In this work,we report observations of three comets:38P/Stephan-Oterma,64P/Swift-Gehrels,and C/2017 M4(ATLAS),conducted with the Nanshan one-meter wide-field telescope in 2018 August and November,and 2019January.We ex...In this work,we report observations of three comets:38P/Stephan-Oterma,64P/Swift-Gehrels,and C/2017 M4(ATLAS),conducted with the Nanshan one-meter wide-field telescope in 2018 August and November,and 2019January.We extracted morphological features through image enhancement techniques and calculated the dust activity parameter,Afρ,along with dust mass loss rates and coma color indices using broadband photometric data.Our morphological analysis uncovered a spectrum of dust characteristics among the observed comets,ranging from a significant twisted structure in comet 38P/Stephan-Oterma’s coma to the regular coma envelope surrounding comet 64P/Swift-Gehrels.The Afρvalues varied between 148.8±0.3 cm for 64P/Swift-Gehrels and1118.5±6.2 cm for C/2017 M4(ATLAS)(measured within a reference aperture radius ofρ=6″),indicating a range from moderate to high activity levels.Dust mass loss rates were estimated from 328.1 kg s^(-1)for comet 64P/Swift-Gehrels to 1395.5 kg s^(-1)for comet C/2017 M4(ATLAS).The color indices of comets 38P/Stephan-Oterma and C/2017 M4(ATLAS)closely resemble the average colors of active short-period comets and active longperiod comets,respectively.In contrast,64P/Swift-Gehrels exhibits a significantly bluer hue than typical Jupiter family comets.展开更多
The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms an...The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules arise mainly in three ways:(i) the outgassing from the nucleus,(ii) the photochemical process, and(iii) the sublimation of icy grains from the nucleus. In this paper, we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3(ZTF) using the Giant Metrewave Radio Telescope(GMRT) band L and the Atacama Large Millimeter/submillimeter Array(ALMA) band 6. We do not detect continuum emissions and an emission line of atomic hydrogen(H I) at rest frequency 1420 MHz from this comet using the GMRT. Based on ALMA observations, we detect the dust continuum emission and rotational emission lines of methanol(CH_(3)OH) from comet C/2022 E3(ZTF). From the dust continuum emission, the dust production(Afρ) activity of comet ZTF is 2280 ± 50 cm. Based on LTE spectral modeling, the column density and excitation temperature of CH_(3)OH toward C/2022 E3(ZTF) are(4.50 ± 0.25) × 10^(14)cm^(-2)and 70 ± 3 K respectively. The integrated emission maps show that CH_(3)OH was emitted from the coma region of the comet. The production rate of CH_(3)OH toward C/2022 E3(ZTF) is(7.32 ± 0.64) × 10^(26) molecules s^(-1). The fractional abundance of CH_(3)OH with respect to H2O in the coma of the comet is 1.52%. We also compare our derived abundance of CH_(3)OH with the existence modeled value, and we see the observed and modeled values are quite similar. We claim that CH_(3)OH is formed via the subsequential hydrogenation of formaldehyde(H2CO) on the grain surface of comet C/2022 E3(ZTF).展开更多
基金supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region of China(grant No.2021D01B112)Tianshan Talent Training Program through the grant 2023TSYCCX0101。
文摘In this work,we report observations of three comets:38P/Stephan-Oterma,64P/Swift-Gehrels,and C/2017 M4(ATLAS),conducted with the Nanshan one-meter wide-field telescope in 2018 August and November,and 2019January.We extracted morphological features through image enhancement techniques and calculated the dust activity parameter,Afρ,along with dust mass loss rates and coma color indices using broadband photometric data.Our morphological analysis uncovered a spectrum of dust characteristics among the observed comets,ranging from a significant twisted structure in comet 38P/Stephan-Oterma’s coma to the regular coma envelope surrounding comet 64P/Swift-Gehrels.The Afρvalues varied between 148.8±0.3 cm for 64P/Swift-Gehrels and1118.5±6.2 cm for C/2017 M4(ATLAS)(measured within a reference aperture radius ofρ=6″),indicating a range from moderate to high activity levels.Dust mass loss rates were estimated from 328.1 kg s^(-1)for comet 64P/Swift-Gehrels to 1395.5 kg s^(-1)for comet C/2017 M4(ATLAS).The color indices of comets 38P/Stephan-Oterma and C/2017 M4(ATLAS)closely resemble the average colors of active short-period comets and active longperiod comets,respectively.In contrast,64P/Swift-Gehrels exhibits a significantly bluer hue than typical Jupiter family comets.
文摘The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules arise mainly in three ways:(i) the outgassing from the nucleus,(ii) the photochemical process, and(iii) the sublimation of icy grains from the nucleus. In this paper, we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3(ZTF) using the Giant Metrewave Radio Telescope(GMRT) band L and the Atacama Large Millimeter/submillimeter Array(ALMA) band 6. We do not detect continuum emissions and an emission line of atomic hydrogen(H I) at rest frequency 1420 MHz from this comet using the GMRT. Based on ALMA observations, we detect the dust continuum emission and rotational emission lines of methanol(CH_(3)OH) from comet C/2022 E3(ZTF). From the dust continuum emission, the dust production(Afρ) activity of comet ZTF is 2280 ± 50 cm. Based on LTE spectral modeling, the column density and excitation temperature of CH_(3)OH toward C/2022 E3(ZTF) are(4.50 ± 0.25) × 10^(14)cm^(-2)and 70 ± 3 K respectively. The integrated emission maps show that CH_(3)OH was emitted from the coma region of the comet. The production rate of CH_(3)OH toward C/2022 E3(ZTF) is(7.32 ± 0.64) × 10^(26) molecules s^(-1). The fractional abundance of CH_(3)OH with respect to H2O in the coma of the comet is 1.52%. We also compare our derived abundance of CH_(3)OH with the existence modeled value, and we see the observed and modeled values are quite similar. We claim that CH_(3)OH is formed via the subsequential hydrogenation of formaldehyde(H2CO) on the grain surface of comet C/2022 E3(ZTF).
