BP Crucis

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BP Crucis
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Crux
Right ascension 12h 26m 37.561s [1]
Declination −62° 46′ 13.16″ [1]
Apparent magnitude  (V)10.83 [2]
Characteristics
Spectral type B1 Ia+ [3]
U−B color index +0.42 [2]
B−V color index +1.76 [2]
Variable type Ellipsoidal + X-ray [4]
Astrometry
Parallax (π)0.34 ± 0.75  mas [5]
Distance 3,040 [2]   pc
Absolute magnitude  (MV)−7.47 [3]
Orbit
Period (P)41.498 days [2]
Semi-major axis (a)0.00029"
(191.7 R☉ [6] )
Eccentricity (e)0.462 [2]
Inclination (i)60 [6] °
Details
Mass 43 [3]   M☉
Radius 70 [3]   R☉
Luminosity (bolometric)470,000 [3]   L☉
Surface gravity (log g)2.38 [3]   cgs
Temperature 18,100 [3]   K
Rotational velocity (v sin i)55 [3]  km/s
Other designations
BP  Cru, Hen 3-788, Wray 15-977, 2MASS  J12263756-6246132, GX 301-2, AAVSO  1221-62
Database references
SIMBAD data

BP Crucis (x-ray source GX 301-2) is an X-ray binary system containing a blue hypergiant and a pulsar.

Contents

System

BP Crucis is considered as the optical counterpart to the X-ray source GX 301-2. The system consists of a massive hypergiant star and a neutron star in an eccentric 41.5 day orbit. The distance is likely to be between three and four thousand parsecs. It is heavily reddened and has a K-band infrared magnitude of 5.72. [2]

There is a mass transfer from the hypergiant to the pulsar which occurs via a dense accretion disc. This produces a cyclotron effect with electron energies of 37 and 48 keV. [7]

Variability

Visual V band light curve, 41.498 period BPCruLightCurve.png
Visual V band light curve, 41.498 period

The system shows both optical and x-ray variability. Although no eclipses are observed, the x-ray luminosity varies during the orbit with large x-ray flares being observed during periastron passages. [7] The system is an optical variable showing brightness changes of up to 0.08 magnitudes at visible wavelengths. These have been attributed to ellipsoidal variations as the hypergiant rotates and to α Cygni variability. There is an intrinsic pseudo-period of 11.9 days as well as small variations corresponding to the orbital period. [8] That X-ray emission comes not from the neutron star itself, but rather represent a radiation re-emitted by optically thick accretion shell. [9]

Properties

BP Crucis is around 43 times as massive as the Sun, it is also one of the most luminous stars known in the Galaxy, with an estimated bolometric luminosity of around 470,000 times that of the Sun and a radius 70 times that of the Sun.

The neutron star appears to belong to the "high mass" variety being at least 1.85 M☉. It is very likely to have a mass less than 2.5 M☉ as the theoretical maximum mass based on the equation of state for a neutron star. [2] The pulsar has a spin period of 685 seconds, but shows relatively large spindown rates thought to be due to its strong magnetic field, and also occasional spinups due to interaction with the accretion disk. It is calculated that a slowly spinning neutron star could be spun up to the current rotation rate by accretion in only ten years. [10]

Related Research Articles

<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, 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, neutron stars are the smallest and densest currently known class of stellar objects. Neutron stars have a radius on the order of 10 kilometres (6 mi) and a mass of about 1.4 solar masses. 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">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 very compact: a neutron star or black hole. The infalling matter releases gravitational potential energy, up to several tenths 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.

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 gas in a short time. As the gas falls onto the neutron star, a bright flare in hard X-rays is seen.

<span class="mw-page-title-main">Millisecond pulsar</span> Pulsar with a rotational period less than about 10 milliseconds

A millisecond pulsar (MSP) is a pulsar with a rotational period less than about 10 milliseconds. Millisecond pulsars have been detected in radio, X-ray, and gamma ray portions of the electromagnetic spectrum. The leading theory for the origin of millisecond pulsars is that they are old, rapidly rotating neutron stars that have been spun up or "recycled" through accretion of matter from a companion star in a close binary system. For this reason, millisecond pulsars are sometimes called recycled pulsars.

<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">DI Lacertae</span> 1910 Nova in the constellation Lacerta

DI Lacertae or Nova Lacertae 1910 was a nova in constellation Lacerta which appeared in 1910. It was discovered by Thomas Henry Espinell Compton Espin at Wolsingham Observatory on 30 Dec 1910, at which time it was an 8th magnitude object. Subsequent examination of pre-discovery photographic plates showed that the outburst occurred sometime between 17 November 1910 and 23 November 1910. It reached a peak brightness of magnitude 4.6 on 26 November 1910, making it visible to the naked eye. Before the nova event DI Lacertae was a 14th magnitude star, and by 1950 it had returned to 14th magnitude.

<span class="mw-page-title-main">Binary pulsar</span> Two pulsars orbiting each other

A binary pulsar is a pulsar with a binary companion, often a white dwarf or neutron star. Binary pulsars are one of the few objects which allow physicists to test general relativity because of the strong gravitational fields in their vicinities. Although the binary companion to the pulsar is usually difficult or impossible to observe directly, its presence can be deduced from the timing of the pulses from the pulsar itself, which can be measured with extraordinary accuracy by radio telescopes.

LS I +61 303 is a microquasar, 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.

<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.

Z Andromedae is a binary star system consisting of a red giant and a white dwarf. It is the prototype of a type of cataclysmic variable star known as symbiotic variable stars or simply Z Andromedae variables. The brightness of those stars vary over time, showing a quiescent, more stable phase and then an active one with a more pronounced variability and stronger brightening and/or dimming.

<span class="mw-page-title-main">Cygnus OB2-12</span> Blue hypergiant star

Cygnus OB2 #12 is an extremely luminous blue hypergiant with an absolute bolometric magnitude of −10.9, among the most luminous stars known in the galaxy. This makes the star nearly two million times more luminous than the Sun, although estimates were even higher when the star was first discovered. It is now known to be a binary, with the companion approximately a tenth as bright. A very approximate initial estimate of the orbit gives the total system mass as 120 M☉ and the period as 30 years.

<span class="mw-page-title-main">4U 1700-37</span>

4U 1700-37 is one of the stronger binary X-ray sources in the sky, and is classified as a high-mass X-ray binary. It was discovered by the Uhuru satellite. The "4U" designation refers to the fourth Uhuru catalog.

<span class="mw-page-title-main">HD 110432</span> Star in the constellation Crux

HD 110432 is a Be star in the south-east of Crux, behind the center of the southern hemisphere's dark Coalsack Nebula. It has a stellar classification of B1IVe, which means it is a subgiant star of class B that displays emission lines in its spectrum. This is a variable star of the Gamma Cassiopeiae type, indicating it is a shell star with a circumstellar disk of gas about the equator, and has the variable star designation BZ Crucis. It is not known to be a member of a binary system, although it is probably a member of the open cluster NGC 4609. This star is moderately luminous in the X-ray band, with a variable energy emission of 1032–33 erg s−1 in the range 0.2−12 keV. The X-ray emission may be caused by magnetic activity, or possibly by accretion onto a white dwarf companion.

<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">Aquila X-1</span> Star in the constellation Aquila

Aquila X-1 is a low-mass x-ray binary (LMXB) and the most luminous X-Ray source in the constellation Aquila. It was first observed by the satellite Vela 5B which detected several outbursts from this source between 1969 and 1976. Its optical counterpart is variable, so it was named V1333 Aql according to the IAU standards. The system hosts a neutron star that accretes matter from a main sequence star of spectral type K4. The binary's orbital period is 18.9479 hours.

<span class="mw-page-title-main">V691 Coronae Australis</span> Star in the constellation Corona Australis

X1822–371, associated with the optically visible star V691 Coronae Australis, is a neutron-star X-ray binary system at a distance of approximately 2-2.5 kiloparsecs. It is known to have a high inclination of i = 82.5°± 1.5°. This source displays relatively high brightness in the optical wavelengths when compared to the X-ray, making it a prototypical Accretion Disk Coronae (ADC) source, i.e. a source with a corona extending above and below its accretion disk. The only-partial eclipses in its light curve, even at such a high inclination, support this hypothesis. Estimates of the mass of its neutron star lies between 1.14–2.32 solar masses. The optical spectrum of X1822–371 displays strong Hα, Hβ, He I, He II and Bowen Blend features. These features have been extensively studied using the technique of Doppler tomography.

<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.

OAO 1657-415 is a high-mass X-ray binary (HMXB) located in the constellation of Scorpius, over 20,000 light years away. It is believed to be composed of a compact object and a highly evolved massive slash star, with Wolf–Rayet and O-type features in its spectrum, with a spectral type of Ofpe/WN9. OAO 1657-415 is special as it has the largest eccentricity and orbital period of any HMXB, and also because its donor star is much more evolved than many other HMXB donor stars.

<span class="mw-page-title-main">Westerlund 1-243</span> Luminous blue variable star undergoing an eruptive phase in Westerlund 1

Westerlund 1-243 or Wd 1-243 is a luminous blue variable (LBV) star undergoing an eruptive phase located within the outskirts of the super star cluster Westerlund 1. Located about 13,400 ly (4,100 pc) from Earth, it has a luminosity of 0.73 million L☉ making it one of the most luminous stars known.

<span class="mw-page-title-main">BG Canis Minoris</span> Variable star in the constellation of Canis Minor

BG Canis Minoris is a binary star system in the equatorial constellation of Canis Minor, abbreviated BG CMi. With an apparent visual magnitude that fluctuates around 14.5, it is much too faint to be visible to the naked eye. Parallax measurements provide a distance estimate of approximately 2,910 light years from the Sun.

References

  1. 1 2 van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: 0708.1752v1 , Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID   18759600 Note: see VizieR catalogue I/311.
  2. 1 2 3 4 5 6 7 8 Kaper, L.; Van Der Meer, A.; Najarro, F. (2006). "VLT/UVES spectroscopy of Wray 977, the hypergiant companion to the X-ray pulsar GX301-2". Astronomy and Astrophysics. 457 (2): 595–610. arXiv: astro-ph/0607613 . Bibcode:2006A&A...457..595K. doi:10.1051/0004-6361:20065393. S2CID   18984191.
  3. 1 2 3 4 5 6 7 8 Clark, J. S.; Najarro, F.; Negueruela, I.; Ritchie, B. W.; Urbaneja, M. A.; Howarth, I. D. (2012). "On the nature of the galactic early-B hypergiants". Astronomy & Astrophysics. 541: A145. arXiv: 1202.3991 . Bibcode:2012A&A...541A.145C. doi:10.1051/0004-6361/201117472. S2CID   11978733.
  4. ↑ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  5. ↑ Gaia Collaboration (2016). "VizieR Online Data Catalog: Gaia DR1 (Gaia Collaboration, 2016)". VizieR On-line Data Catalog: I/337. Originally Published in: Astron. Astrophys. 1337. Bibcode:2016yCat.1337....0G.
  6. 1 2 Waisberg, I.; Dexter, J.; Pfuhl, O.; Abuter, R.; Amorim, A.; Anugu, N.; Berger, J. P.; Blind, N.; Bonnet, H.; Brandner, W.; Buron, A.; Clénet, Y.; Wit, W. de; Deen, C.; Delplancke-Ströbele, F.; Dembet, R.; Duvert, G.; Eckart, A.; Eisenhauer, F.; Fédou, P.; Finger, G.; Garcia, P.; Lopez, R. Garcia; Gendron, E.; Genzel, R.; Gillessen, S.; Haubois, X.; Haug, M.; Haussmann, F.; et al. (2017). "Submilliarcsecond Optical Interferometry of the High-mass X-Ray Binary BP Cru with VLTI/GRAVITY". The Astrophysical Journal. 844 (1): 72. arXiv: 1705.02351 . Bibcode:2017ApJ...844...72W. doi:10.3847/1538-4357/aa79f1. S2CID   41999096.
  7. 1 2 Walter, Roland; Lutovinov, Alexander A.; Bozzo, Enrico; Tsygankov, Sergey S. (2015). "High-mass X-ray binaries in the Milky Way. A closer look with INTEGRAL". The Astronomy and Astrophysics Review. 23: 2. arXiv: 1505.03651 . Bibcode:2015A&ARv..23....2W. doi:10.1007/s00159-015-0082-6. S2CID   118574093.
  8. ↑ Van Genderen, A. M.; Sterken, C. (2007). "Orbital effects on the light curves of eta Car, BP Cru, and Other Eccentric Binaries". Information Bulletin on Variable Stars. 5782: 1. Bibcode:2007IBVS.5782....1V.
  9. ↑ Ji, L.; et al. (2021), "X-ray reprocessing in accreting pulsar GX 301-2 observed with Insight-HXMT", Monthly Notices of the Royal Astronomical Society, 501 (2): 2522–2530, arXiv: 2012.02556 , doi:10.1093/mnras/staa3788
  10. ↑ Ikhsanov, N. R.; Likh, Yu. S.; Beskrovnaya, N. G. (2014). "Spin evolution of long-period X-ray pulsars". Astronomy Reports. 58 (6): 376. arXiv: 1402.1029 . Bibcode:2014ARep...58..376I. doi:10.1134/S1063772914050035. S2CID   119240955.
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