Discovery of Cyclotron line from GX 304-1 during the Brightest Outburst in August 2010, observed by MAXI/GSC, Suzaku, and RXTE.
Abstract
GX 304-1 is a classical Be/X-ray binary pulsar with a 272-second period, discovered by high energy X-ray balloon observations in 1967. Transient outburst activities by 132-day interval had been frequently observed during 1970s. Since 1980s, the source had been in a quiescent state and no significant X-ray flux had been detected for 28 years until the outburst detection by INTEGRAL in June, 2008(ATel #1613). It suggested that the source might return to the active phase by 2008. MAXI/GSC has detected outbursts from GX 304-1 three times every 132-day interval during the first one-year operation since August 2009. The third outburst in August 2010 reached a flux of 700 mCrab in a 4-10 keV band, which is the brightest among the outbursts ever observed from this source. We conducted the follow-up observation by Suzaku and RXTE, then discovered the cyclotron line at around 51 keV as reported in ATel #2796. We present the change of the spectral shape and the pulsation period during the outburst obtained from the MAXI/GSC, Suzaku and RXTE data, then discuss about the physical condition of magnetic field on the neutron star.
- Publication:
-
The First Year of MAXI: Monitoring Variable X-ray Sources
- Pub Date:
- December 2010
- Bibcode:
- 2010fym..confP..13Y