Search Publications
Investigation of the connection between X-ray binaries and compact star clusters in NGC 628
Akyuz, A.; Aksaker, N.; Avdan, S. +3 more
We investigated for a possible connection between the types of X-ray binaries (XRBs) and the properties of compact star clusters in the nearby galaxy NGC 628. Using Chandra archival data covering the years 2001-2018, 75 X-ray sources were detected within the field of view of observations. A total of 69 XRBs, one of which is an ultraluminous X-ray …
Discovery of a radio jet in the Cloverleaf quasar at z = 2.56
Tsai, Chao-Wei; Wang, Junzhi; Zhang, Zhi-Yu +10 more
The fast growth of supermassive black holes and their feedback to the host galaxies play an important role in regulating the evolution of galaxies, especially in the early Universe. However, due to cosmological dimming and the limited angular resolution of most observations, it is difficult to resolve the feedback from the active galactic nuclei (…
Chemical abundances of the young inner-disc open cluster NGC 6705 observed by APOGEE: sodium-rich and not α-enhanced
Holtzman, J. A.; Allende Prieto, C.; Bizyaev, D. +19 more
Previous results in the literature have found the young inner-disc open cluster NGC 6705 to be mildly α-enhanced. We examined this possibility via an independent chemical abundance analysis for 11 red-giant members of NGC 6705. The analysis is based on near-infrared APOGEE spectra and relies on LTE calculations using spherical model atmospheres an…
Broad-band X-ray properties of black holes GRS 1758-258 and 1E 1740.7-2942: AstroSat and NuSTAR results
Agrawal, Vivek K.; Mandal, Samir; Nandi, Anuj +4 more
We present the results on broad-band X-ray properties of persistent black hole binaries GRS 1758-258 and 1E 1740.7-2942 using AstroSat, NuSTAR, and Swift-XRT observations carried out during 2016-2022. We perform spectral modelling of both sources after eliminating the contamination in their LAXPC spectra from nearby X-ray sources. Preliminary spec…
A candidate magnetic helium-core white dwarf in the globular cluster NGC 6397
Bahramian, Arash; Maccarone, Thomas J.; Althaus, Leandro G. +5 more
We report a peculiar variable blue star in the globular cluster (GC) NGC 6397, using Hubble Space Telescope optical imaging. Its position in the colour-magnitude diagrams and its spectrum are consistent with this star being a helium-core white dwarf (He WD) in a binary system. The optical light curve shows a periodicity at 18.5 h. We argue that th…
The 2175 Å interstellar extinction bump: is the wavelength variable?
Li, Aigen; Yang, X. J.; Wang, Qian
The most striking characteristics of the mysterious 2175$\mathring{\rm A}$ extinction bump, the strongest spectroscopic absorption feature seen on the interstellar extinction curve, are the invariant central wavelength and variable bandwidth: its peak position at 2175$\mathring{\rm A}$ is remarkably constant, while its bandwidth varies from one li…
Total electron content depression in the nightside Martian ionosphere: statistical results from Mars Express MARSIS measurements and implications
Rong, Zhaojin; Li, Lei; Wei, Yong +7 more
Thermal electron depression and energetic electron depletion are two well-known features of the nightside Martian ionosphere. While the latter has been extensively studied in the past, there is no report of systematic and firm identification of the former and hence the correlation between them is unknown. Applying an automatic procedure to the Mar…
Binarity and beyond in A stars II. Disentangling the four stars in the vicinity of the triple HIP 87813 within the quintuple system HJ2814
Katz, Boaz; Waisberg, Idel; Klein, Ygal
A-type stars are the progenitors of about half of the white dwarfs (WDs) that currently exist. The observational mappings of both multiplicities are far from complete and their connection is not known. We are in the process of obtaining tight constraints on a sample of 108 southern and nearby A-stars that are part of the VAST sample by conducting …
Eclipse timing variations in the WD + dM eclipsing binary RR Cae
Reichart, D. E.; Awiphan, S.; Haislip, J. B. +9 more
We present the binary model and the eclipse timing variations of the eclipsing binary RR Cae, which consists of a white dwarf eclipsed by an M-type dwarf companion. The multiwavelength optical photometry from the Transiting Exoplanet Survey Satellite (TESS), the 0.6-m PROMPT-8 telescope, and the 0.7-m Thai Robotic Telescope at Spring Brook Observa…
Distribution and dynamics of decimetre-sized dust agglomerates in the coma of 67P/Churyumov-Gerasimenko
Agarwal, Jessica; Schröter, Matthias; Lemos, Pablo
We present a method to analyse images of the coma of 67P/Churyumov-Gerasimenko obtained using OSIRIS, the main imaging system on-board Rosetta, where dust aggregates can be seen as bright tracks because of their relative velocity with respect to the spacecraft. We applied this method to 105 images taken in 2015 July, 2015 December, and 2016 Januar…