[Paper Review] GRS 1915+105

J. Greiner|arXiv (Cornell University)|Nov 28, 2001

Astrophysical Phenomena and Observations3 citations

TL;DR

This study uses near-infrared spectroscopy from the ESO/VLT to identify the donor star in the microquasar GRS 1915+105, measure its orbital period and radial velocity amplitude, and determine the black hole mass at 14 ± 4 solar masses. The mass measurement constrains models of X-ray variability, binary evolution, and stable QPO behavior in GRS 1915+105 and GRO J1655-40.

ABSTRACT

I summarize recent near-infrared spectroscopy of the microquasar GRS 1915+105 with the ESO/VLT which allowed to (i) identify the donor and (ii) measure the orbital period and radial velocity amplitude. Assuming that the jet ejections occur perpendicular to the accretion disk and orbital plane, the mass of the black hole is determined to M = 14 +- 4 solar masses. I discuss the implications of this mass determination on (a) the understanding of the large-amplitude X-ray variability in GRS 1915+105, (b) binary formation scenarios, and (c) models to explain the stable QPO frequencies in GRS 1915+105 and GRO J1655-40.

Motivation & Objective

• To identify the donor star in the microquasar GRS 1915+105 through near-infrared spectroscopy.
• To measure the orbital period and radial velocity amplitude of the binary system using spectroscopic data.
• To determine the black hole mass using the assumption that jet ejections are perpendicular to the accretion disk and orbital plane.
• To assess the implications of the derived black hole mass for X-ray variability, binary formation, and QPO frequency stability.
• To compare the results with models of GRS 1915+105 and the similar system GRO J1655-40.

Proposed method

• Conducted near-infrared spectroscopy of GRS 1915+105 using the ESO/VLT to detect Doppler shifts in the donor star's spectral lines.
• Analyzed radial velocity variations to derive the orbital period and velocity amplitude of the binary system.
• Applied the inclination-dependent mass function to estimate the black hole mass, assuming jet ejections are perpendicular to the orbital plane.
• Used the measured radial velocity amplitude and orbital period to constrain the mass function and infer the black hole mass.
• Assessed the consistency of the derived mass with existing models of X-ray variability and QPO behavior in microquasars.
• Evaluated the implications for binary evolution scenarios and the stability of QPO frequencies in GRS 1915+105 and GRO J1655-40.

Experimental results

Research questions

• RQ1 What is the identity of the donor star in the GRS 1915+105 binary system?
• RQ2 What is the orbital period and radial velocity amplitude of the system as measured from near-infrared spectroscopy?
• RQ3 What is the mass of the black hole in GRS 1915+105, given the orbital parameters and jet orientation assumptions?
• RQ4 How does the derived black hole mass affect interpretations of the system's large-amplitude X-ray variability?
• RQ5 What do the results imply for models explaining the stable QPO frequencies observed in GRS 1915+105 and GRO J1655-40?

Key findings

• The donor star in GRS 1915+105 was successfully identified through near-infrared spectroscopy.
• The orbital period and radial velocity amplitude of the binary system were measured from the spectroscopic data.
• The black hole mass in GRS 1915+105 was determined to be 14 ± 4 solar masses, based on the mass function and jet orientation assumptions.
• The derived black hole mass provides critical constraints on models of large-amplitude X-ray variability in the system.
• The mass measurement supports specific binary formation scenarios involving high-mass X-ray binaries with compact orbits.
• The results are consistent with models explaining the stable QPO frequencies in GRS 1915+105 and GRO J1655-40, particularly those involving relativistic precession or disk-magnetosphere interactions.