Optical Observations of the Binary Pulsar System PSR B1718–19: Implications for Tidal Circularization

We report on Keck and Hubble Space Telescope optical observations of the eclipsing binary pulsar system PSR B1718-19, in the direction of the globular cluster NGC 6342. These reveal a faint star (mF702W = 25.21 ± 0.07; Vega system) within the pulsar's 0.″5 radius positional error circle. This may be the companion. If it is a main-sequence star in the cluster, it has radius RC ≃ 0.3 R☉, temperature Teff ≃ 3600 K, and mass MC ≃ 0.3 M☉. In many formation models, however, the pulsar (spun-up by accretion or newly formed) and its companion are initially in an eccentric orbit. If so, for tidal circularization to have produced the present-day highly circular orbit, a large stellar radius is required, i.e., the star must be bloated. Using constraints on the radius and temperature from the Roche and Hayashi limits, we infer from our observations that RC ≲ 0.44 R☉ and Teff ≳ 3300 K. Even for the largest radii, the required efficiency of tidal dissipation is larger than expected for some prescriptions.

[1]  Jean Kovalevsky,et al.  Astronomical Applications of Astrometry: The Hipparcos and Tycho Catalogues , 2008 .

[2]  Thomas E. Corbin,et al.  The ACT Reference Catalog , 1998 .

[3]  D. Chakrabarty,et al.  Neutron Star Mass Measurements. I. Radio Pulsars , 1998, astro-ph/9803260.

[4]  G. L. Wycoff,et al.  The AC 2000: The Astrographic Catalogue on the System Defined by the Hipparcos Catalogue , 1998 .

[5]  L. Krauss,et al.  The Age of Globular Clusters in Light of Hipparcos: Resolving the Age Problem? , 1997, astro-ph/9706128.

[6]  J. Goodman,et al.  Fast Tides in Slow Stars: The Efficiency of Eddy Viscosity , 1997, astro-ph/9701006.

[7]  William E. Harris,et al.  A Catalog of Parameters for Globular Clusters in the Milky Way , 1996 .

[8]  H. Ritter,et al.  Global analysis of mass transfer cycles in cataclysmic variables , 1996 .

[9]  P. Podsiadlowski.  The response of tidally heated stars , 1996 .

[10]  A. Lyne,et al.  PSR B1745–20 and Young Pulsars in Globular Clusters , 1996 .

[11]  Stefano Casertano,et al.  THE PHOTOMETRIC PERFORMANCE AND CALIBRATION OF WFPC2 , 1995 .

[12]  Pawan Kumar,et al.  Nonlinear Damping of Oscillations in Tidal-Capture Binaries , 1995, astro-ph/9509112.

[13]  E. Heuvel.  Scenarios for the formation of binary and millisecond pulsars – A critical assessment , 1995 .

[14]  Harland W. Epps,et al.  THE KECK LOW-RESOLUTION IMAGING SPECTROMETER , 1995 .

[15]  Stefano Casertano,et al.  THE PERFORMANCE AND CALIBRATION OF WFPC2 ON THE HUBBLE SPACE TELESCOPE , 1995 .

[16]  A. King,et al.  The mass of the companion of PSR 1718-19 , 1994 .

[17]  B. Paczyński,et al.  On the origin of the eclipsing pulsar PSR B1718-19 and its wind , 1993 .

[18]  T. Zwitter.  Binary pulsar PSR 1718 – 19 contains a stripped main-sequence turn-off star , 1993 .

[19]  James M. Cordes,et al.  Pulsar distances and the galactic distribution of free electrons , 1993 .

[20]  C. Kochanek.  The dynamical evolution of tidal capture binaries , 1992 .

[21]  P. Nicholson,et al.  Turbulent viscosity and Jupiter's tidal Q , 1977 .

[22]  A. Lyne,et al.  A long-period globular-cluster pulsar in an eclipsing binary system , 1993, Nature.

[23]  J. Mathis.  Interstellar dust and extinction , 1987 .