X Persei is a

high-mass X-ray binary X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are produced by matter falling from one component, called the ''donor'' (usually a relatively normal star), to the other component, called the ''accretor'', which ...

system located in the constellation

Perseus In Greek mythology, Perseus (Help:IPA/English, /ˈpɜːrsiəs, -sjuːs/; Greek language, Greek: Περσεύς, Romanization of Greek, translit. Perseús) is the legendary founder of Mycenae and of the Perseid dynasty. He was, alongside Cadmus ...

, approximately 950 parsecs away. It is catalogued as 4U 0352+309 in the final

Uhuru Uhuru (a Swahili word meaning ''freedom'') may refer to: People * Uhuru Hamiter (born 1973), American football player * Uhuru Kenyatta (born 1961), President of Kenya since 2013 Places *Uhuru (Tanzanian ward), an administrative ward in the Dodoma ...

catalog of

X-ray X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...

objects.

The conventional star component of X Persei has been classified either as an

O-type giant In astronomy, a blue giant is a hot star with a luminosity class of III ( giant) or II (bright giant). In the standard Hertzsprung–Russell diagram, these stars lie above and to the right of the main sequence. The term applies to a variety of ...

or a B-type main sequence star. It is 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 ...

, rotating rapidly, and at times surrounded by a disk of expelled material. This qualifies it as a

Gamma Cassiopeiae variable A Gamma Cassiopeiae variable (γ Cassiopeiae variable) is a type of variable star, named for its prototype γ Cassiopeiae. Variability γ Cassiopeiae variables show irregular changes in brightness on a timescale of decades. These typically have ...

, and the visual range is magnitude 6 - 7. In 1989 and 1990, the spectrum of X Persei changed from a

to a normal B class star while it faded significantly. This appears to have been caused by the loss of the excretion disk. The disk has since reformed and shows strong

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. The system also contains 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. w ...

which is a

pulsar A pulsar (from ''pulsating radio source'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward E ...

with an unusually long period of 837 seconds. The pulsar has shown period changes that are associated with mass transfer from the more massive primary star. Between 1973 and 1979 it was seen to increase its rate of spin, associated with a strong x-ray flare and presumed strong mass transfer. Since then the spin has been slowing despite small x-ray flares. The combination of a neutron star and OB

star places X Persei in the Be/X-ray binary class of stars. There is a faint optical companion separated by 22.5" which the Catalog of Components of Double and Multiple Stars refers to as X Persei B. It is a background

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

and a candidate

long period variable The descriptive term long-period variable star refers to various groups of cool luminous pulsating variable stars. It is frequently abbreviated to LPV. Types of variation The General Catalogue of Variable Stars does not define a long-period va ...

with 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 constel ...

V397 Persei.

References

{{DEFAULTSORT:X Persei Perseus (constellation) O-type giants B-type main-sequence stars Neutron stars X-ray binaries Persei, X Pulsars Durchmusterung objects 018350

1209 Year 1209 ( MCCIX) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. Events By place Europe * May – The First Parliament of Ravennika, convened by Emperor Henry of Flanders, ...

024534 J03552309+3102449 Gamma Cassiopeiae variable stars Emission-line stars