Results 41 to 50 of about 353 (134)

A spectral-line survey of CIT 6 between 30 and 50 GHz with the eQ receiver at NRO 45 m

Astronomy & Astrophysics
Context. At the end of the long H-burning phase (main sequence), low-mass to intermediate-mass stars evolve into asymptotic giant branch (AGB) stars that can have carbon-rich envelopes depending on the initial C/O ratio. In their circumstellar envelopes (
Nguyen-Luong Quang, Nakamura Fumitaka, Taniguchi Kotomi, Dinh-V-Trung, Liu Sheng-Yuan, Shimoikura Tomomi, Chiong Chau-Ching, Dobashi Kazuhito, Hirano Naomi, Yonekura Yoshinori, Nishimura Atsushi, Ogawa Hideo, Chien Chen, Ho Chin-Ting, Hwang Yuh-Jing, Yeh You-Ting, Lai Shih-Ping, Fujii Yasunori, Yamasaki Yasumasa, Kawabe Ryohei, Nolan Adam, Dung Pham Viet   +21 more
doaj   +1 more source

Limitations of the modified blackbody fit method for determining molecular cloud properties

Astronomische Nachrichten, Volume 345, Issue 4, May 2024.
Abstract Achieving a comprehensive understanding of the star and planet formation process is one of the fundamental tasks of astrophysics, requiring detailed knowledge of the physical conditions during the different phases of this process. During the earliest stages, that is, concerning physical processes in molecular clouds and filaments, the column ...
Niko Zielinski, Sebastian Wolf
wiley   +1 more source

Effects of Metallicity on Graphite, TiC, and SiC Condensation in Carbon Stars

The Astrophysical Journal
From transmission electron microscopy and other laboratory studies of presolar grains, the implicit condensation sequence of carbon-bearing condensates in circumstellar envelopes of carbon stars is (from first to last) TiC-graphite-SiC.
Gabrielle M. Adams, Katharina Lodders
doaj   +1 more source

Characterizing the dynamical magnetosphere of the extremely slowly rotating magnetic O9.7 V star HD 54879 using rotational modulation of the Hα profile

Astronomische Nachrichten, Volume 345, Issue 4, May 2024.
Abstract The magnetic field in the O9.7 V star HD 54879 has been monitored for almost a decade. Spectropolarimetric observations reveal a rather strong mean longitudinal magnetic field that varies with a period of about 7.41 years. Observations in the Hα$$ \alpha $$ line show a variation with the same period, while the Hβ$$ \beta $$ line shows only ...
Manfred Küker, S. P. Järvinen, S. Hubrig, Ilya Ilyin, M. Schöller   +4 more
wiley   +1 more source

Early Planet Formation in Embedded Disks (eDisk). XIII. Aligned Disks with Nonsettled Dust around the Newly Resolved Class 0 Protobinary R CrA IRAS 32

The Astrophysical Journal
Young protostellar binary systems, with expected ages less than ∼10 ^5 yr, are little modified since birth, providing key clues to binary formation and evolution. We present a first look at the young, Class 0 binary protostellar system R CrA IRAS 32 from
Frankie J. Encalada, Leslie W. Looney, Shigehisa Takakuwa, John J. Tobin, Nagayoshi Ohashi, Jes K. Jørgensen, Zhi-Yun Li, Yuri Aikawa, Yusuke Aso, Patrick M. Koch, Woojin Kwon, Shih-Ping Lai, Chang Won Lee, Zhe-Yu Daniel Lin, Alejandro Santamaría-Miranda, Itziar de Gregorio-Monsalvo, Nguyen Thi Phuong, Adele Plunkett, Jinshi Sai (Insa Choi), Rajeeb Sharma, Hsi-Wei Yen, Ilseung Han   +21 more
doaj   +1 more source

A deep search for C2H in the oxygen-rich post-AGB star OH 231.8+4.2

Frontiers in Astronomy and Space Sciences
In carbon-rich environment, C2H emission is seen to be associated with HC3N, but whether it can trace the HC3N molecule in oxygen-rich environment is unknown.
Jianchao Yang, Jianchao Yang, Xiaofeng Yang, Xiaofeng Yang, Cheng Zhu, Cheng Zhu   +5 more
doaj   +1 more source

Observations of Molecular CN toward S-type Asymptotic Giant Branch Stars

The Astronomical Journal
S-type asymptotic giant branch (AGB) stars are defined by their carbon-to-oxygen (C/O) ratio approaching unity. However, observations of circumstellar molecules in these stars are limited and challenging.
Yanan Feng, Xiaohu Li, Xiaofeng Yang, Tom J. Millar, Ryszard Szczerba, Sheng-Li Qin, Xuejian Jiang, Donghui Quan, Juan Tuo, Zhenzhen Miao, Sheng-Yuan Liu, Xiang Liu   +11 more
doaj   +1 more source

Gas-phase Molecules in Protoplanetary Nebulae with the 21 μm Emission Feature. II. Carbon Monosulfide

The Astronomical Journal
The carrier of the 21 μ m emission feature discovered in a handful of protoplanetary nebulae (PPNe) is one of the most intriguing enigmas in circumstellar chemistry.
Jian-Jie Qiu, Yong Zhang, Deng-Rong Lu, Zheng-Xue Chang, Jiang-Shui Zhang, Xiao-Hu Li, Xin-Di Tang, Yisheng Qiu, Jun-ichi Nakashima, Lan-Wei Jia   +9 more
doaj   +1 more source

The unique chemistry in the envelopes of massive stars

Frontiers in Astronomy and Space Sciences
The envelopes of evolved massive stars (M ∼9–40 M⊙) on the Red Supergiant (RSG) Branch offer a unique situation to examine extreme circumstellar chemistry.
Lucy M. Ziurys
doaj   +1 more source

Velocity Structure of Circumstellar Environment around Class 0/I Protostars: Uncertainty in the Protostellar Mass Estimation Using Circumstellar Velocities

The Astrophysical Journal
Recent high-resolution observations have enabled detailed investigations of the circumstellar environments around Class 0/I protostars. Several studies have reported that the infall velocity of the envelope is a few times smaller than the freefall ...
Shingo Hirano, Yuri Aikawa, Masahiro N. Machida   +2 more
doaj   +1 more source