Central Bureau for Astronomical Telegrams
IAUC 3190: PERSISTENT X-RAY EMISSION FROM MXB1659-29; OTHER X-RAY BURST SOURCES; MCG 5-23-16; T Tau
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Read IAUC 3191
Circular No. 3190
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Cable Address: SATELLITES, NEWYORK Telex: 921428
Telephone: (617) 864-5758
PERSISTENT X-RAY EMISSION FROM MXB1659-29
W. Lewin, J. Hoffman, H. Marshall, F. Primini, W. Wheaton, L.
Cominsky, G. Jernigan and W. Ossman, Massachusetts Institute of
Technology, report the discovery of persistent x-ray emission from
a source located within 5' of a 0o.6-long line with end points R.A. =
l6h57m.6, Decl. = -30o08' and R.A. = 16h59m.8, Decl. = -29o42' (equinox
1950.0). The highly variable source was observed by SAS 3 between Mar.
6d23h08m and 8d13h43m UT. On two occasions (1.6 hr apart) the
source showed a rapid (in ~ 40s) decrease in intensity (by a factor
of 4) to a low state that lasted ~ 15.5 min in both cases. The
transition to the high state also took place in ~ 40s. In the high
state the flux is ~ 8 percent that of the Crab (1-10 keV). It is
likely that the persistent emission comes from MXB1659-29 (cf. IAUC
2994). This burst source has been observed by SAS 3 several times.
On each occasion it produced about 10 bursts per day at very regular
intervals, however, and no persistent emission was ever observed
(Lewin 1977, Ann. N.Y. Acad. Sci. 302, 213). This time only
one burst (on Mar. 8d07h47m32s UT) was detected in the entire
39-hr observing period.
G. Share, K. Wood, D. Yentis, N. Johnson, S. Shulman, J.
Meekins, W. Evans, E. Byram, T. Chubb and H. Friedman, Naval Research
Laboratory, report that the source was observed by the large-area
survey instrument on HEAO 1 during seven quick-look scans made
during Mar. 6-10. Its 1-10-keV intensity was ~ 5 x 10**-10 erg cm**-2
s**-1 during six of the ~ 5s scans but was < 10**-10 erg cm**-2 s**-1
during the scan on Mar. 9d10h09m54s UT. The corners of the HEAO A1
error box are: R.A. = 16h58m05s, Decl. = -29o45'.8; 16h57m59s, -29o57'.7;
16n59m48s, -30o00'.2; 16h59m54s, -29o48'.3 (equinox 1950.0).
R. Griffiths, M. Johnston, H. Bradt, R. Doxsey, H. Gursky, D.
Schwartz and J. Schwarz, Center for Astrophysics and Massachusetts
Institute of Technology, report that HEAO-1 scanning modulation
collimator (A3) observations near Mar. 7d12h and 9d10h UT of the
persistent x-ray source reported above by Lewin et al. and by Share et
al. result in a small (~ 1.3 arcmin**2) error box having a center at
R.A. = 16h58m54s.8, Decl. = -29o49'55" (equinox 1950.0) and corners at R.A. =
16h58m54s.5, Decl. = -29o52'02"; 16h58m53s.5, -29o49'00"; 16h58m55s.1,
-29o47'48"; 16h58m56s.1, -29o50'50". Of the several possible A3
positions this is the only one that falls entirely within the HEAO
A1 error box. It is also within the SAS-3 error ellipse for the
burster MXB1659-29 (IAUC 2994). Three other possible A3 positions
fall near but outside the edges of the A1 box. The globular cluster
NGC 6266, which falls within the SAS-3 error box for the persistent
source, lies just outside the A1 box and is independently
excluded by the A3 positions. It can be noted that the above
source locations are consistent with the 4o-long error box for 4U
1704-30 (3.1 Uhuru cts/s). Another possible example of a similar
type of persistent or transient emission from a burster is that of
MX1608-52 (Fabbiano et al. 1978, Astrophys. J. Lett. Apr. 15).
OTHER X-RAY BURST SOURCES
Hoffman, Lewin, Marshall, Primini, Wheaton and Cominsky also
report that MXB1728-34 has been observed with SAS 3 since Mar.
8d13h43m UT. Seven bursts were detected, on Mar. 8d15h04m17s,
8d19h31m04s, 9d21h24m13s, 10d02h11m10s, 10d08h10m335, 10d14h00m34s
and 10d18h41m18s; at the request of the SAS-3 Group the last of
these bursts was also observed by HEAO 1. The SAS-3 burst observations
will continue through Mar. 15. The Rapid Burster MXB1730-335
was observed at the same time but no bursts were detected.
MCG 5-23-16
F. Pineda and H. W. Schnopper, Center for Astrophysics, report
the detection of x-ray emission from a ~ 1' diameter (90-percent
confidence) region containing the galaxy MCG 5-23-16. The 2-10-keV
flux is ~ 1 x 10**-10 erg cm**-2 s**-1 The galaxy lies within the error
boxes quoted for 4U 0945-30 and 2A 0946-310 but is not one of the
suggested candidates. SAS-3 data were obtained during 1977 Feb.
19-23 and yield the x-ray position R.A. = 9h45m28s.7, Decl. = -30o42'24"
(equinox 1950.0). The position of MCG 5-23-16 is R.A. = 9h45m28s.43 +/-
0s.13, Decl. = -30o42'57".0 +/- 1".7. Observations in the radio, infrared
and optical wavelength bands are urged.
T TAURI
Y. Andrillat and C. Fehrenbach, Observatoire de Haute Provence,
report that observations with the nebular spectrograph (resolution
5000) at the Cassegrain focus of the 193-cm reflector on Mar. 2 revealed
large and rapid variations in the profile of H-alpha in the star
T Tau. Fourteen spectrograms (integration times ~ 200s) were obtained
~ 6 min apart between 20h12m and 21h41m UT. The H-alpha line
consists of a 13-A-wide emission, on which is superimposed a 9-A-wide
absorption; a 1-A-wide emission is situated at the center of this
absorption. The intensity of the central emission doubled between
20h12m and 20h40m; it then decreased (to zero at 21h34m) and reappeared
weakly on the last spectrogram at 21h41m. The absorption
was practically invisible between 20h40m and 20h45m. The mean
radial velocities from the 14 plates are: violet emission, -213 +/- 3
km/s; absorption, -77 +/- 6 km/s; central emission, +1 +/- 3 km/s;
absorption, +77 +/- 4 km/s; red emission, +238 +/- 10 km/s. The weak
emissions of [N II] 6548 and 6584 A do not show structure.
1978 March 13 (3190) Brian G. Marsden
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