Detecting Changing Polarization Structures in Sagittarius A* with High Frequency VLBI (2009)
Fish, Vincent L., Doeleman, Sheperd S., Broderick, Avery E., Loeb, Abraham, Rogers, Alan E. E.
Sagittarius A* is the source of near infrared, X-ray, radio, and (sub)millimeter emission associated with the supermassive black hole at the Galactic Center. In the submillimeter regime, Sgr A*...
Observing a Black Hole Event Horizon: (Sub)Millimeter VLBI of Sgr A* (2009)
Fish, Vincent L., Doeleman, Sheperd S.
Very strong evidence suggests that Sagittarius A*, a compact radio source at the center of the Milky Way, marks the position of a super massive black hole. The proximity of Sgr A* in combination with...
Using Millimeter VLBI to Constrain RIAF Models of Sagittarius A* (2008)
Fish, Vincent L., Broderick, Avery E., Doeleman, Sheperd S., Loeb, Abraham
The recent detection of Sagittarius A* at lambda = 1.3 mm on a baseline from Hawaii to Arizona demonstrates that millimeter wavelength very long baseline interferometry (VLBI) can now spatially...
Estimating the Parameters of Sgr A*'s Accretion Flow Via Millimeter VLBI (2008)
Broderick, Avery E., Fish, Vincent L., Doeleman, Sheperd S., Loeb, Abraham
Recent millimeter-VLBI observations of Sagittarius A* (Sgr A*) have, for the first time, directly probed distances comparable to the horizon scale of a black hole. This provides unprecedented access...
Methods for detecting flaring structures in Sagittarius A* with high frequency VLBI (2008)
Doeleman, Sheperd S., Fish, Vincent L., Broderick, Avery E., Loeb, Abraham, Rogers, Alan E. E.
The super massive black hole candidate, Sagittarius A*, exhibits variability from radio to X-ray wavelengths on time scales that correspond to < 10 Schwarzschild radii. We survey the potential of...
Detecting Flaring Structures in Sagittarius A* with (Sub)Millimeter VLBI (2008)
Fish, Vincent L., Doeleman, Sheperd S., Broderick, Avery E., Loeb, Abraham, Rogers, Alan E. E.
Multiwavelength monitoring observations of Sagittarius A* exhibit variability on timescales of minutes to hours, indicating emission regions localized near the event horizon....
Excited-state OH Masers and Supernova Remnants (2007)
Pihlström, Ylva M., Fish, Vincent L., Sjouwerman, Loránt O., Zschaechner, Laura K., Lockett, Philip B., Elitzur, Moshe
The collisionally pumped, ground-state 1720 MHz maser line of OH is widely recognized as a tracer for shocked regions and observed in star forming regions and supernova remnants. Whereas some lines...
Effelsberg Observations of Excited-State (6.0 GHz) OH in Supernova Remnants and W3(OH) (2007)
Fish, Vincent L., Sjouwerman, Loránt O., Pihlström, Ylva M.
While masers in the 1720 MHz transition of OH are detected toward many supernova remnants (SNRs), no other OH transition is seen as a maser in SNRs. We present a search for masers at 6049 MHz, which...
EVLA Observations of OH Masers in ON 1 (2007)
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...
Proper Motions of OH Masers and Magnetic Fields in Massive Star-Forming Regions (2007)
Fish, Vincent L., Reid, Mark J.
We present data of proper motions of OH masers in the massive star-forming regions ON 1, K3-50, and W51 Main/South. OH maser motions in ON 1 are consistent with expansion at approximately 5 km/s,...
Excited-state OH Mainline Masers in AU Geminorum and NML Cygni (2007)
Sjouwerman, Lorant O., Fish, Vincent L., Claussen, Mark J., Pihlstroem, Ylva M., Zschaechner, Laura K.
Excited-state OH maser emission has previously been reported in the circumstellar envelopes of only two evolved stars: the Mira star AU Geminorum and the hypergiant NML Cygni. We present Very Large...
OH Masers in G11.904-0.141 (2007)
The massive star-forming region G11.904-0.141 is one of only 11 sources to show maser emission in the highly-excited 13441 MHz transition of OH. VLBA observations of the 1665, 1667, 4765, and 13441...
Structure of W3(OH) from Very High Spectral Resolution Observations of 5 Centimeter OH Masers (2007)
Fish, Vincent L., Sjouwerman, Loránt O.
Recent studies of methanol and ground-state OH masers at very high spectral resolution have shed new light on small-scale maser processes. The nearby source W3(OH), which contains numerous bright...
Masers and star formation (2007)
Recent observational and theoretical advances concerning astronomical masers in star forming regions are reviewed. Major masing species are considered individually and in combination. Key results are...
Large Magnetic Fields and Motions of OH Masers in W75 N (2006)
Fish, Vincent L., Reid, Mark J.
We report on a second epoch of VLBA observations of the 1665 and 1667 MHz OH masers in the massive star-forming region W75 N. We find evidence to confirm the existence of very strong (~40 mG)...
Observations of the 6 Centimeter Lines of OH in Evolved (OH/IR) Stars (2006)
Fish, Vincent L., Zschaechner, Laura K., Sjouwerman, Loránt O., Pihlström, Ylva M., Claussen, Mark J.
Recent observational and theoretical advances have called into question traditional OH maser pumping models in evolved (OH/IR) stars. The detection of excited-state OH lines would provide additional...
Enhanced density and magnetic fields in interstellar OH masers (2006)
Fish, Vincent L., Reid, Mark J., Menten, Karl M., Pillai, Thushara
Aims: We have observed the 6030 and 6035 MHz transitions of OH in high-mass star-forming regions to obtain magnetic field estimates in both maser emission and absorption. Methods: Observations were...
Search for Lambda-Doubling Transitions of SiH in Orion KL (2006)
A recent submillimeter line survey of Orion KL claimed detection of SiH. This paper reports on GBT observations of the 5.7 GHz Lambda-doubling transitions of SiH in Orion. Many recombination lines,...
A Very High Spectral Resolution Study of Ground-State OH Masers in W3(OH) (2006)
Fish, Vincent L., Brisken, Walter F., Sjouwerman, Loránt O.
We present VLBA observations of the ground-state hydroxyl masers in W3(OH) at 0.02 km s-1 spectral resolution. Over 250 masers are detected, including 56 Zeeman pairs. Lineshapes are predominantly...
Fish, Vincent L., Reid, Mark J.
We analyze full-polarization VLBA data of ground-state, main-line OH masers in 18 massive star-forming regions previously presented in a companion paper. The OH masers often arise in the shocked...
Full-Polarization Observations of OH Masers in Massive Star-Forming Regions: I. Data (2005)
Fish, Vincent L., Reid, Mark J., Argon, Alice L., Zheng, Xing-Wu
We present full-polarization VLBA maps of the ground-state, main-line, 2 Pi 3/2, J = 3/2 OH masers in 18 Galactic massive star-forming regions. This is the first large polarization survey of...
Fish, Vincent L., Reid, Mark J., Menten, Karl M.
We have observed six high-mass star-forming regions in the 2 Pi 3/2, J = 7/2 lines of OH using the GBT in order to investigate whether the magnetic field, and hence the density, measured in...
Interstellar Hydroxyl Masers in the Galaxy. II. Zeeman Pairs and the Galactic Magnetic Field (2003)
Fish, Vincent L., Reid, Mark J., Argon, Alice L., Menten, Karl M.
We have identified and classified Zeeman pairs in the survey by Argon, Reid, & Menten of massive star-forming regions with 18 cm (2 Pi 3/2, J = 3/2) OH maser emission. We have found a total of more...