Search Publications
The mystery of unidentified infrared emission bands
Kwok, Sun
A family of unidentified infrared emission (UIE) bands has been observed throughout the Universe. The current observed spectral properties of the UIE bands are summarized. These properties are discussed in the frameworks of different models of the chemical carriers of these bands. The UIE carriers represent a large reservoir of carbon in the Unive…
Ultraviolet Spectropolarimetry: on the origin of rapidly rotating B stars
Hillier, D. J.; Carciofi, A. C.; Nazé, Y. +12 more
UV spectroscopy and spectropolarimetry hold the key to understanding certain aspects of massive stars that are largely inaccessible (or exceptionally difficult) with optical or longer wavelength observations. As we demonstrate, this is especially true for the rapidly-rotating Be and Bn stars, owing to their high temperatures, geometric asymmetries…
Characterization of ionospheric irregularities over the equatorial and low latitude Nigeria region
Simi, K. G.; Ogwala, Aghogho; Oyedokun, Oluwole John +5 more
Ionospheric irregularity poses severe challenges to the highly dynamic satellite communication, navigation and tracking operations that rely on transionospheric satellite services like the operation of the Global Navigation Satellite System (GNSS). Although numerous studies on the effect of geomagnetic storms on the inhibition or suppression of ir…
Understanding structure in line-driven stellar winds using ultraviolet spectropolarimetry in the time domain
Nazé, Yaël; Ignace, Richard; Scowen, Paul A. +13 more
The most massive stars are thought to lose a significant fraction of their mass in a steady wind during the main-sequence and blue supergiant phases. This in turn sets the stage for their further evolution and eventual supernova, and preconditions the surrounding medium for all following events, with consequences for ISM energization, chemical enr…
Ultraviolet spectropolarimetry with Polstar: using Polstar to test magnetospheric mass-loss quenching
Cheung, M. C. M.; Wade, G. A.; Nazé, Y. +17 more
Polstar is a proposed NASA MIDEX space telescope that will provide high-resolution, simultaneous full-Stokes spectropolarimetry in the far ultraviolet, together with low-resolution linear polarimetry in the near ultraviolet. This observatory offers unprecedented capabilities to obtain unique information on the magnetic and plasma properties of the…
Discovery of pulsating components in eclipsing binary systems through the TESS light curves: the cases of CPD-30 740, HD 97329, V1637 Ori and TYC 683-640-1
Ulaş, Burak; Ulusoy, Ceren; Erkan, Naci +2 more
We present the first evidence for the pulsations of primary components of four eclipsing binary systems. The TESS light curves of the targets are analyzed, the light and the absolute parameters are derived. Fourier analyses are applied to the residual data subtracted from the binary models to reveal the pulsational characteristics of the primaries…
The use of the Pearson differential equation to test energetic distributions in space physics as Kappa distributions; implication for Tsallis nonextensive entropy: II
Shizgal, Bernie D.
This paper presents a mathematical demonstration that particular observed energetic particle distributions of space physics in the particle velocity magnitude,
Updated fundamental parameters of the old open cluster NGC 188 based on G a i a
Gao, Xinhua; Fang, Dan
This paper revisits fundamental properties of the old open cluster NGC 188 based on more reliable cluster members in
Theoretical mass-luminosity relations in Gaia G-band
Malkov, Oleg; Kovaleva, Dana; Zhukov, Aleksandr +1 more
We have analyzed the retrieval of the relation between mass and absolute Gaia G magnitude as obtained from theoretical models by Bressan et al. (Mon. Not. R. Astron. Soc. 427:127, 2012) for the stars of different luminosity classes. For subgiant and main-sequence stars, we provide approximate analytical direct and inverse relations based on the mo…
Timing and spectral studies of the X-ray pulsar 2S 1417–624 during the outburst in 2021
Mandal, Manoj; Pal, Sabyasachi
We study the timing and spectral properties of the X-ray pulsar 2S 1417–624 during the recent outburst in January 2021 based on the Neutron Star Interior Composition Explorer (NICER) observation. We also used some early data from the 2018 outburst to compare different temporal and spectral properties. The evolution of the spin period and pulsed fl…