The NANOGrav 15 yr Dataset: Search for Gravitational Scattering of Pulsars by Free-floating Objects in Interstellar Space

Abstract Free-floating objects (FFOs) in interstellar space—rogue planets, brown dwarfs, and large asteroids that are not gravitationally bound to any star—are expected to be ubiquitous throughout the Milky Way. Recent microlensing surveys have discovered several free-floating planets that are not bound to any known stellar systems. Additionally, three interstellar objects, namely 1I/’Oumuamua, 2I/Borisov, and 3I/ATLAS, have been detected passing through our solar system on hyperbolic trajectories. In this work, we search for FFOs on hyperbolic orbits that pass near millisecond pulsars (MSPs), where their gravitational influence can induce detectable perturbations in pulse arrival times. Using the NANOGrav 15 yr narrow band dataset, which contains high-precision timing data for 68 MSPs, we conduct a search for such hyperbolic scattering events between FFOs and pulsars. Although no statistically significant events were detected, this nondetection enables us to place upper limits (ULs) on the number density of FFOs as a function of their mass within our local region of the Galaxy. For example, the UL on the number density for Jupiter-mass FFOs (∼10 −2.5 –10 −3.5 M ⊙ ) obtained from different pulsars ranges from 5.25 × 10 6 pc −3 to 5.37 × 10 9 pc −3 , while the UL calculated by combining results from all the pulsars is 6.03 × 10 5 pc −3 . These results represent the first constraints on FFO population derived from pulsar timing data.

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Publication Details

Journal
The Astrophysical Journal
Published
2026-01-19
DOI
https://doi.org/10.3847/1538-4357/ae279d
Citations
1
Primary Topic
Pulsars and Gravitational Waves Research
Type
article
Field-Weighted Citation Impact
23.83
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article

The NANOGrav 15 yr Dataset: Search for Gravitational Scattering of Pulsars by Free-floating Objects in Interstellar Space

Carl Schmiedekamp, S. M. Ransom, Akash Anumarlapudi, William Fiore et al.
1 citations
The Astrophysical Journal
Pulsars and Gravitational Waves Research
23.83
article

The NANOGrav 15 yr Dataset: Search for Gravitational Scattering of Pulsars by Free-floating Objects in Interstellar Space

Carl Schmiedekamp, S. M. Ransom, Akash Anumarlapudi, William Fiore, Gabriel E. Freedman, Deborah C. Good, Abhimanyu Susobhanan, Peter A. Gentile, Kathryn Crowter, Ann Schmiedekamp, Paul S. Ray, Joseph K. Swiggum, Justin A. Ellis, Joseph Glaser, Kevin Stovall, Lankeswar Dey, Timothy Dolch, Nihan S. Pol, Alexander McEwen, Michael T. Lam, Ryan S. Lynch, David J. Nice, Haley M. Wahl, Paul R. Brook, Gabriella Agazie, Natasha McMann, Jeffrey S. Hazboun, T. Joseph W. Lazio, Jackson D. Taylor, Paul T. Baker, H. Thankful Cromartie, Jing Luo, Megan E. DeCesar, Bradley W. Meyers, Anne M. Archibald, David L. Kaplan, Emmanuel Fonseca, Paul B. Demorest, Benetge B. P. Perera, Brent J. Shapiro-Albert, Ingrid H. Stairs, Duncan R. Lorimer, Maura A. McLaughlin, Cherry Ng, Nate Garver-Daniels, Zaven Arzoumanian, Elizabeth C. Ferrara, Timothy T. Pennucci, Henri A. Radovan, Megan L. Jones, Matthew Kerr
article en
1 citations

Abstract

Abstract Free-floating objects (FFOs) in interstellar space—rogue planets, brown dwarfs, and large asteroids that are not gravitationally bound to any star—are expected to be ubiquitous throughout the Milky Way. Recent microlensing surveys have discovered several free-floating planets that are not bound to any known stellar systems. Additionally, three interstellar objects, namely 1I/’Oumuamua, 2I/Borisov, and 3I/ATLAS, have been detected passing through our solar system on hyperbolic trajectories. In this work, we search for FFOs on hyperbolic orbits that pass near millisecond pulsars (MSPs), where their gravitational influence can induce detectable perturbations in pulse arrival times. Using the NANOGrav 15 yr narrow band dataset, which contains high-precision timing data for 68 MSPs, we conduct a search for such hyperbolic scattering events between FFOs and pulsars. Although no statistically significant events were detected, this nondetection enables us to place upper limits (ULs) on the number density of FFOs as a function of their mass within our local region of the Galaxy. For example, the UL on the number density for Jupiter-mass FFOs (∼10 −2.5 –10 −3.5 M ⊙ ) obtained from different pulsars ranges from 5.25 × 10 6 pc −3 to 5.37 × 10 9 pc −3 , while the UL calculated by combining results from all the pulsars is 6.03 × 10 5 pc −3 . These results represent the first constraints on FFO population derived from pulsar timing data.

The Astrophysical JournalVol. 997(1)
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Pulsars and Gravitational Waves Research
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