MACHO project photometry of RR Lyrae stars in the Sagittarius dwarf galaxy

C. Alcock, R. A. Allsman, D. R. Alves, T. S. Axelrod, A. C. Becker, D. P. Bennett, K. H. Cook, K. C. Freeman, K. Griest, J. A. Guern, M. J. Lehner, S. L. Marshall, D. Minniti, B. A. Peterson, M. R. Pratt, P. J. Quinn, A. W. Rodgers, C. W. Stubbs, W. Sutherland, D. L. Welch

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


We report the discovery of 30 type a, b RR Lyrae (RRab) stars that are likely members of the Sagittarius dwarf galaxy (Sgr). Accurate positions, periods, amplitudes, and magnitudes are presented. Their distances are determined with respect to RRab stars in the Galactic bulge found also in the MACHO 1993 data. For R = 8 kpc, the mean distance to these stars is D = 22 ± 1 kpc, smaller than previous determinations for this galaxy. This indicates that Sgr has an elongated main body extending for more than 10 kpc, which is inclined along the line of sight, with its northern part (in Galactic coordinates) closer to us. The size and shape of Sgr give clues about the past history of this galaxy. If the shape of Sgr follows the direction of its orbit, the observed spatial orientation suggests that Sgr is moving away from the Galactic plane. Also, Sgr stars may be the sources of some of the microlensing events seen toward the bulge.

Original languageEnglish
Pages (from-to)217-222
Number of pages6
JournalAstrophysical Journal
Issue number1 PART I
Publication statusPublished - 1997


  • Galaxies: distances and redshifts
  • Galaxies: individual (Sgr)
  • Galaxies: kinematics and dynamics
  • Galaxy: halo
  • Local Group
  • Stars: variables: other (RR Lyrae)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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