Strongly magnetized (B ≥ 1012 G) accreting neutron stars (NSs) are prime targets for studying the launching of jets by objects with a solid surface; while classical jet-launching models predict that such NSs cannot launch jets, recent observations and models argue otherwise. Transient Be/X-ray binaries (BeXRBs) are critical laboratories for probing this poorly explored parameter space for jet formation. Here, we present the coordinated monitoring campaigns of three BeXRBs across four outbursts: giant outbursts of SAX 2103.5+4545, 1A 0535+262, and GRO J1008–57, as well as a Type-I outburst of the latter. We obtain radio detections of 1A 0535+262 during ten out of twenty observations, while the other targets remained undetected at typical limits of 20–50 $\mu$Jy. The radio luminosity of 1A 0535+262 positively correlates with its evolving X-ray luminosity, and inhabits a region of the LX–LR plane continuing the correlation observed previously for the BeXRB Swift J0243.6+6124. We measure a BeXRB LX–LR coupling index of β = 0.86 ± 0.06 ($L_R \propto L_X^\beta$), similar to the indices measured in NS and black hole low-mass X-ray binaries. Strikingly, the coupling’s LR normalization is ∼275 and ∼6.2 × 103 times lower than in those two comparison samples, respectively. We conclude that jet emission likely dominates during themore »
NGC 4472 is home to five ultraluminous X-ray sources hosted by globular clusters. These sources have been suggested as good black hole candidates in extragalactic globular clusters—a highly sought after population that may provide observational information regarding the progenitors of merging black hole binaries. In this body of work, we present X-ray and optical follow-up to one of these sources, CXOUJ1229410+075744 (GCU1). We find no evidence of [OIII] optical emission in GCU1 which indicates a lack of significant evidence for super-Eddington outflows, unlike what is seen in a handful of ULXs in extragalactic GCs. X-ray monitoring from 2019 to 2021 shows no detected X-ray emission above a few × 1038 erg/s. Comparisons of the multiwavelength properties to disc-dominated, near Eddington Galactic black hole low-mass X-ray binaries (GRS 1915+105 and XTEJ1817-330) suggests that GCU1 may show similar behaviour to GRS 1915+105 in terms of X-ray variability and similar relationships between LX and kT, with GCU1 showing maximum X-ray luminosities on order of higher magnitude.
- Publication Date:
- NSF-PAR ID:
- 10380600
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 518
- Issue:
- 1
- Page Range or eLocation-ID:
- p. 855-859
- ISSN:
- 0035-8711
- Publisher:
- Oxford University Press
- Sponsoring Org:
- National Science Foundation
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