Answers to frequently asked questions about the pulsar timing array Hellings and Downs curve

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

Autoren

  • J. D. Romano
  • B. Allen

Organisationseinheiten

Externe Organisationen

  • University of Texas Rio Grande Valley
  • Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut)
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Details

OriginalspracheEnglisch
Aufsatznummer175008
Seitenumfang33
FachzeitschriftClassical and quantum gravity
Jahrgang41
Ausgabenummer17
PublikationsstatusVeröffentlicht - 30 Juli 2024

Abstract

We answer frequently asked questions (FAQs) about the Hellings and Downs correlation curve—the ‘smoking-gun’ signature that pulsar timing arrays (PTAs) have detected gravitational waves (GWs). Many of these questions arise from inadvertently applying intuition about the effects of GWs on LIGO-like detectors to the case of pulsar timing, where not all of it applies. This is because Earth-based detectors, like LIGO and Virgo, have arms that are short (km scale) compared to the wavelengths of the GWs that they detect ( ≈ 10 2 -104 km). In contrast, PTAs respond to GWs whose wavelengths (tens of light-years) are much shorter than their arms (a typical PTA pulsar is hundreds to thousands of light-years from Earth). To demonstrate this, we calculate the time delay induced by a passing GW along an Earth-pulsar baseline (a ‘one-arm, one-way’ detector) and compare it in the ‘short-arm’ (LIGO-like) and ‘long-arm’ (PTA) limits. This provides qualitative and quantitative answers to many questions about the Hellings and Downs curve. The resulting FAQ sheet should help in understanding the ‘evidence for GWs’ recently announced by several PTA collaborations.

ASJC Scopus Sachgebiete

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Answers to frequently asked questions about the pulsar timing array Hellings and Downs curve. / Romano, J. D.; Allen, B.
in: Classical and quantum gravity, Jahrgang 41, Nr. 17, 175008, 30.07.2024.

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

Romano JD, Allen B. Answers to frequently asked questions about the pulsar timing array Hellings and Downs curve. Classical and quantum gravity. 2024 Jul 30;41(17):175008. doi: 10.48550/arXiv.2308.05847, 10.1088/1361-6382/ad4c4c
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abstract = "We answer frequently asked questions (FAQs) about the Hellings and Downs correlation curve—the {\textquoteleft}smoking-gun{\textquoteright} signature that pulsar timing arrays (PTAs) have detected gravitational waves (GWs). Many of these questions arise from inadvertently applying intuition about the effects of GWs on LIGO-like detectors to the case of pulsar timing, where not all of it applies. This is because Earth-based detectors, like LIGO and Virgo, have arms that are short (km scale) compared to the wavelengths of the GWs that they detect ( ≈ 10 2 -104 km). In contrast, PTAs respond to GWs whose wavelengths (tens of light-years) are much shorter than their arms (a typical PTA pulsar is hundreds to thousands of light-years from Earth). To demonstrate this, we calculate the time delay induced by a passing GW along an Earth-pulsar baseline (a {\textquoteleft}one-arm, one-way{\textquoteright} detector) and compare it in the {\textquoteleft}short-arm{\textquoteright} (LIGO-like) and {\textquoteleft}long-arm{\textquoteright} (PTA) limits. This provides qualitative and quantitative answers to many questions about the Hellings and Downs curve. The resulting FAQ sheet should help in understanding the {\textquoteleft}evidence for GWs{\textquoteright} recently announced by several PTA collaborations.",
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