1. Harvard University Department of Astronomy, 60 Garden Street, MS-10, Cambridge, Massachusetts 02138, USA

Correspondence to: Joseph Neilsen¹ Correspondence and requests for materials should be addressed to J.N. (Email: jneilsen@cfa.harvard.edu).

Abstract

Stellar-mass black holes with relativistic jets, also known as microquasars, mimic the behaviour of quasars and active galactic nuclei¹. Because timescales around stellar-mass black holes are orders of magnitude smaller than those around more distant supermassive black holes, microquasars are ideal nearby 'laboratories' for studying the evolution of accretion disks and jet formation in black-hole systems². Whereas studies of black holes have revealed a complex array of accretion activity, the mechanisms that trigger and suppress jet formation remain a mystery. Here we report the presence of a broad emission line in the faint, hard states and narrow absorption lines in the bright, soft states of the microquasar GRS 1915+105. ('Hard' and 'soft' denote the character of the emitted X-rays.) Because the hard states exhibit prominent radio jets³, we argue that the broad emission line arises when the jet illuminates the inner accretion disk. The jet is weak or absent during the soft states⁴, and we show that the absorption lines originate when the powerful radiation field around the black hole drives a hot wind off the accretion disk^{5, 6, 7}. Our analysis shows that this wind carries enough mass away from the disk to halt the flow of matter into the radio jet.

1. Harvard University Department of Astronomy, 60 Garden Street, MS-10, Cambridge, Massachusetts 02138, USA

Correspondence to: Joseph Neilsen¹ Correspondence and requests for materials should be addressed to J.N. (Email: jneilsen@cfa.harvard.edu).

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