributions in circumstellar disks.
Aims. We assess the relationships between the surface densities of the gas and star formation rate (SFR) within spiral arms of the nearby late-type spiral galaxies M 81 and M 101. By analyzing these ...relationships locally, we empirically derive a kiloparsec scale Kennicutt-Schmidt Law (ΣSFR $\propto$ ΣgasN). Methods. Both M 81 and M 101 were observed with the Far-Infrared Surveyor (FIS) aboard AKARI in four far-infrared bands at 65, 90, 140, and 160 μm. Results. The spectral energy distributions of the whole galaxies show the presence of the cold dust component (TC ~ 20 K) in addition to the warm dust component (TW ~ 60 K). We deconvolved the cold and warm dust emission components spatially by making the best use of the multi-band photometric capability of the FIS. The cold and warm dust components show power-law correlations in various regions, which can be converted into the gas mass and the SFR, respectively. We find a power-law correlation between the gas and SFR surface densities with significant differences in the power-law index N between giant H ii regions (N = 1.0 ± 0.5) and spiral arms (N = 2.2 ± 0.2) in M 101. The power-law index for spiral arms in M 81 is similar (N = 1.9 ± 0.4) to that of spiral arms in M 101. Conclusions. The power-law index is not always constant within a galaxy. The difference can be attributed to the difference in the star formation processes on a kiloparsec scale. N $\simeq$ 2 seen in the spiral arms in M 81 and M 101 supports the scenario of star formation triggered by cloud-cloud collisions enhanced by a spiral density wave, while N $\simeq$ 1 derived in giant H ii regions in M 101 suggests the star formation induced by the Parker instability triggered by high-velocity H i gas infall. The present method can be applied to a large galaxy sample for which the AKARI All Sky Survey provides the same 4 far-infrared band data.
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Aims. We assess the relationships between the surface densities of the gas and star formation rate (SFR) within spiral arms of the nearby late-type spiral galaxies M81 and M101. By analyzing these ...relationships locally, we empirically derive a kiloparsec scale Kennicutt-Schmidt Law ( capital sigma sub(SFR) alpha capital sigma sub(gas) super(N)). Methods. Both M81 and M101 were observed with the Far-Infrared Surveyor (FIS) aboard AKARI in four far-infrared bands at 65, 90, 140, and 160 mu m. Results. The spectral energy distributions of the whole galaxies show the presence of the cold dust component (T sub(C) ~ 20 K) in addition to the warm dust component (T sub(W) ~ 60 K). We deconvolved the cold and warm dust emission components spatially by making the best use of the multi-band photometric capability of the FIS. The cold and warm dust components show power-law correlations in various regions, which can be converted into the gas mass and the SFR, respectively. We find a power-law correlation between the gas and SFR surface densities with significant differences in the power-law index N between giant H ii regions (N = 1.0 plus or minus 0.5) and spiral arms (N = 2.2 plus or minus 0.2) in M101. The power-law index for spiral arms in M81 is similar (N = 1.9 plus or minus 0.4) to that of spiral arms in M101. Conclusions. The power-law index is not always constant within a galaxy. The difference can be attributed to the difference in the star formation processes on a kiloparsec scale. N 2 seen in the spiral arms in M81 and M101 supports the scenario of star formation triggered by cloud-cloud collisions enhanced by a spiral density wave, while N 1 derived in giant H ii regions in M101 suggests the star formation induced by the Parker instability triggered by high-velocity H i gas infall. The present method can be applied to a large galaxy sample for which the AKARI All Sky Survey provides the same 4 far-infrared band data.
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The core-accretion and disk instability models have so far been used to explain planetary formation. These models have different conditions, such as planet mass, disk mass, and metallicity for ...formation of gas giants. The core-accretion model has a metallicity condition (Fe/H > -1.17 in the case of G-type stars), and the mass of planets formed is less than 6 times that of the Jupiter mass unk. On the other hand, the disk instability model does not have the metallicity condition, but requires the disk to be 15 times more massive than the minimum mass solar nebulae model. The mass of planets formed is more than 2 unk. These results are compared to the 161 detected planets for each spectral type of the central stars. The results show that 90% of the detected planets are consistent with the core-accretion model regardless of the spectral type. The remaining 10% are not in the region explained by the core-accretion model, but are explained by the disk instability model. We derived the metallicity dependence of the formation probability of gas giants for the core-accretion model. Comparing the result with the observed fraction having gas giants, they are found to be consistent. On the other hand, the observation cannot be explained by the disk instability model, because the condition for gas giant formation is independent of the metallicity. Consequently, most of planets detected so far are thought to have been formed by the core-accretion process, and the rest by the disk instability process.
We have made a Galactic extinction map of the Cygnus region with 5' spatial resolution. The selected area is 80{sup 0} to 90{sup 0} in the Galactic longitude and -4{sup 0} to 8{sup 0} in the Galactic ...latitude. The intensity at 140 {mu}m is derived from the intensities at 60 and 100 {mu}m of the IRAS data using the tight correlation between 60, 100, and 140 {mu}m found in the Galactic plane. The dust temperature and optical depth are calculated with 5' resolution from the 140 and 100 {mu}m intensity, and A{sub V} is calculated from the optical depth. In the selected area, the mean dust temperature is 17 K, the minimum is 16 K, and the maximum is 30 K. The mean A{sub V} is 6.5 mag, the minimum is 0.5 mag, and the maximum is 11 mag. The dust temperature distribution shows significant spatial variation on smaller scales down to 5'. Because the present study can trace the 5'-scale spatial variation of the extinction, it has an advantage over the previous studies, such as the one by Schlegel, Finkbeiner, and Davis, who used the COBE/DIRBE data to derive the dust temperature distribution with a spatial resolution of 1{sup 0}. The difference of A{sub V} between our map and Schlegel et al.'s is {+-} 3 mag. A new extinction map of the entire sky can be produced by applying the present method.
ASTRO-F mission Shibai, H
Advances in space research,
2004, 2004-1-00, 20040101, Volume:
34, Issue:
3
Journal Article
Peer reviewed
In order to perform an advanced infrared sky survey, the ASTRO-F (IRIS) satellite has been developed and will be launched in early 2004. ASTRO-F is dedicated to infrared astronomy, and its primary ...purpose is to investigate birth and evolution of galaxies in the young universe by deep and wide-field surveys in wavelengths of 2–200 μm. Two focal-plane instruments, an Infrared Camera (IRC) and a Far-Infrared Surveyor (FIS), have been designed and built. Laboratory measurements show that a satisfying performance has been achieved. The most important feature of ASTRO-F is its wide-sky coverage. In the far-infrared region, from 50 to 200 μm, an all-sky survey will be made. The expected point source sensitivity is almost 100 mJy, a significant improvement w.r.t the IRAS Point Source Catalog. In the near- and mid-infrared regions, wide and deep surveys of pre-selected sky areas will be made with large low-noise arrays. In addition to wide-band photometric capabilities, low-resolution spectroscopy is provided for all bands. ASTRO-F will produce a fundamental database for advanced observatories of the next generation, e.g., Herschel and JWST.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The
ASTRO-F (
IRIS) is the first Japanese satellite dedicated for infrared astronomy. The telescope has a 70 cm diameter aperture and is cooled down to 6 K by a small amount of liquid helium assisted ...by a mechanical cooling system. The primary purpose of this project is to investigate the birth and evolution of galaxies in the early universe by deep and wide-field surveys in wavelengths of 2 to 200 microns. The spatial resolution and the point source sensitivity are nearly the same as those of the aperture diffraction limit and the natural background and/or confusion limit, respectively. In the far-infrared wavelength band, the
ASTRO-F will achieve an all-sky survey like the
IRAS all-sky survey with much higher sensitivity and better spatial resolution. In the near- and mid-infrared regions, wide area sky-surveys will be performed for pre-selected sky areas. In addition to these photometric surveys, low-resolution spectroscopic capabilities are available for the all wavelength bands. The
ASTRO-F mission will produce a fundamental database for advanced observatories in the next generation, for example
FIRST, NGST, and so on, complementing to the
SIRTF in the respect of its wide sky coverage. The launch by an M-V rocket is scheduled in February or in March of 2004.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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