LS I +61 303 is a

microquasar A microquasar, the smaller version of a quasar, is a compact region surrounding a stellar black hole with a mass several times that of its companion star. The matter being pulled from the companion star forms an accretion disk around the black hol ...

, a

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that th ...

containing a massive

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

and a compact object. The compact object is a pulsar and the system is around 7,000

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away.

Discovery

LS I +61 303 is an 11th-magnitude star that was recognised as a luminous object and catalogued as an

OB star OB stars are hot, massive stars of spectral types O or early-type B that form in loosely organized groups called OB associations. They are short lived, and thus do not move very far from where they formed within their life. During their lifet ...

in 1959. It was included in the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

survey as HIP 12469 and had its

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

measured at

milliarcseconds A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

(mas), revised to − mas in the new reduction. The first ''Gaia'' data release gave a parallax of mas. The galactic radio source GT 0236+610 was found at the same position as LS I +61 303. A

gamma-ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nucleus, atomic nuclei. It consists of the shortest wavelength electromagnetic wav ...

source 2CG 135+01 was found within a degree of its position, and the

MAGIC Magic or Magick most commonly refers to: * Magic (supernatural), beliefs and actions employed to influence supernatural beings and forces * Ceremonial magic, encompasses a wide variety of rituals of magic * Magical thinking, the belief that unrela ...

telescope confirmed that LS I +61 303 was the source of the gamma rays. Periodic

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

outbursts also occur.

Binary system

LS I +61 303 shows the spectrum of a

Be star Be stars are a heterogeneous set of stars with B spectral types and emission lines. A narrower definition, sometimes referred to as ''classical Be stars'', is a non-supergiant B star whose spectrum has, or had at some time, one or more Balmer e ...

, a B0

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

star with disk that produces

emission line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s in its spectrum. Variations in its radial velocity show that it is in orbit with an unseen compact object having a mass between . The pair orbit every 26.496 days. Although the uncertain mass of the compact object would allow it to be a

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...

, it is thought likely to be a

black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...

. In March 2022, a period of ~0.27 s was reported to be detected in observations using the FAST telescope, confirming the neutron star nature of the compact object. This promotes the possibility that the system is indeed the first one detected containing a pulsar with magnetar behavior in it.

Variability

LS I +61 303 varies slightly at optical wavelengths, but measurements going back to 1887 show no obvious period. It also shows regular X-ray outbursts coinciding with its orbital period, and strong radio variability. It was given the

variable star designation In astronomy, a variable star designation is a unique identifier given to variable stars. It uses a variation on the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constell ...

V615 Cassiopeiae.

Microquasar

LS I +61 303 emits ''HE'' and ''VHE'' (High Energy and Very High Energy) gamma rays. It is only one of several known

star system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speak ...

s that produce such energetic rays. Other such systems are PSR B1259–63, LS 5039 and HESS J0632+057.

References

External links

Astronomers Discovery Very High Energy Gamma-ray Emission From Microquasar
(ScienceDaily) May 19, 2006
MAGIC Telescope
home page
TeV gamma ray source catalog
home page {{Stars of Cassiopeia Neutron stars Microquasars Cassiopeia (constellation) Cassiopeiae, V615 012469 Be stars B-type main-sequence stars