Central Bureau for Astronomical Telegrams
IAUC 6173: X-RAY N 1994 IN Sco; NRAO 530
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Circular No. 6173
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 TWX 710-320-6842 ASTROGRAM CAM
MARSDEN@CFA.HARVARD.EDU or GREEN@CFA.HARVARD.EDU (science)
X-RAY NOVA 1994 IN SCORPIUS
C. Bailyn and J. Orosz, Yale University; J. McClintock, Center
for Astrophysics; and R. Remillard, Massachusetts Institute of
Technology, report: "Optical spectroscopy of GRO J1655-40 obtained
with the Cerro Tololo (CTIO) 4-m telescope (+ RC spectrograph) from
Apr. 29 to May 3 reveals a spectrum containing high-excitation
emission lines, superposed on an F- or early-G-type stellar
absorption spectrum. The latter is presumably due to the secondary
star. The observed velocity of the secondary exhibits clear
variations that indicate an orbital period of 2.62 +/- 0.03 days
with maximum redshift at May 1.538 UT and a velocity semi-amplitude
of 231 +/- 3 km/s. The inferred mass function of the binary system
is 3.35 +/- 0.14 solar masses. This value is above the maximum
stable mass of a neutron star, confirming the generally-held belief
that the compact primary of this binary system is a black hole.
Photometry of the source with the CTIO 0.9-m and 1.5-m telescopes,
obtained by us and by S. Barnes and M. Schaefer (Yale) and M.
Postman (Space Telescope Science Institute) between Mar. 17 and May
2, clearly shows a lightcurve in which primary and secondary
eclipses recur at a period compatible with the spectroscopic
results. However, an exact photometric ephemeris is hard to
determine due to night-to-night variations in overall luminosity;
offsets of up to +/- 0.05 in phase from the spectroscopic phase
given above were observed. The existence of eclipses indicates
that the inclination of the system is near 90 deg. In this case,
the mass of the primary is between 4.0 and 5.2 solar masses for
secondary star masses between 0.4 and 1.3 solar masses."
NRAO 530
G. C. Bower, J. R. Forster, M. Wright, and D. Backer,
University of California, Berkeley, write: "We report an unusual
flare in this QSO (cf. Pauliny-Toth 1966, Ap.J. Suppl. 13, 65; V =
18.5, z = 0.902), which has an extremely flat spectrum and was
discovered during a recent very-long-baseline interferometry
experiment at wavelength 3 mm. The flux density at 86 GHz
(measured with the Hat Creek interferometer) has varied between 8.5
and 15 Jy in the last three months and may now be declining.
Observations with the Kitt Peak 12-m telescope at 232 GHz reveal a
flux density of 6.5 Jy on May 4. From 1986 to 1994, the 3-mm flux
density was between 3 and 7 Jy and kept a steady average of 5.5 Jy.
At centimeter wavelengths, this source is noted for its steady flux
density of 5 Jy. Please communicate observations at other bands to
gcbower@astron.berkeley.edu."
1995 May 13 (6173) Daniel W. E. Green
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