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====== What is journal club? ====== Journal club is informal setting where volunteers/authors present papers. The slot is for one hour. You can either make a presentation and/or scroll through the paper. Sometimes there can be discussions after going through the paper. It can be like 30mins paper+30mins discussion (or ending early). Meetings happen in person unless otherwise advertized. Participation via Zoom is possible upon request. In which case, zoom link: https://eu02web.zoom-x.de/j/62726414514 ====== November 15, 2024 ====== **Lucía Gebauer** Paper: On the mean profiles of radio pulsars I: Theory of the propagation effects https://arxiv.org/abs/1107.3775 ====== November 8, 2024 ====== **Lynn Hansen** Paper: Ho'oleilana: An Individual Baryon Acoustic Oscillation? https://arxiv.org/abs/2309.00677 ====== November 1, 2024 ====== **CANCELLED DUE TO PUBLIC HOLIDAY** ====== October 24, 2024 ====== **Jonah Wagenveld** Paper: The First Billion Years, According to JWST https://arxiv.org/pdf/2405.21054 ====== October 17, 2024 ====== **Rutger van Haasteren, AEI Hannover** Bayesian Noise Analysis and Heirarchical Modelling https://arxiv.org/abs/2406.05081 https://arxiv.org/abs/2409.06050 - Online! ====== October 10, 2024 ====== **Pranav Limaye** Paper: Bayesian Insights into post-Glitch Dynamics: Model comparison and parameter constraint from decades long observation data of the Crab pulsar https://arxiv.org/abs/2409.18432 ====== September 12, 2024 ====== **Tim Sprenger** Paper: A Cyclic Spectroscopy Scintillation Study of PSR B1937+21. I. Demonstration of Improved Scintillometry https://ui.adsabs.harvard.edu/abs/2024ApJ...972...16T/abstract ====== September 5, 2024 ====== **Pranav Limaye** Paper: A 2.9-hour periodic radio transient with an optical counterpart https://ui.adsabs.harvard.edu/abs/2024arXiv240815757H/abstract ====== July 25, 2024 ====== **surya bethapudi** Paper: Complex rotational dynamics of the neutron star in Hercules X-1 revealed by X-ray polarization https://ui.adsabs.harvard.edu/abs/2024NatAs.tmp..113H/abstract ====== July 18, 2024 ====== **Jedrzej Jawor** Paper: An unusual pulse shape change event in PSR J1713+0747 observed with the Green Bank Telescope and CHIME https://arxiv.org/pdf/2210.12266 ====== July 11, 2024 ====== **Lucia Werner Gebauer** Paper: The Thousand-Pulsar-Array programme on MeerKAT - XIV. On the high linearly polarized pulsar signals The Thousand-Pulsar-Array programme on MeerKAT - XI. Application of the rotating vector model https://ui.adsabs.harvard.edu/abs/2024MNRAS.530.4839J/abstract https://ui.adsabs.harvard.edu/abs/2023MNRAS.520.4801J/abstract ====== July 3, 2024 ====== **Nicholas John O'Niell** Paper: Analysing radio pulsar timing noise with a Kalman filter: a demonstration involving PSR J1359−6038 https://academic.oup.com/mnras/article/530/4/4648/7635689 ====== June 27, 2024 ====== **Isabella Rammala** Paper: The SARAO MeerKAT 1.3 GHz Galactic Plane Survey https://arxiv.org/abs/2312.07275 ====== June 13, 2024 ====== **Kathrin Grunthal** Paper: Pulsar Timing Arrays require hierarchical models https://ui.adsabs.harvard.edu/abs/2024arXiv240605081V/abstract ====== June 6, 2024 ====== **Pranav Limaye** Paper: Decoding the nature of Coherent radio emission in Pulsars I: Observational constraints https://arxiv.org/abs/2405.20634 ====== March 21, 2024 ====== **Tim Sprenger** Paper: Pulsar scintillation through thick and thin: bow shocks, bubbles, and the broader interstellar medium https://ui.adsabs.harvard.edu/abs/2024MNRAS.527.7568O/abstract ====== March 14, 2024 ====== **Kathrin Grunthal** Paper: Artificial Precision Timing Array: bridging the decihertz gravitational-wave sensitivity gap with clock satellites https://ui.adsabs.harvard.edu/abs/2024arXiv240113668A/abstract ====== February 15, 2024 ====== **Isabella Rammala** Paper: The RATT PARROT: serendipitous discovery of a peculiarly scintillating pulsar in MeerKAT imaging observations of the Great Saturn-Jupiter Conjunction of 2020. I. Dynamic imaging and data analysis https://arxiv.org/abs/2312.12165 ====== February 8, 2024 ====== **Weiberfastnacht - do we have journal club? ** ====== February 1, 2024 ====== **Dany Vohl** Paper: Topology of Pulsar Profiles (ToPP). I. Graph theory method and classification of the EPN https://ui.adsabs.harvard.edu/abs/2023arXiv231109201V/abstract ====== January 11, 2024 ====== **Pravir Kumar** Finding pulsars in Short-period binary systems using a novel pruning algorithm Most pulsars are extremely faint astrophysical sources, necessitating extended observation times to be coherently integrated for a significant detection. In a typical binary pulsar system, the number of potential orbits, periods, and spin-down combinations ranges from 10^25 to 10^35, rendering exhaustive enumeration impractical. Approximations such as uniform acceleration compromise the sensitivity of pulsar searches, leaving a significant portion of the detectable parameter space unexplored. We present a novel pruning algorithm that will significantly improve pulsar detection in short-period binary systems, allowing for observation times longer than an orbital period. Our current implementation of this pruning algorithm systematically evaluates all valid options for circular orbits within small data segments with statistically significant detection for the entire dataset. The computational efficiency gained through the pruning process can be channeled into extending integration times as much as possible, ultimately enhancing our ability to detect faint binary pulsars. ====== December 7, 2023 ====== **Fun papers** (1) Gugelhupf cake (2) spass zu haben (3) fun papers ====== November 30, 2023 ====== **Pablo Torne** Paper: A search for pulsars around Sgr A* in the first Event Horizon Telescope dataset https://ui.adsabs.harvard.edu/abs/2023arXiv230815381T/abstract ====== November 23, 2023 ====== **Jompoj Wongphechauxsorn** Thesis practice talk!! ====== November 16, 2023 ====== **Kuo Liu** Paper linking microstructure widths and rotational periods with implications on FRB periodicities Paper TBD ====== November 2, 2023 ====== **Paulo Freire** ** JWST uncovers helium and water abundance variations in the bulge globular cluster NGC 6440(https://arxiv.org/abs/2310.13056) ** ====== October 26, 2023 ====== **Lucy Oswald** ** Pulsar polarization: a partial-coherence model(https://academic.oup.com/mnras/article/525/1/840/7232540) ** ====== October 19, 2023 ====== **Sebastiano D. von Fellenberg** The Young Stars in the Galactic Center (https://ui.adsabs.harvard.edu/abs/2022ApJ...932L...6V/abstract) =============== OLD ================== ====== February 6, 2020 ====== **Papers of the week:** https://iopscience.iop.org/journal/2041-8205/page/Focus_on_NICER_Constraints_on_the_Dense_Matter_Equation_of_State **Presenters:** Robert Wharton and Vivek Venkatraman Krishnan **Title:** NICER papers (Papers 1,2,4,5 and 6) ====== June 5, 2019 ====== **Pulsar of the week:** J1746-2850 (aka Aris' Star) **Presenter:** Robert Wharton **Paper of the week:** https://arxiv.org/abs/1905.05209 **Presenter:** Vishnu Balakrishnan **Title:** Intermediate mass black holes in globular clusters: effects on jerks and jounces of millisecond pulsars **Abstract:** Globular clusters may host intermediate mass black holes (IMBHs) at their centres. Here we propose a new method for their identification using millisecond pulsars (MSPs) as probes. We show that measuring the first (jerk) and second (jounce) derivatives of the accelerations of an ensemble of MSPs will let us infer the presence of an IMBH in a globular cluster better than measuring the sole accelerations. We test this concept by simulating a set of star clusters with and without a central IMBH to extract the distributions of the stellar jerks and jounces. We then apply this technique to the ensemble of MSPs in the Galactic globular cluster 47 Tucanae. Current timing observations are insufficient to constrain the presence of an IMBH and can only be used to pose upper limits on its mass. But, with few more years of observations it will be possible to test for the presence of a central IMBH with mass smaller than ∼ 1000 M⊙. We conclude that jerks and jounces help significantly in reducing the upper limit of the mass of IMBHs in Galactic globular clusters. ====== May 29, 2019 ====== Cancelled: Lack of interest :( ====== May 22, 2019 ====== **Pulsar of the week:** B0834+06 **Presenter:** Robert Main {{:journalclub:b0834-pulsaroftheweek.pdf| PDF }} ====== May 15, 2019 ====== **Paper of the week:** https://arxiv.org/abs/1904.11618 **Presenter:** Ms. Tasha Gautam **Title:** A Radio Bursts Detection Method Based on Hough Transform **Abstract:** We present a simple and fast method for incoherent dedispersion and fast radio burst (FRB) detection based on the Hough transform, which is widely used for feature extraction in image analysis. The Hough transform maps a point in the data maps to a straight line in the parameter space, and points on the same dispersed f−2 curve to a bundle of lines all crossing at the same point, thus the curve is transformed to a single point in the parameter space, enabling a simple way for the detection of radio burst. By choosing an appropriate truncation threshold, the method has a complexity of max(Nt,Nf)Nd where Nf, Nt and Nd are the dimension of the data in frequency, time, and dispersion measure, respectively, this is lower than other existing methods. Using simulation data of different noise levels, we studied how the detected peak varies with different truncation thresholds. We also tested the method with some real pulsar and FRB data. ====== May 08, 2019 ====== **Special talk:** Pulsar evolution on the short and long time scales **Presenter:** Dr. Simon Johnston ====== May 01, 2019 ====== Cancelled: Labour day holiday ====== April 24, 2019 ====== **Pulsar of the week:** PSR J1022+1001 **Presenter:** Mr. Prajwal Padmanabh {{:journalclub:potw_24042019.pdf | PDF}} **Papers of the week:** Jist of M87 black hole papers: https://iopscience.iop.org/issue/2041-8205/875/1 {{:journalclub: journal_190424.pdf | PDF}} **Presenter:** Dr. Roebrt Wharton ====== April 17, 2019 ====== **Pulsar of the week:** PSR J1756-2251 **Presenter:** Ms. Huanchen Hu {{:journalclub: potw_17042019.pdf | PDF}} **Papers of the week:** Astro2020 white papers: https://arxiv.org/abs/1903.08653 https://arxiv.org/abs/1903.08194 https://arxiv.org/abs/1903.08183 https://arxiv.org/abs/1903.07644 https://arxiv.org/abs/1903.06526 **Presenter:** Dr. Vivek Venkatraman Krishnan ====== April 10, 2019 ====== Cancelled: EHT press release ====== April 3, 2019 ====== **Pulsar of the week:** PSR J0737-3039B **Presenter:** Dr. Aris Noutsos {{:journalclub: 03042019_potw.pdf|PDF}} **Paper of the week:** https://arxiv.org/abs/1606.00449 **Presenter:** Mr. Akash Mantri **Title:** KNOWN PULSARS IDENTIFIED IN THE GMRT 150 MHz ALL-SKY SURVEY {{:journalclub: frail_2016_apj_829_119.pdf |PDF}} **Abstract:** We have used the 150 MHz radio continuum survey (TGSS ADR) from the Giant Metrewave Radio Telescope (GMRT) to search for phase-averaged emission toward all well-localized radio pulsars north of −53° decl. We detect emission toward 200 pulsars with high confidence (5s) and another 88 pulsars at fainter levels. We show that most of our identifications are likely from pulsars, except for a small number where the measured flux density is confused by an associated supernova or pulsar-wind nebula, or a globular cluster. We investigate the radio properties of the 150 MHz sample and find an unusually high number of gamma-ray binary millisecond pulsars with very steep spectral indices. We also note a discrepancy in the measured flux densities between GMRT and LOFAR pulsar samples, suggesting that the flux density scale for the LOFAR pulsar sample may be in error by approximately a factor of two. We carry out a separate search of 30 well-localized gamma-ray, radio-quiet pulsars in an effort to detect a widening of the radio beam into the line of sight at lower frequencies. No steep-spectrum emission was detected either toward individual pulsars or in a weighted stack of all 30 images. ====== March 28, 2019 ====== **Pulsar of the week:** PSR J0737-3039A **Presenter:** Prof. Michael Kramer {{:journalclub: doublepulsar.pdf|PDF}} ====== March 20, 2019 ====== **Pulsar of the week:** PSR B1257+12 **Presenter:** Mr. Lorenz Haase {{:journalclub: doublepulsar.pdf|PDF}} **Paper of the week:** https://arxiv.org/abs/1902.03814 **Presenter:** Dr. Eleni Graikou **Title:** First detection of frequency-dependent, time-variable dispersion measures **Abstract:** Context. High-precision pulsar-timing experiments are affected by temporal variations of the Dispersion Measure (DM), which are related to spatial variations in the interstellar electron content. Correcting for DM variations relies on the cold-plasma dispersion law which states that the dispersive delay varies with the squared inverse of the observing frequency. This may however give incorrect measurements if the probed electron content (and therefore the DM) varies with observing frequency, as is predicted theoretically. Aims. We study small-scale density variations in the ionised interstellar medium. These structures may lead to frequency-dependent DMs in pulsar signals and could inhibit the use of lower-frequency pulsar observations to correct time-variable interstellar dispersion in higher-frequency pulsar-timing data. Methods. We used high-cadence, low-frequency observations with three stations from the German LOng-Wavelength (GLOW) consortium, which are part of the Low Frequency ARray (LOFAR). Specifically, 3.5 years of weekly observations of PSR J2219+4754 are presented. Results. We present the first detection of frequency-dependent DMs towards any interstellar object and a precise multi-year time-series of the time- and frequency-dependence of the measured DMs. The observed DM variability is significant and may be caused by extreme scattering events. Potential causes for frequency-dependent DMs are quantified and evaluated. Conclusions. We conclude that frequency-dependence of DMs has been reliably detected and is caused by small-scale (up to 10s of AUs) but steep density variations in the interstellar electron content. We find that long-term trends in DM variability equally affect DMs measured at both ends of our frequency band and hence the negative impact on long-term high-precision timing projects is expected to be limited. ====== March 13, 2019 ====== **Paper of the week:**: https://arxiv.org/pdf/1903.01573v1.pdf **Presenter:** Dr. Vivek Venkatraman Krishnan **Title:** Mode switching and oscillations in PSR B1828−11 **Abstract:** The young pulsar PSR B1828−11 has long been known to show correlated shape and spin-down changes with timescales of roughly 500 and 250 days, perhaps associated with large-scale magnetospheric switching. Here we present multi-hour observations with the Parkes and Green Bank Telescopes at multiple phases across the ∼500-day cycle and show that the pulsar undergoes mode-changing between two stable, extreme profile states. The fraction of time spent in each profile state naturally accounts for the observed overall ”shape parameter” (defined to be 0 for wide profiles and 1 for narrow ones); this and the variable rate of the mode transitions are directly related to the spin-down changes. We observe that the mode transition rate could plausibly function as an additional parameter governing the chaotic behaviour in this object which was proposed earlier by Seymour & Lorimer. Free precession is not needed to account for the variations. ====== March 06, 2019 ====== **Special talk:** Millisecond pulsars II **Presenter:** Dr. Paulo Freire. ====== February 27, 2019 ====== **Pulsar of the week:** J0453+1559, J1411+2551, J0154+1833, J0509+0856, J0709+0458, J0732+2314, J0824+0028, J2204+2700 **Presenter:** Mr. Joey Martinez {{:journalclub: 27022019_potw.pdf|PDF}} **Paper of the week:** https://arxiv.org/pdf/1902.03996.pdf **Presenter:** Dr. Vivek Venkatraman Krishnan **Title:** The Period-Width relationship for radio pulsars revisited **Abstract:** In the standard picture of radio pulsars, the radio emission arises from a set of open magnetic field lines, the extent of which is primarily determined by the pulsar’s spin period, P, and the emission height. We have used a database of parameters from 600 pulsars to show that the observed profile width, W, follows W ∝ P −0.3 albeit with a large scatter, emission occurs from heights below 400 km and that the beam is underfilled. Furthermore, the prevalence in the data for long period pulsars to have relatively wide profiles can only be explained if the angle between the magnetic and rotation axis decays with time. ====== February 20, 2019 ====== **Pulsar of the week:** PSR B0950+08 **Presenter:** Ms. Madhuri Gaikwad {{:journalclub: 27022019_potw.pdf |PDF}} **Paper of the week:** https://arxiv.org/abs/1902.00356 **Presenter:** Dr. Kuo Liu **Title:** A LOFAR search for steep-spectrum pulsars in Supernova Remnants and Pulsar Wind Nebulae **Abstract:** Pinpointing a pulsar in its parent supernova remnant (SNR) or resulting pulsar wind nebula (PWN) is key for understanding its formation history, and the pulsar wind mechanism. Yet, only about half the SNRs and PWNe appear associated with a pulsar. We aim to find the pulsars in a sample of eight known and new SNRs and PWNe. Using the LOFAR radio telescope at 150 MHz, each source was observed for 3 hours. We covered the entire remnants where needed, by employing many tied-array beams to tile out even the largest objects. For objects with a confirmed point source or PWN we constrained our search to those lines of sight. We identify a promising radio pulsar candidate towards PWN G141.2+5.0. The candidate, PSR J0337+61, has a period of 94 ms and a DM of 226 pc cm−3. We re-observed the source twice with increased sensitivities of 30% and 50% but did not re-detect it. It thus remains unconfirmed. For our other sources we obtain very stringent upper limits of 0.8-3.1 mJy at 150 MHz. Generally we can rule out that the pulsars travelled out of the remnant. From these strict limits we conclude our non-detections towards point-sources and PWNe are the result of beaming and propagation effects. Some of the remaining SNRs should host a black hole rather than a neutron star. ====== February 13, 2019 ====== **Paper of the week:** https://arxiv.org/abs/1807.07900 **Presenter:** Dr. Robert Wharton **Title:** A Fourier Domain 'Jerk' Search for Binary Pulsars **Abstract:** While binary pulsar systems are fantastic laboratories for a wide array of astrophysics, they are particularly difficult to detect. The orbital motion of the pulsar changes its apparent spin frequency over the course of an observation, essentially "smearing" the response of the time series in the Fourier domain. We review the Fourier domain acceleration search (FDAS), which uses a matched filtering algorithm to correct for this smearing by assuming constant acceleration for a small enough portion of the orbit. We discuss the theory and implementation of a Fourier domain "jerk" search, developed as part of the PRESTO software package, which extends the FDAS to account for a linearly changing acceleration, or constant orbital jerk, of the pulsar. We test the performance of our algorithm on archival Green Bank Telescope observations of the globular cluster Terzan~5, and show that while the jerk search has a significantly longer runtime, it improves search sensitivity to binaries when the observation duration is 5 to 15% of the orbital period. Finally, we present the jerk-search-enabled detection of Ter5am (PSR~J1748−2446am), a new highly-accelerated pulsar in a compact, eccentric, and relativistic orbit, with a likely pulsar mass of 1.649+0.037−0.11\,\msun. ====== February 6, 2019 ====== **Pulsar of the week:** PSR J1757-1854 **Presenter:** Mr.Vishnu Balakrishnan {{:journalclub: potw_07022019.pdf|PDF}} **Paper of the week:** https://arxiv.org/pdf/1305.4842.pdf **Presenter:** Mr. Jompoj Wongphecauxson **Title:** Autonomous Spacecraft Navigation With Pulsars **Abstract:** An external reference system suitable for deep space navigation can be defined by fast spinning and strongly magnetized neutron stars, called pulsars. Their beamed periodic signals have timing stabilities comparable to atomic clocks and provide characteristic temporal signatures that can be used as natural navigation beacons, quite similar to the use of GPS satellites for navigation on Earth. By comparing pulse arrival times measured on-board a spacecraft with predicted pulse arrivals at a reference location, the spacecraft position can be determined autonomously and with high accuracy everywhere in the solar system and beyond. The unique properties of pulsars make clear already today that such a navigation system will have its application in future astronautics. In this paper, we describe the basic principle of spacecraft navigation using pulsars and report on the current development status of this novel technology. Presentation link: https://prezi.com/view/Y7rx4MatCOaw2d3ORvhg/ ====== January 23, 2019 ====== **Paper of the week:** https://arxiv.org/abs/1808.09471 **Presenter:** Dr. Ralph Eatough {{:journalclub: 23012019_paper_1.pdf|PDF}} {{:journalclub: 23012019_paper_2.pdf|PDF}} **Title:** Induced Polarization from Birefringent Pulse Splitting in Magnetoionic Media **Abstract:** Birefringence in ionized, magnetized media is usually measured as Faraday rotation of linearly polarized radiation. However, pulses propagating through regions with very large Faraday rotation measures (RMs) can split into circularly polarized components with measurable differences in arrival times ∝ν−3RM, where ν is the radio frequency. Differential refraction from gradients in DM (dispersion measure) and RM can contribute a splitting time ∝|∇⊥DM||∇⊥RM|ν−5. Regardless of whether the emitted pulse is unpolarized or linearly polarized, net circular polarization will be measured when splitting is a significant fraction of the pulse width. However, the initial polarization may be inferable from the noise statistics of the bursts. Extreme multipath scattering that broadens pulses can mask splitting effects. We discuss particular cases such as the Galactic center magnetar, J1749−2900, and the repeating fast radio burst source, FRB 121102. Both lines of sight have RM∼105 rad m−2 that yields millisecond splittings at frequencies well below ∼1 GHz. We also consider the splitting of nanosecond shot pulses in giant pulses from the Crab pulsar and the minimal effects of birefringence on precision pulsar timing. Finally, we explore the utility of two-dimensional coherent dedispersion with DM and RM as parameters. ====== January 30, 2019 ====== **Special talk:** Millisecond pulsars I **Presenter:** Dr. Paulo Freire. ====== Winter break ====== December 6 2018 to January 29 2019 ====== December 5, 2018 ====== **Pulsar of the week:** PSR J0337+1715 **Presenter:** Ms. Tasha Gautam {{:journalclub: 05122018_potw.pdf|PDF}} **Paper of the week:** https://arxiv.org/abs/1811.04519 **Presenter:** Mr. Prajwal Padmanabh **Title:** The Frequency Dependence of Scintillation Arc Thickness in Pulsar B1133+16 **Abstract:** Scintillation arcs have become a powerful tool for exploring scattering in the ionized interstellar medium. There is accumulating evidence that the scattering from many pulsars is extremely anisotropic resulting in highly elongated, linear brightness functions. We present a three-frequency (327~MHz, 432~MHz, 1450~MHz) Arecibo study of scintillation arcs from one nearby, bright, high-velocity pulsar, PSR~B1133+16. We show that a one-dimensional (1D), linear brightness function is in good agreement with the data at all three observing frequencies. We use two methods to explore the broadening of the 1D brightness function B(θ) as a function of frequency: 1) crosscuts of the forward arc at constant delay and 2) a 1D modeling of B(θ) using a comparison between model and observed secondary spectrum as a goodness-of-fit metric. Both methods show that the half-power width of B(θ) deviates from the expected dependence ∝ν−a, where ν is the observing frequency . Our estimates of a have moderately large uncertainties but imply a≲1.8, and so are inconsistent with the expected a=2.0 for plasma refraction or a=2.2 for Kolmogorov turbulence. In addition the shape of B(θ) cuts off more steeply than predicted for Kolmogorov turbulence. Ultimately, we conclude that the underlying physics of the broadening mechanism remains unexplained. Our results place the scattering screen at a distance that is broadly consistent with an origin at the boundary of the Local Bubble. ---- ---- ---- ---- ====== November 28, 2018 ====== **Pulsar of the week:** PSR J1638-4725 and PSR J1259-63 **Presenter:** Dr. Ralph Eatough {{:journalclub: 281118_j1638-4725.pdf|PDF}} **Paper of the week:** https://arxiv.org/abs/1811.05766 **Presenter:** Dr. Robert Main **Title:** Unusually bright single pulses from B1744-24A binary: a case of strong lensing? **Abstract:** We present a study of unusually bright single pulses (BSPs) from a millisecond pulsar in an ablating binary system, B1744-24A, based on several multi-orbit observations with the Green Bank Telescope. These pulses come predominantly in time near eclipse ingress and egress, have intensities up to 40 times the average pulse intensity, and pulse widths similar to that of the average pulse profile. The average intensity, spectral index of radio emission, and the dispersion measure do not vary in connection with BSP outbursts. The average profile obtained from BSPs has the same shape as the average profile from all pulses. These properties make it difficult to explain BSPs via scintillation in the interstellar medium, as a separate emission mode, or as conventional giant pulses. BSPs from B1744-24A have similar properties to the strong pulses observed from the Black Widow binary pulsar B1957+10, which were recently attributed to strong lensing by the intrabinary material (Main et al. 2018). We argue that the strong lensing likely occurs in B1744-24A as well. For this system, the sizes and locations of the lenses are not well constrained by simple 1D lensing models from Cordes et al. (2017) and Main et al. (2018). This partly stems from the poor knowledge of several important physical parameters of the system. ---- ---- ---- ---- ====== November 21, 2018 ====== **Pulsar of the week:** PSR J0250+5854 **Presenter:** Mr. Jompoj Wongphecauxson {{:journalclub: 211118_j0250_5854.pdf|PDF}} **Paper of the week:** https://academic.oup.com/mnras/article/478/2/2835/4999917 [https://arxiv.org/abs/1805.05482] **Presenter:** Dr. Aris Noutsos {{:journalclub: 211118_aris.pdf|PDF}} **Title:** An all-sky survey of circular polarization at 200 MHz **Abstract:** We present results from the first all-sky radio survey in circular polarisation. The survey uses the Murchison Widefield Array (MWA) to cover 30900 sq. deg., over declinations south of +30∘ and north of -86∘ centred at 200 MHz (over a 169-231 MHz band). We achieve a spatial resolution of approx. 3' and a typical sensitivity of 3.0 mJy PSF−1 over most of the survey region. We demonstrate a new leakage mitigation technique that reduces the leakage from total intensity into circular polarisation by an order of magnitude. In a blind survey of the imaged region, we detect 14 pulsars in circular polarisation above a 6σ threshold. We also detect six transient sources associated with artificial satellites. A targeted survey of 2376 pulsars within the surveyed region yielded 33 detections above 4σ. Looking specifically at pulsars previously detected at 200 MHz in total intensity, this represents a 35% detection rate. We also conducted a targeted survey of 2400 known flare stars, this resulted in two tentative detections above 4σ. A similar targeted search for 1506 known exoplanets in the field yielded no detections above 4σ. The success of the survey suggests that similar surveys at longer wavelength bands and of deeper fields are warranted. ---- ---- ---- ---- ====== November 14, 2018 ====== **Pulsar of the week:** PSR J0218+4232 **Presenter:** Mr. Aakash Mantri **Paper of the week:** https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/sty2945/5151343 [https://arxiv.org/abs/1810.12922] **Presenter:** Mr. Vishnu Balakrishnan **Title:** Ages of radio pulsar: long-term magnetic field evolution **Abstract:** We use the Bayesian approach to write the posterior probability density for the three-dimensional velocity of a pulsar and for its kinematic age. As a prior, we use the bimodal velocity distribution found in a recent article by Verbunt, Igoshev & Cator (2017). When we compare the kinematic ages with spin-down ages we find that in general they agree with each other. In particular, maximum likelihood analysis sets the lower limit for the exponential magnetic field decay timescale at 8 Myr with slight preference of t_dec ≈ 12 Myr and compatible with no decay at all. One of the objects in the study, pulsar B0950+08 has kinematic and cooling ages ≈2 Myr which is in strong contradiction with its spin-down age τ ≈ 17 Myr. The 68 per cent credible range for the kinematic age is 1.2–8.0 Myr. We conclude that the most probable explanation for this contradiction is a combination of magnetic field decay and long initial period. Further timing, UV and X-ray observations of B0950+08 are required to better constrain its origin and evolution. ---- ---- ---- ---- ====== November 07, 2018 ====== **Pulsar of the week:** PSR J1723-2837 **Presenter:** Dr. John Antoniadis Quick reference on the pulsar, in chronological order: http://adsabs.harvard.edu/abs/2004MNRAS.355..147F http://iopscience.iop.org/article/10.1088/0004-637X/776/1/20/pdf http://iopscience.iop.org/article/10.1088/0004-637X/781/1/6/pdf http://iopscience.iop.org/article/10.1088/2041-8205/781/1/L21/pdf http://iopscience.iop.org/article/10.3847/2041-8213/833/1/L12/pdf http://iopscience.iop.org/article/10.3847/1538-4357/aa6aa2/pdf **Paper of the week:** https://link.springer.com/article/10.1007%2Fs10509-018-3322-1 **Presenter:** Mr. Ashwin Manohar **Title:** Timing irregularities of PSR J1705−1906 **Abstract:** Timing analysis of PSR J1705−1906 using data from Nanshan 25-m and Parkes 64-m radio telescopes, which span over fourteen years, shows that the pulsar exhibits significant proper motion, and rotation instability. We updated the astrometry parameters and the spin parameters of the pulsar. In order to minimize the effect of timing irregularities on measuring its position, we employ the Cholesky method to analyse the timing noise. We obtain the proper motion of −77(3) \,mas\,yr−1 in right ascension and −38(29) \,mas\,yr−1 in declination. The power spectrum of timing noise is analyzed for the first time, which gives the spectral exponent α=−5.2 for the power-law model indicating that the fluctuations in spin frequency and spin-down rate dominate the red noise. We detect two small glitches from this pulsar with fractional jump in spin frequency of Δν/ν∼2.9×10−10 around MJD~55199 and Δν/ν∼2.7×10−10 around MJD~55953. Investigations of pulse profile at different time segments suggest no significant changes in the pulse profiles around the two glitches. ---- ---- ---- ---- ====== October 31, 2018 ====== **Pulsar of the week:** J1906+0746 **Presenter:** Dr. Gregory Desvignes **Paper of the week:** https://arxiv.org/abs/1809.05064 **Presenter:** Mr. Jose Martinez **Title:** PSR J2234+0611: A NEW LABORATORY FOR STELLAR EVOLUTION **Abstract:** We report timing results for PSR J2234+0611, a 3.6-ms pulsar in a 32-day, eccentric (e = 0.13) orbit with a helium white dwarf companion discovered as part of the Arecibo Observatory 327 MHz drift scan survey. The precise timing and the eccentric nature of the orbit allow precise measurements of an unusual number of parameters: a) a precise proper motion of 27.10(3) mas/yr and a parallax of 1.05(4) mas resulting in a pulsar distance of 0.95(4) kpc; this allows a precise estimate of the transverse velocity, 123(5) km/s. Together with previously published spectroscopic measurements of the systemic radial velocity, this allows a full 3-D determination of the system's velocity; b) precise measurements of the rate of advance of periastron, which after subtraction of the contribution of the proper motion yields a total system mass of 1.6518+0.0033−0.0035 solar masses; c) a Shapiro delay measurement, h_3 = 82±14 ns despite the orbital inclination not being near 90 deg; combined with the measurement of the total mass, this yields a pulsar mass of 1.353+0.014−0.017 solar masses and a companion mass of 0.298+0.015−0.012 solar masses; d) we measure precisely the secular variation of the projected semi-major axis and detect significant annual orbital parallax; together these allow a determination of the full 3-D orbital geometry, including an unambiguous orbital inclination (i = 138.7+2.5−2.2 deg) and a position angle for the line of nodes (Omega = 44+5−4 deg). We discuss the component masses to investigate hypotheses previously advanced to explain the origin of eccentric MSPs. The unprecedented determination of the full 3-D position, motion and orbital orientation of the system, plus the precisely measured pulsar and WD mass and the latter's optical detection make this system an unique test of our understanding of white dwarfs and their atmospheres. ---- ---- ---- ---- ====== October 24, 2018 ====== **Pulsar of the week:** PSR J1745-2900 **Presenter:** Dr. Robert Wharton {{:journalclub:241018_j1745-2900.pdf|PDF}} **Paper of the week:** http://science.sciencemag.org/content/362/6411/201 **Presenter:** Dr. Vivek Venkatraman Krishnan **Title:** A hot and fast ultra-stripped supernova that likely formed a compact neutron star binary **Abstract:** Compact neutron star binary systems are produced from binary massive stars through stellar evolution involving up to two supernova explosions. The final stages in the formation of these systems have not been directly observed. We report the discovery of iPTF 14gqr (SN 2014ft), a type Ic supernova with a fast-evolving light curve indicating an extremely low ejecta mass (≈0.2 solar masses) and low kinetic energy (≈2 × 1050 ergs). Early photometry and spectroscopy reveal evidence of shock cooling of an extended helium-rich envelope, likely ejected in an intense pre-explosion mass-loss episode of the progenitor. Taken together, we interpret iPTF 14gqr as evidence for ultra-stripped supernovae that form neutron stars in compact binary systems. ---- ---- ---- ----

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