skip to main content


Title: Probing the Local Interstellar Medium with Scintillometry of the Bright Pulsar B1133 + 16
Abstract

The interstellar medium hosts a population of scattering screens, most of unknown origin. Scintillation studies of pulsars provide a sensitive tool for resolving these scattering screens and a means of measuring their properties. In this paper, we report our analysis of 34 yr of Arecibo observations of PSR B1133 + 16, from which we have obtained high-quality dynamic spectra and their associated scintillation arcs, arising from the scattering screens located along the line of sight to the pulsar. We have identified six individual scattering screens that are responsible for the observed scintillation arcs, which persist for decades. Using the assumption that the scattering screens have not changed significantly in this time, we have modeled the variations in arc curvature throughout the Earth’s orbit and extracted information about the placement, orientation, and velocity of five of the six screens, with the highest-precision distance measurement placing a screen at just5.460.59+0.54pc from the Earth. We associate the more distant of these screens with an underdense region of the Local Bubble.

 
more » « less
Award ID(s):
2009759
NSF-PAR ID:
10363780
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
927
Issue:
1
ISSN:
0004-637X
Format(s):
Medium: X Size: Article No. 99
Size(s):
["Article No. 99"]
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    The repeating fast radio burst FRB 20190520B is localized to a galaxy atz= 0.241, much closer than expected given its dispersion measure DM = 1205 ± 4 pc cm−3. Here we assess implications of the large DM and scattering observed from FRB 20190520B for the host galaxy’s plasma properties. A sample of 75 bursts detected with the Five-hundred-meter Aperture Spherical radio Telescope shows scattering on two scales: a mean temporal delayτ(1.41 GHz) = 10.9 ± 1.5 ms, which is attributed to the host galaxy, and a mean scintillation bandwidth Δνd(1.41 GHz) = 0.21 ± 0.01 MHz, which is attributed to the Milky Way. Balmer line measurements for the host imply an Hαemission measure (galaxy frame) EMs= 620 pc cm−6× (T/104K)0.9, implying DMHαof order the value inferred from the FRB DM budget,DMh=1121138+89pc cm−3for plasma temperatures greater than the typical value 104K. Combiningτand DMhyields a nominal constraint on the scattering amplification from the host galaxyF˜G=1.50.3+0.8(pc2km)1/3, whereF˜describes turbulent density fluctuations andGrepresents the geometric leverage to scattering that depends on the location of the scattering material. For a two-screen scattering geometry whereτarises from the host galaxy and Δνdfrom the Milky Way, the implied distance between the FRB source and dominant scattering material is ≲100 pc. The host galaxy scattering and DM contributions support a novel technique for estimating FRB redshifts using theτ–DM relation, and are consistent with previous findings that scattering of localized FRBs is largely dominated by plasma within host galaxies and the Milky Way.

     
    more » « less
  2. Abstract

    We present a catalog of 536 fast radio bursts (FRBs) detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project between 400 and 800 MHz from 2018 July 25 to 2019 July 1, including 62 bursts from 18 previously reported repeating sources. The catalog represents the first large sample, including bursts from repeaters and nonrepeaters, observed in a single survey with uniform selection effects. This facilitates comparative and absolute studies of the FRB population. We show that repeaters and apparent nonrepeaters have sky locations and dispersion measures (DMs) that are consistent with being drawn from the same distribution. However, bursts from repeating sources differ from apparent nonrepeaters in intrinsic temporal width and spectral bandwidth. Through injection of simulated events into our detection pipeline, we perform an absolute calibration of selection effects to account for systematic biases. We find evidence for a population of FRBs—composing a large fraction of the overall population—with a scattering time at 600 MHz in excess of 10 ms, of which only a small fraction are observed by CHIME/FRB. We infer a power-law index for the cumulative fluence distribution ofα=1.40±0.11(stat.)0.09+0.06(sys.), consistent with the −3/2 expectation for a nonevolving population in Euclidean space. We find thatαis steeper for high-DM events and shallower for low-DM events, which is what would be expected when DM is correlated with distance. We infer a sky rate of[820±60(stat.)200+220(sys.)]/sky/dayabove a fluence of 5 Jy ms at 600 MHz, with a scattering time at 600 MHz under 10 ms and DM above 100 pc cm−3.

     
    more » « less
  3. Abstract

    Fast radio bursts (FRBs) are brief, energetic, typically extragalactic flashes of radio emission whose progenitors are largely unknown. Although studying the FRB population is essential for understanding how these astrophysical phenomena occur, such studies have been difficult to conduct without large numbers of FRBs and characterizable observational biases. Using the recently released catalog of 536 FRBs published by the Canadian Hydrogen Intensity Mapping Experiment/Fast Radio Burst (CHIME/FRB) collaboration, we present a study of the FRB population that also calibrates for selection effects. Assuming a Schechter function, we infer a characteristic energy cut-off ofEchar=2.381.64+5.35×1041erg and a differential power-law index ofγ=1.30.4+0.7. Simultaneously, we infer a volumetric rate of [7.33.8+8.8(stat.)1.8+2.0(sys.)]×104Gpc−3yr−1above a pivot energy of 1039erg and below a scattering timescale of 10 ms at 600 MHz, and find we cannot significantly constrain the cosmic evolution of the FRB population with star-formation rate. Modeling the host’s dispersion measure (DM) contribution as a log-normal distribution and assuming a total Galactic contribution of 80 pc cm−3, we find a median value ofDMhost=8449+69pc cm−3, comparable with values typically used in the literature. Proposed models for FRB progenitors should be consistent with the energetics and abundances of the full FRB population predicted by our results. Finally, we infer the redshift distribution of FRBs detected with CHIME, which will be tested with the localizations and redshifts enabled by the upcoming CHIME/FRB Outriggers project.

     
    more » « less
  4. Abstract

    The repeating fast radio burst FRB 20190520B is an anomaly of the FRB population thanks to its high dispersion measure (DM = 1205 pc cm−3) despite its low redshift ofzfrb= 0.241. This excess has been attributed to a large host contribution of DMhost≈ 900 pc cm−3, far larger than any other known FRB. In this paper, we describe spectroscopic observations of the FRB 20190520B field obtained as part of the FLIMFLAM survey, which yielded 701 galaxy redshifts in the field. We find multiple foreground galaxy groups and clusters, for which we then estimated halo masses by comparing their richness with numerical simulations. We discover two separateMhalo> 1014Mgalaxy clusters atz= 0.1867 and 0.2170 that are directly intersected by the FRB sight line within their characteristic halo radiusr200. Subtracting off their estimated DM contributions, as well that of the diffuse intergalactic medium, we estimate a host contribution ofDMhost=430220+140or280170+140pccm3(observed frame), depending on whether we assume that the halo gas extends tor200or 2 ×r200. This significantly smaller DMhost—no longer the largest known value—is now consistent with Hαemission measures of the host galaxy without invoking unusually high gas temperatures. Combined with the observed FRB scattering timescale, we estimate the turbulent fluctuation and geometric amplification factor of the scattering layer to beF˜G4.511(pc2km)1/3, suggesting that most of the gas is close to the FRB host. This result illustrates the importance of incorporating foreground data for FRB analyses both for understanding the nature of FRBs and to realize their potential as a cosmological probe.

     
    more » « less
  5. Abstract

    We present 10 seasons of Sloan Digital Sky Surveyr-band monitoring observations and five seasons ofH-band observations of the two-image system FBQ J0951+2635 from the Kaj Strand Astrometric Reflector at the United States Naval Observatory, Flagstaff Station. We supplement our light curves with six seasons of monitoring data from the literature to yield a 10 + 6 season combined data set, which we analyzed with our Monte Carlo microlensing analysis routine to generate constraints on the structure of this system’s continuum emission source and the properties of the lens galaxy. Complementing our optical light curves with the five-season near-infrared light curves, we ran a joint Monte Carlo analysis to measure the size of the continuum emission region at both wavelengths, yielding log(r1/2cm−1) =16.240.36+0.33in therband and17.040.30+0.26in theHband at rest wavelengths of 2744 and 7254 Å, respectively, correcting for an assumed inclination angle of 60°. Modeling the accretion disk temperature profile as a power lawT(r) ∝rβ, we successfully constrain the slope for FBQ J0951+2635 toβ=0.500.18+0.50, shallower than, but nominally consistent with, the predictions of standard thin-disk theory,β= 0.75.

     
    more » « less