# The First NuSTAR Observation of 4U 1538–522: Updated Orbital Ephemeris and a Strengthened Case for an Evolving Cyclotron Line Energy

> Research article (Maryland Shared Open Access Repository (USMAI Consortium), 2019) · cited 19× · AI/ML

**Wikidata**: [openalex:W3103612490](https://www.wikidata.org/wiki/openalex:W3103612490)  
**Source**: https://4ort.xyz/entity/the-first-nustar-observation-of-4u-1538522-updated-orbital-ephemeris-and-a-strengthened-case-for-an-evolving-cyclotron-l