We report on the firm detection of a cyclotron resonance scattering feature ( CRSF ) in the X-ray spectrum of the Be X-ray binary pulsar , GRO J1008 - 57 , achieved by the Suzaku Hard X-ray Detector during a giant outburst which was detected by the MAXI Gas Slit Camera in 2012 November .
The Suzaku observation was carried out on 2012 November 20 , outburst maximum when the X-ray flux reached \sim 0.45 Crab in 4–10 keV , which corresponds to a luminosity of 1.1 \times 10 ^ { 38 } erg s ^ { -1 } in 0.5–100 keV at 5.8 kpc .
The obtained broadband X-ray spectrum from 0.5 keV to 118 keV revealed a significant absorption feature , considered as the fundamental CRSF , at \sim 76 keV .
This unambiguously reconfirm the previously suggested \sim 80 keV spectral feature in GRO J1008 - 57 .
The implied surface magnetic field , 6.6 \times 10 ^ { 12 } G , is the highest among binary X-ray pulsars from which CRSFs have ever been detected .