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J/PASP/110/1012 New double stars from HST (Schneider+, 1998)
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Duplicity in Hubble Space Telescope Guide Stars:
Fine Guidance Sensor serendipitous survey results.
Schneider G., Hershey J.L., Wenz M.T.
<Publ. Astron. Soc. Pac. 110, 1012 (1998)>
=1998PASP..110.1012S
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ADC_Keywords: Stars, double and multiple ; Interferometry
Mission_Name: HST
Abstract:
Data from the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS)
interferometers, covering 22 months of guide-star acquisition
operations, have been analyzed for evidence of stellar duplicity. The
data comprise a survey of observed guide stars, all of which are taken
from the HST Guide Star Catalog, ranging in magnitude from 9 to 14.
The survey results cover a parameter space for the newly found
doubles, for the fainter stars, which are of smaller limiting angular
separations than in any previous surveys. The normal HST engineering
telemetry data from 13,979 acquisitions on 4882 stars have been
processed. The FGS guidance data can reveal duplicity with separations
ranging from approximately 30mas, for the brighter stars, with small
magnitude differences, up to the neighborhood of 500mas, and in some
cases to 1000mas. The fraction of guide stars indicating duplicity is
a function of the statistical criteria used but is over 5% at a very
high level of confidence. It is possible that if some of the brighter
and closer pairs could be identified as nearby, then their orbital
motions would be rapid enough to allow a mass and distance
determination on a timescale of a decade if followed with ground-based
interferometric and spectroscopic instruments. A brief catalog of
doubles is given, nearly all of which are of certain duplicity.
Information for accessing on-line catalogs of large numbers of stars
with lesser, but nevertheless strong, probabilities of duplicity and
also for the solutions for duplicity from all acquisitions is
provided.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 120 278 Selected doubles from HST acquisition data
names.dat 23 2348 List of Observed HST Guide Stars Searched
For Duplicity
acquis.dat 204 16164 *Planned Acquisition Description
doubles.dat 85 63515 *Double Star Solutions
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Note on acquis.dat, doubles.dat :
Copied at http://nicmosis.as.arizona.edu:8000/pub/gsdoubles.html
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See also:
http://nicmosis.as.arizona.edu:8000/pub/gsdoubles.html :
Catalog of HST Guide Star acquisitions serendipitous duplicity survey
I/220 : The HST Guide Star Catalog, Version 1.1 (Lasker+ 1992)
I/254 : The HST Guide Star Catalog, Version 1.2 (Lasker+ 1996)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension, GSC position (J2000.0)
4- 5 I2 min RAm Right ascension, GSC position (J2000.0)
7- 10 F4.1 s RAs Right ascension, GSC position (J2000.0)
12 A1 --- DE- Declination sign (J2000.0)
13- 14 I2 deg DEd Declination, GSC position (J2000.0)
16- 17 I2 arcmin DEm Declination, GSC position (J2000.0)
19- 20 I2 arcsec DEs Declination, GSC position (J2000.0)
22- 31 A10 --- GSC Guide Star Catalog number (G1)
34- 37 I4 yr Epoch.Y Year of the epoch of observation
39- 41 I3 d Epoch.D Day of the epoch of observation
43- 44 I2 h Epoch.h Hour of the epoch of observation
45 A1 --- --- [:]
46- 47 I2 min Epoch.m Minute of the epoch of observation
49- 53 F5.2 mag mag Magnitude from the GSC (1)
55- 56 A2 --- XY Symbol for the FGS coordinate of
duplicity detection (2)
58- 63 F6.1 mas Sep Separation (3)
65- 69 F5.1 deg PA Position angle (4)
71- 74 F4.2 mag Dmag Magnitude difference between the components as
computed from the ratio of the amplitudes of
the component S-curves (5)
76- 79 F4.2 mag e_mag ? Standard error of the observations that
formed the delta magnitude mean if more
than one observation
81- 82 I2 --- o_SepX ? Number of observations in the X coordinate
combined to form the entries in the table line
84- 90 F7.1 mas SepX ? Mean of the X separations, or the X separation
if only one observation
92- 95 F4.1 mas seX ? Standard error of the observations that formed
the X mean
97-100 F4.1 mas e_SepX ? Error of the mean separation X
102-103 I2 --- o_SepY ? Number of observations in the Y coordinate
combined to form the entries in the table line
105-110 F6.1 mas SepY ? Mean of the Y separations, or the Y separation
if only one observation
112-115 F4.1 mas seY ? Standard error of the observations that formed
the Y mean
117-120 F4.1 mas e_SepY ? Error of the mean separation Y
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Note (1): Photographic V in northern hemisphere, J in southern hemisphere;
see GSC references
Note (2): X: X-only duplicity
Y: Y-only duplicity
XY: duplicity in both X and Y
Note (3): For a single coordinate, the separation is only the projection of the
separation of the double onto the FGS coordinate of observation.
For a two-coordinate observation, it is the angular separation of
the components. The scale errors of the separations are estimated to
be at the level of a few parts per thousand.
Note (4): For one-coordinate observations, it is the position angle (equatorial
coordinates) of the FGS coordinate at the time of observation
(0{deg}-180{deg}).
For a two-coordinate observation, it is the traditional double-star
position angle, the angle from North to East of the fainter component
relative to the brighter component.
Note (5): The bandpass of the FGSs in guidance is centered near the V
photometric band but spans spectra that range from the U to the R
bands, the mid-3000s to 7000s in Angstrom units.
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Byte-by-byte Description of file: names.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Filename Source catalog file containing entry
13- 22 A10 --- GSC Guide star catalog ID number (G1)
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Byte-by-byte Description of file: acquis.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Filename Source catalog file containing entry
13- 22 A10 --- GSC Guide star catalog ID number (G1)
24- 32 F9.5 deg RAdeg J2000.0 GS right ascension
34- 42 F9.5 deg DEdeg J2000.0 GS declination
44- 52 F9.5 deg Roll Spacecraft roll angle (360 - Orient)
54- 62 F9.5 deg Sunangle Angular distance of V1 axis to sun
64- 68 F5.2 mag OBmag Observed magnitude in FGS instrumental system
70- 74 F5.2 mag CTmag Magnitude in guide star catalog
76- 80 A5 --- Filtr Filter used in FGS for acquisition
82- 86 A5 ms FESTM Fine error sensor averaging time (mnemonic)
88 I1 --- FGS [1/3] FGS interferometer number (1)
90 I1 --- Acq [1/3] Acquisition type (2)
92- 99 A8 --- CPName Guiding scenario (PCS logic)
101-104 I4 --- LCT Low (PMT) count threshold for star detection
106-110 F5.2 arcsec WdlX Walk-down length along X axis
112-116 F5.2 arcsec WdlY Wald-down length along Y axis
118-126 F9.5 deg RAV1deg RA J2000.0 of S/C V1 axis
128-136 F9.5 deg DEV1deg DEC J2000.0 of S/C V1 axis
138-144 F7.5 --- K1X FGE X-axis interferometer coefficient
146-152 F7.5 --- K1Y FGE Y-axis interferometer coefficient
154-160 F7.5 --- K3X FGE X-axis Q-signal limit
162-168 F7.5 --- K3Y FGE Y-axis Q-signal limit
170 I1 --- PP [0/1] Planetary Parallax (S/C rate)
correction, 0 = off, 1 = on
172-179 A8 --- RefCurve Reference S-curve used in fitting process
181-184 I4 arcsec PicX Predicted FGS X coordinate of star
186-189 I4 arcsec PicY Predicted FGS Y coordinate of star
191-194 I4 yr Epoch.Y Planned U.T. of acquisition start
195 A1 --- --- [.]
196-198 I3 d Epoch.D [0/365] Planned U.T. of acquisition start
199 A1 --- --- [:]
200-201 I2 h Epoch.h [0/24] Planned U.T. of acquisition start
202 A1 --- --- [:]
203-204 I2 min Epoch.m [0/60] Planned U.T. of acquisition start
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Note (1): For 1, FGS1 replacement by FGS1R on 1997 February, Servicing Mission
Note (2): Acquisition type:
1 = Double-star fitting for FGS in lock case (2-star FL)
2 = Double-star fitting for FGS in no-lock case (2-star CT)
3 = One-star fitting for FGS in lock case (1-star FL)
See Sect. 2, 3.2, and 3.3 of the paper.
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Byte-by-byte Description of file: doubles.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Filename Source catalog file containing entry
13 A1 --- n_Filename [CDEF] Index for the different solutions
15- 18 A4 --- Code Type of fitting process/solution (1)
20- 28 F9.1 mas Null1 Relative position of star-1 X or Y null
30- 38 F9.1 mas Null2 Relative position of star-2 X or Y null
40- 43 F4.2 --- B1 Star-1 amplitude normalized to reference S-curve
45- 48 F4.2 --- B2 Star-2 amplitude normalized to reference S-curve
51- 58 F8.1 mas Sepmas Separation of stars
60- 64 F5.2 mag Dmag Magnitude difference between the components as
computed from the ratio of the amplitudes of
the component S-curves (2)
66- 69 F4.1 mas e_Null1 1-sigma error in star-1 null position
71- 74 F4.1 mas e_Null2 1-sigma error in star-2 null position
75- 79 F5.2 --- e_B1 ? 1-sigma error in star-1 to ref amplitude ratio
80- 84 F5.2 --- e_B2 ? 1-sigma error in star-2 to ref amplitude ratio
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Note (1): Code table:
Col 1: S/D for Single/Double
Col 2: X/Y indicates which axis of interferometer
Col 3: L/N for Lock/Nolock
Col 4: W/C for Wide/Close solution
Note (2): The bandpass of the FGSs in guidance is centered near the V
photometric band but spans spectra that range from the U to the R
bands, the mid-3000s to 7000s in angstrom units.
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Global Notes:
Note (G1): this column contains either the GSC designation (Cat. <I/220>)
when the leftmost digit is a 0, or a designation in one of the
"Special Catalogs" when the leftmost digit is a 3 or 4. These "Special
Catalogs" were constructed for calibration targets or for regions of
the sky where the GSC, derived from Schmidt Survey plates, may not
have adequate data.
Acknowledgements: Glenn Schneider <gschneider@stsci.edu>
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(End) James Marcout, Patricia Bauer [CDS] 09-Nov-1998