Details
| Original language | English |
|---|---|
| Article number | 175008 |
| Number of pages | 33 |
| Journal | Classical and quantum gravity |
| Volume | 41 |
| Issue number | 17 |
| Publication status | Published - 30 Jul 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.
Keywords
- gravitational waves, Hellings and Downs correlation, pulsar timing
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physics and Astronomy (miscellaneous)
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In: Classical and quantum gravity, Vol. 41, No. 17, 175008, 30.07.2024.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Answers to frequently asked questions about the pulsar timing array Hellings and Downs curve
AU - Romano, J. D.
AU - Allen, B.
N1 - Publisher Copyright: © 2024 The Author(s). Published by IOP Publishing Ltd.
PY - 2024/7/30
Y1 - 2024/7/30
N2 - 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.
AB - 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.
KW - gravitational waves
KW - Hellings and Downs correlation
KW - pulsar timing
UR - http://www.scopus.com/inward/record.url?scp=85200355900&partnerID=8YFLogxK
U2 - 10.48550/arXiv.2308.05847
DO - 10.48550/arXiv.2308.05847
M3 - Article
AN - SCOPUS:85200355900
VL - 41
JO - Classical and quantum gravity
JF - Classical and quantum gravity
SN - 0264-9381
IS - 17
M1 - 175008
ER -