gravitational waves - 2025 NAFTA

Packet 1: Bonus 3

In the presence of an isotropic, unpolarized, stochastic background of these phenomena, pulsar timing arrays have residuals whose correlation follows the Hellings-Downs curve. For 10 points each:

[10m] What phenomena are causing the orbital decay of the Hulse-Taylor binary pulsar?

ANSWER: gravitational waves [or gravitational radiation; or GWs; accept stochastic gravitational wave background or SGWb; prompt on waves; prompt on gravity; reject “gravity waves”]

[10h] Pulsar timing arrays typically use this class of pulsars due to their stable periods. Pulsars in this class are formed by a “recycling” mechanism in which they are spun up by accretion from a companion star.

ANSWER: millisecond pulsars [accept MSPs]

[10e] In 1992, the first confirmed detection of these objects studied timing variations in the millisecond pulsar Lich. The Kepler space telescope used the transit method to detect these objects.

ANSWER: exoplanets [or extrasolar planets; accept descriptions of planets outside the solar system; prompt on planets]

<LK, Other Science (Astronomy)> | NAFTA-Packet-1

Heard	PPB	E %	M %	H %
15	16.67	100%	40%	27%

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Conversion

Team	Opponent	Part 1	Part 2	Part 3	Total	Parts
Ana Pauker? I hardly know her!	Say It Ain't Zhou	10	0	10	20	ME
Berkeley A	Not Old! (Old)	10	0	10	20	ME
Berkeley B	Team 7	10	10	10	30	MHE
Copán Seethe	Polish Orthographers Posting Their Łs	0	0	10	10	E
David Foster Gromit	It's something unpredictable/that in the end is right/please refrain from e-mailing my wife	0	0	10	10	E
Georgia Tech 𓂈𓆉𓃡	Girls who Just Want to Have Fun + Liam	0	0	10	10	E
Lex	four high school generalists shock natives with fluent stock in Tocharian B	10	10	10	30	MHE
Stanford A	Team 8	0	0	10	10	E
Stanford B	Constans Constantius and Constantine Jr.	0	0	10	10	E
The Umayyad Caliphate be like REPEAL NAPHTHA	Tennessee A	0	0	10	10	E
The Worst Trade Deal in the History of Trade Deals	St. Marx	10	10	10	30	MHE
UBC A	The Unbearable Heaviness of History Players	0	0	10	10	E
UBC B	Abbas I founded the Abbasids	0	0	10	10	E
WashU	W&L+Friend	10	10	10	30	MHE
[Redacted]	Maybe Ever	0	0	10	10	E

Summary

Tournament	Edition	Match	Heard	PPB	E %	M %	H %
2026 NAFTA at Stanford	01/17/2026	✓	4	17.50	100%	50%	25%
2026 NAFTA at UBC	01/17/2026	✓	2	10.00	100%	0%	0%
2025 NAFTA Online	02/14/2026	✓	4	25.00	100%	75%	75%
2026 NAFTA at Vanderbilt	02/14/2026	✓	3	13.33	100%	33%	0%
2025 NAFTA at Toronto	09/13/2025	✕	4	15.00	100%	50%	0%
2025 NAFTA at Maryland	09/27/2025	✕	5	18.00	100%	40%	40%
2025 NAFTA at Harvard	10/04/2025	✕	3	13.33	100%	33%	0%
2025 NAFTA at Oxford	10/11/2025	✕	3	10.00	100%	0%	0%
2025 NAFTA at Chicago	11/08/2025	✕	6	20.00	100%	67%	33%
2025 NAFTA at Columbia	11/08/2025	✕	5	20.00	100%	80%	20%
2025 NAFTA at Richmond	12/20/2025	✓	2	10.00	100%	0%	0%