arXiv subjects

K. Vanderlinde

Publications and source records attributed to K. Vanderlinde.

At least 19 recordsLinked to original sources

arXiv2021

Scintillation of PSR B1508+55 -- the view from a 10,000-km baseline

We report on the simultaneous Giant Metrewave Radio Telescope (GMRT) and Algonquin Radio Observatory (ARO) observations at 550-750 MHz of the scintillation of PSR B1508+55, resulting in a $\sim$10,000-km baseline. This regime of measurement lies between the shorter few 100-1000~km baselines of earlier multi-station observations and the much longer earth-space baselines. We measure a scintillation cross-correlation coefficient of $0.22$, offset from zero time lag due to a $\sim 45$~s traversal time of the scintillation pattern. The scintillation time of 135~s is $3\times$ longer, ruling out isotropic as well as strictly 1D scattering. Hence, the low cross-correlation coefficient is indicative of highly anisotropic but 2D scattering. The common scintillation detected on the baseline is confined to low delays of $\lesssim 1 μ$s, suggesting that this correlation may not be associated with the parabolic scintillation arc detected at the GMRT. Detection of pulsed echoes and their direct imaging with the Low Frequency Array (LOFAR) by a different group enable them to measure a distance of 125~pc to the screen causing these echoes. These previous measurements, alongside our observations, lead us to propose that there are at least two scattering screens: the closer 125 pc screen causing the scintillation arc detected at GMRT, and a screen further beyond causing the scintillation detected on the GMRT-ARO baseline. We advance the hypothesis that the 125-pc screen partially resolves the speckle images on the screen beyond leading to loss of coherence in the scintillation dynamic spectrum, to explain the low cross-correlation coefficient.

astro-ph.HE↗

arXiv2021

The CHIME Pulsar Project: System Overview

We present the design, implementation and performance of a digital backend constructed for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) that uses accelerated computing to observe radio pulsars and transient radio sources. When operating, the CHIME correlator outputs 10 independent streams of beamformed data for the CHIME/Pulsar backend that digitally track specified celestial positions. Each of these independent streams are processed by the CHIME/Pulsar backend system which can coherently dedisperse, in real-time, up to dispersion measure values of 2500 pc/cm$^{-3}$ . The tracking beams and real-time analysis system are autonomously controlled by a priority-based algorithm that schedules both known sources and positions of interest for observation with observing cadences as small as one day. Given the distribution of known pulsars and radio-transient sources, the CHIME/Pulsar system can monitor up to 900 positions once per sidereal day and observe all sources with declinations greater than $-20^\circ$ once every $\sim$2 weeks. We also discuss the science program enabled through the current modes of data acquisition for CHIME/Pulsar that centers on timing and searching experiments.

astro-ph.IM↗

arXiv2021

An analysis pipeline for CHIME/FRB full-array baseband data

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has become a leading facility for detecting fast radio bursts (FRBs) through the CHIME/FRB backend. CHIME/FRB searches for fast transients in polarization-summed intensity data streams that have 24-kHz spectral and 1-ms temporal resolution. The intensity beams are pointed to pre-determined locations in the sky. A triggered baseband system records the coherent electric field measured by each antenna in the CHIME array at the time of FRB detections. Here we describe the analysis techniques and automated pipeline developed to process these full-array baseband data recordings. Whereas the real-time FRB detection pipeline has a localization limit of several arcminutes, offline analysis of baseband data yields source localizations with sub-arcminute precision, as characterized by using a sample of pulsars and one repeating FRB with known positions. The baseband pipeline also enables resolving temporal substructure on a micro-second scale and the study of polarization including detections of Faraday rotation.

astro-ph.HE↗

arXiv2020

Searching for Anisotropic Cosmic Birefringence with Polarization Data from SPTpol

We present a search for anisotropic cosmic birefringence in 500 deg$^2$ of southern sky observed at 150 GHz with the SPTpol camera on the South Pole Telescope. We reconstruct a map of cosmic polarization rotation anisotropies using higher-order correlations between the observed cosmic microwave background (CMB) $E$ and $B$ fields. We then measure the angular power spectrum of this map, which is found to be consistent with zero. The non-detection is translated into an upper limit on the amplitude of the scale-invariant cosmic rotation power spectrum, $L(L+1)C_L^{αα}/2π< 0.10 \times 10^{-4}$ rad$^2$ (0.033 deg$^2$, 95% C.L.). This upper limit can be used to place constraints on the strength of primordial magnetic fields, $B_{1 \rm Mpc} < 17 {\rm nG} $ (95% C.L.), and on the coupling constant of the Chern-Simons electromagnetic term $g_{aγ} < 4.0 \times 10^{-2}/H_I $ (95% C.L.), where $H_I$ is the inflationary Hubble scale. For the first time, we also cross-correlate the CMB temperature fluctuations with the reconstructed rotation angle map, a signal expected to be non-vanishing in certain theoretical scenarios, and find no detectable signal. We perform a suite of systematics and consistency checks and find no evidence for contamination.

astro-ph.CO↗

arXiv2020

The Discovery of Nulling and Mode Switching Pulsars with CHIME/Pulsar

The Pulsar backend of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) has monitored hundreds of known pulsars in the northern sky since Fall 2018, providing a rich data set for the study of temporal variations in pulsar emission. Using a matched filtering technique, we report, for the first time, nulling behaviour in five pulsars as well as mode switching in nine pulsars. Only one of the pulsars is observed to show both nulling and moding signals. These new nulling and mode switching pulsars appear to come from a population with relatively long spin periods, in agreement with previous findings in the literature.

astro-ph.HE↗

arXiv2020

Periodic activity from a fast radio burst source

Fast radio bursts (FRBs) are bright, millisecond-duration radio transients originating from extragalactic distances. Their origin is unknown. Some FRB sources emit repeat bursts, ruling out cataclysmic origins for those events. Despite searches for periodicity in repeat burst arrival times on time scales from milliseconds to many days, these bursts have hitherto been observed to appear sporadically, and though clustered, without a regular pattern. Here we report the detection of a $16.35\pm0.15$ day periodicity (or possibly a higher-frequency alias of that periodicity) from a repeating FRB 180916.J0158+65 detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB). In 38 bursts recorded from September 16th, 2018 through February 4th, 2020, we find that all bursts arrive in a 5-day phase window, and 50% of the bursts arrive in a 0.6-day phase window. Our results suggest a mechanism for periodic modulation either of the burst emission itself, or through external amplification or absorption, and disfavour models invoking purely sporadic processes.

astro-ph.HE↗

arXiv2020

A bright millisecond-duration radio burst from a Galactic magnetar

Magnetars are highly magnetized young neutron stars that occasionally produce enormous bursts and flares of X-rays and gamma-rays. Of the approximately thirty magnetars currently known in our Galaxy and Magellanic Clouds, five have exhibited transient radio pulsations. Fast radio bursts (FRBs) are millisecond-duration bursts of radio waves arriving from cosmological distances. Some have been seen to repeat. A leading model for repeating FRBs is that they are extragalactic magnetars, powered by their intense magnetic fields. However, a challenge to this model has been that FRBs must have radio luminosities many orders of magnitude larger than those seen from known Galactic magnetars. Here we report the detection of an extremely intense radio burst from the Galactic magnetar SGR 1935+2154 using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB project. The fluence of this two-component bright radio burst and the estimated distance to SGR 1935+2154 together imply a 400-800 MHz burst energy of $\sim 3 \times 10^{34}$ erg, which is three orders of magnitude brighter than those of any radio-emitting magnetar detected thus far. Such a burst coming from a nearby galaxy would be indistinguishable from a typical FRB. This event thus bridges a large fraction of the radio energy gap between the population of Galactic magnetars and FRBs, strongly supporting the notion that magnetars are the origin of at least some FRBs.

astro-ph.HE↗

arXiv2020

Faraday rotation measures of northern-hemisphere pulsars using CHIME/Pulsar

Using commissioning data from the first year of operation of the Canadian Hydrogen Intensity Mapping Experiment's (CHIME) Pulsar backend system, we conduct a systematic analysis of the Faraday Rotation Measure (RM) of the northern hemisphere pulsars detected by CHIME. We present 55 new RMs as well as obtain improved RM uncertainties for 25 further pulsars. CHIME's low observing frequency and wide bandwidth between 400-800 MHz contribute to the precision of our measurements, whereas the high cadence observation provide extremely high signal-to-noise co-added data. Our results represent a significant increase of the pulsar RM census, particularly regarding the northern hemisphere. These new RMs are for sources that are located in the Galactic plane out to 10 kpc, as well as off the plane to a scale height of ~16 kpc. This improved knowledge of the Faraday sky will contribute to future Galactic large-scale magnetic structure and ionosphere modelling.

astro-ph.IM↗

arXiv2020

Detection of Repeating FRB 180916.J0158+65 Down to Frequencies of 300 MHz

We report on the detection of seven bursts from the periodically active, repeating fast radio burst (FRB) source FRB 180916.J0158+65 in the 300-400-MHz frequency range with the Green Bank Telescope (GBT). Emission in multiple bursts is visible down to the bottom of the GBT band, suggesting that the cutoff frequency (if it exists) for FRB emission is lower than 300 MHz. Observations were conducted during predicted periods of activity of the source, and had simultaneous coverage with the Low Frequency Array (LOFAR) and the FRB backend on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. We find that one of the GBT-detected bursts has potentially associated emission in the CHIME band (400-800 MHz) but we detect no bursts in the LOFAR band (110-190 MHz), placing a limit of $α> -1.0$ on the spectral index of broadband emission from the source. We also find that emission from the source is severely band-limited with burst bandwidths as low as $\sim$40 MHz. In addition, we place the strictest constraint on observable scattering of the source, $<$ 1.7 ms, at 350 MHz, suggesting that the circumburst environment does not have strong scattering properties. Additionally, knowing that the circumburst environment is optically thin to free-free absorption at 300 MHz, we find evidence against the association of a hyper-compact HII region or a young supernova remnant (age $<$ 50 yr) with the source.

astro-ph.HE↗

arXiv2020

Measurements of B-mode Polarization of the Cosmic Microwave Background from 500 Square Degrees of SPTpol Data

We report a B-mode power spectrum measurement from the cosmic microwave background (CMB) polarization anisotropy observations made using the SPTpol instrument on the South Pole Telescope. This work uses 500 deg$^2$ of SPTpol data, a five-fold increase over the last SPTpol B-mode release. As a result, the bandpower uncertainties have been reduced by more than a factor of two, and the measurement extends to lower multipoles: $52 < \ell < 2301$. Data from both 95 and 150 GHz are used, allowing for three cross-spectra: 95 GHz x 95 GHz, 95 GHz x 150 GHz, and 150 GHz x 150 GHz. B-mode power is detected at very high significance; we find $P(BB < 0) = 5.8 \times 10^{-71}$, corresponding to a $18.1 σ$ detection of power. An upper limit is set on the tensor-to-scalar ratio, $r < 0.44$ at 95% confidence (the expected $1 σ$ constraint on $r$ given the measurement uncertainties is 0.22). We find the measured B-mode power is consistent with the Planck best-fit $Λ$CDM model predictions. Scaling the predicted lensing B-mode power in this model by a factor Alens, the data prefer Alens = $1.17 \pm 0.13$. These data are currently the most precise measurements of B-mode power at $\ell > 320$.

astro-ph.CO↗

arXiv2020

Simultaneous X-ray and Radio Observations of the Repeating Fast Radio Burst FRB 180916.J0158+65

We report on simultaneous radio and X-ray observations of the repeating fast radio burst source FRB 180916.J0158+65 using the Canadian Hydrogen Intensity Mapping Experiment (CHIME), Effelsberg, and Deep Space Network (DSS-14 and DSS-63) radio telescopes and the Chandra X-ray Observatory. During 33 ks of Chandra observations, we detect no radio bursts in overlapping Effelsberg or Deep Space Network observations and a single radio burst during CHIME/FRB source transits. We detect no X-ray events in excess of the background during the Chandra observations. These non-detections imply a 5-$σ$ limit of $<5\times10^{-10}$ erg cm$^{-2}$ for the 0.5--10 keV fluence of prompt emission at the time of the radio burst and $1.3\times10^{-9}$ erg cm$^{-2}$ at any time during the Chandra observations at the position of FRB 180916.J0158+65. Given the host-galaxy redshift of FRB 180916.J0158+65 ($z\sim0.034$), these correspond to energy limits of $<1.6\times10^{45}$ erg and $<4\times10^{45}$ erg, respectively. We also place a 5-$σ$ limit of $<8\times10^{-15}$ erg s$^{-1}$ cm$^{-2}$ on the 0.5--10\,keV absorbed flux of a persistent source at the location of FRB 180916.J0158+65. This corresponds to a luminosity limit of $<2\times10^{40}$ erg s$^{-1}$. Using Fermi/GBM data we search for prompt gamma-ray emission at the time of radio bursts from FRB 180916.J0158+65 and find no significant bursts, placing a limit of $4\times10^{-9}$ erg cm$^{-2}$ on the 10--100 keV fluence. We also search Fermi/LAT data for periodic modulation of the gamma-ray brightness at the 16.35-day period of radio-burst activity and detect no significant modulation. We compare these deep limits to the predictions of various fast radio burst models, but conclude that similar X-ray constraints on a closer fast radio burst source would be needed to strongly constrain theory.

astro-ph.HE↗

arXiv2020

Millimeter-wave Point Sources from the 2500-square-degree SPT-SZ Survey: Catalog and Population Statistics

We present a catalog of emissive point sources detected in the SPT-SZ survey, a contiguous 2530-square-degree area surveyed with the South Pole Telescope (SPT) from 2008 - 2011 in three bands centered at 95, 150, and 220 GHz. The catalog contains 4845 sources measured at a significance of 4.5 sigma or greater in at least one band, corresponding to detections above approximately 9.8, 5.8, and 20.4 mJy in 95, 150, and 220 GHz, respectively. Spectral behavior in the SPT bands is used for source classification into two populations based on the underlying physical mechanisms of compact, emissive sources that are bright at millimeter wavelengths: synchrotron radiation from active galactic nuclei and thermal emission from dust. The latter population includes a component of high-redshift sources often referred to as submillimeter galaxies (SMGs). In the relatively bright flux ranges probed by the survey, these sources are expected to be magnified by strong gravitational lensing. The survey also contains sources consistent with protoclusters, groups of dusty galaxies at high redshift undergoing collapse. We cross-match the SPT-SZ catalog with external catalogs at radio, infrared, and X-ray wavelengths and identify available redshift information. The catalog splits into 3980 synchrotron-dominated and 865 dust-dominated sources and we determine a list of 506 SMGs. Ten sources in the catalog are identified as stars. We calculate number counts for the full catalog, and synchrotron and dusty components, using a bootstrap method and compare our measured counts with models. This paper represents the third and final catalog of point sources in the SPT-SZ survey.

astro-ph.IM↗

arXiv2020

Broadband, millimeter-wave antireflection coatings for large-format, cryogenic aluminum oxide optics

We present two prescriptions for broadband (~77 - 252 GHz), millimeter-wave antireflection coatings for cryogenic, sintered polycrystalline aluminum oxide optics: one for large-format (700 mm diameter) planar and plano-convex elements, the other for densely packed arrays of quasi-optical elements, in our case 5 mm diameter half-spheres (called "lenslets"). The coatings comprise three layers of commercially-available, polytetrafluoroethylene-based, dielectric sheet material. The lenslet coating is molded to fit the 150 mm diameter arrays directly while the large-diameter lenses are coated using a tiled approach. We review the fabrication processes for both prescriptions then discuss laboratory measurements of their transmittance and reflectance. In addition, we present the inferred refractive indices and loss tangents for the coating materials and the aluminum oxide substrate. We find that at 150 GHz and 300 K the large-format coating sample achieves (97 +/- 2)% transmittance and the lenslet coating sample achieves (94 +/- 3)% transmittance.

physics.ins-det↗

arXiv2020

An Improved Measurement of the Secondary Cosmic Microwave Background Anisotropies from the SPT-SZ + SPTpol Surveys

We report new measurements of millimeter-wave power spectra in the angular multipole range $2000 \le \ell \le 11,000$ (angular scales $5^\prime \gtrsim θ\gtrsim 1^\prime$). By adding 95 and 150\,GHz data from the low-noise 500 deg$^2$ SPTpol survey to the SPT-SZ three-frequency 2540 deg$^2$ survey, we substantially reduce the uncertainties in these bands. These power spectra include contributions from the primary cosmic microwave background, cosmic infrared background, radio galaxies, and thermal and kinematic Sunyaev-Zel'dovich (SZ) effects. The data favor a thermal SZ (tSZ) power at 143\,GHz of $D^{\rm tSZ}_{3000} = 3.42 \pm 0.54~ μ{\rm K}^2$ and a kinematic SZ (kSZ) power of $D^{\rm kSZ}_{3000} = 3.0 \pm 1.0~ μ{\rm K}^2$. This is the first measurement of kSZ power at $\ge 3\,σ$. We study the implications of the measured kSZ power for the epoch of reionization, finding the duration of reionization to be $Δz_{re} = 1.0^{+1.6}_{-0.7}$ ($Δz_{re}< 4.1$ at 95% confidence), when combined with our previously published tSZ bispectrum measurement.

astro-ph.CO↗

arXiv2020

Constraints on Cosmological Parameters from the 500 deg$^2$ SPTpol Lensing Power Spectrum

We present cosmological constraints based on the cosmic microwave background (CMB) lensing potential power spectrum measurement from the recent 500 deg$^2$ SPTpol survey, the most precise CMB lensing measurement from the ground to date. We fit a flat $Λ$CDM model to the reconstructed lensing power spectrum alone and in addition with other data sets: baryon acoustic oscillations (BAO) as well as primary CMB spectra from Planck and SPTpol. The cosmological constraints based on SPTpol and Planck lensing band powers are in good agreement when analysed alone and in combination with Planck full-sky primary CMB data. With weak priors on the baryon density and other parameters, the CMB lensing data alone provide a 4\% constraint on $σ_8Ω_m^{0.25} = 0.0593 \pm 0.025$.. Jointly fitting with BAO data, we find $σ_8=0.779 \pm 0.023$, $Ω_m = 0.368^{+0.032}_{-0.037}$, and $H_0 = 72.0^{+2.1}_{-2.5}\,\text{km}\,\text{s}^{-1}\,\text{Mpc}^{-1} $, up to $2\,σ$ away from the central values preferred by Planck lensing + BAO. However, we recover good agreement between SPTpol and Planck when restricting the analysis to similar scales. We also consider single-parameter extensions to the flat $Λ$CDM model. The SPTpol lensing spectrum constrains the spatial curvature to be $Ω_K = -0.0007 \pm 0.0025$ and the sum of the neutrino masses to be $\sum m_ν < 0.23$ eV at 95\% C.L. (with Planck primary CMB and BAO data), in good agreement with the Planck lensing results. With the differences in the $S/N$ of the lensing modes and the angular scales covered in the lensing spectra, this analysis represents an important independent check on the full-sky Planck lensing measurement.

astro-ph.CO↗

arXiv2020

Nine New Repeating Fast Radio Burst Sources from CHIME/FRB

We report on the discovery and analysis of bursts from nine new repeating fast radio burst (FRB) sources found using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. These sources span a dispersion measure (DM) range of 195 to 1380 pc cm$^{-3}$. We detect two bursts from three of the new sources, three bursts from four of the new sources, four bursts from one new source, and five bursts from one new source. We determine sky coordinates of all sources with uncertainties of $\sim$10$^\prime$. We detect Faraday rotation measures for two sources, with values $-20(1)$ and $-499.8(7)$ rad m$^{-2}$, that are substantially lower than the RM derived from bursts emitted by FRB 121102. We find that the DM distribution of our events, combined with the nine other repeaters discovered by CHIME/FRB, is indistinguishable from that of thus far non-repeating CHIME/FRB events. However, as previously reported, the burst widths appear statistically significantly larger than the thus far non-repeating CHIME/FRB events, further supporting the notion of inherently different emission mechanisms and/or local environments. These results are consistent with previous work, though are now derived from 18 repeating sources discovered by CHIME/FRB during its first year of operation. We identify candidate galaxies that may contain FRB 190303.J1353+48 (DM = 222.4 pc cm$^{-3}$).

astro-ph.HE↗

arXiv2020

Fractional Polarisation of Extragalactic Sources in the 500-square-degree SPTpol Survey

We study the polarisation properties of extragalactic sources at 95 and 150 GHz in the SPTpol 500 deg$^2$ survey. We estimate the polarised power by stacking maps at known source positions, and correct for noise bias by subtracting the mean polarised power at random positions in the maps. We show that the method is unbiased using a set of simulated maps with similar noise properties to the real SPTpol maps. We find a flux-weighted mean-squared polarisation fraction $\langle p^2 \rangle= [8.9\pm1.1] \times 10^{-4}$ at 95 GHz and $[6.9\pm1.1] \times 10^{-4}$ at 150~GHz for the full sample. This is consistent with the values obtained for a sub-sample of active galactic nuclei. For dusty sources, we find 95 per cent upper limits of $\langle p^2 \rangle_{\rm 95}<16.9 \times 10^{-3}$ and $\langle p^2 \rangle_{\rm 150}<2.6 \times 10^{-3}$. We find no evidence that the polarisation fraction depends on the source flux or observing frequency. The 1-$σ$ upper limit on measured mean squared polarisation fraction at 150 GHz implies that extragalactic foregrounds will be subdominant to the CMB E and B mode polarisation power spectra out to at least $\ell\lesssim5700$ ($\ell\lesssim4700$) and $\ell\lesssim5300$ ($\ell\lesssim3600$), respectively at 95 (150) GHz.

astro-ph.CO↗

arXiv2020

Galaxy Clusters Selected via the Sunyaev-Zel'dovich Effect in the SPTpol 100-Square-Degree Survey

We present a catalog of galaxy cluster candidates detected in 100 square degrees surveyed with the SPTpol receiver on the South Pole Telescope. The catalog contains 89 candidates detected with a signal-to-noise ratio greater than 4.6. The candidates are selected using the Sunyaev-Zel'dovich effect at 95 and 150 GHz. Using both space- and ground-based optical and infrared telescopes, we have confirmed 81 candidates as galaxy clusters. We use these follow-up images and archival images to estimate photometric redshifts for 66 galaxy clusters and spectroscopic observations to obtain redshifts for 13 systems. An additional 2 galaxy clusters are confirmed using the overdensity of near-infrared galaxies only, and are presented without redshifts. We find that 15 candidates (18% of the total sample) are at redshift of $z \geq 1.0$, with a maximum confirmed redshift of $z_{\rm{max}} = 1.38 \pm 0.10$. We expect this catalog to contain every galaxy cluster with $M_{500c} > 2.6 \times 10^{14} M_\odot h^{-1}_{70}$ and $z > 0.25$ in the survey area. The mass threshold is approximately constant above $z = 0.25$, and the complete catalog has a median mass of approximately $ M_{500c} = 2.7 \times 10^{14} M_\odot h^{-1}_{70}$. Compared to previous SPT works, the increased depth of the millimeter-wave data (11.2 and 6.5 $μ$K-arcmin at 95 and 150 GHz, respectively) makes it possible to find more galaxy clusters at high redshift and lower mass.

astro-ph.CO↗