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The star NGC2004#115 in the LMC, originally classified as an (SB1) Bespectroscopic binary, bears some morphological resemblance to the Galacticsystems LB-1 and HR 6819, both of which are proposed as either Be+black hole(BH) or Be+stripped He-star systems. Two data-sets (ESO/VLT and SALT) ofmulti-epoch optical spectra of NGC 2004#115, separated by baseline of $\sim$20years, lead us conclude it is a triple system hosting an inner binary with aperiod of 2.92 d, eccentricity $\sim$0.0 and mass function $\sim$0.07$M_\odot$. The inner binary harbours a B-type star (the primary) with projectedrotational velocity of 10km/s, and luminosity $\log L/L_\odot$=3.87,contributing $\sim$60% of the V-band light to the system. The secondary is notdetected, while the tertiary, which contributes 40% of the light, istentatively identified as a less luminous B-type star with high projectedrotational velocity. No ellipsoidal light variability is detected, withstringent limits being set by MACHO and Gaia data. Assuming the primary to be amain sequence star yields a mass of 8.6$ M_\odot$, while the additionalassumption of synchronous rotation constrains the inclination to be almostpole-on with i~9 degrees, implying the secondary is a BH with a mass of$\sim$25 $M_\odot$. A low mass stripped star with similar luminosity is ruledout as a potential solution as its mass implies a Roche radius that issubstantially smaller than the stellar radius. The outer period likely exceeds120 days and, while the disk-like emission is variable (it is almost absent inthe SALT dataset), it may be associated with the inner binary rather than therapidly rotating tertiary. XMM-Newton provides an upper limit of 5x$10^{33}$ergs/s on the X-ray flux, consistent with, though not constraining of, thesystem hosting a quiescent B+BH binary. A number of caveats to this scenarioare discussed in the paper.

The VLT-FLAMES survey of massive stars. NGC2004#115: A triple system hosting a possible short period B+BH binary