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A kinematic check of the distance scale of Galactic Cepheids

Thorsbro, Brian LU (2014) In Lund Observatory Examensarbeten ASTK01 20141
Department of Astronomy and Theoretical Physics - Has been reorganised
Lund Observatory - Has been reorganised
Abstract
A selection of well known period luminosity relations for cepheid variables are studied under the assumption that cepheid variables have a mean vertical velocity of zero in the galactic plane. Proper motion data from Hipparcos and Thyco-2 catalogues are coupled with the distances obtained from applying the period luminosity relations on a database of known classical cepheids to calculate the velocities of the cepheids. A statistical analysis is performed on the velocities to identify the best sample of cepheids to perform the kinematic check on. Two samples are found depending on whether the period luminosity relation has a colour term or not. Examining the samples leads to rejecting one sample and the other sample shows that in order to... (More)
A selection of well known period luminosity relations for cepheid variables are studied under the assumption that cepheid variables have a mean vertical velocity of zero in the galactic plane. Proper motion data from Hipparcos and Thyco-2 catalogues are coupled with the distances obtained from applying the period luminosity relations on a database of known classical cepheids to calculate the velocities of the cepheids. A statistical analysis is performed on the velocities to identify the best sample of cepheids to perform the kinematic check on. Two samples are found depending on whether the period luminosity relation has a colour term or not. Examining the samples leads to rejecting one sample and the other sample shows that in order to agree with the above assumption the solar vertical velocity is unlikely to be around the conventional 7 km/s, but has to be lowered to around 6.5 km/s or less; or the period luminosity relations have to be corrected on the order of -0.2 mag, i.e.\ a little brighter than previously assumed. It is further argued that the correction to the period luminosity relations is more in agreement with other studies than lowering the solar velocity. (Less)
Please use this url to cite or link to this publication:
author
Thorsbro, Brian LU
supervisor
organization
course
ASTK01 20141
year
type
M2 - Bachelor Degree
subject
keywords
cepheid, period-luminosity relation, distance scale, kinematics
publication/series
Lund Observatory Examensarbeten
report number
2014-EXA84
language
English
id
4463277
date added to LUP
2014-09-09 10:45:13
date last changed
2014-09-09 10:45:13
@misc{4463277,
  abstract     = {{A selection of well known period luminosity relations for cepheid variables are studied under the assumption that cepheid variables have a mean vertical velocity of zero in the galactic plane. Proper motion data from Hipparcos and Thyco-2 catalogues are coupled with the distances obtained from applying the period luminosity relations on a database of known classical cepheids to calculate the velocities of the cepheids. A statistical analysis is performed on the velocities to identify the best sample of cepheids to perform the kinematic check on. Two samples are found depending on whether the period luminosity relation has a colour term or not. Examining the samples leads to rejecting one sample and the other sample shows that in order to agree with the above assumption the solar vertical velocity is unlikely to be around the conventional 7 km/s, but has to be lowered to around 6.5 km/s or less; or the period luminosity relations have to be corrected on the order of -0.2 mag, i.e.\ a little brighter than previously assumed. It is further argued that the correction to the period luminosity relations is more in agreement with other studies than lowering the solar velocity.}},
  author       = {{Thorsbro, Brian}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Lund Observatory Examensarbeten}},
  title        = {{A kinematic check of the distance scale of Galactic Cepheids}},
  year         = {{2014}},
}