Distance to M33 determined from magnitude corrections to Hubble's original cepheid photometry

Journal Article · Mon Aug 01 04:00:00 EDT 1983 · Astron. J.; (United States)

DOI:https://doi.org/10.1086/113400· OSTI ID:5831784

Sandage, A

New photoelectric photometry in Selected Area 45, and transfers from a faint photoelectric sequence adjacent to the south-preceding arm in M33 have been made to the comparison stars for Hubble's Cepheids in M33. Progressive magnitude corrections are required to Hubble's M33 scales, reaching 2.8 mag at the limit of the Mount Wilson 2.5-m Hooker reflector. Hubble's Cepheid light curves have been corrected to the B photoelectric system, and new photometric parameters are given for 35 of his variables. The P-L relation agrees in zero point to within 0.2 mag of the P-L relation from independent data by Sandage and Carlson for 12 new Cepheids in an outlying region of M33. Application of an adopted absolute P-L relation, calibrated by Martin, Warren, and Feast, to these data gives an apparent blue modulus of (m-M)/sup AB//sub M33/ = 25.35, which is 0.67 mag fainter than a previously adopted value, and represents a factor of 4.2 increase of Hubble's earliest distance. Three consequences of this larger apparent distance modulus are (1) the mean absolute magnitude of the first three brightest red supergiants is M/sup max//sub left-angle-bracketV/(3)> = -8.7 rather than approx.-8.0 in M33, complicating but not destroying use of red supergiants as distance indicators, (2) the mean absolute magnitude of the two brightest blue irregular supergiant variables is M/sub left-angle-bracketB/(2)> = -9.95, which is close to the value for the brightest known supergiants in the galaxy, and (3) the absolute magnitude of M33 itself is brighter than heretofore assumed.

• Research Organization: Mount Wilson and Las Campanas Observatories, Carnegie Institution of Washington, Pasadena, California 91101
• OSTI ID: 5831784
• Journal Information: Astron. J.; (United States), Journal Name: Astron. J.; (United States) Vol. 88:8; ISSN ANJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102 -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CEPHEIDS
CORRECTIONS
DISTANCE
ERRORS
GALAXIES
LUMINOSITY
OPTICAL PROPERTIES
PHOTOMETRY
PHYSICAL PROPERTIES
PULSATING VARIABLE STARS
STARS
VARIABLE STARS