Main meetings/events from December 2016 until March 2017
Despite the season is not usually the most favourable for conferences and congresses, the Members of the SKA Pulsar Science Working Group (SKA-PSWG) have had various opportunities for meetings and discussions during the last months. These include the following:
1) Fast Radio Bursts: New probes of fundamental physics and cosmology
Aspen Center for Physics, Aspen, Colorado, 12-17 February 2017
This conference was planned to finally establish a direct contact between the pulsar community (which began this field of research) and other astrophysical communities, which are nowadays fruitfully involved in the studies of the Fast Radio Bursts. Various members of the SKA Pulsar SWG attended the meeting, as well as many people belonging to the SKA Transients SWG and other SKA SWGs.
2) Detecting gravitational waves with a pulsar timing array
Veldhoven, NL, 17/18 Jan 2017
In the context of the yearly Dutch general Physics conference, members of the SKA Pulsar SWG were invited to report and to discuss the detection of Gravitational Waves with the use of pulsar timing array, including an outlook to future SKA efforts in this intriguing line of research
3) Detecting gravitational waves with a pulsar timing array
Leuven, Belgium , 8 Mar 2017,
At the yearly meeting of the Dutch/Belgian gravitational wave forum, members of the SKA Pulsar SWG met and talked about the capabilities and the European Pulsar Timing Array (EPTA) and how SKA1 will significantly impact on this field.
Publications related to the PSWG from December 2016 to March 2017
During the 4 months from December 2016 to March 2017, about 120 papers related to the subjects of interest for the SKA-PSWG have been published, accepted and/or submitted to international refereed journals by the members of the PSWG and their collaborators. In the following, we report a selection of some of the announced works.
a) Barr, E. D., Freire, P. C. C., Kramer, M., Champion, D. J., Berezina, M., Bassa, C. G., Lyne, A. G., Stappers, B. W., 2017, Monthly Notices of the Royal Astronomical Society, http://cdsads.u-strasbg.fr/abs/2017MNRAS.465.1711B A massive millisecond pulsar in an eccentric binary
The paper reports on the results of an extensive timing campaign focused on PSR J1946+3417, a member of the population of eccentric millisecond pulsar binaries with low-mass white dwarf companions in the Galactic field. The mass of the pulsar and of the companion, as well as the inclination of the orbit, have been determined and implications for the still obscure evolutionary models discussed. SKA1 is expected to discover a large population of this kind of binaries.
b) Smits, C. G. Bassa, G. H. Janssen, R. Karuppusamy, M. Kramer, K. J. Lee, K. Liu, J. McKee, D. Perrodin, M. Purver, S. Sanidas, B. W. Stappers, W. W. Zhu 2017, The beamformer and correlator for the Large European Array for Pulsars
http://adsabs.harvard.edu/abs/2017arXiv170306438S (accepted for publication in Astronomy and Computing) This paper deals with the software correlator and the beamformer which enables tied-array beamforming from the raw voltages for LEAP. This software represents a new step on the way to build the most suitable suite of codes for pulsar investigations with SKA1.
c) Luo, J.-T., Chen, L., Han, J.-L., Esamdin, A., Wu, Y.-J., Li, Z.-X., Hao, L.-F., Zhang, X.-Z., 2017, Research in Astronomy and Astrophysics, http://cdsads.u-strasbg.fr/abs/2017RAA….17….9L A digital pulsar backend based on FPGA. The authors present tests of pulsar observations obtained with a digital backend based on a Field Programmable Gate Array (FPGA, a key technology also for the development of SKA1 pulsar backends).
d) Wright, G., Weltevrede, P., 2017, Monthly Notices of the Royal Astronomical Society, http://cdsads.u-strasbg.fr/abs/2017MNRAS.464.2597W Pulsar bi-drifting: implications for polar cap geometry It is here investigated the hypothesis that the carousels of sub-beams seen in a few pulsars, and hence their emission beams, are not circular but elliptical with axes tilted with respect to the fiducial plane. The sensitivity of SKA1 is expected to allow the astronomers to finally share light on the emission mechanisms underlying these carousels.
e) Shannon, R. M., Cordes, J. M., 2017, Monthly Notices of the Royal Astronomical Society, http://cdsads.u-strasbg.fr/abs/2017MNRAS.464.2075S Modelling and mitigating refractive propagation effects in precision pulsar timing observations This paper examines both the strength of propagation effects associated with large-scale electron-density variations in the Interstellar Medium and the methodology used to estimate infinite frequency arrival times of the pulsar pulses, a very important investigation in the context of SKA1 low-frequency pulsar observations. It is found that the frequency dependence of the trajectories of the propagating radio waves can limit the efficacy of low-frequency (metre-wavelength) observations, especially when dealing with pulsars with large dispersion measure.
f) Rookyard, S. C., Weltevrede, P., Johnston, S., Kerr, M., 2017, Monthly Notices of the Royal Astronomical Society, http://cdsads.u-strasbg.fr/abs/2017MNRAS.464.2018R On the difference between gamma-ray-detected and non-gamma-ray-detected pulsars Various correlations are found and discussed in this papers, on the basis of which it is proposed that the gamma-ray-detected pulsars form a single population where the main factors determining gamma-ray detectability are the rate of rotational energy loss and the proximity of the line of sight to the rotation axis. The relation among the geometry of the radio emission and that of the gamma-ray emission will be in the focus of SKA1.
g) Ho, W. C. G., Ng, C.-Y., Lyne, A. G., Stappers, B. W., Coe, M. J., Halpern, J. P., Johnson, T. J., Steele, I. A., 2017, Monthly Notices of the Royal Astronomical Society, http://cdsads.u-strasbg.fr/abs/2017MNRAS.464.1211H Multiwavelength monitoring and X-ray brightening of Be X-ray binary PSR J2032+4127/MT91 213 on its approach to periastron The paper describes radio, X-ray, and optical monitoring of PSR J2032+4127, a pulsar in a decades-long orbit with the Be star MT91 213, and now moving rapidly towards periastron. Coordinated multiwavelength observations of this and other similar systems will strongly benefit of SKA1, the instantaneous sensitivity of which is instrumental for studying the short phases during which a pulsar interacts with the material released by the companion star.
h) Yao, J. M., Manchester, R. N., Wang, N., 2017, The Astrophysical Journal, http://cdsads.u-strasbg.fr/abs/2017ApJ…835…29Y A New Electron-density Model for Estimation of Pulsar and FRB Distances This manuscript presents a new model (dubbed YMW16) for the distribution of free electrons in the Galaxy, the Magellanic Clouds, and the intergalactic medium (IGM) that can be used to estimate distances to real or simulated pulsars and fast radio bursts (FRBs) based on their dispersion measure (DM). The predictions of YMW16 are compared to those of the previous TC93 and NE2001 models showing that YMW16 performs significantly better: 95% of predicted Galactic pulsar distances will have a relative error of less than a factor of 0.9. Thanks to thousands of additional pulsar discoveries and the capabilities of obtaining many direct determinations of pulsar distances, SKA1 is expected to test the new YMW16 model and to trigger another step ahead in constraining the distribution of free electrons in the Galaxy.
i) Lyne, A. G., Stappers, B. W., Bogdanov, S., Ferdman, R. D., Freire, P. C. C., Kaspi, V. M., Knispel, B., Lynch, R., Allen, B., Brazier, A., Camilo, F., Cardoso, F., Chatterjee, S., Cordes, J. M., Crawford, F., Deneva, J. S., Hessels, J. W. T., Jenet, F. A., Lazarus, P., van Leeuwen, J., Lorimer, D. R., Madsen, E., McKee, J., McLaughlin, M. A., Parent, E., Patel, C., Ransom, S. M., Scholz, P., Seymour, A., Siemens, X., Spitler, L. G., Stairs, I. H., Stovall, K., Swiggum, J., Wharton, R. S., Zhu, W. W., Aulbert, C., Bock, O., Eggenstein, H.-B., Fehrmann, H., Machenschalk, B., 2017, The Astrophysical Journal, http://cdsads.u-strasbg.fr/abs/2017ApJ…834..137L Timing of 29 Pulsars Discovered in the PALFA Survey Following discovery with the Arecibo Telescope, confirmation and timing observations of 29 pulsars over several years at Jodrell Bank Observatory are reported in this paper. These observations have yielded high-precision positions and measurements of rotation and radiation properties.
j) Lyne, A. G., Stappers, B. W., Freire, P. C. C., Hessels, J. W. T., Kaspi, V. M., Allen, B., Bogdanov, S., Brazier, A., Camilo, F., Cardoso, F., Chatterjee, S., Cordes, J. M., Crawford, F., Deneva, J. S., Ferdman, R. D., Jenet, F. A., Knispel, B., Lazarus, P., van Leeuwen, J., Lynch, R., Madsen, E., McLaughlin, M. A., Parent, E., Patel, C., Ransom, S. M., Scholz, P., Seymour, A., Siemens, X., Spitler, L. G., Stairs, I. H., Stovall, K., Swiggum, J., Wharton, R. S., Zhu, W. W., 2017, The Astrophysical Journal, http://cdsads.u-strasbg.fr/abs/2017ApJ…834…72L Two Long-Term Intermittent Pulsars Discovered in the PALFA Survey The discoveries reported in this paper increase the number of known long-term intermittent pulsars to five indicating the existence of a large population of these objects, most of which will be finally detected by SKA1.
k) Lam, M. T., Cordes, J. M., Chatterjee, S., Arzoumanian, Z., Crowter, K., Demorest, P. B., Dolch, T., Ellis, J. A., Ferdman, R. D., Fonseca, E., Gonzalez, M. E., Jones, G., Jones, M. L., Levin, L., Madison, D. R., McLaughlin, M. A., Nice, D. J., Pennucci, T. T., Ransom, S. M., Shannon, R. M., Siemens, X., Stairs, I. H., Stovall, K., Swiggum, J. K., Zhu, W. W., 2017, The Astrophysical Journal, http://cdsads.u-strasbg.fr/abs/2017ApJ…834…35L The NANOGrav Nine-year Data Set: Excess Noise in Millisecond Pulsar Arrival Times It is shown that 26 out of 37 pulsars of the NANOGrav database show inconsistencies with a white-noise-only model based on the short timescale analysis of each pulsar, and the excess noise has a red power spectrum for 15 pulsars. The effects of that on the detection of Gravitational Waves at nanohertz frequencies (one of the key aim of SKA1) are discussed.
l) Bassa, C. G., Pleunis, Z., Hessels, J. W. T., 2017, Astronomy and Computing, http://cdsads.u-strasbg.fr/abs/2017A&C….18…40B Enabling pulsar and fast transient searches using coherent dedispersion This work introduces the implementation, called cdmt, of a coherent dedispersion algorithm capable of dedispersing high-time-resolution radio observations to many different dispersion measures. The software is used in an ongoing LOFAR survey which led to the discovery of a millisecond pulsar, the first ever at 135 MHz. This new approach for searching for pulsars seems very promising also for SKA1-LOW targeted searches.
m) Liu, K., Bassa, C. G., Janssen, G. H., Karuppusamy, R., McKee, J., Kramer, M., Lee, K. J., Perrodin, D., Purver, M., Sanidas, S., Smits, R., Stappers, B. W., Weltevrede, P., Zhu, W. W., 2016, Monthly Notices of the Royal Astronomical Society, http://cdsads.u-strasbg.fr/abs/2016MNRAS.463.3239L Variability, polarimetry, and timing properties of single pulses from PSR J1713+0747 using the Large European Array for Pulsars This paper reports on the analysis of single pulses from PSR J1713+0747 with data collected by the Large European Array for Pulsars (LEAP). Single pulses preserve information about the pulsar radio emission and propagation in the pulsar magnetosphere, and understanding the behaviour of their variability is essential for estimating the fundamental limit on the achievable pulsar timing precision, a key ingredient for properly planning SKA1 pulsar activities.
n) Stovall, K., Allen, B., Bogdanov, S., Brazier, A., Camilo, F., Cardoso, F., Chatterjee, S., Cordes, J. M., Crawford, F., Deneva, J. S., Ferdman, R., Freire, P. C. C., Hessels, J. W. T., Jenet, F., Kaplan, D. L., Karako-Argaman, C., Kaspi, V. M., Knispel, B., Kotulla, R., Lazarus, P., Lee, K. J., van Leeuwen, J., Lynch, R., Lyne, A. G., Madsen, E., McLaughlin, M. A., Patel, C., Ransom, S. M., Scholz, P., Siemens, X., Stairs, I. H., Stappers, B. W., Swiggum, J., Zhu, W. W., Venkataraman, A., 2016, The Astrophysical Journal, http://cdsads.u-strasbg.fr/abs/2016ApJ…833..192S Timing of Five PALFA-discovered Millisecond Pulsars Timing observations of five millisecond pulsars were conducted with the Arecibo and Lovell telescopes for time spans ranging from 1.5 to 3.3 years. All of them except one are in binary systems with low eccentricities and one of them is likely a redback pulsar. SKA1 is expected to discover and time thousands of binaries similar to these.
o) Fonseca, E., Pennucci, T. T., Ellis, J. A., Stairs, I. H., Nice, D. J., Ransom, S. M., Demorest, P. B., Arzoumanian, Z., Crowter, K., Dolch, T., Ferdman, R. D., Gonzalez, M. E., Jones, G., Jones, M. L., Lam, M. T., Levin, L., McLaughlin, M. A., Stovall, K., Swiggum, J. K., Zhu, W., 2016, The Astrophysical Journal, http://cdsads.u-strasbg.fr/abs/2016ApJ…832..167F The NANOGrav Nine-year Data Set: Mass and Geometric Measurements of Binary Millisecond Pulsars
This paper analyzes 24 binary radio pulsars in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) nine-year data set. Fourteen significant measurements of the Shapiro delay – including new detections in four pulsar-binary systems – are obtained and the mass of the two stars derived. SKA1 will provide a wealth of additional Shapiro delay determinations, finally assessing the overall pulsar mass distribution.
p) Jones, M.L., McLaughlin, M.A., Lam, M.T., Cordes, J.M., Levin, L., Chatterjee, S., Arzoumanian, Z., Crowter, K., Demorest, P.B., Dolch, T., Ellis, J.A., Ferdman, R.D., Fonseca, E., Gonzalez, M.E., Jones, G., Lazio, T.J.W., Nice, D.J., Pennucci, T.T., Ransom, S.M., Stinebring, D.R., Stairs, I. H., Stovall, K., Swiggum, J.K., Zhu, W.W., 2016, ApJ, submitted, http://adsabs.harvard.edu/abs/2016arXiv161203187J The NANOGrav Nine-Year Data Set: Measurement and Interpretation of Variations in Dispersion Measures. This paper analyzes dispersion measure (DM) variations of 37 millisecond pulsars in the 9-year NANOGrav data release and constrain the sources of these variations. Variations are significant for nearly all pulsars, with characteristic timescales comparable to or even shorter than the average spacing between observations. Understanding such effects will be essential to the SKA1 project to detect gravitational waves using pulsars.