2018/11/29 by Alicia Rouco Escorial, A. Rouco Escorial, J. van den Eijnden +1
Engineering · Physics and Astronomy · #Accretion (finance) #Accretion disc #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Context (archaeology) #Galaxy #Gamma-ray bursts and supernovae #Luminosity #Mechanics and Biomechanics Studies #Neutron star #Nuclear physics #Physics #X-ray #X-ray transient #astro-ph.HE
paper · pdf · doi:10.1051/0004-6361/201834572
published as A&A 620, L13 (2018) · 5 pages, 2 figures, accepted for A&A Letters
openalex created_date 2018/11/09 · arxiv created 2018/11/29 · openalex publication_date 2018/12/01 · arxiv updated 2018/12/19 · openalex updated_date 2026/08/05
We present our Swift monitoring campaign of the slowly rotating neutron star Be/X-ray transient GX 304–1 (spin period of ∼275 s) when the source was not in outburst. We found that between its type I outbursts, the source recurrently exhibits a slowly decaying low-luminosity state (with luminosities of 10 34 − 35 erg s −1 ). This behaviour is very similar to what has been observed for another slowly rotating system, GRO J1008–57. For that source, this low-luminosity state has been explained in terms of accretion from a non-ionised (“cold”) accretion disc. Because of the many similarities between the two systems, we suggest that GX 304–1 enters a similar accretion regime between its outbursts. The outburst activity of GX 304–1 ceased in 2016. Our continued monitoring campaign shows that the source is in a quasi-stable low-luminosity state (with luminosities a few factors lower than previously seen) for at least one year now. Using our NuSTAR observation in this state, we found pulsations at the spin period, demonstrating that the X-ray emission is due to accretion of matter onto the neutron star surface. If the accretion geometry during this quasi-stable state is the same as during the cold-disc state, then matter indeed reaches the surface (as predicted) during this later state. We discuss our results in the context of the cold-disc accretion model.