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
-
Dark matter is an invisible substance that makes up more than eighty percent of the matter content of the universe. We know of its existence due to its gravitational influence, being a key ingredient to understand everything from the large-scale evolution of the universe to the formation of galaxies like the Milky Way, of which we are part of . However, very little is known about its nature, which constitutes one of the greatest unsolved problems in contemporary physics. The fuzzy dark matter model has recently been studied as a promising candidate. In this model , it is postulated that darkAdvertised on
-
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
-
The standard cosmological model states that massive galaxies contain a large fraction of dark matter. Dark matter is a transparent substance that does not interact through regular baryonic matter and is only detected through its gravitational pull over the stars and the gas. NGC 1277 is known as the prototype of a relic galaxy, that is, a galaxy that has not accreted other galaxies since it formed. Relic galaxies are extremely rare and are the untouched remains of the giant galaxies that populated the early Universe. Since relic galaxies are very important to understand the conditions in theAdvertised on