skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: High-energy gamma-ray observations of the accreting black hole V404 Cygni during its 2015 June outburst

Abstract

In this paper, we report on Fermi/Large Area Telescope observations of the accreting black hole low-mass X-ray binary V404 Cygni during its outburst in 2015 June–July. Detailed analyses reveal a possible excess of γ-ray emission on 2015 26 June, with a very soft spectrum above 100 MeV, at a position consistent with the direction of V404 Cyg (within the 95 per cent confidence region and a chance probability of 4 × 10 -4). This emission cannot be associated with any previously known Fermi source. Its temporal coincidence with the brightest radio and hard X-ray flare in the light curve of V404 Cyg, at the end of the main active phase of its outburst, strengthens the association with V404 Cyg. If the γ-ray emission is associated with V404 Cyg, the simultaneous detection of 511 keV annihilation emission by INTEGRAL reqires that the high-energy γ-rays originate away from the corona, possibly in a Blandford–Znajek jet. Finally, the data give support to models involving a magnetically arrested disc where a bright γ-ray jet can re-form after the occurrence of a major transient ejection seen in the radio.

Authors:
 [1];  [2];  [3];  [1];  [1];  [4];  [5];  [5];  [6];  [6]
  1. Alternative Energies and Atomic Energy Commission (CEA-Saclay), Gif-sur-Yvette (France). AIM Lab.
  2. Alternative Energies and Atomic Energy Commission (CEA-Saclay), Gif-sur-Yvette (France). AIM Lab.; Univ. of Orleans, Nancay (France). PSL Research Univ. Observatory of Paris. Radio-Astronomical Station of Nancay
  3. Grenoble Alpes Univ. (France); National Centre for Scientific Research (CNRS), Grenoble (France)
  4. Aalto Univ. Metsahovi Radio Observatory, Kylmala (Finland); Aalto Univ., Otaniemi (Finland). Dept. of Radio Science and Engineering
  5. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  6. Univ. of Oxford (United Kingdom). Dept. of Astrophysics
Publication Date:
Research Org.:
Alternative Energies and Atomic Energy Commission (CEA-Saclay), Gif-sur-Yvette (France); California Inst. of Technology (CalTech), Pasadena, CA (United States)
Sponsoring Org.:
USDOE; National Aeronautic and Space Administration (NASA); National Science Foundation (NSF); The French National Research Agency (ANR) (France); Hintze Foundation (United Kingdom)
OSTI Identifier:
1355702
Grant/Contract Number:
NNX08AW31G; NNX11A043G; AST-0808050; AST-1109911; ANR-12-BS05-0009; ANR-10-LABX-0023; ANR-11-IDEX-0005-02
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society: Letters
Additional Journal Information:
Journal Volume: 462; Journal Issue: 1; Journal ID: ISSN 1745-3925
Publisher:
Royal Astronomical Society
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; black hole physics; V404 Cygni star; gamma-rays; radio continuum; X-rays binaries

Citation Formats

Loh, A., Corbel, S., Dubus, G., Rodriguez, J., Grenier, I., Hovatta, T., Pearson, T., Readhead, A., Fender, R., and Mooley, K.. High-energy gamma-ray observations of the accreting black hole V404 Cygni during its 2015 June outburst. United States: N. p., 2016. Web. doi:10.1093/mnrasl/slw142.
Loh, A., Corbel, S., Dubus, G., Rodriguez, J., Grenier, I., Hovatta, T., Pearson, T., Readhead, A., Fender, R., & Mooley, K.. High-energy gamma-ray observations of the accreting black hole V404 Cygni during its 2015 June outburst. United States. doi:10.1093/mnrasl/slw142.
Loh, A., Corbel, S., Dubus, G., Rodriguez, J., Grenier, I., Hovatta, T., Pearson, T., Readhead, A., Fender, R., and Mooley, K.. 2016. "High-energy gamma-ray observations of the accreting black hole V404 Cygni during its 2015 June outburst". United States. doi:10.1093/mnrasl/slw142. https://www.osti.gov/servlets/purl/1355702.
@article{osti_1355702,
title = {High-energy gamma-ray observations of the accreting black hole V404 Cygni during its 2015 June outburst},
author = {Loh, A. and Corbel, S. and Dubus, G. and Rodriguez, J. and Grenier, I. and Hovatta, T. and Pearson, T. and Readhead, A. and Fender, R. and Mooley, K.},
abstractNote = {In this paper, we report on Fermi/Large Area Telescope observations of the accreting black hole low-mass X-ray binary V404 Cygni during its outburst in 2015 June–July. Detailed analyses reveal a possible excess of γ-ray emission on 2015 26 June, with a very soft spectrum above 100 MeV, at a position consistent with the direction of V404 Cyg (within the 95 per cent confidence region and a chance probability of 4 × 10-4). This emission cannot be associated with any previously known Fermi source. Its temporal coincidence with the brightest radio and hard X-ray flare in the light curve of V404 Cyg, at the end of the main active phase of its outburst, strengthens the association with V404 Cyg. If the γ-ray emission is associated with V404 Cyg, the simultaneous detection of 511 keV annihilation emission by INTEGRAL reqires that the high-energy γ-rays originate away from the corona, possibly in a Blandford–Znajek jet. Finally, the data give support to models involving a magnetically arrested disc where a bright γ-ray jet can re-form after the occurrence of a major transient ejection seen in the radio.},
doi = {10.1093/mnrasl/slw142},
journal = {Monthly Notices of the Royal Astronomical Society: Letters},
number = 1,
volume = 462,
place = {United States},
year = 2016,
month = 7
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 1work
Citation information provided by
Web of Science

Save / Share:
  • The black hole binary GS 2023+338 exhibited an unprecedently bright outburst in 2015 June. On 2015 June 17, the high energy instruments on board INTEGRAL detected an extremely variable emission during both bright and low luminosity phases, with dramatic variations of the hardness ratio on timescales of approximately seconds. The analysis of the IBIS and SPI data reveals the presence of hard spectra in the brightest phases, compatible with thermal Comptonization with a temperature of kT{sub e} ∼ 40 keV. The seed photon’s temperature is best fit by kT{sub 0} ∼ 7 keV, which is too high to be compatiblemore » with blackbody emission from the disk. This result is consistent with the seed photons being provided by a different source, which we hypothesize to be a synchrotron driven component in the jet. During the brightest phase of flares, the hardness shows a complex pattern of correlation with flux, with the maximum energy released in the range of 40–100 keV. The hard-X-ray variability for E > 50 keV is correlated with flux variations in the softer band, showing that the overall source variability cannot originate entirely from absorption, but at least part of it is due to the central accreting source.« less
  • In 2015 June, the source V404 Cygni (= GS2023+38) underwent an extraordinary outburst. We present the results obtained during the first revolution dedicated to this target by the INTEGRAL mission and focus on the spectral behavior in the hard X-ray domain, using both SPI and IBIS instruments. The source exhibits extreme variability and reaches fluxes of several tens of Crab. However, the emission between 20 and 650 keV can be understood in terms of two main components, varying on all the observable timescales, similar to what is observed in the persistent black hole system Cyg X-1. The low-energy component (upmore » to ∼200 keV) presents a rather unusual shape, probably due to the intrinsic source variability. Nonetheless, a satisfactory description is obtained with a Comptonization model, if an unusually hot population of seed photons (kT{sub 0} ∼ 7 keV) is introduced. Above this first component, a clear excess extending up to 400–600 keV leads us to investigate a scenario where an additional (cutoff) power law could correspond to the contribution of the jet synchrotron emission, as proposed in Cyg X-1. A search for an annihilation feature did not provide any firm detection, with an upper limit of 2 × 10{sup −4} ph cm{sup −2} s{sup −1} (2σ) for a narrow line centered at 511 keV, on the averaged obtained spectrum.« less
  • In 2015 June, the black hole X-ray binary (BHXRB) V404 Cygni went into outburst for the first time since 1989. Here, we present a comprehensive search for quasi-periodic oscillations (QPOs) of V404 Cygni during its recent outburst, utilizing data from six instruments on board five different X-ray missions: Swift /XRT, Fermi /GBM, Chandra /ACIS, INTEGRAL ’s IBIS/ISGRI and JEM-X, and NuSTAR . We report the detection of a QPO at 18 mHz simultaneously with both Fermi /GBM and Swift /XRT, another example of a rare but slowly growing new class of mHz-QPOs in BHXRBs linked to sources with a highmore » orbital inclination. Additionally, we find a duo of QPOs in a Chandra /ACIS observation at 73 mHz and 1.03 Hz, as well as a QPO at 136 mHz in a single Swift /XRT observation that can be interpreted as standard Type-C QPOs. Aside from the detected QPOs, there is significant structure in the broadband power, with a strong feature observable in the Chandra observations between 0.1 and 1 Hz. We discuss our results in the context of current models for QPO formation.« less
  • High-speed photometric observations are presented of the optical counterpart of the X-ray transient GS 2023 + 338 (V404 Cygni) obtained during the decline from a major outburst. The low-frequency flickering previously reported in X-rays, optical, and radio waves is confirmed. From four night's coverage in September 1989, no evidence is found in the light curve for a unique coherent period. However, transient broad features are observed in the power spectra at periods in the range of 3-10 minutes. Similar features are commonly seen in the optical light curves of erupting dwarf novae; they may be a characteristic signature of diskmore » accretion onto any type of compact star. 35 refs.« less
  • As one of the best-characterized stellar-mass black holes, with good measurements of its mass, distance, and inclination, V404 Cyg is the ideal candidate to study Eddington-limited accretion episodes. After a long quiescent period, V404 Cyg underwent a new outburst in 2015 June. We obtained two Chandra HETG exposures of 20 and 25 ks. Many strong emission lines are observed; the ratio of Si He-like triplet lines gives an estimate for the formation region distance of 4 × 10{sup 11} cm. A narrow Fe Kα line is detected with an equivalent width greater than 1 keV in many epochs, signaling that we domore » not directly observe the central engine. Obscuration of the central engine and strong narrow emission lines signal that the outer disk may be illuminated, and its structure may help to drive the strong variability observed in V404 Cyg. In the highest flux phases, strong P-Cygni profiles consistent with a strong disk wind are observed, likely radiation or thermally driven as V404 Cyg approaches its Eddington limit. The kinetic power of this wind may be extremely high at >0.1 L{sub Bol}.« less