A5080852603- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Astro and Planetary Science
- Molecular Spectroscopy and Structure
- Atmospheric Ozone and Climate
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Particle Accelerators and Free-Electron Lasers
- Galaxies: Formation, Evolution, Phenomena
- Spectroscopy and Laser Applications
- Superconducting and THz Device Technology
- Astronomical Observations and Instrumentation
- Mechanics and Biomechanics Studies
- Geophysics and Gravity Measurements
- Ionosphere and magnetosphere dynamics
- Dermatologic Treatments and Research
- Scientific Research and Discoveries
- Acne and Rosacea Treatments and Effects
- Advanced X-ray Imaging Techniques
- Neutrino Physics Research
- Muon and positron interactions and applications
Center for Astrophysics Harvard & Smithsonian
2015-2024
Harvard University
1998-2022
Max Planck Institute for Radio Astronomy
2016
Boston University
2016
W.M. Keck Observatory
2016
Institut de Radioastronomie Millimétrique
2016
European Southern Observatory
2016
Chalmers University of Technology
2016
University of Arizona
2016
Istituto di Radioastronomia di Bologna
2016
Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by accretion matter onto super massive black holes. While the measured width profiles such jets on large scales agree with theories magnetic collimation, predicted structure disk at jet launch point has not been detected. We report radio interferometry observations 1.3mm wavelength elliptical galaxy M87 that spatially resolve base in this source. The derived size 5.5 +/- 0.4 Schwarzschild radii is...
Magnetic fields near the event horizon Astronomers have long sought to examine a black hole's horizon—the boundary around hole within which nothing can escape. Johnson et al. used sophisticated interferometry techniques combine data from millimeter-wavelength telescopes world. They measured polarization just outside of Sgr A*, supermassive at center our galaxy, Milky Way. The is signature ordered magnetic generated in accretion disk hole. results help explain how holes accrete gas and launch...
Sagittarius A*, the ~4 x 10^6 solar mass black hole candidate at Galactic Center, can be studied on Schwarzschild radius scales with (sub)millimeter wavelength Very Long Baseline Interferometry (VLBI). We report 1.3 mm observations of Sgr A* using a VLBI array consisting JCMT Mauna Kea, ARO/SMT Mt. Graham in Arizona, and two telescopes CARMA Cedar Flat California. Both quasar calibrator 1924-292 were observed over three consecutive nights, both sources clearly detected all baselines. For...
Abstract Based on sub-arcsecond Atacama Large Millimeter/submillimeter Array (ALMA) and Submillimeter (SMA) 1.3 mm continuum images of the massive protocluster NGC 6334I obtained in 2015 2008, we find that dust emission from MM1 has increased by a factor 4.0 ± 0.3 during intervening years, undergone significant change morphology. The other cluster members (MM2, MM4, UCH ii region MM3 = 6334F) remained constant. Long-term single-dish maser monitoring at HartRAO finds multiple species toward...
We report on 230 GHz (1.3 mm) VLBI observations of M87 with the Event Horizon Telescope using antennas Mauna Kea in Hawaii, Mt. Graham Arizona and Cedar Flat California. For first time, we have acquired interferometric phase information through measurement closure triangle long baselines. Most measured phases are consistent 0$^{\circ}$ as expected by physically-motivated models for structure such jet accretion disk models. The brightness temperature event-horizon-scale is $\sim 1 \times...
This paper describes observations of a new phenomenon in evolved mass-losing AGB stars: the presence two winds with different expansion velocities. CO(2-1) and CO(3-2) line emission was observed for 45 stars at high velocity resolution double found 20% sample. Highly asymmetric lines were six other stars. The data tentatively suggest that occur when star undergoes change (pulsational mode, chemical composition) very narrow components represent onset phase mass loss.
We report the discovery in space of a disilicon species, SiCSi, from observations between 80 and 350 GHz with IRAM 30m radio telescope. Owing to close coordination laboratory experiments astrophysics, 112 lines have now been detected carbon-rich star CWLeo. The derived frequencies yield improved rotational centrifugal distortion constants up sixth order. From line profiles interferometric maps Submillimeter Array, bulk SiCSi emis- sion arises region 6 arcseconds radius. abundance is...
Phosphorus-bearing compounds have only been studied in the circumstellar environments (CSEs) of asymptotic giant branch (AGB) star IRC +10216 and protoplanetary nebula CRL 2688, both C-rich objects, O-rich red supergiant VY CMa. The current chemical models cannot reproduce high abundances PO PN derived from observations No reported phosphorus CSEs AGB stars. We aim to set observational constraints on phosphorous chemistry stars, by focussing Mira-type variable IK Tau. Using IRAM 30m...
The Galactic Center black hole Sagittarius A* (Sgr A*) is a prime observing target for the Event Horizon Telescope (EHT), which can resolve 1.3 mm emission from this source on angular scales comparable to that of general relativistic shadow. Previous EHT observations have used visibility amplitudes infer morphology millimeter-wavelength emission. Potentially much richer information contained in phases. We report phase Sgr obtained with total 13 nights over 4 years. Closure phases, sum phases...
Abstract We report results from very long baseline interferometric (VLBI) observations of the supermassive black hole in Galactic center, Sgr A*, at 1.3 mm (230 GHz). The were performed 2013 March using six VLBI stations Hawaii, California, Arizona, and Chile. Compared to earlier observations, addition APEX telescope Chile almost doubles longest length array, provides additional uv coverage N–S direction, leads a spatial resolution ∼30 μ as (∼3 Schwarzschild radii) for A*. source is detected...
We report a spectral-line survey of the extreme carbon star IRC+10216 carried out between 293.9 and 354.8 GHz with Submillimeter Array. A total 442 lines were detected, more than 200 for first time; 149 are unassigned. Maps at an angular resolution ~3" obtained each line. substantial new population narrow expansion velocity ~4 km/s (i.e. ~ 30% terminal velocity) was detected. Most these attributed to rotational transitions within vibrationally excited states, emitted from energy levels above...
Using the SMA and VLA, we have imaged massive protocluster NGC6334I(N) at high angular resolution (0.5"~650AU) from 6cm to 0.87mm, detecting 18 new compact continuum sources. Three of sources are coincident with previously-identified water masers. Together previously-known sources, these data bring number likely members 25 for a protostellar density ~700 pc^-3. Our preliminary measurement Q-parameter minimum spanning tree is 0.82 -- close value uniform volume distribution. All (nine)...
We report the results from recent observations of Sgr A* at short-/sub-millimeter wavelengths made with partially finished Sub-Millimeter Array (SMA) on Mauna Kea. A total 25 epochs were carried out over past 15 months in 2001 March to 2002 May. Noticeable variations flux density 1.3 mm observed showing three ``flares''. The SMA suggest that highly increases towards submillimeter during a flare suggesting presence break wavelength spectral index around 3 mm. cross-correlation data 1 VLA cm...
view Abstract Citations (93) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS First Measurements of Extragalactic CO(4--3) Guesten, R. ; Serabyn, E. Kasemann, C. Schinckel, A. Schneider, G. Schulz, Young, K. We report the first measurements extragalactic CO(4-3) toward a sample prominent nearby galactic nuclei (NGC 253, IC 342, M82, and NGC 6946). With J = 4 level 55 K above ground, critical densities for excitation order ~10^4^-10^5^ cm^-3^,...
We report the first detection of pure rotational transitions TiO and TiO_2 at (sub-)millimeter wavelengths towards red supergiant VY CMa. A temperature, T_rot, about 250 K was derived for TiO_2. Although T_rot not well constrained TiO, it is likely somewhat higher than that The Ti oxides confirms they are formed in circumstellar envelopes cool oxygen-rich stars may be "seeds" inorganic-dust formation, but alternative explanations our observation cooler regions envelope cannot ruled out this...
view Abstract Citations (94) References (45) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A CO(3--2) Survey of Nearby Mira Variables Young, K. survey CO(3-2) emission from optically visible oxygen-rich variable stars within 500 pc the sun was conducted. molecular envelope detected surrounding 36 66 examined. Some these have lower outflow velocities than any Miras previously in CO. The average terminal velocity ejected material 7.0 km/sec, about half value...
We report the astronomical discovery of 110→101 rotational transition within ν2 = 1 vibrationally excited state water vapor (H2O). Using 10.4 m telescope Caltech Submillimeter Observatory, we detect strong maser emission in this line, which has a frequency near 658 GHz, toward diverse sample oxygen-rich red giant and supergiant stars. In circumstellar envelopes these GHz H2O masers appear to be as common SiO other transitions, while fail W49 N W51 star-forming regions. For all 11 stars...
We present a fully sampled map of the Helix Nebula in 1.3 mm CO J = 2-1 line, made using Caltech Submillimeter Observatory. The angular resolution is 31'', and velocity 1.5 km s-1. emission found to extend over region ~1000'' × 800'' delineates well-known double ring or "helix" seen optical images ionized gas. Our observations provide first complete view global kinematics envelope reveal three-dimensional structure helix be an expanding, equatorial around nebula, with arcs extending higher...
Red novae are optical transients erupting at luminosities typically higher than those of classical novae. Their outbursts believed to be caused by stellar mergers. We present millimeter/submillimeter-wave observations with ALMA and SMA the three best known Galactic red novae, V4332 Sgr, V1309 Sco, V838 Mon. The were taken 22, 8, 14 yr after their respective eruptions reveal presence molecular gas excitation temperatures 35-200 K. displays emission in rotational transitions very broad lines...
We report infrared images of the Helix Nebula centered at 6.9 μm (LW2 filter) and 15 (LW3 obtained with ISOCAM on board Infrared Space Observatory (ISO). Three fields were also measured using circular variable filter (CVF). The CVF data show that 5-16.6 spectrum is dominated by pure (v=0-0) rotational lines molecular hydrogen from S(7) to S(2) transitions. strong S(5) H2 line accounts for most emission detected in LW2 filter. only atomic are [Ne II] 12.81 [Ar III] 8.99 μm, which weak, 15.55...
Using the partially completed Submillimeter Array with five antennas, we have observed CO J = 2-1 and 3-2 emission from envelope surrounding carbon star V Hya. The high angular resolution (2''-4'') maps show that Hya is powering a bipolar molecular jet an extreme velocity of 70-185 km s-1. axis this high-velocity perpendicular to major flattened disklike envelope, which expanding ~16 There third kinematic component, medium-velocity wind deprojected 40-120 s-1 moving along disk plane. Both...
We report observations of the 3 P 1 → 0 transition atomic carbon at 492 GHz in IRC+10216, made Caltech Submillimeter Observatory. The C I emission from central position IRC+10216 was found to have a main beam temperature about 0.4 K and be doubly peaked expansion velocity CO envelope. Its spatial distribution can modeled by two shells radius ∼15″ 45″ with column densities star state 7×10 15 4×10 cm -2 , respectively
We report high angular resolution (~1'') CO J = 3-2 interferometric mapping using the Submillimeter Array (SMA) of IRAS 22036+5306 (I22036), a bipolar preplanetary nebula (PPN) with knotty jets discovered in our HST snapshot survey young PPNs. In addition, we have obtained supporting lower (~10'') and 13CO 1-0 observations Owens Valley Radio Observatory (OVRO) interferometer, as well optical long-slit echelle spectra at Palomar Observatory. The show presence very fast (~220 km s-1), highly...