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Post Info TOPIC: HD 15407
Blobrana


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HD 15407
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Title: The Absence of Cold Dust around Warm Debris Disk Star HD 15407A
Authors: Hideaki Fujiwara, Takashi Onaka, Satoshi Takita, Takuya Yamashíita, Misato Fukagawa, Daisuke Ishihara, Hirokazu Kataza, Hiroshi Murakami

We report Herschel and AKARI photometric observations at far-infrared (FIR) wavelengths of the debris disk around the F3V star HD 15407A, in which the presence of an extremely large amount of warm dust (~500-600 K) has been suggested by mid-infrared (MIR) photometry and spectroscopy. The observed flux densities of the debris disk at 60-160 micron are clearly above the photospheric level of the star, suggesting excess emission at FIR as well as at MIR wavelengths previously reported. The observed FIR excess emission is consistent with the continuum level extrapolated from the MIR excess, suggesting that it originates in the inner warm debris dust and cold dust (~50-130 K) is absent in the outer region of the disk. The absence of cold dust does not support a late heavy bombardment-like event as an origin of the large amount of warm debris dust around HD 15047A.

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Blobrana


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Title: Silica-Rich Bright Debris Disk around HD 15407A
Authors: Hideaki Fujiwara, Takashi Onaka, Takuya Yamashěta, Daisuke Ishihara, Hirokazu Kataza, Misato Fukagawa, Yoichi Takeda, Hiroshi Murakami

We report an intriguing debris disk towards the F3V star HD 15407A, in which an extremely large amount of warm fine dust (~ 10^(-7) Msun) is detected. The dust temperature is derived as ~ 500--600 K and the location of the debris dust is estimated as 0.6--1.0 AU from the central star, a terrestrial planet region. The fractional luminosity of the debris disk is ~ 0.005, which is much larger than those predicted by steady-state models of the debris disk produced by planetesimal collisions. The mid-infrared spectrum obtained by Spitzer indicates the presence of abundant micron-sized silica dust, suggesting that the dust comes from the surface layer of differentiated large rocky bodies and might be trapped around the star.

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Blobrana


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Title: The Age of the HD 15407 System and the Epoch of Final Catastrophic Mass Accretion onto Terrestrial Planets around Sun-like Stars
Authors: C. Melis (1), B. Zuckerman (2), Joseph H. Rhee (2), Inseok Song (3) ((1) UC San Diego, (2) UCLA, (3) University of Georgia)

From optical spectroscopic measurements we determine that the HD 15407 binary system is ~80 Myr old. The primary, HD 15407A (spectral type F5V), exhibits strong mid-infrared excess emission indicative of a recent catastrophic collision between rocky planetary embryos or planets in its inner planetary system. Synthesis of all known stars with large quantities of dust in their terrestrial planet zone indicates that for stars of roughly Solar mass this warm dust phenomenon occurs at ages between 30 and 100 Myr. In contrast, for stars of a few Solar masses, the dominant era of the final assembling of rocky planets occurs earlier, between 10 and 30 Myr age. The incidence of the warm dust phenomenon, when compared against models for the formation of rocky terrestrial-like bodies, implies that rocky planet formation in the terrestrial planet zone around Sun-like stars is common.

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