Now showing items 1-15 of 15

    • 23 GHz VLBI Observations of SN 2008ax 

      Marti-Vidal, I.; Alberdi, A.; Ros, E.; Shapiro, Irwin Ira; Beswick, R.J.; Pedlar, A.; Immler, S.; Panagia, N.; Van Dyk, S.; Marcaide, J. M.; Guirado, J. C.; Perrez-Torres, M. A.; Muxlow, T. W. B.; Argo, M. K.; Stockdale, C. J.; Sramek, R. A.; Weiler, K. W. (EDP Sciences, 2009)
      We report on phase-referenced 23 GHz Very-Long-Baseline-Interferometry (VLBI) observations of the type IIb supernova SN 2008ax, made with the Very Long Baseline Array (VLBA) on 2 April 2008 (33 days after explosion). These ...
    • The Central Component of Gravitational Lens Q0957+561 

      Shapiro, Irwin; Haarsma, Deborah B.; Winn, Joshua N.; Lehar, Joseph (American Institute of Physics (IOP Publishing), 2008)
      In 1981, a faint radio source (G′) was detected near the center of the lensing galaxy of the famous “twin quasar” Q0957+561. It is still unknown whether this central radio source is a third quasar image or an active nucleus ...
    • Confronting the Need for Conceptual Change in Pre-Service Science Education 

      Schwartz, Marc S.; Shapiro, Irwin I.; Gregory, Bruce (Canadian Center of Science and Education, 2013)
      During a five-year period the authors taught over 100 students in a graduate course (The Nature of Science) counting toward teacher certification at the Harvard Graduate School of Education. Despite the fact that students ...
    • A Decade of SN 1993J: Discovery of Radio Wavelength Effects in the Expansion Rate 

      Marcaide, J.M.; Marti-Vidal, I.; Alberdi, A.; Perrez-Torres, M.A.; Ros, E.; Diamond, P.J.; Guirado, J.C.; Lara, L.; Shapiro, Irwin Ira; Stockdale, C.J.; Weiler, K.W.; Mantovani, F.; Preston, R.A.; Schilizzi, R.T.; Sramek, R.A.; Trigilio, C.; Van Dyk, S.D.; Whitney, A.R. (EDP Sciences, 2009)
      We studied the growth of the shell-like radio structure of supernova SN 1993J in M 81 from September 1993 to October 2003 with very-long-baseline interferometry (VLBI) observations at the wavelengths of 3.6, 6, and 18 cm. ...
    • Equivalence Principle's Test with Improved Accuracy using a Cryogenic Differential Accelerometer Installed on a Pendulum. 

      Iafolla, V.A.; Fiorenza, E.; Lefevre, C.; Lucchesi, D.M.; Lucente, M.; Magnafico, C.; Nozzoli, S.; Peron, R.; Santoli, F.; Lorenzini, Enrico C.; Milyukov, Vadim; Shapiro, Irwin I.; Glashow, Sheldon Lee (2013)
      We present here a concept for a new experimental test of the Weak Equivalence Principle (WEP) carried out in the gravity field of the Sun. Two test masses of different materials are the central elements of a differential ...
    • The Gravity Probe B test of general relativity 

      Everitt, C W F; Muhlfelder, B; DeBra, D B; Parkinson, B W; Turneaure, J P; Silbergleit, A S; Acworth, E B; Adams, M; Adler, R; Bencze, W J; Berberian, J E; Bernier, R J; Bower, K A; Brumley, R W; Buchman, S; Burns, K; Clarke, B; Conklin, J W; Eglington, M L; Green, G; Gutt, G; Gwo, D H; Hanuschak, G; He, X; Heifetz, M I; Hipkins, D N; Holmes, T J; Kahn, R A; Keiser, G M; Kozaczuk, J A; Langenstein, T; Li, J; Lipa, J A; Lockhart, J M; Luo, M; Mandel, I; Marcelja, F; Mester, J C; Ndili, A; Ohshima, Y; Overduin, J; Salomon, M; Santiago, D I; Shestople, P; Solomonik, V G; Stahl, K; Taber, M; Van Patten, R A; Wang, S; Wade, J R; Worden, P W; Bartel, N; Herman, L; Lebach, D E; Ratner, M; Ransom, R R; Shapiro, Irwin I.; Small, H; Stroozas, B; Geveden, R; Goebel, J H; Horack, J; Kolodziejczak, J; Lyons, A J; Olivier, J; Peters, P; Smith, M; Till, W; Wooten, L; Reeve, W; Anderson, M; Bennett, N R; Burns, K; Dougherty, H; Dulgov, P; Frank, D; Huff, L W; Katz, R; Kirschenbaum, J; Mason, G; Murray, D; Parmley, R; Ratner, M I; Reynolds, G; Rittmuller, P; Schweiger, P F; Shehata, S; Triebes, K; VandenBeukel, J; Vassar, R; Al-Saud, T; Al-Jadaan, A; Al-Jibreen, H; Al-Meshari, M; Al-Suwaidan, B (IOP Publishing, 2015)
      The Gravity Probe B mission provided two new quantitative tests of Einstein's theory of gravity, general relativity (GR), by cryogenic gyroscopes in Earth's orbit. Data from four gyroscopes gave a geodetic drift-rate of ...
    • Measurement of the quality factor of a new low-frequency differential accelerometer for testing the equivalence principle 

      Nozzoli, S; Magnafico, C.; Iafolla, V.; Fiorenza, E.; Lucente, M.; Lucchesi, D.; Peron, R.; Lorenzini, E.C.; Shapiro, Irwin Ira; Shapiro, Irwin Ira; Glashow, S.; Lorenzini, E. C. (American Institute of Physics (AIP), 2014)
      A cryogenic differential accelerometer has been developed to test the weak equivalence principle to a few parts in 1015 within the framework of the general relativity accuracy test in an Einstein elevator experiment. The ...
    • VLBI for Gravity Probe B. I. Overview 

      Shapiro, Irwin Ira; Bartel, N.; Bietenholz, M. F.; Lebach, D. E.; Lestrade, J.-F.; Ransom, R. R.; Ratner, M. I. (IOP Publishing, 2012)
      We describe the NASA/Stanford gyroscope relativity mission, Gravity Probe B (GP-B), and provide an overview of the following series of six astrometric and astrophysical papers that report on our radio observations and ...
    • VLBI for Gravity Probe B. II. Monitoring of the Structure of the Reference Sources 3C 454.3, B2250+194, and B2252+172 

      Ransom, R. R.; Bartel, N.; Bietenholz, M. F.; Lebach, D. E.; Lederman, J. I.; Luca, P.; Ratner, M. I.; Shapiro, Irwin Ira (IOP Publishing, 2012)
      We used 8.4 GHz very long baseline interferometry images obtained at up to 35 epochs between 1997 and 2005 to examine the radio structures of the main reference source, 3C 454.3, and two secondary reference sources, B2250+194 ...
    • VLBI for Gravity Probe B. III. A Limit on the Proper Motion of the "Core" of the Quasar 3C 454.3 

      Bartel, N.; Bietenholz, M. F.; Lebach, D. E.; Lederman, J. I.; Petrov, L.; Ransom, R. R.; Ratner, M. I.; Shapiro, Irwin Ira (IOP Publishing, 2012)
      We made very long baseline interferometry observations at 8.4 GHz between 1997 and 2005 to estimate the coordinates of the "core" component of the superluminal quasar, 3C 454.3, the ultimate reference point in the distant ...
    • VLBI for Gravity Probe B. IV. A New Astrometric Analysis Technique and a Comparison with Results from Other Techniques 

      Lebach, D. E.; Bartel, N.; Bietenholz, M. F.; Campbell, R. M.; Gordon, D.; Lederman, J. I.; Lestrade, J.-F.; Ransom, R. R.; Ratner, M. I.; Shapiro, Irwin Ira (IOP Publishing, 2012)
      When very long baseline interferometry (VLBI) observations are used to determine the position or motion of a radio source relative to reference sources nearby on the sky, the astrometric information is usually obtained ...
    • VLBI for Gravity Probe B. V. Proper Motion and Parallax of the Guide StarR, IM Pegasi 

      Ratner, M. I.; Bartel, N.; Bietenholz, M. F.; Lebach, D. E.; Lestrade, J.-F.; Ransom, R. R.; Shapiro, Irwin Ira (IOP Publishing, 2012)
      We present the principal astrometric results of the very long baseline interferometry (VLBI) program undertaken in support of the Gravity Probe B (GP-B) relativity mission. VLBI observations of the GP-B guide star, the RS ...
    • VLBI for Gravity Probe B. VI., the Orbit of IM Pegasi and the Location of the Source of Radio Emission 

      Ransom, R. R.; Bartel, N.; Bietenholz, M. F.; Lebach, D. E.; Lestrade, J.-F.; Ratner, M. I.; Shapiro, Irwin Ira (IOP Publishing, 2012)
      We present a physical interpretation for the locations of the sources of radio emission in IM Pegasi (IM Peg, HR 8703), the guide star for the NASA/Stanford relativity mission Gravity Probe B. This emission is seen in each ...
    • VLBI for Gravity Probe B. VII. The Evolution of the Radio Structure of IM Pegasi 

      Bietenholz, M. F.; Bartel, N.; Lebach, D. E.; Ransom, R. R.; Ratner, M. I.; Shapiro, Irwin Ira (IOP Publishing, 2012)
      We present measurements of the total radio flux density as well as very-long-baseline interferometry (VLBI) images of the star, IM Pegasi, which was used as the guide star for the NASA/Stanford relativity mission Gravity ...
    • VLBI for Gravity Probe B: the guide star, IM Pegasi 

      Bartel, N; Bietenholz, MF; Lebach, DE; Ransom, RR; Ratner, MI; Shapiro, Irwin I. (IOP Publishing, 2015)
      We review the radio very long baseline interferometry (VLBI) observations of the guide star, IM Peg, and three compact extragalactic reference sources, made in support of the NASA/Stanford gyroscope relativity mission, ...