Search Publications
A study of pulsation & rotation in a sample of A-K type stars in the Kepler field
Paul, K. T.; Engelbrecht, Chris A.; Joshi, Santosh +3 more
We present the results of time-series photometric analysis of 15106 A-K type stars observed by the Kepler space mission. We identified 513 new rotational variables and measured their starspot rotation periods as a function of spectral type and discuss the distribution of their amplitudes. We examined the well-established period-color relationship …
Properties of dust in the detached shells around U Antilae, DR Serpentis, and V644 Scorpii
De Beck, E.; Mecina, M.; Maercker, M. +3 more
Context. Asymptotic giant branch (AGB) stars experience strong mass loss driven by dust particles formed in the upper atmospheres. The dust is released into the interstellar medium, and replenishes galaxies with synthesised material from the star. The dust grains further act as seeds for continued dust growth in the diffuse medium of galaxies. As …
Variability-selected Low-luminosity Active Galactic Nuclei Candidates in the 7 Ms Chandra Deep Field-South
Lehmer, B. D.; Brandt, W. N.; Vignali, C. +13 more
In deep X-ray surveys, active galactic nuclei (AGNs) with a broad range of luminosities have been identified. However, cosmologically distant low-luminosity AGN (LLAGN, {L}{{X}}≲ {10}42 erg s-1) identification still poses a challenge because of significant contamination from host galaxies. Based on the 7 Ms Chandra…
Water vapor deposition from the inner gas coma onto the nucleus of Comet 67P/Churyumov-Gerasimenko
Thomas, N.; Marschall, R.; Su, C. C. +4 more
Rosetta has detected water ice existing on the surface of Comet 67P/Churyumov-Gerasimenko in various types of features. One of particular interest is the frost-like layer observed at the edge of receding shadows during the whole mission, interpreted as the recondensation of a thin layer of water ice. Two possible mechanisms, (1) subsurface ice sub…
Discovery of 6.4 keV line and soft X-ray emissions from G323.7-1.0 with Suzaku
Koyama, Katsuji; Matsumoto, Hironori; Nobukawa, Masayoshi +4 more
In this paper, the Suzaku X-ray data of the Galactic supernova remnant (SNR) candidate G323.7-1.0 are analyzed to search for X-ray emissions. Spatially extended enhancements in the 6.4 keV line and in soft X-rays are found inside or on the radio shell. The soft X-ray enhancement would be the hottest part of the shell-like X-ray emission along the …
The Mass and Absorption Column Densities of Galactic Gaseous Halos. II. The High Ionization State Ions
Bregman, Joel N.; Qu, Zhijie
The high ionization state ions trace the hot gases in the universe, of which gaseous halos around galaxies are a major contributor. Following Qu & Bregman, we calculate the gaseous halo contribution to the observed column density distributions for these ions by convolving the gaseous halo model with the observed stellar mass function. The pred…
Ongoing astrometric microlensing events of two nearby stars
Demleitner, M.; Bastian, U.; Wambsganss, J. +1 more
Context. Astrometric microlensing is an excellent tool to determine the mass of stellar objects. By measuring the astrometric shift of a background source star in combination with precise predictions of its unlensed position and of the lens position, gravitational lensing allows to one determine the mass of the lensing star with a precision of 1%,…
Identifying quasars with astrometric and mid-infrared methods from APOP and ALLWISE
Yan, Qing-Zeng; Liao, Shilong; Qi, Zhaoxiang +5 more
Context. Quasars are spatially stationary, and they are essential objects in astrometry when defining reference frames. However, the census of quasars is far from complete. Mid-infared colors can be used to find quasar candidates because active galactic nuclei (AGNs) show a peculiar appearance in mid-infrared color, but these methods are incapable…
Memberships, distance and proper-motion of the open cluster NGC 188 based on a machine learning method
Gao, Xin-Hua
In this paper, we present an investigation of the memberships, distance and proper motion for the old open cluster NGC 188 using a machine-learning-based method. This method combines two widely used algorithms: spectral clustering (SC) and random forest (RF). The former one is used to construct a reliable training set, the membership probabilities…
Reconstruction of the Dark Energy Equation of State from the Latest Observations
Xia, Jun-Qing; Yang, Yang; Dai, Ji-Ping
Since the discovery of the accelerating expansion of our universe in 1998, studying the features of dark energy has remained a hot topic in modern cosmology. In the literature, dark energy is usually described by w ≡ P/ρ, where P and ρ denote its pressure and energy density. Therefore, exploring the evolution of w is the key approach to understand…