Be/X-ray binary

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Be/X-ray binaries (BeXRBs) are a class of high-mass X-ray binaries that consist of a Be star and a neutron star. The neutron star is usually in a wide highly elliptical orbit around the Be star. The Be stellar wind forms a disk confined to a plane often different from the orbital plane of the neutron star. When the neutron star passes through the Be disk, it accretes a large mass of hot gas in a short time. As the gas falls onto the neutron star, a bright flare in hard X-rays is seen. [1]

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X Persei

X Persei is a binary system containing a γ Cassiopeiae variable and a pulsar. It has a relatively long period and low eccentricity for this type of binary, which means the x-ray emission is persistent and not usually strongly variable. Some strong x-ray flares have been observed, presumably related to changes in the accretion disc, but no correlations have been found with the strong optical variations. [2]

LSI+61°303

LSI+61°303 is a possible example of a Be/X-ray binary star. It is a periodic, radio-emitting binary system that is also the gamma-ray source, CG135+01. It is also a variable radio source characterized by periodic, non-thermal radio outbursts with a period of 26.496 d. The 26.5 d period is attributed to the eccentric orbital motion of a compact object, possibly a neutron star, around a rapidly rotating B0 Ve star. Photometric observations at optical and infrared wavelengths also show a 26.5 d modulation. [3] Although the mass of the compact object in the LS I +61 303 system is not known accurately, it is likely that it is too large to be a neutron star and so it is likely to be a black hole. [4]

Of the 20 or so members of the Be/X-ray binary class, as of 1996, only X Persei and LSI+61°303 have X-ray outbursts of much higher luminosity and harder spectrum ( kT  ≈ 10–20 keV) vs. (kT ≤ 1 keV). LSI+61°303 also shows strong radio outbursts, more similar to those of the "standard" short-period high-mass X-ray binaries such as SS 433, Cyg X-3 and Cir X-1. [3]

RX J0209.6-7427

RX J0209.6-7427 is a Be/X-ray binary star located in the Magellanic Bridge. [5] A couple of rare outbursts have been observed from this source hosting a neutron star. The last outburst was detected in 2019 after about 26 years. The accreting neutron star in this Be/X-ray binary system is an ultraluminous X-ray Pulsar (ULXP) making it the second closest ULXP and the first ULXP in our neighbouring Galaxy in the Magellanic Clouds. [6] [7] [8]

Swift J010902.6-723710

Swift J010902.6-723710 is a Be/X-ray binary system detected by the Swift Small Magellanic Cloud (SMC) Survey (S-CUBED). An X-ray outburst, detected on October 10, 2023, had characteristics of Type I and II outbursts. Proposed orbital period is 60.623 days. Companion star of the system is "B0-0.5 star of spectral class Ve". The system's neutron star has large accretion disk. [9] [10]

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<span class="mw-page-title-main">Neutron star</span> Collapsed core of a massive star

A neutron star is the collapsed core of a massive supergiant star. The stars that later collapse into neutron stars have a total mass of between 10 and 25 solar masses (M☉), possibly more if the star was especially rich in elements heavier than hydrogen and helium. Except for black holes, neutron stars are the smallest and densest known class of stellar objects. Neutron stars have a radius on the order of 10 kilometers (6 mi) and a mass of about 1.4 M☉. They result from the supernova explosion of a massive star, combined with gravitational collapse, that compresses the core past white dwarf star density to that of atomic nuclei.

<span class="mw-page-title-main">Small Magellanic Cloud</span> Dwarf irregular galaxy, satellite galaxy of the Milky Way

The Small Magellanic Cloud (SMC) is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a D25 isophotal diameter of about 5.78 kiloparsecs (18,900 light-years), and contains several hundred million stars. It has a total mass of approximately 7 billion solar masses. At a distance of about 200,000 light-years, the SMC is among the nearest intergalactic neighbors of the Milky Way and is one of the most distant objects visible to the naked eye.

A Thorne–Żytkow object, also known as a hybrid star, is a conjectured type of star wherein a red giant or red supergiant contains a neutron star at its core, formed from the collision of the giant with the neutron star. Such objects were hypothesized by Kip Thorne and Anna Żytkow in 1977. In 2014, it was discovered that the star HV 2112, located in the Small Magellanic Cloud (SMC), was a strong candidate. Another possible candidate is the star HV 11417, also located in the SMC.

<span class="mw-page-title-main">X-ray binary</span> Class of binary stars

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, to the other component, called the accretor, which is either a neutron star or black hole. The infalling matter releases gravitational potential energy, up to 30 percent of its rest mass, as X-rays. The lifetime and the mass-transfer rate in an X-ray binary depends on the evolutionary status of the donor star, the mass ratio between the stellar components, and their orbital separation.

Soft X-ray transients (SXTs), also known as X-ray novae and black hole X-ray transients, are composed of a compact object and some type of "normal", low-mass star. These objects show dramatic changes in their X-ray emission, probably produced by variable transfer of mass from the normal star to the compact object, a process called accretion. In effect the compact object "gobbles up" the normal star, and the X-ray emission can provide the best view of how this process occurs. The "soft" name arises because in many cases there is strong soft X-ray emission from an accretion disk close to the compact object, although there are exceptions which are quite hard.

X-ray pulsars or accretion-powered pulsars are a class of astronomical objects that are X-ray sources displaying strict periodic variations in X-ray intensity. The X-ray periods range from as little as a fraction of a second to as much as several minutes.

<span class="mw-page-title-main">47 Tucanae</span> Globular cluster in the constellation Tucana

47 Tucanae or 47 Tuc is a globular cluster located in the constellation Tucana. It is about 4.45 ± 0.01 kpc (15,000 ± 33 ly) away from Earth, and 120 light years in diameter. 47 Tuc can be seen with the naked eye, with an apparent magnitude of 4.1. It appears about 44 arcminutes across including its far outreaches. Due to its far southern location, 18° from the south celestial pole, it was not catalogued by European astronomers until the 1750s, when the cluster was first identified by Nicolas-Louis de Lacaille from South Africa.

<span class="mw-page-title-main">Pulsar</span> Highly magnetized, rapidly rotating neutron star

A pulsar 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 Earth, and is responsible for the pulsed appearance of emission. Neutron stars are very dense and have short, regular rotational periods. This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are one of the candidates for the source of ultra-high-energy cosmic rays.

<span class="mw-page-title-main">SAX J1808.4−3658</span> Neutron star in the constellation Sagittarius

The first accreting millisecond pulsar discovered in 1998 by the Italian-Dutch BeppoSAX satellite, SAX J1808.4−3658 revealed X-ray pulsations at the 401 Hz neutron star spin frequency when it was observed during a subsequent outburst in 1998 by NASA's RXTE satellite. The neutron star is orbited by a brown dwarf binary companion with a likely mass of 0.05 solar masses, every 2.01 hours. X-ray burst oscillations and quasi-periodic oscillations in addition to coherent X-ray pulsations have been seen from SAX J1808.4-3658, making it a Rosetta stone for interpretation of the timing behavior of low-mass X-ray binaries.

<span class="mw-page-title-main">Centaurus X-3</span> Binary star with an X-ray pulsar in the constellation Centaurus

Centaurus X-3 is an X-ray pulsar with a period of 4.84 seconds. It was the first X-ray pulsar to be discovered, and the third X-ray source to be discovered in the constellation Centaurus. The system consists of a neutron star orbiting a massive, O-type supergiant star dubbed Krzeminski's star after its discoverer, Wojciech Krzemiński. Matter is being accreted from the star onto the neutron star, resulting in X-ray emission.

<span class="mw-page-title-main">Ultraluminous X-ray source</span>

An ultraluminous X-ray source (ULX) is an astronomical source of X-rays that is less luminous than an active galactic nucleus but is more consistently luminous than any known stellar process (over 1039 erg/s, or 1032 watts), assuming that it radiates isotropically (the same in all directions). Typically there is about one ULX per galaxy in galaxies which host them, but some galaxies contain many. The Milky Way has not been shown to contain a ULX, although SS 433 may be a possible source. The main interest in ULXs stems from their luminosity exceeding the Eddington luminosity of neutron stars and even stellar black holes. It is not known what powers ULXs; models include beamed emission of stellar mass objects, accreting intermediate-mass black holes, and super-Eddington emission.

LS I +61 303 is a binary system containing a massive star and a compact object. The compact object is a pulsar and the system is around 7,000 light-years away.

In X-ray astronomy, quasi-periodic oscillation (QPO) is the manner in which the X-ray light from an astronomical object flickers about certain frequencies. In these situations, the X-rays are emitted near the inner edge of an accretion disk in which gas swirls onto a compact object such as a white dwarf, neutron star, or black hole.

<i>AstroSat</i> Space observatory

AstroSat is India's first dedicated multi-wavelength space telescope. It was launched on a PSLV-XL on 28 September 2015. With the success of this satellite, ISRO has proposed launching AstroSat-2 as a successor for AstroSat.

<span class="mw-page-title-main">Vela X-1</span> X-ray emission source in the constellation Vela

Vela X-1 is a pulsing, eclipsing high-mass X-ray binary (HMXB) system, associated with the Uhuru source 4U 0900-40 and the supergiant star HD 77581. The X-ray emission of the neutron star is caused by the capture and accretion of matter from the stellar wind of the supergiant companion. Vela X-1 is the prototypical detached HMXB.

X-ray emission occurs from many celestial objects. These emissions can have a pattern, occur intermittently, or as a transient astronomical event. In X-ray astronomy many sources have been discovered by placing an X-ray detector above the Earth's atmosphere. Often, the first X-ray source discovered in many constellations is an X-ray transient. These objects show changing levels of X-ray emission. NRL astronomer Dr. Joseph Lazio stated: " ... the sky is known to be full of transient objects emitting at X- and gamma-ray wavelengths, ...". There are a growing number of recurrent X-ray transients. In the sense of traveling as a transient, the only stellar X-ray source that does not belong to a constellation is the Sun. As seen from Earth, the Sun moves from west to east along the ecliptic, passing over the course of one year through the twelve constellations of the Zodiac, and Ophiuchus.

<span class="mw-page-title-main">Astrophysical X-ray source</span> Astronomical object emitting X-rays

Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays.

<span class="mw-page-title-main">X Persei</span> Variable star in the constellation Perseus

X Persei is a high-mass X-ray binary system located in the constellation Perseus, approximately 950 parsecs away. It is catalogued as 4U 0352+309 in the final Uhuru catalog of X-ray objects.

<span class="mw-page-title-main">UY Volantis</span> Low mass X-ray binary in the constellation Volans

UY Volantis, also known as EXO 0748-676, is a low mass X-ray binary system located in the constellation Volans. With an apparent magnitude of 16.9, it requires a powerful telescope to see. With a radial velocity of 20 km/s, it is drifting away from the Solar System, and is currently located 26,000 light years away.

<span class="mw-page-title-main">PSR J0952–0607</span> Massive millisecond pulsar in the Milky Way

PSR J0952–0607 is a massive millisecond pulsar in a binary system, located between 3,200–5,700 light-years (970–1,740 pc) away from Earth in the constellation Sextans. It holds the record for being the most massive neutron star known as of 2022, with a mass 2.35±0.17 times as much as the Sun—potentially close to the Tolman–Oppenheimer–Volkoff mass upper limit for neutron stars. The pulsar rotates at a frequency of 707 Hz, making it the second-fastest-spinning pulsar known, and the fastest-spinning pulsar known within the Milky Way.

References

  1. ↑ Reig, Pablo (2011). "Be/X-ray binaries". Astrophysics and Space Science. 332 (1): 1–29. arXiv: 1101.5036 . Bibcode:2011Ap&SS.332....1R. doi:10.1007/s10509-010-0575-8.
  2. ↑ Li, Hui; Yan, Jingzhi; Zhou, Jianeng; Liu, Qingzhong (2014). "Long-term Optical Observations of the Be/X-Ray Binary X Per". The Astronomical Journal. 148 (6): 113. arXiv: 1408.3542 . Bibcode:2014AJ....148..113L. doi:10.1088/0004-6256/148/6/113.
  3. 1 2 Taylor AR, Young G, Peracaula M, Kenny HT, Gregory PC (1996). "An X-ray outburst from the radio emitting X-ray binary LSI+61°303". Astron. Astrophys. 305: 817–24. Bibcode:1996A&A...305..817T.
  4. ↑ Massi, M; Migliari, S; Chernyakova, M (2017). "The black hole candidate LS I +61°0303". Monthly Notices of the Royal Astronomical Society. 468 (3): 3689. arXiv: 1704.01335 . Bibcode:2017MNRAS.468.3689M. doi:10.1093/mnras/stx778.
  5. ↑ Kahabka, P.; Hilker, M. (2005). "Discovery of an X-ray binary in the outer SMC wing". Astronomy and Astrophysics. 435 (1): 9–16. Bibcode:2005A&A...435....9K. doi: 10.1051/0004-6361:20042408 .
  6. ↑ Chandra, A. D.; Roy, J.; Agrawal, P. C.; Choudhury, M. (2020). "Study of recent outburst in the Be/X-ray binary RX J0209.6−7427 with AstroSat: a new ultraluminous X-ray pulsar in the Magellanic Bridge?". Monthly Notices of the Royal Astronomical Society. 495 (3): 2664–2672. arXiv: 2004.04930 . Bibcode:2020MNRAS.495.2664C. doi:10.1093/mnras/staa1041.
  7. ↑ "Ultra-bright X-ray source awakens near a galaxy not so far away". Royal Astronomical Society. June 2020.
  8. ↑ "Ultra-Bright Pulsar Awakens Next Door To The Milky Way After 26-Year Slumber". Alfredo Carpineti. June 2020.
  9. ↑ Nowakowski, Tomasz. "Astronomers discover a rare eclipsing X-ray binary". phys.org. Retrieved 28 March 2024.
  10. ↑ Gaudin, Thomas M.; Kennea, Jamie A.; Coe, Malcolm J.; Monageng, Itumeleng M.; Udalski, Andrzej; Townsend, Lee J.; Buckley, David A. H.; Evans, Phil A. (2024). "Discovery of a Rare Eclipsing Be/X-ray Binary System, Swift J010902.6-723710 = SXP 182". The Astrophysical Journal. 965 (1): L10. arXiv: 2403.05648 . Bibcode:2024ApJ...965L..10G. doi: 10.3847/2041-8213/ad354a .


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