Search Publications
Kinetic Alfvén solitary waves in a plasma with two-temperature superthermal electron populations: the case of Saturn's magnetosphere
Singh, Manpreet; Saini, N. S.; Kourakis, I.
Thanks to the evidence provided by the Cassini spacecraft mission, it is now established that Saturn's magnetospheric plasma consists of various types of positive ions, as well as two distinct populations of electrons, at different temperatures. The electron population energy distributions are characterized by long suprathermal tails and have been…
The 11 yr of low activity of the magnetar XTE J1810-197
Pintore, Fabio; Mereghetti, Sandro; Esposito, Paolo +5 more
In 2003, the magnetar XTE J1810-197 started an outburst that lasted until early 2007. In the following 11 yr, the source stayed in a quiescent/low-activity phase. XTE J1810-197 is one of the closest magnetars, hence its X-ray properties can be studied in detail even in quiescence and an extended monitoring has been carried out to study its long-te…
Comprehensive abundance analysis of red giants in the open clusters Stock 2, NGC 2168, 6475, 6991, and 7762
Lambert, David L.; Reddy, Arumalla B. S.
We have analysed high-dispersion Echelle spectra (R = 60 000) of red giant members of five open clusters to derive abundances for many elements from Na to Eu. The [Fe/H] values are -0.06 ± 0.03 for Stock 2, -0.11 ± 0.03 for NGC 2168, -0.01 ± 0.03 for NGC 6475, 0.00 ± 0.03 for NGC 6991, and -0.07 ± 0.03 for NGC 7662. Sodium is enriched in the giant…
Exoplanet transits with next-generation radio telescopes
Pope, Benjamin J. S.; Withers, Paul; Vogt, Marissa F. +1 more
Nearly everything we know about extrasolar planets to date comes from optical astronomy. While exoplanetary aurorae are predicted to be bright at low radio frequencies (<1 GHz), we consider the effect of an exoplanet transit on radio emission from the host star. As radio emission from solar-like stars is concentrated in active regions, a planet…
Ongoing astrometric microlensing events from VVV and Gaia
Evans, N. W.; Belokurov, V.; Lucas, P. W. +2 more
We extend predictive microlensing event searches using the Vista Variables in the Via Lactea survey and the second Gaia data release. We identify two events with maxima in 2019 that require urgent follow-up. First, we predict that the nearby M2 dwarf L 338-152 will align with a background source with a closest approach of 35^{+35}_{-23} mas on 201…
Directly testing gravity with Proxima Centauri
Kroupa, Pavel; Banik, Indranil
The wide binary orbit of Proxima Centauri around α Centauri A and B differs significantly between Newtonian and Milgromian dynamics (MOND). By combining previous calculations of this effect with mock observations generated using a Monte Carlo procedure, we show that this prediction can be tested using high precision astrometry of Proxima Centauri.…
High-degree gravity modes in the single sdB star HD 4539
Heber, U.; Reed, M. D.; Silvotti, R. +6 more
HD 4539 (alias PG 0044 + 097 or EPIC 220641886) is a bright (V = 10.2) long-period V1093 Her-type subdwarf B (sdB) pulsating star that was observed by the Kepler spacecraft in its secondary (K2) mission. We use the K2 light curve (78.7 d) to extract 169 pulsation frequencies, 124 with a robust detection. Most of these frequencies are found in the …
Luminous AGB variables in the dwarf irregular galaxy, NGC 3109
Matsunaga, Noriyuki; Whitelock, Patricia A.; Feast, Michael W. +1 more
In a shallow near-infrared survey of the dwarf irregular galaxy, NGC 3109, near the periphery of the Local Group, we have found eight Mira variables, seven of which appear to be oxygen-rich (O-Miras). The periods range from about 430 d to almost 1500 d. Because of our relatively bright limiting magnitude, only 45 of the more than 400 known carbon …
Machine-learning identification of asteroid groups
Carruba, V.; Aljbaae, S.; Lucchini, A.
Asteroid families are groups of asteroids that share a common origin. They can be the outcome of a collision or be the result of the rotational failure of a parent body or its satellites. Collisional asteroid families have been identified for several decades using hierarchical clustering methods (HCMs) in proper elements domains. In this method, t…
Membership and fundamental parameters of the Praesepe cluster based on Gaia-DR2
Gao, Xin-hua
In this paper, we investigate membership and fundamental astrophysical parameters of the nearby, intermediate-age Praesepe star cluster (M44) based on the Gaia data release 2 (Gaia-DR2). Based on 54 425 stars within a sky area of 5.5° radius, we identify 1111 likely cluster members (≥0.6) in an 11D parameter space based on a combined machine-learn…