J/AJ/121/1192 Proper-motion measurements with the VLA (McGary+, 2001)
Proper-motion measurements with the VLA.
I. Wide-field imaging and pulse-gating techniques.
McGary R.S., Brisken W.F., Fruchter A.S., Goss W.M., Thorsett S.E.
<Astron. J. 121, 1192 (2001)>
=2001AJ....121.1192M 2001AJ....121.1192M
ADC_Keywords: Pulsars ; Proper motions ; Interferometry
Keywords: astrometry - pulsars: general - techniques: interferometric
Abstract:
The pulsar velocity distribution provides information about the binary
history of pulsar progenitors, as well as the asymmetries of the
supernova events in which pulsars are born. Studies of local pulsars
present a biased view of this distribution, because they
preferentially select low-velocity pulsars that have remained near
their birthplaces in the Galactic plane. Using the VLA, we have
studied the proper motions of a large sample of distant pulsars. These
pulsars are generally faint, and the expected proper motions are
small. In this paper, we describe the data analysis techniques that we
have developed to allow precise astrometric measurements of faint
sources with the VLA. These techniques include "gating" the VLA
correlator to increase the signal-to-noise ratio of the pulsar by
gathering data only during the pulse. Wide-field imaging techniques,
including multiband imaging to account for bandwidth smearing, were
used to allow identification of multiple in-beam background sources
for astrometric calibration. We present the analysis of three pulsars
and demonstrate that astrometric accuracy of about 10 mas can be
obtained for individual sources with our technique, allowing
measurement of proper motions with errors of only a few
milliarcseconds per year over our 7 year baseline.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 74 44 Reference sources for proper motions
table2.dat 69 3 Proper motions of B0919+06, B1237+25 and B1937-26
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Pulsar name, Bhhmm+dd (1)
10- 13 F4.1 mJy F20 The 20cm flux density of reference
15- 17 F3.1 mJy e_F20 Uncertainty in F20
19- 20 I2 h RAh Right Ascension of reference (J2000)
22- 23 I2 min RAm Right Ascension of reference (J2000)
25- 29 F5.2 s RAs Right Ascension of reference (J2000)
31- 33 F3.2 s e_RAs Uncertainty in RAs
35 A1 --- DE- Sign of the reference Declination (J2000)
36- 37 I2 deg DEd Declination of reference (J2000)
39- 40 I2 arcmin DEm Declination of reference (J2000)
42- 45 F4.1 arcsec DEs Declination of reference (J2000)
47- 48 F2.1 arcsec e_DEs Uncertainty in DEs
50- 54 I5 arcsec dRA RA offset from pulsar position
56- 60 I5 arcsec dDE Dec offset from pulsar position
62- 64 I3 mas/yr pmRA ? Proper Motion along RA
66- 67 I2 mas/yr e_pmRA ? Uncertainty in pmRA
69- 70 I2 mas/yr pmDE ? Proper Motion along Dec
72- 73 I2 mas/yr e_pmDE ? Uncertainty in pmDE
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Note (1): The objects are identified in Simbad as [MBF2001] JHHMMSS.ss+DDMMSS.s
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Pulsar Name
10- 12 F3.1 mJy F20 The 20cm flux density
14- 16 F3.1 mJy e_F20 Uncertainty in F20
18- 22 F5.1 mJy GF20 Gated 20cm flux density
24- 26 F3.1 mJy e_GF20 Uncertainty in GF20
28- 29 I2 yr Epoch1 Epoch of observation (1900+)
30 A1 --- n_Epoch1 [a] a: gated observation
32- 33 I2 yr Epoch2 Epoch of observation (1900+)
34 A1 --- n_Epoch2 [a] a: gated observation
36- 37 I2 yr Epoch3 Epoch of observation (1900+)
38 A1 --- n_Epoch3 [a] a: gated observation
40- 41 I2 yr Epoch4 ? Epoch of observation (1900+)
42 A1 --- n_Epoch4 [a] a: gated observation
44- 45 I2 --- Num Number of reference objects used
47- 52 F6.1 mas/yr pmRA Proper motion along RA
54- 56 F3.1 mas/yr e_pmRA Uncertainty in pmRA
58- 61 F4.1 mas/yr pmDE Proper motion along Dec
63- 65 F3.1 mas/yr e_pmDE Uncertainty in pmDE
67- 69 F3.1 --- Cov Covariance of RA & Dec proper motion
components
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 24-Apr-2001