A. N. Lommen

Haverford College

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Zaven Arzoumanian

Goddard Space Flight Center

S. M. Ransom

National Radio Astronomy Observatory

M. A. McLaughlin

West Virginia University

D. R. Lorimer

West Virginia University

D. J. Nice

Lafayette College

I. H. Stairs

University of British Columbia

Paul Demorest

National Radio Astronomy Observatory

J. M. Cordes

Cornell University

Paul S. Ray

United States Naval Research Laboratory

R. D. Ferdman

University of East Anglia

Cooperative Institutions

Max Planck Institute for Radio Astronomy

116

Max Planck Society

116

Campbell Collaboration

116

California Institute of Technology

Goddard Space Flight Center

Commonwealth Scientific and Industrial Research Organisation

West Virginia University

Astronomy and Space

Australia Telescope National Facility

University of Wisconsin–Milwaukee

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Structure and phase transition of the 6,5-annulene isomer ofC61H2

Physical review. B, Condensed matter (1994)

A. N. Lommen Paul A. Heiney G. Vaughan Peter W. Stephens Dengfa Liu

We have used differential scanning calorimetry and x-ray diffraction to study the crystalline phases of the 6,5-annulene isomer of ${\mathrm{C}}_{61}$${\mathrm{H}}_{2}$. At 308 K the methylenated fullerenes are orientationally disordered in a face-centered cubic lattice with lattice parameter 14.19\ifmmode\pm\else\textpm\fi{}0.02 \AA{}. Below ${\mathit{T}}_{\mathit{c}}$=290 K the symmetry is lowered to Pa3\ifmmode\bar\else\textasciimacron\fi{}, a simple-cubic structure. At 20 K the lattice parameter is 14.06\ifmmode\pm\else\textpm\fi{}0.02 \AA{}, with substantial statistical disorder remaining. The transition temperature in ${\mathrm{C}}_{61}$${\mathrm{H}}_{2}$ is slightly higher than in ${\mathrm{C}}_{60}$O and higher still than in ${\mathrm{C}}_{60}$, but the three compounds exhibit orientationally ordering transitions between qualitatively similar phases.

Lattice (music)

Cubic crystal system

10.1103/physrevb.49.12572

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Citations (17)

Long-Term Density Trend in the Mesosphere and Lower Thermosphere from Occultations of the Crab Nebula with X-Ray Astronomy Satellites

Satoru Katsuda Teruaki Enoto A. N. Lommen Koji Mori Yuko Motizuki

Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Journal of Geophysical Research - Space Physics. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing the latest version by default [v1]Long-Term Density Trend in the Mesosphere and Lower Thermosphere from Occultations of the Crab Nebula with X-Ray Astronomy SatellitesAuthorsSatoruKatsudaTeruakiEnotoAndrea NLommenKojiMoriiDYukoMotizukiMotokiNakajimaNathaniel CRuhlKosukeSatoGunterStoberMakoto STashiroiDYukikatsuTeradaiDKent SWoodSee all authors Satoru KatsudaCorresponding Author• Submitting AuthorSaitama Universityview email addressThe email was not providedcopy email addressTeruaki EnotoRIKENview email addressThe email was not providedcopy email addressAndrea N LommenHaverford Collegeview email addressThe email was not providedcopy email addressKoji MoriiDUniversity of MiyazakiiDhttps://orcid.org/0000-0002-0018-0369view email addressThe email was not providedcopy email addressYuko MotizukiRIKEN Nishina Centerview email addressThe email was not providedcopy email addressMotoki NakajimaNihon Universityview email addressThe email was not providedcopy email addressNathaniel C RuhlHaverford Collegeview email addressThe email was not providedcopy email addressKosuke SatoSaitama Universityview email addressThe email was not providedcopy email addressGunter StoberUniversity of Bernview email addressThe email was not providedcopy email addressMakoto S TashiroiDSaitama UniversityiDhttps://orcid.org/0000-0002-5097-1257view email addressThe email was not providedcopy email addressYukikatsu TeradaiDSaitama UniversityiDhttps://orcid.org/0000-0002-2359-1857view email addressThe email was not providedcopy email addressKent S WoodLiving in Coloradoview email addressThe email was not providedcopy email address

10.1002/essoar.10511820.1

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An Arecibo Drift-Scan Search for Rapidly Rotating Radio Pulsars

American Astronomical Society Meeting Abstracts #200 (2002)

D. R. Lorimer McLaughlin K. M. Xilouris D. C. Backer J. M. Cordes

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Massive Black Holes, Gravitational Waves and Pulsars

D. C. Backer Andrew H. Jaffe A. N. Lommen

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Nanohertz Gravitational Waves and Space-based Navigation using Pulsars

43rd COSPAR Scientific Assembly. Held 28 January - 4 February (2021)

A. N. Lommen

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Pulsar Timing Array Sensitivity Investigations Using PTASM

American Astronomical Society Meeting Abstracts #215 (2010)

Brian Burt L. S. Finn H. Williams A. N. Lommen D. Menéndez

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OPTIMIZATION OF NANOGRAV'S TIME ALLOCATION FOR MAXIMUM SENSITIVITY TO SINGLE SOURCES

The Astrophysical Journal (2014)

B. Christy R. Anella A. N. Lommen L. S. Finn Richard Camuccio

Pulsar timing arrays (PTAs) are a collection of precisely timed millisecond pulsars (MSPs) that can search for gravitational waves (GWs) in the nanohertz frequency range by observing characteristic signatures in the timing residuals. The sensitivity of a PTA depends on the direction of the propagating GW source, the timing accuracy of the pulsars, and the allocation of the available observing time. The goal of this paper is to determine the optimal time allocation strategy among the MSPs in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) for a single source of GW under a particular set of assumptions. We consider both an isotropic distribution of sources across the sky and a specific source in the Virgo cluster. This work improves on previous efforts by modeling the effect of intrinsic spin noise for each pulsar. We find that, in general, the array is optimized by maximizing time spent on the best-timed pulsars, with sensitivity improvements typically ranging from a factor of 1.5 to 4.

10.1088/0004-637x/794/2/163

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MEASURING THE MASS OF SOLAR SYSTEM PLANETS USING PULSAR TIMING

The Astrophysical Journal Letters (2010)

D. J. Champion G. Hobbs R. N. Manchester Roderick Edwards D. C. Backer

High-precision pulsar timing relies on a solar system ephemeris in order to convert times of arrival (TOAs) of pulses measured at an observatory to the solar system barycenter. Any error in the conversion to the barycentric TOAs leads to a systematic variation in the observed timing residuals; specifically, an incorrect planetary mass leads to a predominantly sinusoidal variation having a period and phase associated with the planet's orbital motion about the Sun. By using an array of pulsars (PSRs J0437−4715, J1744−1134, J1857+0943, J1909−3744), the masses of the planetary systems from Mercury to Saturn have been determined. These masses are consistent with the best-known masses determined by spacecraft observations, with the mass of the Jovian system, 9.547921(2) ×10−4 M☉, being significantly more accurate than the mass determined from the Pioneer and Voyager spacecraft, and consistent with but less accurate than the value from the Galileo spacecraft. While spacecraft are likely to produce the most accurate measurements for individual solar system bodies, the pulsar technique is sensitive to planetary system masses and has the potential to provide the most accurate values of these masses for some planets.

Ephemeris

Jupiter (rocket family)

10.1088/2041-8205/720/2/l201

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Correlations between Pulsed X-Ray Flux and Radio Arrival Time in the Vela Pulsar

A. N. Lommen Jennifer L. Donovan C. R. Gwinn Zaven Arzoumanian A. K. Harding

We report the results of simultaneous observations of the Vela pulsar in X-rays and radio from the RXTE satellite and the Mount Pleasant Radio Observatory in Tasmania. We sought correlations between the Vela's X-ray and radio flux densities and radio arrival times on a pulse by pulse basis. We found significantly higher flux density in Vela's main X-ray peak during radio pulses that arrived early. This excess flux shifts to the 'trough' following the 2nd X-ray peak during radio pulses that arrive later. We suggest that the mechanism producing the radio pulses is intimately connected to the mechanism producing X-rays. Current models using resonant absorption in the outer magnetosphere as a cause of the radio emission, and less directly of the X-ray emission, are explored as a possible explanation for the correlation.

Vela

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Sensitivity of Pulsar Timing Arrays to Gravitational Waves

arXiv (Cornell University) (2010)

Brian Burt A. N. Lommen L. S. Finn

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