分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a new optical transmission spectrum of the hot Jupiter HAT-P-32Ab acquired with the Carnegie Observatories Spectrograph and Multiobject Imaging Camera (COSMIC) on the Palomar 200 inch Hale Telescope (P200). The P200/COSMIC transmission spectrum, covering a wavelength range of 3990--9390 \AA, is composed of 25 spectrophotometric bins with widths ranging from 200 to 400 \AA and consistent with previous transit measurements obtained in the common wavelength range. We derive a combined optical transmission spectrum based on measurements from five independent instruments, which, along with the 1.1--1.7 $\mu$m spectrum acquired by the Hubble Space Telescope and two Spitzer measurements, exhibits an enhanced scattering slope blueward of a relatively flat optical continuum, a water absorption feature at 1.4 $\mu$m, and a carbon dioxide feature at 4.4 $\mu$m. We perform Bayesian spectral retrieval analyses on the 0.3--5.1 $\mu$m transmission spectrum and find that it can be well explained by a two-limb approximation of $134^{+45}_{-33}\times$ solar metallicity, with a strongly hazy morning limb of $1134^{+232}_{-194}$ K and a haze-free evening limb of $1516^{+33}_{-44}$~K. This makes HAT-P-32Ab a promising target for James Webb Space Telescope to look for asymmetric signatures directly in the light curves.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Variable stars play a key role in understanding the Milky Way and the universe. The era of astronomical big data presents new challenges for quick identification of interesting and important variable stars. Accurately estimating the periods is the most important step to distinguish different types of variable stars. Here, we propose a new method of determining the variability periods. By combining the statistical parameters of the light curves, the colors of the variables, the window function and the GLS algorithm, the aperiodic variables are excluded and the periodic variables are divided into eclipsing binaries and NEB variables (other types of periodic variable stars other than eclipsing binaries), the periods of the two main types of variables are derived. We construct a random forest classifier based on 241,154 periodic variables from the ASAS-SN and OGLE datasets of variables. The random forest classifier is trained on 17 features, among which 11 are extracted from the light curves and 6 are from the Gaia Early DR3, ALLWISE and 2MASS catalogs. The variables are classified into 7 superclasses and 17 subclasses. In comparison with the ASAS-SN and OGLE catalogs, the classification accuracy is generally above approximately 82% and the period accuracy is 70%-99%. To further test the reliability of the new method and classifier, we compare our results with the results of Chen et al. (2020) for ZTF DR2. The classification accuracy is generally above 70%. The period accuracy of the EW and SR variables is 50% and 53%, respectively. And the period accuracy of other types of variables is 65%-98%.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Variable stars play a key role in understanding the Milky Way and the universe. The era of astronomical big data presents new challenges for quick identification of interesting and important variable stars. Accurately estimating the periods is the most important step to distinguish different types of variable stars. Here, we propose a new method of determining the variability periods. By combining the statistical parameters of the light curves, the colors of the variables, the window function and the GLS algorithm, the aperiodic variables are excluded and the periodic variables are divided into eclipsing binaries and NEB variables (other types of periodic variable stars other than eclipsing binaries), the periods of the two main types of variables are derived. We construct a random forest classifier based on 241,154 periodic variables from the ASAS-SN and OGLE datasets of variables. The random forest classifier is trained on 17 features, among which 11 are extracted from the light curves and 6 are from the Gaia Early DR3, ALLWISE and 2MASS catalogs. The variables are classified into 7 superclasses and 17 subclasses. In comparison with the ASAS-SN and OGLE catalogs, the classification accuracy is generally above approximately 82% and the period accuracy is 70%-99%. To further test the reliability of the new method and classifier, we compare our results with the results of Chen et al. (2020) for ZTF DR2. The classification accuracy is generally above 70%. The period accuracy of the EW and SR variables is 50% and 53%, respectively. And the period accuracy of other types of variables is 65%-98%.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a new optical transmission spectrum of the hot Jupiter HAT-P-32Ab acquired with the Carnegie Observatories Spectrograph and Multiobject Imaging Camera (COSMIC) on the Palomar 200 inch Hale Telescope (P200). The P200/COSMIC transmission spectrum, covering a wavelength range of 3990--9390 \AA, is composed of 25 spectrophotometric bins with widths ranging from 200 to 400 \AA and consistent with previous transit measurements obtained in the common wavelength range. We derive a combined optical transmission spectrum based on measurements from five independent instruments, which, along with the 1.1--1.7 $\mu$m spectrum acquired by the Hubble Space Telescope and two Spitzer measurements, exhibits an enhanced scattering slope blueward of a relatively flat optical continuum, a water absorption feature at 1.4 $\mu$m, and a carbon dioxide feature at 4.4 $\mu$m. We perform Bayesian spectral retrieval analyses on the 0.3--5.1 $\mu$m transmission spectrum and find that it can be well explained by a two-limb approximation of $134^{+45}_{-33}\times$ solar metallicity, with a strongly hazy morning limb of $1134^{+232}_{-194}$ K and a haze-free evening limb of $1516^{+33}_{-44}$~K. This makes HAT-P-32Ab a promising target for James Webb Space Telescope to look for asymmetric signatures directly in the light curves.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Chan-Kao Chang
Ying-Tung Chen
Wesley C. Fraser
Fumi Yoshida
Matthew J. Lehner
Shiang-Yu Wang
JJ Kavelaars
Rosemary E. Pike
Mike Alexandersen
Takashi Ito
Young-Jun Choi
A. Paula Granados Contreras
Youngmin JeongAhn
Jianghui Ji
Myung-Jin Kim
Samantha M. Lawler
Jian Li
Zhong-Yi Lin
Patryk Sofia Lykawka
Hong-Kyu Moon
摘要： Rotation periods of 53 small (diameters $2 < D < 40$ km) Jupiter Trojans (JTs) were derived using the high-cadence light curves obtained by the FOSSIL phase I survey, a Subaru/Hyper Suprime-Cam intensive program. These are the first reported periods measured for JTs with $D < 10$ km. We found a lower limit of the rotation period near 4 hr, instead of the previously published result of 5 hr (Ryan et al. 2017; Szabo et al. 2017, 2020) found for larger JTs. Assuming a rubble-pile structure for JTs, a bulk density of 0.9 gcm$^{-3}$ is required to withstand this spin rate limit, consistent with the value $0.8-1.0$ gcm$^{-3}$ (Marchis et al. 2006; Mueller et al. 2010; Buie et al. 2015; Berthier et al. 2020) derived from the binary JT system, (617) Patroclus-Menoetius system.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Linhua Jiang
Shu Wang
Bing Zhang
Nobunari Kashikawa
Luis C. Ho
Zheng Cai
Eiichi Egami
Gregory Walth
Yi-Si Yang
Bin-Bin Zhang
Hai-Bin Zhao
摘要： In Jiang et al., we detected a bright flash (hereafter GN-z11-flash) that appeared as compact continuum emission during our Keck MOSFIRE observations of the galaxy GN-z11 at z ~ 11. We performed a comprehensive analysis of the origin of the flash using all available information and our current understanding of known man-made objects or moving objects in the solar system. We found that GN-z11-flash was likely a rest-frame UV flash associated with a long gamma-ray burst (GRB) from GN-z11. Recently, Steinhardt et al., Michalowski et al., and Nir et al. reported that GN-z11-flash was more likely from a satellite. While one cannot completely rule out the possibility of unknown satellites (or debris), we find that either the chance probabilities of being a satellite estimated by these authors have been largely overestimated or their identified satellites have been ruled out in our original analysis. Our new calculations show that the probability of GN-z11-flash being a satellite is still lower than that of it being a signal originated from GN-z11.
点击量
待评议
点击量
下载量
评论
