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Co-moving groups around massive stars in the nuclear stellar disk
Najarro, F.; Nogueras-Lara, F.; Schödel, R. +2 more
Context. Over the last ∼30 Myr, the nuclear stellar disk in the Galactic center has been the most prolific star-forming region of the Milky Way when averaged by volume. Remarkably, the combined mass of the only three clusters present today in the nuclear stellar disk adds up to only ∼10% of the total expected mass of young stars formed in this per…
Cloud-cloud collision in S235: triggered the formation of high-mass stars and young star clusters
Fang, Min; Gao, Yu; Zhang, Shiyu +7 more
We present the analysis of cloud-cloud collision (CCC) process in the Galactic molecular complex S235. Our new CO observations performed with the PMO-13.7 m telescope reveal two molecular clouds, namely the S235-Main and the S235-ABC, with ~4 km s-1 velocity separation. The bridge feature, the possible colliding interface and the comple…
Fast and Robust Noise Background Modeling and Quasiperiodic Oscillation Detection for Astronomical Time Series
Xu, Chang
Spectrum with confidence levels is a commonly used method for quasiperiodic oscillation (QPO) detection, but it is prone to yield false positives for two reasons: poor choice and/or biased modeling of the null hypothesis (or noise background). Motivated by this, we propose a new time-domain maximum-likelihood estimation method, which can quickly a…
Generalized Rotation Curves of the Milky Way from the GAIA DR3 Data Set: Constraints on Mass Models
Sylos Labini, Francesco
The circular velocity curve traced by stars provides a direct means of investigating the potential and mass distribution of the Milky Way. Recent measurements of the Galaxy's rotation curve have revealed a significant decrease in velocity for Galactic radii larger than approximately 15 kpc. While these determinations have primarily focused on the …
The star formation history of the first bulge fossil fragment candidate Terzan 5
Dalessandro, E.; Cignoni, M.; Massari, D. +6 more
Context. Terzan 5 and Liller 1 are the only bulge stellar clusters hosting multi-iron and multi-age stellar populations. They are therefore claimed to constitute a novel class of astrophysical objects: the fossils of massive star-forming clumps that possibly sank to the center of the Milky Way and contributed to the formation of the bulge. This is…
Surface properties of the seas of Titan as revealed by Cassini mission bistatic radar experiments
Soderblom, Jason M.; Lorenz, Ralph D.; Tortora, Paolo +9 more
Saturn's moon Titan was explored by the Cassini spacecraft from 2004 to 2017. While Cassini revealed a lot about this Earth-like world, its radar observations could only provide limited information about Titan's liquid hydrocarbons seas Kraken, Ligeia and Punga Mare. Here, we show the results of the analysis of the Cassini mission bistatic radar e…
Edge-on galaxies in the HST COSMOS field: the evolution of stellar discs up to z 0.5
Usachev, Pavel A.; Reshetnikov, Vladimir P.; Savchenko, Sergey S.
We present a sample of 950 edge-on spiral galaxies found with the use of an artificial neural network in the Hubble Space Telescope COSMOS field. This is currently the largest sample of distant edge-on galaxies. For all galaxies we analysed the 2D brightness distributions in the F814W filter and measured the radial and vertical exponential scales …
Exploring the stellar rotation of early-type stars in the LAMOST medium-resolution survey: III. Evolution
Chiappini, Cristina; Sun, Weijia
Context. Stellar rotation significantly shapes the evolution of massive stars, yet the interplay of mass and metallicity remains elusive, limiting our capacity to construct accurate stellar evolution models and to better estimate the impact of rotation on the chemical evolution of galaxies. Aims. Our goal is to investigate how mass and metallicity…
Atmospheric Retrievals of the Phase-resolved Spectra of Irradiated Brown Dwarfs WD-0137B and EPIC-2122B
Lothringer, Joshua D.; Apai, Dániel; Parmentier, Vivien +3 more
We present an atmospheric retrieval analysis of Hubble Space Telescope/Wide Field Camera 3/G141 spectroscopic phase curve observations of two brown dwarfs, WD-0137B and EPIC-2122B, in ultrashort period orbits around white dwarf hosts. These systems are analogous to hot and ultra-hot Jupiter systems, enabling a unique and high-precision comparison …
AstroSat and Insight-HXMT Observations of the Long-period X-Ray Pulsar 4U 2206+54
Wang, Wei; Epili, Prahlad R.
We report the timing and spectral studies of the accreting X-ray pulsar 4U 2206+54 using AstroSat and Insight-HXMT observations taken in 2016 and 2020 respectively. X-ray pulsations from the system are detected by both missions. The AstroSat discovered a significant periodic signal at ∼5619 s in 2016, and Insight-HXMT found a pulsation period at ∼…