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| 4U 1700-37 | |
|---|---|
| Name | 4U 1700-37 |
| Caption | X-ray binary associated with HD 153919 |
| Constellation | Scorpius |
| Epoch | J2000 |
| Ra | 17h03m56s |
| Dec | −37°50′38″ |
| Distance | ~1.9–2.5 kpc |
| Primary | HD 153919 |
| Compact | Uncertain (neutron star or black hole) |
| Discovery | 1970s (Uhuru) |
| Other names | 4U1700-37, V884 Scorpii |
4U 1700-37 is a bright, persistent high-mass X-ray binary in the constellation Scorpius associated with the O6.5 Iaf+ supergiant HD 153919. Discovered in early X-ray surveys, it has been extensively observed by observatories such as Uhuru, Einstein Observatory (HEAO-2), EXOSAT, ROSAT, ASCA, Ginga, BeppoSAX, Chandra X-ray Observatory, XMM-Newton, RXTE, Suzaku, and NuSTAR and is notable for an ambiguous compact object that has driven debate between neutron star and black hole interpretations.
4U 1700-37 is a prototype of wind-fed high-mass X-ray binaries linked to massive stars and compact remnants studied alongside systems like Vela X-1, Cen X-3, GX 301-2, Cygnus X-1, and SAX J1808.4−3658. The system’s optical counterpart HD 153919 places it in the Galactic plane near associations such as Scorpius OB1 and star-forming regions investigated by missions including Spitzer Space Telescope and Gaia. Because pulsations are absent or intermittent, comparisons are often drawn to both pulsar-hosting and black hole binaries examined by collaborations at European Space Agency and NASA.
The binary comprises the luminous supergiant HD 153919, classified in the Morgan–Keenan system and analyzed in spectroscopic work by groups at European Southern Observatory and Cerro Tololo Inter-American Observatory, and a compact object in a close, ~3.412-day orbit determined from radial-velocity campaigns and X-ray timing performed by teams affiliated with Royal Observatory Edinburgh and institutions such as California Institute of Technology. The orbital parameters—period, eccentricity constraints, and inclination estimates—derive from combined optical spectroscopy, ultraviolet studies with International Ultraviolet Explorer, and X-ray eclipse and modulation analyses by instruments on HEAO-1 and RXTE.
Mass determinations hinge on the radial-velocity curve of HD 153919 and the system inclination inferred from eclipse geometry and light-curve modeling used by researchers at University of Oxford and Max Planck Institute for Astrophysics. Published mass estimates have overlapped the canonical neutron star mass range and the low-mass black hole regime, prompting debate involving authors from Harvard–Smithsonian Center for Astrophysics, University of Southampton, Monash University, and University of Cambridge. Absence of persistent coherent pulsations, contrasted with detection of transient quasi-periodic oscillations and cyclotron resonance scattering features in some datasets analyzed by teams at JAXA and Italian Space Agency (ASI), complicates classification; proposals include a massive neutron star approaching the Tolman–Oppenheimer–Volkoff limit studied in theoretical work at Institute for Advanced Study and a low-mass black hole predicted by binary-evolution models from groups at University of Bonn and Institut d’Astrophysique de Paris.
X-ray spectra of the source display continuum shapes, fluorescence lines, and variable absorption similar to phenomena investigated in X-ray astronomy campaigns of sources like Her X-1 and 4U 1705-44, reported in catalogs from HEASARC and literature coordinated by scientists at SRON Netherlands Institute for Space Research. Variability occurs on timescales from seconds to orbital periods with flares, off-states, and orbital modulation attributed to stochastic wind accretion and clump passages studied in hydrodynamic simulations at Princeton University and University of California, Berkeley. Observed iron Kα emission, soft excess components, and high-energy cutoffs have been interpreted using radiative-transfer models developed at Rutherford Appleton Laboratory and Laboratoire d’Astrophysique de Grenoble.
HD 153919’s optical and ultraviolet spectra show strong P Cygni profiles, He II and N III emission consistent with extreme Of characteristics cataloged by observers at Cerro Tololo Inter-American Observatory and European Southern Observatory. Mass-loss rates, terminal wind velocities, and ionization structure have been derived from non-LTE model atmospheres using codes from groups at Leiden University and Universidad de La Laguna, and compared to empirical results for supergiants in the Magellanic Clouds and the Galactic OB sample surveyed with Hubble Space Telescope and International Ultraviolet Explorer. Wind clumping, X-ray photoionization, and the Hatchett–McCray effect have been invoked in analyses by teams at University of Strasbourg and Ohio State University to explain orbital-phase-dependent line variability.
The short orbital period and strong stellar wind promote quasi-spherical Bondi–Hoyle–Lyttleton accretion and focused-wind scenarios modeled in computational work at Max Planck Institute for Astrophysics and University of Pisa. Tidal interactions, angular-momentum transfer, and possible historical common-envelope phases have been explored using population-synthesis frameworks from University of Barcelona and Astrophysical Institute Potsdam, with implications for supernova kick models studied at University of Amsterdam and University of Tokyo. Long-term orbital period changes and episodic torque variations have been monitored by coordinated campaigns involving RXTE and ground-based spectroscopy from SAAO.
Key observations originate from X-ray missions including Uhuru, HEAO-1, EXOSAT, Ginga, ASCA, BeppoSAX, ROSAT, RXTE, Chandra X-ray Observatory, XMM-Newton, Suzaku, and NuSTAR, with optical and ultraviolet follow-up from International Ultraviolet Explorer, Hubble Space Telescope, Gaia, and ground facilities such as European Southern Observatory and Cerro Tololo Inter-American Observatory. Data analyses have been published in journals associated with societies like the American Astronomical Society, Royal Astronomical Society, and International Astronomical Union and continue to inform models developed at institutions including Harvard University, MIT, Princeton University, and Max Planck Institute for Astronomy.
Category:High-mass X-ray binaries Category:Scorpius