分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： To investigate the dynamical properties of globular clusters, the surface brightness and kinematic data were collected and fitted to a family of lowered isothermal models called LIMEPY models. For 18 studied globular clusters, the amounts of concentration, truncation, and anisotropy were determined. In addition, the cluster mass, half-mass radius, distance, and mass-to-light ratio were also obtained. In general, LIMEPY models could describe these clusters well. Among these 18 clusters, NGC 5139, NGC 6388, and NGC 7078 were claimed to be candidates to host intermediate-mass black holes in literature. The models could not appropriately fit the central proper-motion velocity dispersion of NGC 5139 and the slope of proper-motion velocity-dispersion profile of NGC 6388. Thus, more dedicated models with intermediate-mass black holes or a group of stellar-mass black holes at cluster centers may need to be considered. Considering NGC 7078, our model with some degree of anisotropy can fit the data. Finally, the strong concentration-truncation anti-correlation and truncation-semimajor-axis correlation were revealed, which could be the observational imprint of the dynamical evolution of globular clusters.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： By employing N-body simulations, we inestigate the formation of massive black hole binaries (MBHBs) through the sinking of two massive black holes (MBHs) during galaxy mergers. With different impact parameters and different central stellar density of the progenitor galaxies, we analyze the orbits of the MBHs from the beginning of the merger until the time when the bound MBHB forms. Contrary to the previous theory that the timing of the dual MBHs entering their dynamical radius is similar as the timing of the formation of the bound MBHB, we find that these two timings could deviate when the central stellar density of the progenitors galaxies are lower. On the other hand, when the central stellar density of the progenitor galaxies is higher and the mergers have small impact parameters, each MBHs would move directly into the core radius of the other progenitor galaxies, and therefore cause a variation in the timings of the MBHB formation.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
J. J. C. Hayes
A. Priyadarshi
E. Kerins
S. Awiphan
I. McDonald
N. A-thano
J. S. Morgan
A. Humpage
S. Charles
M. Wright
Y. C. Joshi
Ing-Guey Jiang
T. Inyanya
T. Padjaroen
P. Munsaket
P. Chuanraksasat
S. Komonjinda
P. Kittara
V. S. Dhillon
T. R. Marsh
摘要： We present TransitFit, a package designed to fit exoplanetary transit light-curves. TransitFit offers multi-epoch, multi-wavelength fitting of multi-telescope transit data. TransitFit allows per-telescope detrending to be performed simultaneously with transit parameter fitting, including custom detrending. Host limb darkening can be fitted using prior conditioning from stellar atmosphere models. We demonstrate TransitFit in a number of contexts. We model multi-telescope broadband optical data from the ground-based SPEARNET survey of the low-density hot-Neptune WASP-127b and compare results to a higher spectral resolution GTC/OSIRIS transmission spectrum obtained by Chen et al. (2018). Using TransitFit, we fit 26 transit epochs by TESS to recover improved ephemerides of the hot-Jupiter WASP-91b and a transit depth determined to a precision of 70ppm. We use TransitFit to conduct an investigation into the contested presence of TTV signatures in WASP-126b using 169 transits observed by TESS, concluding that there is no statistically significant evidence for such signatures from observations spanning 25 TESS sectors. We fit HST observations of WASP-43b, demonstrating how TransitFit can use custom detrending algorithms to remove complex baseline systematics. Lastly, we present a transmission spectrum of the atmosphere of WASP-96b constructed from simultaneous fitting of JWST NIRISS Early Release Observations and archive HST WFC3 transit data. The transmission spectrum shows generally good correspondence between spectral features present in both datasets, despite very different detrending requirements. However, the joint fit also provides some evidence of epoch-dependent behaviour that may indicate host activity or weather variations in the atmosphere of WASP-96b.
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