Advanced

Using Galactic Cepheids to verify Gaia parallaxes

Windmark, F.; Lindegren, Lennart LU and Hobbs, David LU (2011) In Astronomy & Astrophysics 530.
Abstract
Context. The Gaia satellite will measure highly accurate absolute parallaxes of hundreds of millions of stars by comparing the parallactic displacements in the two fields of view of the optical instrument. The requirements on the stability of the "basic angle" between the two fields are correspondingly strict, and possible variations (on the microarcsec level) are therefore monitored by an on-board metrology system. Nevertheless, since even very small periodic variations of the basic angle might cause a global offset of the measured parallaxes, it is important to find independent verification methods. Aims. We investigate the potential use of Galactic Cepheids as standard candles for verifying the Gaia parallax zero point. Methods. We... (More)
Context. The Gaia satellite will measure highly accurate absolute parallaxes of hundreds of millions of stars by comparing the parallactic displacements in the two fields of view of the optical instrument. The requirements on the stability of the "basic angle" between the two fields are correspondingly strict, and possible variations (on the microarcsec level) are therefore monitored by an on-board metrology system. Nevertheless, since even very small periodic variations of the basic angle might cause a global offset of the measured parallaxes, it is important to find independent verification methods. Aims. We investigate the potential use of Galactic Cepheids as standard candles for verifying the Gaia parallax zero point. Methods. We simulate the complete population of Galactic Cepheids and their observations by Gaia. Using the simulated data, simultaneous fits are made of the parameters of the period-luminosity relation and a global parallax zero point. Results. The total number of Galactic Cepheids is estimated at about 20 000, of which nearly half could be observed by Gaia. In the most favourable circumstances, including negligible intrinsic scatter and extinction errors, the determined parallax zero point has an uncertainty of 0.2 microarcsec. With more realistic assumptions the uncertainty is several times larger, and the result is very sensitive to errors in the applied extinction corrections. Conclusions. The use of Galactic Cepheids alone will not be sufficient to determine a possible parallax zero-point error to the full potential systematic accuracy of Gaia. The global verification of Gaia parallaxes will most likely depend on a combination of many different methods, including this one. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
stars: variables: Cepheids, space vehicles: instruments, parallaxes
in
Astronomy & Astrophysics
volume
530
publisher
EDP Sciences
external identifiers
  • wos:000291027400076
  • scopus:79956081183
ISSN
0004-6361
DOI
10.1051/0004-6361/201116929
language
English
LU publication?
yes
id
b32d1235-c6b9-464e-a1ab-ca483fae003b (old id 1986144)
date added to LUP
2011-06-29 15:42:04
date last changed
2017-10-01 04:18:53
@article{b32d1235-c6b9-464e-a1ab-ca483fae003b,
  abstract     = {Context. The Gaia satellite will measure highly accurate absolute parallaxes of hundreds of millions of stars by comparing the parallactic displacements in the two fields of view of the optical instrument. The requirements on the stability of the "basic angle" between the two fields are correspondingly strict, and possible variations (on the microarcsec level) are therefore monitored by an on-board metrology system. Nevertheless, since even very small periodic variations of the basic angle might cause a global offset of the measured parallaxes, it is important to find independent verification methods. Aims. We investigate the potential use of Galactic Cepheids as standard candles for verifying the Gaia parallax zero point. Methods. We simulate the complete population of Galactic Cepheids and their observations by Gaia. Using the simulated data, simultaneous fits are made of the parameters of the period-luminosity relation and a global parallax zero point. Results. The total number of Galactic Cepheids is estimated at about 20 000, of which nearly half could be observed by Gaia. In the most favourable circumstances, including negligible intrinsic scatter and extinction errors, the determined parallax zero point has an uncertainty of 0.2 microarcsec. With more realistic assumptions the uncertainty is several times larger, and the result is very sensitive to errors in the applied extinction corrections. Conclusions. The use of Galactic Cepheids alone will not be sufficient to determine a possible parallax zero-point error to the full potential systematic accuracy of Gaia. The global verification of Gaia parallaxes will most likely depend on a combination of many different methods, including this one.},
  author       = {Windmark, F. and Lindegren, Lennart and Hobbs, David},
  issn         = {0004-6361},
  keyword      = {stars: variables: Cepheids,space vehicles: instruments,parallaxes},
  language     = {eng},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {Using Galactic Cepheids to verify Gaia parallaxes},
  url          = {http://dx.doi.org/10.1051/0004-6361/201116929},
  volume       = {530},
  year         = {2011},
}