432 research outputs found
The mass of the black hole in GRS 1915+105: new constraints from IR spectroscopy
GRS 1915+105 has the largest mass function of any Galactic black hole system,
although the error is relatively large. Here we present spectroscopic analysis
of medium-resolution IR VLT archival data of GRS 1915+105 in the K-band. We
find an updated ephemeris, and report on attempts to improve the mass function
by a refinement of the radial velocity estimate. We show that the spectra are
significantly affected by the presence of phase-dependent CO bandhead emission,
possibly originating from the accretion disc: we discuss the impact this has on
efforts to better constrain the black hole mass. We report on a possible way to
measure the radial velocity utilising apparent H-band atomic absorption
features and also discuss the general uncertainty of the system parameters of
this well-studied objectComment: 7 pages, 7 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Society Main Journa
Addendum: "The Dynamics of M15: Observations of the Velocity Dispersion Profile and Fokker-Planck Models" (ApJ, 481, 267 [1997])
It has recently come to our attention that there are axis scale errors in
three of the figures of Dull et al. (1997, hereafter D97). D97 presented
Fokker-Planck models for the collapsed-core globular cluster M15 that include a
dense, centrally concentrated population of neutron stars and massive white
dwarfs, but do not include a central black hole. In this Addendum, we present
corrected versions of Figures 9, 10, and 12, and an expanded version of Figure
6. This latter figure, which shows the full run of the velocity dispersion
profile, indicates that the D97 model predictions are in good agreement with
the moderately rising HST-STIS velocity dispersion profile for M15 reported by
Gerssen et al. (2002, astro-ph/0209315). Thus, a central black hole is not
required to fit the new STIS velocity measurements, provided that there is a
sufficient population of neutron stars and massive white dwarfs. This
conclusion is consistent with the findings of Gerssen et al. (2002,
astro-ph/0210158), based on a reapplication of their Jeans equation analysis
using the corrected mass-to-light profile (Figure 12) for the D97 models.Comment: 4 pages, 4 figures, submitted to Ap
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