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AN EAST-ASIAN EXTRA-SOLAR PLANET SEARCH NETWORK
IZUMIURA HIDEYUKI The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.2
We are undertaking an extra-solar planet search around G-type giant stars by means of Doppler technique using an iodine absorption cell installed to the high dispersion echelle spectrograph for the 188 cm reflector at Okayama Astrophysical Observatory (Okayama Planet Search Program, OPSP). Having detected the first planet candidate (Sato et al. 2003)the search has been proved very promising. Taking advantage of this success, we are trying to develop OPSP to an international collaborative work. We here report the current status of our efforts for establishing such collaborations, namely, those with Chinese and Korean astronomers. We also propose to establish an East-Asian network to search for extra-solar planets around G-type giant stars with the transit detecting technique as well as the Doppler technique, asking other persons/groups to join us to enjoy the planet search.
Kambe, Eiji,Ando, Hiroyasu,Sato, Bun’ei,Izumiura, Hideyuki,Sekii, Takashi,Paulson, Diane B.,Yanagisawa, Kenshi,Masuda, Seiji,Shibahashi, Hiromoto,Hatzes, Artie P.,MARTI´C, Milena,LEBRUN, Jean-Claude,M Astronomical Society of Japan 2008 Publications of the Astronomical Society of Japan Vol.60 No.1
An improvement of the radial-velocity measurement accuracy is crucial for the detection of tiny stellar oscillationsand exoplanets. Through the analysis of week-long extensive observations of solar-type stars (Procyon in 2000, 2002, and 2006/2007 and τ Cet in 2002 and 2006/2007), we have carefully examined, revised, and finelytuned the widely used multiple Gaussian IP fitting method for the spectrograph, HIDES. By determining a necessaryand sufficient number of free parameters in the model as well as introducing an iterative process in the radial-velocityanalysis, we can reach a precision of below 3ms<SUP>-1</SUP>, which is much smaller than the precision of 6ms<SUP>-1</SUP> officially announced so far for HIDES. We also make our technique refined for the 2002 McDonald Procyon data. Even with our revised method, slow radial velocity variations with an amplitude of about 10ms<SUP>-1</SUP> are left in the Procyon data. We emphasize that it is neither due to particular observing instruments nor radial-velocity analysis, and thus could be due to stellar origin. The analysis presented here makes the foundations of our next scientific analysis of the radial-velocity variations of Procyon, which will be presented in our forthcoming papers.
DUST AND CHEMICAL ABUNDANCES OF THE SAGITTARIUS DWARF GALAXY PLANETARY NEBULA Hen2-436
Otsuka, Masaaki,Meixner, Margaret,Riebel, David,Hyung, Siek,Tajitsu, Akito,Izumiura, Hideyuki IOP Publishing 2011 The Astrophysical journal Vol.729 No.1
<P>We have estimated elemental abundances of the planetary nebula (PN) Hen2-436 in the Sagittarius (Sgr) spheroidal dwarf galaxy using ESO/VLT FORS2, Magellan/MMIRS, and Spitzer/IRS spectra. We have detected candidates of fluorine [F II] lambda 4790, krypton [Kr III] lambda 6826, and phosphorus [P II] lambda 7875 lines and successfully estimated the abundances of these elements ([F/H] = +1.23, [Kr/H] = +0.26, [P/H] = +0.26) for the first time. These elements are known to be synthesized by the neutron capture process in the He-rich intershell during the thermally pulsing asymptotic giant branch (AGB) phase. We present a relation between C, F, P, and Kr abundances among PNe and C-rich stars. The detections of these elements in Hen2-436 support the idea that F, P, Kr together with C are synthesized in the same layer and brought to the surface by the third dredge-up. We have detected N II and O II optical recombination lines (ORLs) and derived the N2+ and O2+ abundances. The discrepancy between the abundance derived from the oxygen ORL and that derived from the collisionally excited line is > 1 dex. To investigate the status of the central star of the PN, nebula condition, and dust properties, we construct a theoretical spectral energy distribution (SED) model to match the observed SED with Cloudy. By comparing the derived luminosity and temperature of the central star with theoretical evolutionary tracks, we conclude that the initial mass of the progenitor is likely to be similar to 1.5-2.0M(circle dot) and the age is similar to 3000 yr after the AGB phase. The observed elemental abundances of Hen2-436 can be explained by a theoretical nucleosynthesis model with a star of initial mass 2.25 M-circle dot, Z = 0.008, and LMC compositions. We have estimated the dust mass to be 2.9x10(-4) M-circle dot (amorphous carbon only) or 4.0x10(-4) M-circle dot (amorphous carbon and polycyclic aromatic hydrocarbon). Based on the assumption that most of the observed dust is formed during the last two thermal pulses and the dust-to-gas mass ratio is 5.58 x 10(-3), the dust mass-loss rate and the total mass-loss rate are < 3.1x10(-8) M-circle dot yr(-1) and < 5.5x10(-6) M-circle dot yr(-1), respectively. Our estimated dust mass-loss rate is comparable to a Sgr dwarf galaxy AGB star with similar metallicity and luminosity.</P>