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  1. No Access

    Article

    Rapid quasi-periodic oscillations in the relativistic jet of BL Lacertae

    Blazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales1–3. This variability seems mostly random, although some quasi-periodic oscil...

    S. G. Jorstad, A. P. Marscher, C. M. Raiteri, M. Villata, Z. R. Weaver, H. Zhang… in Nature (2022)

  2. No Access

    Article

    Blazar spectral variability as explained by a twisted inhomogeneous jet

    The spectral variability of the blazar CTA 102 during a recent extreme outburst could be explained by a twisted, inhomogeneous jet containing regions of different orientations that vary in time.

    C. M. Raiteri, M. Villata, J. A. Acosta-Pulido, I. Agudo, A. A. Arkharov… in Nature (2017)

  3. No Access

    Article

    On the nature of dark energy: the lattice Universe

    There is something unknown in the cosmos. Something big. Which causes the acceleration of the Universe expansion, that is perhaps the most surprising and unexpected discovery of the last decades, and thus repr...

    M. Villata in Astrophysics and Space Science (2013)

  4. No Access

    Article

    “Dark energy” in the Local Void

    The unexpected discovery of the accelerated cosmic expansion in 1998 has filled the Universe with the embarrassing presence of an unidentified “dark energy”, or cosmological constant, devoid of any physical me...

    M. Villata in Astrophysics and Space Science (2012)

  5. No Access

    Article

    Reply to “Comment to a paper of M. Villata on antigravity”

    In this short paper we reply to the Comment by M.J.T.F. Cabbolet on Villata’s theory of antigravity. The criticisms of methodological and ontological kind presented by that author come from a misinterpretation...

    M. Villata in Astrophysics and Space Science (2012)

  6. No Access

    Article

    Multi-frequency studies of the non-stationary radiation of the blazar 3C 454.3

    Long-term monitoring data at five radio frequencies from 4.8 to 37 GHz obtained at the Crimean Astrophysical Observatory, Metsahovi Radio Observatory of Aalto University, and the University of Michigan Radio A...

    A. E. Vol’vach, L. N. Vol’vach, A. M. Kut’kin, M. G. Larionov… in Astronomy Reports (2011)

  7. No Access

    Article

    Color variations of the blazar 3C 454.3 in 2004–2006

    We present an analysis of multicolor (U BV RI JH K) observations of the blazar 3C 454.3 made in 2004–2006. We used the light curves compiled at the Turin Observatory from coordinated observations in the framework...

    V. A. Hagen-Thorn, N. V. Efimova, V. M. Larionov, C. M. Raiteri… in Astronomy Reports (2009)

  8. No Access

    Article

    Correlations between the development of a flare in the Blazar 3C 454.3 in the radio and optical

    Radio and optical data are used to analyze the development of the flare in the blazar 3C 454.3 observed in 2004–2007. A detailed correspondance between the optical and radio flares is established, with a time ...

    A. E. Vol’vach, L. N. Vol’vach, M. G. Larionov, M. F. Aller… in Astronomy Reports (2008)

  9. No Access

    Chapter and Conference Paper

    MHD Equilibria of Helical Jets

    From recent high angular resolution (~ 0.l arcsec) observations of some extragalactic jets (in particular we refer to the radio, optical, and ultraviolet images of the M 87 jet, of 3C 66B, and 3C 264) it can b...

    M. Villata, A. Ferrari in Extragalactic Radio Sources (1996)

  10. No Access

    Chapter and Conference Paper

    Variability Characteristics of Blazar OJ 287

    Blazar OJ 287 is one of the best observed extragalactic objects. It’s historical light curve goes back to 1890’s. Based on the historical behaviour Sillanpää et al. (1988) showed that OJ 287 displays large per...

    L. O. Takalo, A. Sillanpää, T. Pursimo, H. J. Lehto… in Extragalactic Radio Sources (1996)

  11. No Access

    Chapter and Conference Paper

    Optical Monitoring of Gamma-Ray Loud Blazars

    The observations by the Compton Gamma Ray Observatory (CGRO) have shown that highly variable and radio-loud quasars emit a significant fraction of their energy in the γ band. According to the Inverse Compton mode...

    C.M. Raiteri, G. Ghisellini, M. Villata, G. de Francesco… in Extragalactic Radio Sources (1996)

  12. No Access

    Chapter and Conference Paper

    Optical Monitoring of the Gamma-Ray Loud BL Lac Object S5 0716+714

    We monitored the γ-ray loud BL Lac object S5 0716+714 between November 1994 and April 1995 (J.D. 2449671–2449838), from the Observatories of Torino, Perugia and Roma. The source was always active in the R and B b...

    G. Latini, S. Bosio, G. de Francesco, M. Villata… in Extragalactic Radio Sources (1996)

  13. No Access

    Chapter and Conference Paper

    Angular Momentum Loss in Post-Main Sequence Stellar Evolution Through the PN Stage

    A simple analytical model can explain the large angular momentum loss which a star suffers in its post-main-sequence evolution up to the white dwarf stage.

    M. Villata in Planetary Nebulae (1993)