Central Bureau for Astronomical Telegrams
IAUC 4490: PSR 0656+14
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Read IAUC 4491
Circular No. 4490
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
PSR 0656+14
F. A. Cordova, Los Alamos National Laboratory; R. M. Hjellming,
National Radio Astronomy Observatory; K. O. Mason, Mullard Space
Science Laboratories; and J. Middleditch, Los Alamos National
Laboratory, communicate: "We find evidence that the 0.385-s radio
pulsar PSR 0656+14 is an ultrasoft x-ray source. The x-ray source
position, measured with the Einstein satellite's High Resolution Imager
(HRI), is R.A. = 6h56m58.01, Decl. = +14 18'30.7 (equinox 1950.0),
with an uncertainty radius of 4". A measurement was made with the
Very Large Array (VLA) to locate better the radio position of the
pulsar, which has a large (5') uncertainty in the catalogue of
Manchester and Taylor (1981, A.J., 86, 1953). An unresolved radio
source was found at R.A. = 6h56m57.931 +/- 0s.01, Decl. = +14 18'33.7
+/- 0".2 (equinox 1950.0), corresponding to the x-ray source position.
Observations with the VLA reveal a source spectrum (4.8 mJy at 1.49
GHz, 3.9 mJy at 1.64 GHz, and 0.6 mJy at 4.9 GHz) and the very high
linear polarization (80 percent at both 1.49 and 1.64 GHz)
characteristic of radio pulsars. X-ray pulse height data from the
Einstein Imaging Proportional Counter (IPC) give a countrate for
the source of 0.32 cts/s in the energy region 0.2-0.8 keV, and 0.04
cts/s in the energy region 0.8-3.5 keV. The HRI, which is most
sensitive to photons between 0.15 and 1.5 keV, gives a countrate of
0.27 cts/s. These data indicate a very soft x-ray spectrum. Power
spectral analysis of the IPC data shows a modulation at the 0.385-s
pulsar spin period with an amplitude of 18 +/- 6 percent, but this is
only a 3-sigma detection. Power at the same frequency in the HRI data
is at the 2-sigma level. Deep, multicolor, CCD optical plates of the
region, using the Isaac Newton telescope on La Palma, reveal no
optical counterpart to the x-ray/radio source to limiting magnitudes
of 22 in the V band, 21.5 in R, and 21 in I. The association of
soft x-rays with PSR 0656+14 supports the distance estimate of
< 500 pc derived from its dispersion measure. This, together with
the recent measurement of the period derivative for the pulsar, 54
x 10E-15 s/s (Domingue et al. 1986, A.Ap. 161, 303), which implies a
relatively young age of 1.0 x 10E5 years, is consistent with the
suggestion of Nousek et al. (1981, Ap.J. 248, 152) that the 20-deg-
diameter Gemini-Monoceros soft x-ray enhancement may be a supernova
remnant resulting from the explosion of PSR 0656+14."
1987 November 17 (4490) Daniel W. E. Green
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