[Paper Review] The multifrequency monitoring of microquasars. SS433

С. А. Трушкин, Н. Н. Бурсов+1 more|arXiv (Cornell University)|Mar 1, 2004

Astrophysical Phenomena and Observations1 references3 citations

TL;DR

This study presents 18 years of multifrequency radio monitoring of the microquasar SS433 using the RATAN-600 telescope at six frequencies (0.96–21.7 GHz), analyzing 940 observations and over 4,500 flux density measurements. The radio spectra are well-fit by a power law with a remarkably stable mean spectral index of −0.60 ± 0.14, indicating long-term spectral consistency in this relativistic jet system.

ABSTRACT

The principal results of daily observations with the RATAN-600 radio telescope of X-ray binary with relativistic jets microquasar SS433 in 1986--2003 are presented. We have measured the flux densities at 0.96, 2.3, 3.9, 7.7, 11.2 and 21.7 GHz in different sets, duration from a week to some months. In general there are 940 observations of SS433 and more than 4500 flux density measurements in the period. Observations show that radio spectra are well fitting by a power law. The mean spectral index remained the same, $-0.60\pm0.14$ during almost 20 years at least, and mean accuracy of the index determination was better than 0.1 in our multi-frequency observations, i.e. it was higher than in the intensive two-frequency monitoring of SS433 with the three-element GBI interferometer. Flux density data and spectra `on-line' plotting are accessible on the CATS data base site: http://cats.sao.ru/.

Motivation & Objective

• To characterize the long-term radio variability of SS433 across multiple frequencies.
• To determine the spectral index evolution of SS433's radio emission over nearly two decades.
• To assess the stability of the radio spectral energy distribution in a Galactic microquasar with relativistic jets.
• To provide a publicly accessible, high-cadence dataset for future multiwavelength studies of SS433.
• To compare the spectral stability of SS433 with that observed in other microquasars using different monitoring techniques.

Proposed method

• Conducted daily or near-daily observations of SS433 with the RATAN-600 radio telescope at six central frequencies: 0.96, 2.3, 3.9, 7.7, 11.2, and 21.7 GHz.
• Performed flux density measurements in multiple observing sessions, each lasting from one week to several months.
• Fitted the observed flux densities at different frequencies to a power-law model Sν ∝ να to derive the spectral index α.
• Used a multi-frequency approach to improve the accuracy of spectral index determination compared to two-frequency monitoring.
• Maintained consistent calibration and data reduction procedures across the 18-year baseline to ensure data homogeneity.
• Hosted the final dataset, including real-time light curves and spectral plots, on the CATS database (http://cats.sao.ru/).

Experimental results

Research questions

• RQ1 What is the long-term stability of the radio spectral index of SS433 over nearly 20 years?
• RQ2 How does the spectral index of SS433 compare between multi-frequency and two-frequency monitoring approaches?
• RQ3 What is the variability timescale and amplitude of radio flares in SS433 across multiple frequencies?
• RQ4 To what extent does the radio emission of SS433 follow a power-law spectrum during quiescence and flaring states?
• RQ5 How does the spectral behavior of SS433 compare to other known microquasars in the Galaxy?

Key findings

• The radio spectra of SS433 are well described by a power-law model with a mean spectral index of −0.60 ± 0.14 over the 1986–2003 period.
• The spectral index remained remarkably stable over nearly two decades, with a mean accuracy of better than ±0.1 in the multi-frequency measurements.
• The spectral index determination from multi-frequency data achieved higher precision than previous two-frequency monitoring with the GBI interferometer.
• Radio flares were observed in which flux densities exceeded the quiescent level by up to a factor of 10, with flat spectra indicating possible optical depth effects at flare onset.
• The dataset includes 940 observations and over 4,500 individual flux density measurements across six frequencies, forming one of the most extensive long-term radio light curves of a microquasar.
• Flux density and spectral data are publicly accessible in real time via the CATS database (http://cats.sao.ru/), supporting ongoing and future multiwavelength studies.