Bibcode
Milone, A. P.; Villanova, S.; Bedin, L. R.; Piotto, G.; Carraro, G.; Anderson, J.; King, I. R.; Zaggia, S.
Bibliographical reference
Astronomy and Astrophysics, Volume 456, Issue 2, September III 2006, pp.517-522
Advertised on:
9
2006
Journal
Citations
39
Refereed citations
36
Description
In this paper we present a new, accurate determination of the three
components of the absolute space velocity of the Galactic globular
cluster NGC 6397 (l≃338°, b≃-12°). We used three
HST/WFPC2 fields with multi-epoch observations to obtain astrometric
measurements of objects in three different fields in this cluster. The
identification of 33 background galaxies with sharp nuclei allowed us to
determine an absolute reference point and measure the absolute proper
motion of the cluster. The third component was obtained from radial
velocities measured from spectra from the multi-fiber spectrograph
FLAMES at UT2-VLT. We find (μ_α cosδ,
μ_δ)J2000.0 = (+3.39 ± 0.15, -17.55 ± 0.15) mas
yr-1 and V_rad = +18.36 ± 0.09 (±0.10) km
s-1. Assuming a Galactic potential, we calculate the cluster
orbit for various assumed distances and briefly discuss the
implications.