Details

Autor(en) / Beteiligte

• Pike, Sean N.
• Negoro, Hitoshi
• Tomsick, John A.
• Bachetti, Matteo
• Brumback, McKinley
• Connors, Riley M. T.
• García, Javier A.
• Grefenstette, Brian
• Hare, Jeremy
• Harrison, Fiona A.
• Jaodand, Amruta
• Ludlam, R. M.
• Mastroserio, Guglielmo
• Mihara, Tatehiro
• Shidatsu, Megumi
• Sugizaki, Mutsumi
• Takagi, Ryohei

Titel

MAXI and NuSTAR Observations of the Faint X-Ray Transient MAXI J1848-015 in the GLIMPSE-C01 Cluster

Ist Teil von

• The Astrophysical journal, 2022-03, Vol.927 (2), p.190

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2022

Link zum Volltext

Quelle

Elektronische Zeitschriftenbibliothek (Open access)

Beschreibungen/Notizen

• Abstract We present the results of Monitor of All-sky X-ray Image (MAXI) monitoring and two Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the recently discovered faint X-ray transient MAXI J1848015. Analysis of the MAXI light curve shows that the source underwent a rapid flux increase beginning on 2020 December 20, followed by a rapid decrease in flux after only ∼5 days. NuSTAR observations reveal that the source transitioned from a bright soft state with unabsorbed, bolometric (0.1–100 keV) flux F = 6.9 ± 0.1 × 10 −10 erg cm −2 s −1 , to a low hard state with flux F = 2.85 ± 0.04 × 10 −10 erg cm −2 s −1 . Given a distance of 3.3 kpc, inferred via association of the source with the GLIMPSE-C01 cluster, these fluxes correspond to an Eddington fraction of the order of 10 −3 for an accreting neutron star (NS) of mass M = 1.4 M ⊙ , or even lower for a more massive accretor. However, the source spectra exhibit strong relativistic reflection features, indicating the presence of an accretion disk that extends close to the accretor, for which we measure a high spin, a = 0.967 ± 0.013. In addition to a change in flux and spectral shape, we find evidence for other changes between the soft and hard states, including moderate disk truncation with the inner disk radius increasing from R in ≈ 3 R g to R in ≈ 8 R g , narrow Fe emission whose centroid decreases from 6.8 ± 0.1 keV to 6.3 ± 0.1 keV, and an increase in low-frequency (10 −3 –10 −1 Hz) variability. Due to the high spin, we conclude that the source is likely to be a black hole rather than an NS, and we discuss physical interpretations of the low apparent luminosity as well as the narrow Fe emission.