 A light curve for V884 Scorpii. The main plot, from TESS data, [1] shows the variation over several orbital periods. The inset plot, adapted from van Paradijs et al. (1984), [2] shows the average variation as a function of orbit phase. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 17h 03m 56.77256s [3] |
| Declination | −37° 50′ 38.9133″ [3] |
| Apparent magnitude (V) | 6.51 (- 6.57) - 6.60 [4] |
| Characteristics | |
| Spectral type | O6Iafcp [5] |
| U−B color index | −0.727 [6] |
| B−V color index | +0.253 [6] |
| Variable type | Ellipsoidal + HMXB [4] |
| Astrometry | |
| Radial velocity (Rv) | −75.00±7.4 [7] km/s |
| Proper motion (μ) | RA: 2.414 [3] mas/yr Dec.: 5.022 [3] mas/yr |
| Parallax (π) | 0.6327±0.0259 mas [3] |
| Distance | 5,200 ± 200 ly (1,580 ± 60 pc) |
| Absolute magnitude (MV) | −6.52 [8] |
| Orbit [9] | |
| Period (P) | 3.4118 ± 0.0001 d |
| Semi-major axis (a) | 35±1 R☉ [10] ″ |
| Eccentricity (e) | 0.17±0.06 |
| Inclination (i) | 62±1 [10] ° |
| Periastron epoch (T) | JD 2443702.62±0.21 |
| Argument of periastron (ω) (primary) | 54±24° |
| Semi-amplitude (K1) (primary) | 10.06 ± 0.66 km/s |
| Details [11] | |
| O star | |
| Mass | 46±5 [10] M☉ |
| Radius | 21.9+1.3 −0.5 R☉ |
| Luminosity | 660,000 L☉ |
| Temperature | 35,000±1,000 K |
| X-ray object | |
| Mass | 1.96±0.19 [10] M☉ |
| Other designations | |
| V884 Sco, CD−37°11206, HD 153919, HIP 83499, SAO 208356 [12] | |
| Database references | |
| SIMBAD | data |
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. [13] The "4U" designation refers to the fourth (and final) Uhuru catalog.
The X-ray source is associated with a bright (6.53 V magnitude) blue supergiant star HD 153919, which is orbited by an accreting neutron star. [10] [14] The X-ray source is eclipsed by the star every 3.4 days, but no pulsations have yet been observed. The source is one of the ten brightest persistent X-ray sources in the 10-100 keV hard X-ray energy region.
Evidence of Compton cooling during an X-ray flare recorded by the Chandra X-ray telescope strongly suggests that the compact object is a neutron star; [14] if verified it would be among the most massive known, and near the boundary of the theoretical maximum.
4U 1700-37 is a runaway system. It has a high velocity of 63±5 km/s with respect to its parent cluster, NGC 6231. It was kicked out of the cluster about 2.2 million years ago by a supernova explosion. [15]
