The neutron-star low-mass X-ray binary GX 9+1

Figure - An artist's impression of an accreting Low Mass X-ray Binary. The donor star fills its Roche lobe and its material overflows the inner Lagrangian points and accretes on the relativistic star. Due to the large angular momentum of the infalling material an accretion disk is formed around the compact object. Credit: ESA, NASA, and Felix Mirabel (French Atomic Energy Commission and Institute for Astronomy and Space Physics/Conicet of Argentina)

A low-mass X-ray binary (LMXB) contains a neutron star which is accreting material via Roche lobe overflow from a companion star. Due to the high angular momentum of the accretion flow an accretion disc is formed around the compact object.

In a recent paper (van den Berg & Homan 2016) the authors have determined an improved position for the luminous persistent neutron-star low-mass X-ray binary and atoll source GX 9+1 from archival Chandra X-ray Observatory data and they have identified a new near-infrared (NIR) counterpart to GX 9+1 in Ks-band images obtained with the PANIC and FourStar cameras on the Magellan Baade Telescope.

The NIR spectrum is consistent with thermal emission from a heated accretion disk, possibly with a contribution from the secondary. In this respect, GX 9+1 is similar to other bright atolls and the Z sources (typical types of neutron-star sources in low mass X-ray binaries, which present a wide variety in X-ray spectral and variability properties) whose NIR spectra do not show the slope that is expected for a dominant contribution from optically thin synchrotron emission from the inner regions of a jet.

van den Berg & Homan - 2016 (accepted in Apj) - On the origin of the near-infrared emission from the neutron-star low-mass X-ray binary GX 9+1 (arXiv)

Comments

‘Monster’ Planet Discovery Challenges Formation Theory

Artist’s illustration of a "hot Jupiter". Image Credit: NASA/CXC/M. Weiss A new research presents the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf host in a P~2.6 days orbit discovered as part of the Next Generation Transit Survey (NGTS). The planet has a mass of M~0.8 M(jupiter) making it the most massive planet ever discovered transiting an M-dwarf. NGTS-1b is the third transiting giant planet found around an M-dwarf, reinforcing the notion that close-in gas giants can form and migrate similar to the known population of hot Jupiters around solar type stars. The existence of the 'monster' planet, 'NGTS-1b', challenges theories of planet formation which state that a planet of this size could not be formed around such a small star. According to these theories, small stars can readily form rocky planets but do not gather enough material together to form Jupiter-sized planets. Such massive planets were not thought to exist ar...

ORBITAL PERIODS OF THE PLANETS

For orbital period generally we refer to the sidereal period, that is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference (365,25 days for the earth).

CONSTRAINTS ON THE LOCATION OF A POSSIBLE 9TH PLANET

Image: The six most distant known objects in the solar system with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Such an orbital alignment can only be maintained by some outside force, Batygin and Brown say. Their paper argues that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Credit: Caltech The astronomers have noticed some of the dwarf planets and other small, icy objects tend to follow orbits that cluster together. To explain the unusual distribution of these Kuiper Belt objects, several authors have advocated the existence of a superEarth planet in the outer solar system ( planet Nine or planet X ).

SpaceTime

Search This Blog