Central Bureau for Astronomical Telegrams
IAUC 5228: N Her 1991; GALACTIC CENTER
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Circular No. 5228
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
NOVA HERCULIS 1991
A. Moneti, European Southern Observatory, La Silla, reports:
"The following infrared photometry has been obtained on Mar. 26.4 UT
by P. Bouchet (ESO) at the ESO 3.6-m telescope (+ InSb photometer +
bolometer): J = 5.73 +/- 0.02, H = 5.06 +/- 0.02, K = 4.57 +/- 0.02,
L = 3.56 +/- 0.02, M = 3.18 +/- 0.05, N = 2.60 +/- 0.04, Q = 3.0 +/-
0.8. Magnitudes obtained by F. Catalano (Catania) on the ESO 1-m
telescope with an InSb photometer: Mar. 26.4, J = 5.55, H = 5.21, K
= 4.70; Mar. 27.4, J = 5.76, H = 5.55, K = 5.03; Mar. 28.4, J =
6.47, H = 6.30, K = 5.75, all +/- 0.01 mag. The reason for the 0.2
mag discrepancy between the 3.6-m data and the 1-m data is not
understood at this time. A spectrogram covering the 1.4- to 2.4-
micron range, obtained by P. Bouchet and myself on Mar. 29.4 on the
ESO/MPI 2.2-m telescope (+ CVF spectrometer) shows a blue continuum
with strong, broad lines of hydrogen (H I) Br-gamma, Pa-alpha, Br10,
Br11, and He I (2.058 microns). Measured line intensities are 7.5 x
10E-11 erg sE-1 cmE-2 for Br-gamma, and 5.1 x 10E-11 erg sE-1 cmE-2
for He I."
Visual magnitude estimates (cf. IAUC 5226): Mar. 30.46 UT,
8.5 (P. Sventek, Houston, TX); 30.79, 9.3 (R. H. McNaught, Siding
Spring Observatory); 31.375, 9.4 (J. E. Bortle, Stormville, NY);
Apr. 1.358, 9.9 (Bortle); 1.46, 9.4 (Sventek).
GALACTIC CENTER
J. Bally and M. Leventhal, AT&T Bell Laboratories, report:
"The recently identified source of the 511-keV positron annihilation
line from the Galactic Center (1E 1740.7-2942; cf. IAUC 5140 and
Schwarzschild 1991, Physics Today 44(3), 17) is located within 1' of
the core of a 10E5-solar-mass Galactic Center molecular cloud. New
observations with the Crawford Hill 7-m antenna in the 115-GHz 12CO
(J = 1-0) transition reveal a cloud at V(LSR) = -130 km/s, at a
projected distance of about 120 pc from the core of the galaxy in a
relatively unconfused region. The total column density along the
line-of-sight is N(H2) about 3 x 10E23 cmE-2, corresponding to A(V)
about 200 magnitudes of visual extinction. The average H2 gas density
in the cloud is > 10E4 cmE-3, so Bondi-Hoyle accretion directly
onto a stellar-mass black hole may account for the observed gamma-
ray luminosity."
1991 April 1 (5228) Daniel W. E. Green
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