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Article
The Sub-Pc Scale Accretion Disk of Ngc 4258
Water megamasers have been found to trace parsec/sub-parsec, circumnuclear accretion disks in several AGN (e.g., Circinus, NGC 1068 & NGC 4258). High-spatial (0.5 mas) and velocity resolution (0.2 km s−1) VLBA im...
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Chapter
The Sub-PC Scale Accretion Disk of NGC 4258
Water megamasers have been found to trace parsec/sub-parsec, circumnuclear accretion disks in several AGN (e.g., Circinus, NGC 1068 & NGC 4258). High-spatial (0.5 mas) and velocity resolution (0.2 km s−1) VLBA im...
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Article
A star in a 15.2-year orbit around the supermassive black hole at the centre of the Milky Way
Many galaxies are thought to have supermassive black holes at their centres1—more than a million times the mass of the Sun. Measurements of stellar velocities2,3,4,5,6,7 and the discovery of variable X-ray emissi...
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Chapter and Conference Paper
Shocks in the Radio Photospheres of Long Period Variable Stars
At a distance of a few stellar radii and beyond from the center of a Mira variable, dust condenses (see Danchi et al. 1994) and mass begins to stream away from the star as a result of radiation pressure on the...
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Article
Shocks in the Radio Photospheres of Long Period Variables Stars
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Chapter and Conference Paper
Proper motion studies of H2O masers
The work of the CfA group over the past decade to measure the proper motions of H2O masers in our Galaxy is described. The distances to 7 masers have been measured and the distance to the Galactic Center, Ro, is ...
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Chapter and Conference Paper
VLBI observations of the water vapor megamaser in IC10
We present VLBI synthesis observations of the water vapor megamaser in the south eastern region of IC10. We compare our spectrum with earlier single dish spectra and conclude that the maser is highly variable.
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Chapter and Conference Paper
Preliminary results from a study of the proper motion of water vapor masers in cepheus A
Preliminary results from a study of the proper motions of water vapor masers associated with HII regions in Cepheus A are presented. The masers lie in two distinct clumps near the peaks in intensity of the HII...
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Chapter and Conference Paper
Proper motions of the oh masers in W3(OH)
Using data from a seven-telescope VLBI experiment, we have remapped the 1665-MHz OH maser emission from W3(OH), a site of current star formation roughly 2.2 kpc distant. Both circular polarizations were observ...
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Chapter and Conference Paper
Proper Motions of H2O Masers in W49(N) and the Distance to the Galactic Center
A distance of R 0 = 7.6 ±1.6 kpc for the galactic center is given by comparison of expansion parallax of a cluster of H2O masers in W49(N) with the kinematic distance of that source. Data from add...
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Chapter and Conference Paper
The nuclear jet in M87
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Chapter
VLBI Observations of M87
On 1980 February 20 we conducted an 8-station intercontental VLBI experiment in order to study the nucleus and jet of M87 at 1666.6 MHz in right circular polarization. Our array was sensitive to structures fro...