Rapid Mid-Infrared Spectral-Timing with <i>JWST</i>: I. GRS 1915+105 during a MIR–bright and X-ray–obscured state

Abstract We present mid-infrared (MIR) spectral-timing measurements of the prototypical Galactic microquasar GRS 1915+105. The source was observed with the Mid-Infrared Instrument (MIRI) onboard JWST in June 2023 at a MIR luminosity LMIR ≈ 1036 erg s−1 exceeding past IR levels by about a factor of 10. In contrast, the X-ray flux is much fainter than the historical average, in the source’s now–persistent ‘obscured’ state. The MIRI low-resolution spectrum shows a plethora of emission lines, the strongest of which are consistent with recombination in the hydrogen Pfund (Pf) series and higher. Low amplitude (∼ 1%) but highly significant peak-to-peak photometric variability is found on timescales of ∼ 1,000 s. The brightest Pf (6–5) emission line lags the continuum. Though difficult to constrain accurately, this lag is commensurate with light-travel timescales across the outer accretion disc or with expected recombination timescales inferred from emission line diagnostics. Using the emission line as a bolometric indicator suggests a moderate (∼ 5–30 % Eddington) intrinsic accretion rate. Multiwavelength monitoring shows that JWST caught the source close in-time to unprecedentedly bright MIR and radio long-term flaring. Assuming a thermal bremsstrahlung origin for the MIRI continuum suggests an unsustainably high mass-loss rate during this time unless the wind remains bound, though other possible origins cannot be ruled out. PAH features previously detected with Spitzer are now less clear in the MIRI data, arguing for possible destruction of dust in the interim. These results provide a preview of new parameter space for exploring MIR spectral-timing in XRBs and other variable cosmic sources on rapid timescales.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-01-09
DOI
https://doi.org/10.1093/mnras/staf036
Citations
6
Primary Topic
Astrophysical Phenomena and Observations
Type
article
Field-Weighted Citation Impact
6.93

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article

Rapid Mid-Infrared Spectral-Timing with JWST: I. GRS 1915+105 during a MIR–bright and X-ray–obscured state

F. Vincentelli, J. M. Corral-Santana, John A. Tomsick, C. O. Heinke et al.
6 citations
Monthly Notices of the Royal Astronomical Society
Astrophysical Phenomena and Observations
6.93
article

Rapid Mid-Infrared Spectral-Timing with JWST: I. GRS 1915+105 during a MIR–bright and X-ray–obscured state

F. Vincentelli, J. M. Corral-Santana, John A. Tomsick, C. O. Heinke, C. T. Britt, P. Casella, S. Motta, D. D. Pawar, Michael L. McCollough, Alexander Igl, Oluwashina Adegoke, T. Shahbaz, R. P. Fender, Noel Castro Segura, D. M. Russell, A. W. Shaw, M. George, Thomas J. Maccarone, Sera Markoff, J. M. Mïller, Danny T. H. Steeghs, P. Santos-Sanz, Yash Bhargava, John Byrom, A. Gúrpide, Matthew Middleton, John A. Paice, G. R. Sivakoff, Ramprasad Rao, Michael E. Ressler, R. I. Hynes, D. A. H. Buckley, T D Russell, Richard M. Plotkin, Alexandra J. Tetarenko, C. Knigge, D. Altamirano, Mark Gurwell, J. C. A. Miller‐Jones, V. S. Dhillon, P. Gandhi, Guglielmo Mastroserio, M. C. Baglio, D. J. K. Buisson, Prabhakar Pradhan, P. A. Charles, E. S. Borowski
article en
6 citations

Abstract

Abstract We present mid-infrared (MIR) spectral-timing measurements of the prototypical Galactic microquasar GRS 1915+105. The source was observed with the Mid-Infrared Instrument (MIRI) onboard JWST in June 2023 at a MIR luminosity LMIR ≈ 1036 erg s−1 exceeding past IR levels by about a factor of 10. In contrast, the X-ray flux is much fainter than the historical average, in the source’s now–persistent ‘obscured’ state. The MIRI low-resolution spectrum shows a plethora of emission lines, the strongest of which are consistent with recombination in the hydrogen Pfund (Pf) series and higher. Low amplitude (∼ 1%) but highly significant peak-to-peak photometric variability is found on timescales of ∼ 1,000 s. The brightest Pf (6–5) emission line lags the continuum. Though difficult to constrain accurately, this lag is commensurate with light-travel timescales across the outer accretion disc or with expected recombination timescales inferred from emission line diagnostics. Using the emission line as a bolometric indicator suggests a moderate (∼ 5–30 % Eddington) intrinsic accretion rate. Multiwavelength monitoring shows that JWST caught the source close in-time to unprecedentedly bright MIR and radio long-term flaring. Assuming a thermal bremsstrahlung origin for the MIRI continuum suggests an unsustainably high mass-loss rate during this time unless the wind remains bound, though other possible origins cannot be ruled out. PAH features previously detected with Spitzer are now less clear in the MIRI data, arguing for possible destruction of dust in the interim. These results provide a preview of new parameter space for exploring MIR spectral-timing in XRBs and other variable cosmic sources on rapid timescales.

Monthly Notices of the Royal Astronomical Society
University of Lethbridge (CA), Butler University (US), Tata Institute of Fundamental Research (IN), Louisiana State University (US), California Institute of Technology (US), Texas Tech University (US), Space Telescope Science Institute (US), Jet Propulsion Laboratory (US), University of Nevada, Reno (US), University of Alberta (CA), Universidad de La Laguna (ES), University of Milan (IT), Durham University (GB), Dwarkadas J. Sanghvi College of Engineering (IN), University of Michigan (US), Astronomical Observatory of Rome (IT), Brera Astronomical Observatory (IT), University of Warwick (GB), University of Oxford (GB), South African Radio Astronomy Observatory (ZA), Université Bourgogne Franche-Comté (FR), Center for Astrophysics Harvard & Smithsonian (US), European Southern Observatory (CL), Instituto de Astrofísica de Canarias (ES), Astronomical Institute of the Slovak Academy of Sciences (SK), Instituto de Astrofísica de Andalucía (ES), International Centre for Radio Astronomy Research (AU), University of Southampton (GB), New York University (US), Embry–Riddle Aeronautical University (US), National Institute for Astrophysics (IT), University of Amsterdam (NL), University of Sheffield (GB), University of California, Berkeley (US)
National Aeronautics and Space Administration, California Institute of Technology, New York University Abu Dhabi, Space Telescope Science Institute, UK Research and Innovation, Ministerio de Ciencia, Innovación y Universidades, Royal Society, Indian Space Research Organisation, Nuclear Safety and Security Commission, Tamkeen, Jet Propulsion Laboratory, Goddard Space Flight Center, Natural Sciences and Engineering Research Council of Canada, Science and Technology Facilities Council, Japan Aerospace Exploration Agency, RIKEN, Agencia Estatal de Investigación, Division of Materials Research, Astrophysics Science Division
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Astrophysical Phenomena and Observations
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