The recent discovery that Geminga is a pulsar has been followed by indications of an anomalous second derivative nu double overdot = 2.8(1.6) x 10(-25) Hz s-1 in the COS-B data, yielding a braking index n congruent-to 31 +/- 18. We propose that Geminga is a glitching pulsar with dynamical parameters similar to those of the Vela pulsar, whose interglitch behaviour is characterized by a large second derivative. With the vortex unpinning model for glitches, if we adopt the hypothesis that the number of vortices unpinned in each glitch and the moment of inertia of the crust superfluid involved in the interglitch response are the same in Geminga as in Vela, we find that the expected interglitch second derivative in Geminga agrees with that of the COS-B ephemeris.


X-ray flux and pulse frequency changes of three high mass X-ray binary pulsars: Vela X-1, GX 301-2 and OAO 1657-415
Inam, SC; Baykal, Altan (2000-01-01)
Using archival BATSE (Burst and Transient Source Experiment) 20-50 keV band X-ray flux and pulse frequency time series, we look for correlations between torque, luminosity and specific angular momentum for three high mass X-ray binary pulsars Vela X-1, GX 301-2 and OAO 1657-415. Our results show that there is no correlation between pulse frequency derivative and flux which may be an indication of the absence of stable prograde accretion disk. From the strong correlation of specific angular momentum and torq...
Spectra, vacua, and the unitarity of Lovelock gravity in D-dimensional AdS spacetimes
Sisman, Tahsin Cagri; Gullu, Ibrahim; Tekin, Bayram (2012-08-24)
We explicitly confirm the expectation that generic Lovelock gravity in D dimensions has a unitary massless spin-2 excitation around any one of its constant curvature vacua just like the cosmological Einstein gravity. The propagator of the theory reduces to that of Einstein's gravity, but scattering amplitudes must be computed with an effective Newton's constant which we provide. Tree-level unitarity imposes a single constraint on the parameters of the theory yielding a wide range of unitary region. As an ex...
Design of an X-band 3-bit RF MEMS constant phase shifter
Kuzubaşlı, Ahmet; Akın, Tayfun; Demir, Şimşek; Department of Electrical and Electronics Engineering (2016)
This thesis presents a 3-bit 180° constant phase shifter design implementing Co-Planar Waveguide (CPW) and RF MEMS variable capacitors with ±1.8% accuracy at 10 GHz and ±5.8% maximum peak error between 9-11 GHz. The phase shifter with minimum phase errors is determined by considering exemplary circuit simulations of different phase shifter types designed with a novel in-house RF MEMS fabrication process [1] parameters. Due to its wide-band characteristics and CPW compatibility, the selected topology is the ...
Improving the accuracy of the magnetic field integral equation with the linear-linear basis functions
Ergül, Özgür Salih (American Geophysical Union (AGU), 2006-07-18)
[ 1] Basis functions with linear variations are investigated in terms of the accuracy of the magnetic field integral equation (MFIE) and the combined-field integral equation (CFIE), on the basis of recent reports indicating the inaccuracy of the MFIE. Electromagnetic scattering problems involving conducting targets with arbitrary geometries, closed surfaces, and planar triangulations are considered. Specifically, two functions with linear variations along the triangulation edges in both tangential and norma...
Comprehensive timing and X-ray spectral analysis of GX 1+4
Serim, M. M.; Sahiner, S.; Cerri-Serim, D.; İNAM, SITKI ÇAĞDAŞ; Baykal, Altan (2017-08-01)
We present the analysis of RXTE-PCA observations of GX 1+4 between 2001 March 3 and 2003 January 31 together with the CGRO-BATSE X-ray flux and frequency derivative time series between 1991 and 1999. From the timing analysis of RXTE-PCA observations, we are able to phase connect pulse arrival times of the source within two different time intervals and obtain corresponding timing solutions. Using these pulse arrival times, we contribute to long-term pulse frequency history of the source. We look for episodic...
Citation Formats
M. ALPAR, H. OGELMAN, and J. SHAHAM, “IS GEMINGA A GLITCHING PULSAR,” ASTRONOMY & ASTROPHYSICS, pp. 0–0, 1993, Accessed: 00, 2020. [Online]. Available: