XTE J1946+274 Transient 15.8-s Pulsar (= 3A 1942+274 ?)
ATel #36; D. A. Smith (MIT) & T. Takeshima (NASA/GSFC)
on 16 Sep 1998; 03:38 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Donald A. Smith (dasmith@space.mit.edu)
Subjects: X-ray, Binary, Transient, Pulsar
This is an advance copy of an announcement submitted to the IAU Circulars.
D. A. Smith (MIT) and T. Takeshima (NASA/GSFC) on behalf of the
RXTE/ASM and PCA teams at MIT and GSFC report:
The ASM has detected emission from a celestial location that overlaps
the previous localization of the 1976 Ariel V transient 3A 1942+274
(MNRAS 197, 865; at bII=+1.7o). The corners of the ASM 6' x 26' error
region are at (19h47m06s, +27o16'), (19h46m12s, +27o25'), (19h45m30s,
+27o25'), (19h46m10s, +27o18') (J2000, 90% confidence, total error).
The source first came to our attention at ~90 mCrab (2-12 keV) on
Sept. 15.91 (UT), with a very hard spectrum. A retroactive search
reveals that the one-day average intensity from this location has been
rising from 13 mCrab on Sept 5 to 60 mCrab on Sept 15. The PCA
observed this location on Sept. 16.02 and recorded an intensity of
~110 mCrab (2-60 keV) with a very strong 15.83 s (+/- 0.02) pulsation.
The pulse profile is double-peaked, with a pulse fraction of about
29%. There is, to our knowledge, no previous report of pulsations
from 3A 1942+274. If this is a reoccurrence of the Ariel source, the
8' x 52' Ariel position restricts the location to the westernmost 5'
of the ASM region. Further PCA observations are in progress.
Observations at other wavelengths are encouraged.
Sky Map of ASM and Ariel V positions
