Long-term observations of the pulsars in 47 Tucanae - II. Proper motions, accelerations and jerks

This paper is the second in a series where we report the results of the long-term timing of the millisecond pulsars (MSPs) in 47 Tucanae with the Parkes 64-m radio telescope. We obtain improved timing parameters that provide additional information for studies of the cluster dynamics: a) the pulsar proper motions yield an estimate of the proper motion of the cluster as a whole ($\mu_{\alpha}\, = \, 5.00\, \pm \, 0.14\, \rm mas \, yr^{-1}$, $\mu_{\delta}\, = \, -2.84\, \pm \, 0.12\, \rm mas \, yr^{-1}$) and the motion of the pulsars relative to each other. b) We measure the second spin-period derivatives caused by the change of the pulsar line-of-sight accelerations; 47 Tuc H, U and possibly J are being affected by nearby objects. c) For ten binary systems we now measure changes in the orbital period caused by their acceleration in the gravitational field of the cluster. From all these measurements, we derive a cluster distance no smaller than $\sim\,$4.69 kpc and show that the characteristics of these MSPs are very similar to their counterparts in the Galactic disk. We find no evidence in favour of an intermediate mass black hole at the centre of the cluster. Finally, we describe the orbital behaviour of the four "black widow" systems. Two of them, 47 Tuc J and O, exhibit orbital variability similar to that observed in other such systems, while for 47 Tuc I and R the orbits seem to be remarkably stable. It appears, therefore, that not all "black widows" have unpredictable orbital behaviour.Comment: 21 pages in journal format, 9 figures, 4 tables, accepted for publication in MNRAS, several clarifications made and typos fixe

Long-term observations of the pulsars in 47 Tucanae. I. A study of four elusive binary systems

For the past couple of decades, the Parkes radio telescope has been regularly observing the millisecond pulsars in 47 Tucanae (47 Tuc). This long-term timing program was designed to address a wide range of scientific issues related to these pulsars and the globular cluster where they are located. In this paper, the first of a series, we address one of these objectives: the characterization of four previously known binary pulsars for which no precise orbital parameters were known, namely 47 Tuc P, V, W and X (pulsars 47 Tuc R and Y are discussed elsewhere). We determined the previously unknown orbital parameters of 47 Tuc V and X and greatly improved those of 47 Tuc P and W. For pulsars W and X we obtained, for the first time, full coherent timing solutions across the whole data span, which allowed a much more detailed characterization of these systems. 47 Tuc W, a well-known tight eclipsing binary pulsar, exhibits a large orbital period variability, as expected for a system of its class. 47 Tuc X turns out to be in a wide, extremely circular, 10.9-day long binary orbit and its position is ~3.8 arcmin away from the cluster center, more than three times the distance of any other pulsar in 47 Tuc. These characteristics make 47 Tuc X a very different object with respect to the other pulsars of the cluster.Comment: Accepted for publication by MNRAS, 18 pages, 11 figure

D-branes in 2d Lorentzian black hole

We study D-branes in the Lorentzian signature 2D black hole string theory. We use the technique of gauged WZW models to construct the associated boundary conformal field theories. The main focus of this work is to discuss the (semi-classical) world-volume geometries of the D-branes. We also discuss comparison of our work with results in related gauged WZW models.Comment: 24 pages, 5 figures, uses JHEP3.cl

The Virtue of Defects in 4D Gauge Theories and 2D CFTs

We advance a correspondence between the topological defect operators in Liouville and Toda conformal field theories - which we construct - and loop operators and domain wall operators in four dimensional N=2 supersymmetric gauge theories on S^4. Our computation of the correlation functions in Liouville/Toda theory in the presence of topological defect operators, which are supported on curves on the Riemann surface, yields the exact answer for the partition function of four dimensional gauge theories in the presence of various walls and loop operators; results which we can quantitatively substantiate with an independent gauge theory analysis. As an interesting outcome of this work for two dimensional conformal field theories, we prove that topological defect operators and the Verlinde loop operators are different descriptions of the same operators.Comment: 59 pages, latex; v2 corrections to some formula

't Hooft Operators in Gauge Theory from Toda CFT

We construct loop operators in two dimensional Toda CFT and calculate with them the exact expectation value of certain supersymmetric 't Hooft and dyonic loop operators in four dimensional \Ncal=2 gauge theories with SU(N) gauge group. Explicit formulae for 't Hooft and dyonic operators in \Ncal=2^* and \Ncal=2 conformal SQCD with SU(N) gauge group are presented. We also briefly speculate on the Toda CFT realization of arbitrary loop operators in these gauge theories in terms of topological web operators in Toda CFT.Comment: 49 pages, LaTeX. Typos fixed, references adde

D-branes in a Big Bang/Big Crunch Universe: Nappi-Witten Gauged WZW Model

We study D-branes in the Nappi-Witten model, which is a gauged WZW model based on (SL(2,R) x SU(2)) / (U(1) x U(1)). The model describes a four dimensional space-time consisting of cosmological regions with big bang/big crunch singularities and static regions with closed time-like curves. The aim of this paper is to investigate by D-brane probes whether there are pathologies associated with the cosmological singularities and the closed time-like curves. We first classify D-branes in a group theoretical way, and then examine DBI actions for effective theories on the D-branes. In particular, we show that D-brane metric from the DBI action does not include singularities, and wave functions on the D-branes are well behaved even in the presence of closed time-like curves.Comment: 50 pages, 2 figures, minor change

Long-term variations in the pulse emission from PSR J0737-3039B

Analysis of 20 months of observations at the Parkes radio telescope shows secular changes in the pulsed emission from J0737-3039B, the 2.77 s pulsar of the double-pulsar system. Pulse profiles are becoming single-peaked in both bright phases of the orbital modulation although there is no clear variation in overall pulse width. The shape of the orbital modulation is also varying systematically, with both bright phases shrinking in longitude by ~ 7 deg/yr. However, the combined span of the two bright phases is relatively constant and together they are shifting to higher longitudes at a rate of ~ 3 deg/yr. We discuss the possible contributions of geodetic precession and periastron advance to the observed variations.Comment: 4 pages, 5 figures. Corrected typo

The Parkes Observatory Pulsar Data Archive

The Parkes pulsar data archive currently provides access to 144044 data files obtained from observations carried out at the Parkes observatory since the year 1991. Around 10^5 files are from surveys of the sky, the remainder are observations of 775 individual pulsars and their corresponding calibration signals. Survey observations are included from the Parkes 70cm and the Swinburne Intermediate Latitude surveys. Individual pulsar observations are included from young pulsar timing projects, the Parkes Pulsar Timing Array and from the PULSE@Parkes outreach program. The data files and access methods are compatible with Virtual Observatory protocols. This paper describes the data currently stored in the archive and presents ways in which these data can be searched and downloaded.Comment: Accepted by PAS