Mid-Infrared Emission from Dust around Quiescent Low-Mass X-Ray Binaries

Abstract

We report the discovery of excess 4.5 and 8 mm emission from three quiescent black hole low-mass X-ray binaries, A0620Ϫ00, GS 2023ϩ338, and XTE J1118ϩ480, and the lack of similar excess emission from Cen X-4. The mid-infrared emission from GS 2023ϩ338 probably originates in the accretion disk. However, the excess emission from A0620Ϫ00 and XTE J1118ϩ480 is brighter and peaks at longer wavelengths, and thus most likely originates from circumbinary dust that is heated by the light of the secondary star. For these two sources, we find that the inner edges of the dust distributions lie near 1.7 times the binary separations, which are the minimum radii at which circumbinary disks would be stable against tidal disruption. The excesses are weak at 24 mm, which implies that the dust does not extend beyond about 3 times the binary separations. The total masses of circumbinary material are between and g. The material could be the remains of fallback 22 24 10 10 disks produced in supernovae, or material from the companions injected into circumbinary orbits during mass transfer.

Constraints on relativistic jets in quiescent black hole X-ray binaries from broad-band spectral modelling

“…However, we find an IR excess (relative to the contribution from the companion star), which we account for as synchrotron radiation predominately from the accelerated (non-thermal) electron component. However, since our IR data points are non-simultaneous, we cannot exclude the possibility that a circumbinary disk may instead contribute to some of the excess IR emission, especially in the Spitzer 8-µm band (e.g., Muno & Mauerhan 2006;Wang & Wang 2014). If a circumbinary disk is relevant to the IR, then in order to self-consistently also explain the jet radio emission, the jet break (ν b ) would likely need to fall at lower frequencies than in either fit (i.e., the location of the acceleration region, zacc, would be located farther from the black hole; see Gallo et al 2007).…”

“…The particle acceleration is too weak for non-thermal electrons to contribute significant amounts of high-energy radiation. We do not require a circumbinary disk (e.g., Muno & Mauerhan 2006) in the IR, or thermal emission from the outer disk in the optical/UV, but in reality both components could contribute emission at some level.…”

“…Muno & Mauerhan (2006) estimate that a level of flux variability in the IR of ∼30% could be reasonable. From the overlap between the Spitzer 4.5 µm band and the WISE W2 filter observations, we find a ∼15% dif- and at UTC 21:26 on June 28, and they lasted 7.5 h on each day.…”

“…J1118 was observed on 2004 Nov 21 with the Infrared Array Camera (IRAC; Fazio et al 2004) and detected in both the 4.5 and 8.0 µm bands. J1118 was also observed, but not detected, in the 24 µm band with the Multiband Imaging Photometer for Spitzer (MIPS; Rieke et al 2004) on 2005 May 13 (Muno & Mauerhan 2006). We adopt flux densities of 69 (4.5µm) and 59 µJy (8.0 µm), and an upper limit of <50 µJy at 24 µm, as measured by Gallo et al (2007) who analyzed the same data originally presented in Muno & Mauerhan (2006).…”

“…J1118 was also observed, but not detected, in the 24 µm band with the Multiband Imaging Photometer for Spitzer (MIPS; Rieke et al 2004) on 2005 May 13 (Muno & Mauerhan 2006). We adopt flux densities of 69 (4.5µm) and 59 µJy (8.0 µm), and an upper limit of <50 µJy at 24 µm, as measured by Gallo et al (2007) who analyzed the same data originally presented in Muno & Mauerhan (2006). Gallo et al (2007) estimated that the statistical uncertainties in the flux densities are at the 10% level.…”