1,995 research outputs found
Extremely Luminous Water Vapor Emission from a Type 2 Quasar at Redshift z = 0.66
A search for water masers in 47 Sloan Digital Sky Survey Type 2 quasars using
the Green Bank Telescope has yielded a detection at a redshift of z = 0.660.
This maser is more than an order of magnitude higher in redshift than any
previously known and, with a total isotropic luminosity of 23,000 L_sun, also
the most powerful. The presence and detectability of water masers in quasars at
z ~ 0.3-0.8 may provide a better understanding of quasar molecular tori and
disks, as well as fundamental quasar and galaxy properties such as black hole
masses. Water masers at cosmologically interesting distances may also
eventually provide, via direct distance determinations, a new cosmological
observable for testing the reality and properties of dark energy, currently
inferred primarily through Type 1a supernova measurements.Comment: 8 pages including 1 figure; accepted for publication in ApJ Letter
A high-sensitivity OH 5-cm line survey in late-type stars
We have undertaken a comprehensive search for 5-cm excited OH maser emission
from evolved stars representative of various stages of late stellar evolution.
Observed sources were selected from known 18-cm OH sources. This survey was
conducted with the 100-m Effelsberg telescope to achieve high signal to noise
ratio observations and a sensitivity limit of about 0.05 to 0.1 Jy. A total of
64 stellar sources were searched for both main line and satellite line
emission. We confirm the previous detection of 5 cm OH in Vy 2-2, do not
confirm emission from NML-Cyg and do not report any other new detection within
the above sensitivity limit.
Implications of these results on the pumping mechanism of the OH radical in
circumstellar envelopes are briefly discussed.Comment: 8 pages, 5 figures, A&A in pres
VLBI Astrometry of the Stellar Image of U Herculis, Amplified by the 1667 OH Maser
The OH 1667 MHz maser in the circumstellar shell around the Mira variable U
Herculis has been observed with the NRAO Very Long Baseline Array (VLBA) at 6
epochs, spread over 4 years. Using phase referencing techniques the position of
the most blue-shifted maser spot was monitored with respect to two
extra-galactic radio sources. The absolute radio positions of the maser can be
compared with the stellar optical position measured by the Hipparcos satellite
to 15 mas accuracy. This confirms the model in which one of the maser spots
corresponds to the stellar continuum, amplified by the maser. The stellar
proper motion and the annual parallax (5.3 +/- 2.1 mas) were measured.Comment: 6 pages, 4 figures; to be published in A&
EVLA Observations of OH Masers in ON 1
This Letter reports on initial Expanded Very Large Array (EVLA) observations
of the 6035 MHz masers in ON 1. The EVLA data are of good quality, lending
confidence in the new receiver system. Nineteen maser features, including six
Zeeman pairs, are detected. The overall distribution of 6035 MHz OH masers is
similar to that of the 1665 MHz OH masers. The spatial resolution is sufficient
to unambiguously determine that the magnetic field is strong (~ -10 mG) at the
location of the blueshifted masers in the north, consistent with Zeeman
splitting detected in 13441 MHz OH masers in the same velocity range. Left and
right circularly polarized ground-state features dominate in different regions
in the north of the source, which may be due to a combination of magnetic field
and velocity gradients. The combined distribution of all OH masers toward the
south is suggestive of a shock structure of the sort previously seen in W3(OH).Comment: 4 pages using emulateapj.cls including 2 tables and 2 color figure
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