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The 2005 outburst of the halo black hole X-ray transient XTE J1118+480
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Zurita, C., Torres, M. A. P., Steeghs, D., Rodríguez-Gil, P., Muñoz-Darias, T., Casares, J., Shahbaz, T., Martinez-Pais, I. G., Zhao, P., Garcia, M. R., Piccioni, A., Bartolini, C., Guarnieri, A., Bloom, Joshua S., Blake, C. H., Falco, E. E., Szentgyorgyi, A. and Skrutskie, M. (2006) The 2005 outburst of the halo black hole X-ray transient XTE J1118+480. The Astrophysical Journal, Vol.644 (No.1). pp. 432-438. doi:10.1086/503286
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WRAP_Steeghs_2005_outburst_0602222v1.pdf - Accepted Version Download (1409Kb) | Preview |
Official URL: http://dx.doi.org/10.1086/503286
Abstract
We present optical and infrared monitoring of the 2005 outburst of the halo black hole X-ray transient XTE J1118+480. We measured a total outburst amplitude of ~5.7 ± 0.1 mag in the R band and ~5 mag in the infrared J, H, and Ks bands. The hardness ratio HR2 (5-12 keV : 3-5 keV) from the RXTE ASM data is 1.53 ± 0.02 at the peak of the outburst, indicating a hard spectrum. Both the shape of the light curve and the ratio LX(1-10 keV)/Lopt resemble the minioutbursts observed in GRO J0422+32 and XTE J1859+226. During early decline, we find a 0.02 mag amplitude variation consistent with a superhump modulation, like the one observed during the 2000 outburst. Similarly, XTE J1118+480 displayed a double-humped ellipsoidal modulation distorted by a superhump wave when settled into a near-quiescence level, suggesting that the disk expanded to the 3 : 1 resonance radius after outburst, where it remained until early quiescence. The system reached quiescence at R = 19.02 ± 0.03, about 3 months after the onset of the outburst. The optical rise preceded the X-ray rise by at most 4 days. The spectral energy distributions (SEDs) at the different epochs during outburst are all quasi-power laws with Fν να increasing toward the blue. At the peak of the outburst, we derived α = 0.49 ± 0.04 for the optical data alone and α = 0.1 ± 0.1 when fitting solely the infrared. This difference between the optical and the infrared SEDs suggests that the infrared is dominated by a different component (a jet?), whereas the optical is presumably showing the disk evolution.
| Item Type: | Journal Article | ||||
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| Subjects: | Q Science > QB Astronomy | ||||
| Divisions: | Faculty of Science > Physics | ||||
| Library of Congress Subject Headings (LCSH): | Black holes (Astronomy), X-ray bursts | ||||
| Journal or Publication Title: | The Astrophysical Journal | ||||
| Publisher: | Institute of Physics Publishing Ltd. | ||||
| ISSN: | 0004-637X | ||||
| Official Date: | 2006 | ||||
| Dates: |
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| Volume: | Vol.644 | ||||
| Number: | No.1 | ||||
| Page Range: | pp. 432-438 | ||||
| DOI: | 10.1086/503286 | ||||
| Status: | Peer Reviewed | ||||
| Publication Status: | Published | ||||
| Access rights to Published version: | Restricted or Subscription Access | ||||
| Funder: | United States. National Aeronautics and Space Administration (NASA), Smithsonian Astrophysical Observatory, Harvard University, University of California, Berkeley | ||||
| Grant number: | NAG-5-10889 (NASA) |
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