Dust changes in Sakurai's Object: new PAHs and SiC with coagulation of submicron-sized silicate dust into 10 µm-sized melilite grains
Dust changes in Sakurai's Object: new PAHs and SiC with coagulation of submicron-sized silicate dust into 10 µm-sized melilite grains
复制标题
樱井物体中的灰尘变化：新的 PAH 和 SiC，亚微米大小的硅酸盐灰尘凝结成 10 µm 大小的黄长石颗粒
DOI：
10.1093/mnras/stab1305
复制
发表时间：
2021
影响因子：
4.8
通讯作者：
Bowey J
中科院分区：
文献类型：
--
作者：
Bowey J
利用2005年4月至2008年10月期间6个历元获得的6 - 14 μ mSpitzer光谱，确定了与樱井天体（V4334 Sgr）相关的尘埃特征的时间变化，樱井天体是一颗低质量后AGB星星，自1996年以来一直在爆发事件中形成尘埃。被遮蔽的富碳光球被一个40毫角秒的环面和32角秒的PN所包围。2008年4月21日之后，中红外线通量开始迅速减少。光学薄发射由于纳米尺寸的SiC晶粒在2007年10月达到最低，2008年4月21日至30日之间迅速增加，2008年10月更慢。6.3-μ m的吸收，由于多环芳烃增加整个。2007年5月以后，20 μ m的SiC颗粒可能对6-7 μ m的吸收有贡献。如果大的SiC颗粒形成于1999年5月之前，多环芳烃形成于1999年4 - 6月，则基于光学厚发射的质量估计与吸收特征中的质量估计一致。在2008年10月，PAH和大颗粒SiC的质量估计分别为3 × 10 − 9 M和10 − 8 M。一些造成10 μ m弱吸收特征的亚微米级硅酸盐可能位于PN内，因为2007年10月至2008年10月期间光学厚度减小。2005年4月至2008年10月期间，6.9 μ m的吸收被分配给10 μ m大小的结晶黄长石硅酸盐增加。如果2.8%的亚微米级硅酸盐凝结形成黄长石，则满足光谱和光谱限制。这一数字与黄长石中富含钙铝包体的丰度相似。
6–14μmSpitzerspectra obtained at 6 epochs between 2005 April and 2008 October are used to determine temporal changes in dust features associated with Sakurai’s Object (V4334 Sgr), a low mass post-AGB star that has been forming dust in an eruptive event since 1996. The obscured carbon-rich photosphere is surrounded by a 40-milliarcsec torus and 32 arcsec PN. An initially rapid mid-infrared flux decrease stalled after 2008 April 21. Optically thin emission due to nanometre-sized SiC grains reached a minimum in 2007 October, increased rapidly between 2008 April 21–30 and more slowly to 2008 October. 6.3-μm absorption due to PAHs increased throughout. 20μm-sized SiC grains might have contributed to the 6–7μm absorption after 2007 May. Mass estimates based on the optically thick emission agree with those in the absorption features if the large SiC grains formed before 1999 May and PAHs formed in 1999 April–June. Estimated masses of PAH and large-SiC grains in 2008 October, were 3 × 10−9M⊙and 10−8M⊙, respectively. Some of the submicron-sized silicates responsible for a weak 10μm absorption feature are probably located within the PN because the optical depth decreased between 2007 October and 2008 October. 6.9-μm absorption assigned to ∼10μm-sized crystalline melilite silicates increased between 2005 April and 2008 October. Abundance and spectroscopic constraints are satisfied if2.8 per cent of the submicron-sized silicates coagulated to form melilites. This figure is similar to the abundance of melilite-bearing calcium–aluminium-rich inclusions in chondritic meteorites.