Very Low Frequency QPO in 4U1700-37

Understand

Very low frequency ({\nu} ~ 1.9 mHz) quasi-periodic oscillations (QPO) have been detected in 2 - 60 keV X-rays from 4U1700-37 using auto-correlation function analysis of RXTE archival data.

• No pulsar signal was detected in the data.
• Less than 0.5% of the flux from the source (3{\sigma} upper limit) is coherently pulsed with a period between 250 ms and 40 s.
• This upper limit corresponds to a pulsed flux <0.02 mJy.