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Accretion Flow Properties of MAXI J1834-021 During Its Double-Outbursts In 2023

Dipak Debnath, Hsiang-Kuang Chang

TL;DR

MAXI J1834-021's 2023 activity is analyzed with NICER timing and spectral data to reveal two consecutive outbursts, each remaining in hard spectral states and lacking soft states. By fitting both phenomenological (diskbb+powerlaw) and physical (TCAF) models, the study uncovers a halo-dominated accretion flow, large ARR values, and a moving shock with $X_s$ in the range $48$–$460\,r_s$, with QPO frequencies evolving up to $2.12$ Hz and correlating tightly with soft flux and spectral index. The TCAF fits yield a black hole mass of $M_{\rm BH}=12.3\pm0.2\,M_\odot$, and a kink in the disk rate around MJD 60082.68 suggests a secondary mini-outburst triggered by viscosity changes at the pile-up radius $X_p$, consistent with the pile-up-based outburst framework. These results strengthen the interpretation of outburst evolution in black hole X-ray binaries within the TCAF paradigm and provide a coherent physical picture of accretion-flow geometry changes during complex, multi-episode activity.

Abstract

The Galactic transient black hole candidate MAXI J1834-021 exhibited `faint' outbursting activity for approximately $10$ months following its discovery on February 5, 2023. We study the evolution of both the temporal (hard and soft band photon count rates, hardness ratios, and QPO frequencies) and spectral properties of the source using NICER data between March 7 and October 4, 2023. The outburst profile and the nature of QPOs suggest that the source underwent a mini-outburst following the primary outburst. A monotonic evolution of low-frequency QPOs from higher to lower frequencies is observed during the primary outbursting phase. Both phenomenological (diskbb plus powerlaw) and physical (Two Component Advective Flow) model fitted spectral studies suggest that during the entire epoch, the source remained in harder spectral states, with a clear dominance of nonthermal emissions from the `hot' Compton cloud. Based on the evolution of the spectral and temporal properties, the 2023 outbursting activity of MAXI J1834-021 can be classified as a combination of double `failed' outbursts, as no softer spectral states were observed. The spectral analysis with the TCAF model also gives an estimate of the source mass as $12.3\pm0.2~M_\odot$.

Accretion Flow Properties of MAXI J1834-021 During Its Double-Outbursts In 2023

TL;DR

MAXI J1834-021's 2023 activity is analyzed with NICER timing and spectral data to reveal two consecutive outbursts, each remaining in hard spectral states and lacking soft states. By fitting both phenomenological (diskbb+powerlaw) and physical (TCAF) models, the study uncovers a halo-dominated accretion flow, large ARR values, and a moving shock with in the range –, with QPO frequencies evolving up to Hz and correlating tightly with soft flux and spectral index. The TCAF fits yield a black hole mass of , and a kink in the disk rate around MJD 60082.68 suggests a secondary mini-outburst triggered by viscosity changes at the pile-up radius , consistent with the pile-up-based outburst framework. These results strengthen the interpretation of outburst evolution in black hole X-ray binaries within the TCAF paradigm and provide a coherent physical picture of accretion-flow geometry changes during complex, multi-episode activity.

Abstract

The Galactic transient black hole candidate MAXI J1834-021 exhibited `faint' outbursting activity for approximately months following its discovery on February 5, 2023. We study the evolution of both the temporal (hard and soft band photon count rates, hardness ratios, and QPO frequencies) and spectral properties of the source using NICER data between March 7 and October 4, 2023. The outburst profile and the nature of QPOs suggest that the source underwent a mini-outburst following the primary outburst. A monotonic evolution of low-frequency QPOs from higher to lower frequencies is observed during the primary outbursting phase. Both phenomenological (diskbb plus powerlaw) and physical (Two Component Advective Flow) model fitted spectral studies suggest that during the entire epoch, the source remained in harder spectral states, with a clear dominance of nonthermal emissions from the `hot' Compton cloud. Based on the evolution of the spectral and temporal properties, the 2023 outbursting activity of MAXI J1834-021 can be classified as a combination of double `failed' outbursts, as no softer spectral states were observed. The spectral analysis with the TCAF model also gives an estimate of the source mass as .

Paper Structure

This paper contains 18 sections, 7 figures.

Table of Contents

  1. Introduction
  2. Observation and Data Analysis
  3. Observations
  4. Data Reduction
  5. Data Analysis
  6. Results
  7. Outburst Profile
  8. Hardness Ratio (HR)
  9. Low frequency QPOs
  10. Spectral Study using Phenomenological Model
  11. Spectral Study using Physical Model
  12. Estimation of Mass of the Source
  13. Correlation of Temporal and Spectral Properties
  14. Correlation of QPO Frequency with SXR and Photon Index
  15. Anti-correlation of HR with QPO Frequency and Photon Index
  16. ...and 3 more sections

Figures (7)

  • Figure 1: (a-b) Variation of NICER count rates in the soft X-ray (SXR; $0.5$–$3$ keV), hard X-ray (HXR; $3$–$10$ keV), and total X-ray (TXR; $0.5$–$10$ keV) energy bands, shown in the top two panels. (c) Evolution of the hardness ratio (HR = HXR/SXR) is shown in the next panel. (d) In the bottom panel, the variation of the observed QPOs is shown. The shaded regions mark different phases of the outburst profile. Phases I–III correspond to the primary outburst phase, while Phase IV belongs to the secondary outburst phase.
  • Figure 2: Fourier-transformed power density spectrum (PDS) of the $0.01$ s time-binned $0.5$–$10$ keV NICER light curve from March 09, 2023 (MJD 60012). The Lorentzian model fit reveals a prominent QPO at $2.12$ Hz.
  • Figure 3: NICER spectrum of observation ID: 6203690105 (from March 11, 2023; MJD=60014.13) fitted with two sets of models: $(i)$$tbabs\otimes smedge(diskbb + powerlaw)$ (red dashed line), and $(ii)$$tbabs \otimes smedge \otimes TCAF$ (blue dash-dotted line). The purple and brown colored solid curves are for model set1 fitted disk blackbody and powerlaw components.
  • Figure 4: Variation of the spectral parameters obtained from the combined disk blackbody (DBB) and power-law (PL) model fit: (a) disk temperature ($T_{\rm in}$ in keV), (b) power-law photon index ($\Gamma$), and (c-d) bolometric fluxes of the model components (both in units of $10^{-11}\text{ergs}\text{cm}^{-2}~\text{s}^{-1}$). The shaded regions indicate different Phases of the outburst profile.
  • Figure 5: Variation of the TCAF model fitted spectral parameters: (a) Keplerian disk accretion rate ($\dot{m}_d$ in $\dot{M}_{\rm Edd}$), (b) sub-Keplerian halo accretion rate ($\dot{m}_h$ in $\dot{M}_{\rm Edd}$), (c) Shock Location ($X_s$ in $r_s$), (d) compression ratio (R), and (e) BH Mass (M$_{\rm BH}$ in M$_\odot$) are shown. In the bottom panel (f), variation of the ratio between halo to disk accretion rates (ARR) is shown. The shaded regions indicate different phases of the outburst profile. Note, here 'kink' on MJD=60082.68, indicates possible triggering of the rise in viscosity at pile-up radius $X_p$, which causes secondary mini-outburst (Phase-IV) after the primary outburst (combining Phases I-III).
  • ...and 2 more figures