GSPCII Program

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GSPC-II Program

• GOAL
• extend GSPC-I photometry to B V 20
• add R band to calibrate red second-epoch surveys

• HOW
• take B,V,R CCD exposures centered at GSPC-I
  faintest star OR
• conveniently close to POSS-II centers (for
  POSS-II offset plates)

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The Data

• Given the long time span of this survey project,
  data come from different telescopes as well as
  different CCD cameras
• Size of camera fields vary from 3.5 arc
  minutes to 20 arc minutes
• Pixel scale ranges from 0.35 arc seconds/pixel
  to 0.7 arc seconds/pixel
• When appropriate, both long and short exposures
  are acquired
• Pre-selected sets of standard stars from the
  Landolt catalog are observed each night
• Common fields are also regularly observed

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Example of CCD frames taken at the 0.9m ESO
Dutch
poor
Crowded
medium
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Telescope usage and number of GSPC-II sequences
collected (as of October 2001)
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Relevant Numbers

• Target sequences are 1780 (1478 GSPC-I centers
  302 POSS-II new sequences)
• Current in-house catalog contains 1619
  sequences, of which 776 in the north and 856 in
  the south
• data from one and a half runs performed in
  semester 01A still to be included in catalog
• two more runs of 7 nights each, one at the
  ING/JKT and one at the CTIO 0.9m, to be performed
  in November/December

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Sky Coverage
1794 GSPCII targets - 1679 observed - 115
still remain
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Magnitude limit of current catalog sequences
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Number of stars/sequence in current catalog
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GSPC-II Reduction Pipeline

• Photometry carried out with pipeline software
  (ARLO, Casalegno 1998) developed under IRAF
  2.10.4
• Astrometry done within ARLO - fit to DSS
  positions
• Catalog of all frame data is a flat ASCII file
  including photometric, astrometric and other
  relevant information about the original exposures
• IRAF tables including additional statistical
  information are generated along with the frame
  catalogs
• Object naming performed in IRAF/IDL (naming
  convention S001-AAAA, S002-AAAB, etc)

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Photometric Accuracy

• Only fits to Landolt stars with rms better than
  0.05 are accepted
• Aperture photometry is carried out with fixed
  radius (2.3FWHM or lt 4.5) therefore not reliable
  in crowded fields
• PSF photometry more stable, but need to be
  checked for systematic errors in case of bad
  choice of template stars for analytical PSF
• Zero-point errors of transformation to standard
  system is also critical because it induces a
  photometric error of comparable magnitude

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Released Sequences

• 622 GSPC-II fields ( Bucciarelli, Garcia,
  Casalegno et al. 2001, AA 368, 335), 744
  northern and 444 southern fields
• data are from KPNO, CTIO and ESO, for a total of
  153 observing nights
• Aperture photometry only
• selection criteria based on agreement between
  Aperture and PSF photometry

Linear regression M(apt) - M(psf) Z k M(apt)
sequences for which k lt 0.01 and rms lt 0.3 mag
were retained
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Zero-point errors Cumulative Distributions
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GSPC-I/GSPC-II Comparison
597 V objects rms 0.07 mag, mean 0.001 mag
380 B objects rms 0.06 mag, mean 0.003
mag
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Comparison of 10 common fields CTIO/KPNO
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Comparison of 47 common fields CTIO/ESO
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Summary

• 95 of GSPC-II data secured and practically all
  reduced
• Spin-off of observing activity
• 622 photometric sequences made available to
  community
• QA of new set of sequences for second release in
  progress
• Plan to put images, along with photometric
  reduction files, on-line for easy retrieval