NuSTAR Norma Arm Survey

One part of the Galaxy that was surveyed during the Nuclear Spectroscopic Array (NuSTAR) primary mission is a region of the Norma Arm that was observed with Chandra in 2011. The Norma Arm is a region of recent star formation containing a large number of OB associations and was targeted to search for and study X-ray sources associated with massive stars, such as high-mass X-ray binaries (HMXBs) and colliding wind binaries (CWBs). The Norma Chandra survey covered a 2 deg x 0.8 deg field and NuSTAR has observed about half of this field to date with ~50 ks depth. We detect at least 29 NuSTAR sources in this region and present their spectral and timing properties. Four of these sources are relatively well-studied and have been observed with a number of other instruments; NuSTAR is providing new insights into these sources, which include two pulsar wind nebulae, a black hole binary, and an obscured HMXB. Four sources are NuSTAR discoveries, at least two of which are transients. We have obtained infrared spectra of the IR counterparts of seven of the remaining 21 NuSTAR sources to facilitate their identification. Two sources have high-mass stellar counterparts and are likely HMXBs or CWBs. Five have low-mass counterparts and are likely intermediate polars or low-mass X-ray binaries; one of these sources has spectral and timing properties that are consistent with a black hole binary. The 14 sources without detected IR counterparts are likely a mixture of distant intermediate polars, active galactic nuclei, and magnetars.