The NANOGrav 11 yr data set: Solar wind sounding through pulsar timing

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has observed dozens of millisecond pulsars for over a decade. We have accrued a large collection of dispersion measure (DM) measurements sensitive to the total electron content between Earth and the pulsars at each observation. All lines of sight cross through the solar wind (SW), which produces correlated DM fluctuations in all pulsars. We develop and apply techniques for extracting the imprint of the SW from the full collection of DM measurements in the recently released NANOGrav 11 yr data set. We filter out long-timescale DM fluctuations attributable to structure in the interstellar medium and carry out a simultaneous analysis of all pulsars in our sample that can differentiate the correlated signature of the wind from signals unique to individual lines of sight. When treating the SW as spherically symmetric and constant in time, we find the electron number density at 1 au to be 7.9 +/- 0.2 cm(-3). We find our data to be insensitive to long-term variation in the density of the wind. We argue that our techniques paired with a high-cadence, low-radio-frequency observing campaign of near-ecliptic pulsars would be capable of mapping out large-scale latitudinal structure in the wind.

Title	The NANOGrav 11 yr data set: Solar wind sounding through pulsar timing
Creator	Levin, L.
	DeCesar, M. E.
	Demorest, P. B.
	Zhu, W. W.
	McLaughlin, M. A.
	Jones, M. L.
	Arzoumanian, Z.
	Lam, M. T.
	Cordes, J. M.
	Madison, D. R.
	Jones, G.
	Lorimer, D. R.
	Ray, P. S.
	Dolch, T.
	Stairs, I. H.
	Spiewak, R.
	Gentile, P. A.
	Ng, C.
	Fonseca, E.
	Ransom, S. M.
	Ellis, J. A.
	Lynch, R. S.
	Ferdman, R. D.
	Nice, David J.
	Stovall, K.
	Swiggum, J. K.
	Crowter, K.
	Chatterjee, S.
	Ferrara, E. C.
	Pennucci, T. T.
	Mingarelli, C. M. F.
Publisher	Astrophysical Journal
Academic Department	Physics
Division	Natural Sciences
Organization	Lafayette College
Date Issued	February 20, 2019
Date Available	2019-03-07T14:18:57Z
Type	Article
Language	English
Keyword	ISM: structure
	solar wind
	pulsars: general
Bibliographic Citation	Madison, D. R., et al. (2019 Feb 20) "The NANOGrav 11 yr data set: Solar wind sounding through pulsar timing." Astrophysical Journal 872 (2): Article 150.
Standard Identifier	Handle 10385/2839
Standard Identifier	DOI 10.3847/1538-4357/ab01fd
Permalink	http://hdl.handle.net/10385/2839
Rights Statement	In Copyright
Rights Holders	The American Astronomical Society