Possible detection of a new cyclotron feature in 4U 1700-37

Abstract

We present a spectral and timing study of the High Mass X-ray Binary transient source 4U 1700-37 using NuSTAR and ASTROSAT/LAXPC. The source is observed in two different flux states. A combined spectral analysis of NuSTAR's FPMA and FPMB shows the possible hint of a cyclotron line feature at $\sim$16 keV. The line feature is consistently present in different continuum models with at least 3$\sigma$ confidence level. We do not detect the presence of a previously reported ~39 keV cyclotron line in the combined spectra. A $\sim$16 keV cyclotron feature would suggest that the compact object is a neutron star with a magnetic field strength $\sim 2.1\times$10${}^{12}$ Gauss in the emission region. We also find the presence of a rare Ni $K\alpha$ emission line around 7.6 keV in the NuSTAR spectrum. We searched the NuSTAR and ASTROSAT data for coherent or quasi-periodic oscillation signals but found no evidence in the frequency range 0.1 mHz to 10${}^3$ Hz.

arXiv commentAccepted for publication in MNRAS journal

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Cited by in corpus (3)

• First Detection of X-ray Polarization and Its Short-term Increase Pre- and Post-Eclipse in HMXB 4U 1700-377
• Multiwavelength study of 1eRASS J085039.9-421151 with eROSITA NuSTAR and X-shooter
• Constraints on cyclotron features and accretion regime in the high-mass X-ray binary 4U 1700-37 from NuSTAR