Low mass X-ray binaries consist of two components: a compact object (either a neutron star or a stellar-mass black hole) and a star with a mass similar or lower to that of the Sun. Both objects are close enough for the gravity to strip material from the companion star, which fall onto the compact object forming an accretion disc. Indeed, both objects are so close (typically less than three times the orbit of Mercury) that not even the most powerful telescope can spatially resolve them. Aquila X-1 (Aql X-1) is a canonical X-ray binary harbouring a neutron star. Since its discovery 40 years ago, its quiescent state has been interrupted by violent outbursts where its accretion disc becomes hotter and its luminosity raises several orders of magnitude. However, the fundamental parameters of this canonical system have remained hidden until now. The reason is that, in order to perform a complete study, observations during the quiescent state are mandatory since the companion star cannot be detected in outburst due to the strong accretion disc emission. In addition, in the particular case of Aql X-1, there is an interloper star (completely unrelated to the system) almost along the same line of sight (0.4 arcsec appart), which ruined any previous attempt of obtaining uncontaminated Aql X-1 spectra. Using the 8-m Very Large Telescope (VLT) equipped with an adaptive optics module and SINFONI (a near-infrared integral field spectrograph) we managed to not only single out the interloper and Aql X-1, but to extract independent spectra (see Figure). We found that: i) the system is placed 6±2 Kpc away from us (the interloper is 2-4 Kpc away), ii) the companion star (0.76 solar masses) has a projected orbital velocity of K2=136±4 km/s and iii) the orbital inclination of the system respect to the line of sight is constrained to be in the range 36º<i<47º.
Advertised on
References
It may interest you
-
The transient Swift J1727.8-162 is the latest member of the X-ray binary black hole family to be discovered. They are formed by a black hole and a low-mass star whose gas is stripped off and accreted to the black hole via an accretion disc. The high temperature of the accretion disc makes it shine in all energy bands up to X-rays, and is particularly bright during epochs known as outbursts. In this novel study, published just a few months after the discovery of the system, we present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope. The spectra cover the main accretionAdvertised on
-
Despite the fundamental role that dark matter halos play in our theoretical understanding of galaxy formation and evolution, the interplay between galaxies and their host dark matter halos remains highly debated from an observational perspective. This lack of conclusive observational evidence ultimately arises from the inherent difficulty of reliably measuring dark matter (halo) properties. Based on detailed dynamical modeling of nearby galaxies, in this work we proposed a novel observational approach to quantify the potential effect that dark matter halos may have in modulating galaxyAdvertised on
-
Asteroids are the remnants of the planetary formation in the Solar System and so, their study helps us to understand the conditions during the early stages of the formation of our planetary system. Among asteroids, those classified as primitives present similar spectra to that of carbonaceous chondrites, i.e., they are rich in carbon and organic compounds and silicates altered by the presence of liquid water (phyllosilicates). Primitive asteroids are well characterized in various wavelength regions, showing their most diagnostic feature at 3μm. However, there is a lack of information in theAdvertised on