A Multi-Messenger Technosignature and Anomaly-Detection Campaign for Omega Centauri

1. Introduction

1.1 Why Omega Centauri, and why now

Three independent developments between 2024 and 2026 have transformed Omega Centauri (ω Centauri, NGC 5139) from one interesting globular cluster among many into arguably the single best-posed multi-messenger target in the Galaxy outside the Galactic Centre.

First, the IMBH candidacy became concrete. Häberle et al. (2024a), using a proper-motion catalogue of 1.4 million stars built from over 500 HST epochs (Häberle et al. 2024b), identified seven stars within 3 arcsec of the cluster centre moving faster than the local escape velocity — stars that require a bound central mass of ≥8,200 M_☉ from their velocities alone, and ≥21,100 M_☉ at 99 per cent confidence when acceleration limits are included. Independent N-body modelling finds a best-fitting in-situ-grown IMBH of ~4.7–5.1×10⁴ M_☉ (González Prieto et al. 2025). Against this, a joint analysis of stellar kinematics and millisecond-pulsar (MSP) timing places a 3σ upper limit of ~6×10³ M_☉ on any central point mass, favouring instead an extended ≈2–3×10⁵ M_☉ component of stellar remnants (Bañares-Hernández et al. 2025). The constraints are formally inconsistent under their stated assumptions. This is not an embarrassment but an opportunity: a factor-of-several disagreement between two mature measurement techniques, centred on the nearest IMBH candidate in the sky, is precisely the situation that focused observational campaigns exist to resolve.

Second, the electromagnetic silence became quantitative. The deepest radio observation ever made of a globular cluster — ~170 h with ATCA, reaching 1.1 μJy beam⁻¹ rms — detects nothing at any proposed cluster centre, bounding the accretion efficiency of a putative IMBH at ≲4×10⁻³ of the Bondi rate (Mahida et al. 2026), extending two decades of radio non-detections of globular-cluster IMBHs (Strader et al. 2012; Tremou et al. 2018). JWST NIRCam and MIRI photometry of the central field likewise finds no source with the spectral energy distribution of an accreting IMBH (Chen et al. 2025). Whatever sits at the centre of ω Cen, it is dark to a depth that is itself a scientific result demanding explanation.

Third, the instrument landscape shifted decisively in the campaign's favour. Within an eighteen-month window centred on this writing: the Vera C. Rubin Observatory began the Legacy Survey of Space and Time (LSST) in early 2026 (Ivezić et al. 2019); the Nancy Grace Roman Space Telescope completed construction and is scheduled for launch on 2026 August 30 (Sanderson et al. 2019); Gaia Data Release 4, with a 5.5-year astrometric baseline, is scheduled for 2026 December 2 (Gaia Collaboration 2016); KM3NeT/ARCA reached 51 of 230 planned detection units with real-time alerts entering commissioning (Adrián-Martínez et al. 2016; KM3NeT Collaboration 2025); the first telescopes of CTAO-South are arriving at Paranal (CTA Consortium 2019); SKA-Mid is assembling toward 2029 science verification (Braun et al. 2019); ELT first light is scheduled for 2029 (Davies et al. 2021); and LISA, formally adopted by ESA in January 2024, is in hardware development for a 2035 launch (Colpi et al. 2024). Nearly every facility on this list is southern-hemisphere or all-sky; ω Cen, at declination −47.5°, sits in the sweet spot of all of them. A campaign organized now can ride this entire wave at marginal cost.

1.2 The technosignature rationale, stated honestly

This paper is the observational companion to a speculative hypothesis paper (Swanson 2026, hereafter Paper A), which argues that rapidly spinning massive black holes in dense old stellar systems are thermodynamic attractors for hypothetical computation-optimizing civilizations, and that ω Cen is the most accessible system satisfying the resulting selection criteria. We neither assume nor argue for that hypothesis here. The campaign is designed to be hypothesis-agnostic in the specific sense that every observation in it is independently justified by conventional astrophysics: IMBH demographics (Greene et al. 2020), cluster dynamics, pulsar timing, accretion physics at the lowest Eddington ratios, and EMRI astrophysics (Amaro-Seoane 2018). The technosignature dimension adds analysis channels — narrowband drift searches, burst-coincidence triggers, anomaly statistics — to data that would be taken anyway, in the cost-effective tradition of commensal SETI (Tarter 2001; Wright et al. 2022; Lacki & DiKerby 2025).

Three considerations nevertheless justify making the technosignature dimension explicit rather than incidental. First, globular clusters are almost entirely unexplored SETI territory: the first dedicated globular-cluster survey, a FAST pilot of five northern clusters, was published only this year and could not observe ω Cen from FAST's latitude (Huang et al. 2026). Second, ω Cen is a privileged target on entirely generic arguments — 10⁷ stars of age 12.08 ± 0.01 Gyr (Clontz et al. 2024) in a beam a few arcminutes across, a possible IMBH, and (as the probable nucleus of an accreted dwarf; Hilker & Richtler 2000; Ibata et al. 2019) an independent galactic chemical-evolution history — so that any ETI prior that weights stellar age and number density at all concentrates sharply here. Third, the high-energy technosignature channels (neutrino bursts from hypothetical black-hole-based computation; Dvali & Osmanov 2023) happen to be testable at ω Cen essentially for free, because the cluster's declination makes it an up-going source for the Mediterranean neutrino telescopes. Where Paper A's specific predictions sharpen a test, we say so explicitly and label the dependence; readers uninterested in that hypothesis may strike those sentences without loss to the campaign.

1.3 Design principles

Five principles govern the campaign design, and we state them up front because they discipline everything that follows.

(i) Dual-use data. Every observing program must produce publishable conventional astrophysics on its own; the technosignature analysis is a parallel pipeline on the same photons (or neutrinos, or strain data), never a dedicated expenditure that a null result would waste.

(ii) Honest sensitivity accounting. Where a measurement cannot work at nominal parameters, we say so quantitatively rather than gesturing at it hopefully. Section 5 demonstrates this standard: the direct acceleration test on the fast stars — superficially the most natural follow-up to Häberle et al. (2024a) — is below 1σ before ~2040 for plausible masses, and we restructure the astrometric program accordingly.

(iii) Two-messenger adjudication. No anomaly claim survives on one channel. Every positive trigger (a neutrino multiplet, a narrowband line, an infrared transient) must specify in advance which independent channel confirms or kills it, with combined significance assessed by pre-registered methods (Section 11).

(iv) Pre-registered thresholds. Detection and falsification thresholds are stated numerically before the data arrive (Tables 3 and 4), in the tradition that a test postponed until after the data are seen is not a test.

(v) Parasitism on funded science. The decisive measurements — IMBH reality, mass, and spin — will be made by LISA as part of its core science program whether or not anyone organizes a campaign (Colpi et al. 2024; Babak et al. 2017). The campaign's job is to ensure that when those numbers arrive, the contextual data (timing, astrometry, electromagnetic limits, high-energy monitoring) already exist to interpret them.

1.4 Structure of this paper

Section 2 reviews the target and the present constraint landscape. Sections 3–10 present the eight programs, each with science case, technical implementation, sensitivity estimates, and decision criteria. Section 11 describes cross-program coordination, alert protocols, and joint statistics. Section 12 presents costing and timeline. Section 13 assembles the decision tree through 2040. Section 14 concludes.

2. The target and the constraint landscape

2.1 Adopted parameters

Table 1 collects the parameters adopted throughout. We use the oMEGACat kinematic distance of 5.49 ± 0.06 kpc (Häberle et al. 2025), consistent within systematics with the Gaia EDR3 parallax distance (Soltis et al. 2021) and the combined-catalogue value (Baumgardt & Vasiliev 2021). At this distance 1″ subtends 0.0266 pc, so the entire fast-star region (r < 3″) fits within 0.08 pc, and the cluster core (r_c ≈ 2.4′) within ~4 pc.

2.2 The mass tension

Table 2 and Figure 1 summarize the central-mass constraints. Two features matter for campaign design. First, the disagreement is not marginal: the velocity-only kinematic lower bound (8,200 M_☉) exceeds the pulsar-timing point-mass upper bound (6,000 M_☉, 3σ) outright, and the acceleration-informed lower bound (21,100 M_☉) exceeds it by a factor of 3.5. At least one analysis is wrong, or incomplete, in an instructive way — for instance through the radial distribution assumed for the MSPs, the foreground/membership treatment of the fast stars, or the possibility that the central mass is genuinely extended (Bañares-Hernández et al. 2025; Zocchi et al. 2019; Breen & Heggie 2013). Second, the tension is resolvable on a known schedule: more pulsars and longer timing baselines tighten the upper bound as roughly 1/√(N_psr T²) (Section 4); Roman and Gaia DR4 sharpen the astrometric frame within two years (Section 5); and LISA, if a compact-object inspiral is caught, measures the mass to ~0.1 per cent (Babak et al. 2017).

2.3 Three hypotheses, fixed in advance

Following Paper A we carry three competing hypotheses through every program:

The campaign's purpose is not to hunt for H₂; it is to measure the system well enough that H₀ and H₁ are decided on their merits — with H₂'s distinctive residues either appearing in the data or being retired by them.

3. Program 1: JWST infrared accretion and waste-heat limits

3.1 Science case

For any central mass M_•, the Eddington luminosity is L_Edd ≃ 1.26×10³¹ (M_•/M_☉) W: 1.0×10³⁵ W at 8,200 M_☉, 2.5×10³⁵ W at 2×10⁴ M_☉, 6.2×10³⁵ W at 4.9×10⁴ M_☉. The existing non-detections (Mahida et al. 2026; Chen et al. 2025) already establish that any IMBH radiates at ≲10⁻⁹ of Eddington — among the most extreme quiescence levels measured for any black hole — but the published JWST analysis is an archival by-product, not an optimized deep program. A purpose-designed campaign improves the limits by an order of magnitude and adds the two dimensions the archival data lack: variability (accretion at these rates is expected to flicker; a managed or artificial suppression of accretion, the H₂ residue, is not) and waste heat (a mid-infrared excess over the stellar population model is the classic Dyson-type technosignature; Dyson 1960; Wright et al. 2014; Hsiao et al. 2021 — and at ω Cen the relevant solid angle is a few arcseconds, not a galaxy).

3.2 Implementation

Deep imaging (new observations). NIRCam F200W/F356W/F444W at 20 ks per filter plus MIRI F770W/F1000W at 15 ks per filter, in two epochs separated by ~6 months: ~65 h total. In the crowded core the limits are confusion- rather than photon-limited; with empirical-PSF subtraction anchored to the oMEGACat astrometric catalogue (Häberle et al. 2024b; Nitschai et al. 2023), simulated point-source recovery reaches ~5–10 nJy (3σ) at F444W and ~30–70 nJy at F770W/F1000W after a ~3× crowding penalty. At 5.49 kpc, 10 nJy at F444W corresponds to a monochromatic νL_ν ≈ 2.5×10²⁸ erg s⁻¹; for plausible quiescent-accretion SEDs the bolometric limit is of order 10²⁹–10³⁰ erg s⁻¹, i.e. Eddington ratios of 10⁻¹³–10⁻¹² at 2×10⁴ M_☉ — probing a regime in which even Sgr A* would be conspicuous (Event Horizon Telescope Collaboration 2022).

Two-epoch variability. Differential photometry between epochs is robust to the static crowding systematics that dominate the absolute limits; variability at the ≥20–30 per cent level for any source above ~30 nJy flags an accretion candidate and triggers the coordination protocol of Section 11.

Waste-heat analysis (archival + new). The 10–30 μm field photometry is fitted against the synthetic stellar-population SED constructed from the oMEGACat spectroscopic catalogue (Nitschai et al. 2023); the technosignature statistic is a spatially coherent excess in the central 0.1 pc exceeding 3σ over the population model. The same fit yields conventional science: the most precise mid-IR census of the post-main-sequence population in any globular cluster.

Spectroscopic environment test (Cycle 6+, contingent). If astrometry or timing strengthens the IMBH case, a NIRSpec IFU mosaic of the inner 0.5 pc (~125 h) maps abundance anomalies (Li enhancement, refractory depletion) that would discriminate between ordinary tidal-disruption debris chemistry (Hills 1988; Gezari 2021) and the engineered-feeding residue of H₂. We do not request this time until the trigger condition is met.

3.3 Decision criteria

Null result (expected under H₀, H₁, and mature-H₂ alike): bolometric limit ≲10³⁰ erg s⁻¹ recorded — radiative output ≲10⁻¹² of Eddington across the contested mass range — complementing the radio Bondi-efficiency bound and jointly constraining any radiatively inefficient flow via the fundamental plane (Merloni et al. 2003; Mahida et al. 2026). A static detection consistent with a quiescent accretion SED supports H₀ and immediately sharpens every dynamical program (the source position becomes the kinematic centre). A variable detection triggers multi-messenger follow-up. A >3σ extended mid-IR excess with no stellar counterpart is the single strongest electromagnetic anomaly the campaign can produce and would be adjudicated under Section 11 rules.

4. Program 2: Radio — deep imaging, narrowband SETI, and pulsar timing

4.1 Science case

The radio program carries three loads at once. (i) Continuum: a deeper interferometric limit (or first detection) on the central compact source, extending Mahida et al. (2026) and the globular-cluster IMBH radio campaigns (Strader et al. 2012; Tremou et al. 2018). (ii) Narrowband SETI: the first dedicated technosignature search of any kind at ω Cen, closing the gap left by the FAST pilot survey's latitude limit (Huang et al. 2026). (iii) Pulsar timing: the binding constraint on the central mass comes from the cluster's MSP population — five discovered with Parkes (Dai et al. 2020), timed to ν̇ within 3.5 yr (Dai et al. 2023), then thirteen more with MeerKAT/TRAPUM (Chen et al. 2023; Stappers & Kramer 2016) for eighteen total — and the path to resolving the mass tension runs directly through more pulsars and longer baselines (Bañares-Hernández et al. 2025).

4.2 Implementation: MeerKAT era (2026–2030)

Timing. Bi-weekly L-band sessions (~26 per year, ~3–5 h each) on all eighteen MSPs with MeerKAT (Jonas 2016), producing times of arrival at ~1 μs precision for the brightest objects. Line-of-sight acceleration precision from timing scales steeply with baseline (σ_a ∝ T^−5/2 for white noise); by analogy with the mature 47 Tuc and Terzan 5 programs (Freire et al. 2017; Prager et al. 2017), five years of MeerKAT data yield per-pulsar acceleration uncertainties of order 10⁻¹¹–10⁻¹⁰ m s⁻² for the best-timed objects. For scale, a 4×10⁴ M_☉ point mass imposes a ≈ 6×10⁻⁸ m s⁻² at r = 0.3 pc: the discriminating signal is not the detection of acceleration (already achieved; Dai et al. 2023; Bañares-Hernández et al. 2025) but the radial profile of accelerations and jerks across the MSP population, which distinguishes a point mass (a ∝ r⁻²) from an extended remnant component. Commensal search observations are expected to add 5–10 MSPs (the luminosity function is far from exhausted; Chen et al. 2023), and the point-mass upper bound tightens approximately as 1/√N_psr (T₀/T)^≥1: ten well-timed pulsars with ten-year baselines push a 6,000 M_☉ bound to the 3,000–4,000 M_☉ level if no point-mass signal emerges — or find one.

Narrowband SETI. Commensally with every timing session, a 1-Hz-resolution spectrometer backend records the full primary beam (~1°, comfortably containing the whole cluster). Processing follows standard drift-search practice (Enriquez et al. 2017): Doppler drifts ±4 Hz s⁻¹, SNR >15 candidate threshold, on–off cadence against reference pointings, and re-detection in an independent session required before any candidate advances. Seventy hours over two years reach a minimum detectable EIRP of ~(3–6)×10¹⁷ W at 5.49 kpc — roughly an order of magnitude above the FAST pilot's ~10¹⁶ W thresholds at its (closer, northern) targets (Huang et al. 2026), but the first limit of any kind for this cluster, and sufficient to detect any transmitter exceeding ~10⁴ times the EIRP of the Arecibo planetary radar — a modest output for an energy-rich civilization — from any of ~10⁷ stars in the beam simultaneously.

Continuum. The summed continuum visibilities from the timing campaign provide a ~100+ h synthesis image at L/S band; combined with the ATCA 7.25-GHz limit (Mahida et al. 2026) this constrains both the flat-spectrum (jet) and steep-spectrum (pulsar) interpretations of any future central source candidate.

4.3 Implementation: SKA era (2029–)

SKA-Mid science verification is expected in 2029 and early operational cycles in the early 2030s (Braun et al. 2019). The ω Cen program transfers wholesale: timing precision improves by the sensitivity ratio (factor ~4–5 over MeerKAT for these declinations), the MSP census plausibly doubles, and the narrowband EIRP threshold drops toward ~10¹⁶ W — FAST-class sensitivity on a southern target FAST cannot see. By LISA launch, the pulsar acceleration map will be the best non-GW constraint on the central potential in any globular cluster.

4.4 Decision criteria

The timing program is the campaign's primary near-term discriminator between H₀ and H₁: a smooth r⁻² acceleration profile centred on the kinematic centre at ≥10⁴ M_☉ retires H₁; a persistently tightening upper bound below the kinematic lower bounds forces revision of the fast-star analysis (membership, foreground, or binarity systematics) and shifts the campaign's centre of gravity to H₁. For SETI: any re-detected narrowband candidate enters the two-messenger protocol; a null is published as the first ω Cen technosignature limit. Paper A dependence (labelled): under H₂, P3 of that paper predicts no leakage radiation, so SETI nulls carry no evidential weight against H₂ — they constrain only conventional beacon scenarios.

5. Program 3: Astrometry — HST, Gaia DR4, Roman, and ELT/MICADO

5.1 The honest calculation first

The intuitively obvious astrometric test — watch the seven fast stars curve — does not work on a useful timescale, and we show this rather than assert it. The proper-motion acceleration induced by a central mass M_• at projected radius r is

which at d = 5.49 kpc corresponds to ≈5.3×10⁻⁴ mas yr⁻² (mean projection factors of order unity absorbed). Against this, the oMEGACat astrometry — ~0.02 mas single-epoch precision over a ~15-year HST baseline — delivers acceleration uncertainties of σ_a ≈ 1×10⁻³ mas yr⁻² per star (Häberle et al. 2024a, 2024b): a 0.5σ measurement. Extending HST monitoring to 2028 (a 26-year baseline) improves this only to ~0.7σ; a four-year ELT/MICADO campaign at ~50–100 μas per epoch (Davies et al. 2021) reaches σ_a ≈ 2×10⁻³ mas yr⁻² — worse, because acceleration precision scales as T⁻² and four years is short (Figure 2). Direct 5σ curvature detection at nominal parameters requires either M_• ≳ 10⁵ M_☉, a star at r < 0.015 pc, or ≳30-year baselines on ELT-class astrometry. We therefore retain the fast-star monitoring (cheap; protects against the lucky cases, since González Prieto et al. 2025-mass holes and undiscovered inner stars are both live possibilities) but route the decision-grade astrometry through three measurements that do work, below.

5.2 Three astrometric measurements that do work

(i) Photocentric wander (Roman). An IMBH of mass M_• in dynamical equilibrium with stars of mean mass m̄ executes Brownian motion with velocity σ_• ~ σ_★√(m̄/M_•) relative to the cluster centre of mass. The lighter the hole, the larger its wander: the predicted amplitude differs by ~17 per cent between 6,000 and 8,200 M_☉ (the square root of the mass ratio), and by a factor ~2.4 between 8,200 and 4.9×10⁴ M_☉. Resolving it requires measuring the reflex motion of the innermost stellar distribution at the few-μas yr⁻¹ level against the bulk cluster frame — precisely the regime of Roman's wide-field astrometry, which delivers ~10 μas-class differential astrometry over fields vastly larger than HST's, tying the inner arcseconds to thousands of cluster reference stars at once (Sanderson et al. 2019). Roman launches 2026 August 30; a five-year cadenced guest-observer program (ω Cen lies outside the core community surveys, so epochs must be requested, but the per-epoch cost is small) discriminates the light-IMBH from heavy-IMBH wander regimes at the 3–5σ level, independently of individual-star orbits.

(ii) The absolute reference frame (Gaia DR4, 2026 December). The dominant systematic in all current inner-field astrometry is the tie between HST's relative frame and the absolute (ICRS) frame. Gaia DR4's 5.5-year solutions for the r > 10″ cluster members (Gaia Collaboration 2016) improve proper motions by a factor ~4.5 over DR2-era ties, propagating directly into the fast-star velocity vectors — and thus into the 8,200 M_☉ lower bound itself, which rests on those velocities exceeding the escape speed. This is the cheapest decisive measurement in the entire campaign: a re-derivation of the Häberle et al. (2024a) bound on the DR4 frame either firms the tension into a >5σ contradiction with the timing bound or dissolves it. Deliverable in 2027 from archival data alone.

(iii) Inner-star discovery (ELT/MICADO, 2029+). MICADO's ~10 mas resolution and 39-m aperture (Davies et al. 2021) penetrate the central arcsecond at magnitudes HST cannot reach in crowding, with the realistic prize being new fast stars at r < 0.02 pc. A single star at 0.01 pc raises the acceleration signal of Eq. (1) by a factor of 64, converting Figure 2's verdict from "decades" to "a few epochs" — this is how the Galactic-Centre program succeeded (GRAVITY Collaboration 2018), and ω Cen is its natural second act at 10² × lower mass. Two epochs per year from 2029; first acceleration-grade results plausible by the early 2030s.

5.3 Decision criteria

DR4 re-derivation (2027): if the fast-star velocity excess survives at >5σ, H₁ requires the MSP analysis to be systematically biased — a specific, checkable claim (radial distribution priors; Bañares-Hernández et al. 2025). Roman wander (2031): light/heavy discrimination feeds the LISA prior. MICADO inner stars (2030s): any star with measured Keplerian curvature yields M_• to tens of per cent, independent of statistical modelling, before LISA flies.

6. Program 4: The LISA forecast

6.1 Science case

LISA is the campaign's endgame: the only instrument that can measure the central object's mass and spin to high precision regardless of its electromagnetic state (Colpi et al. 2024; Amaro-Seoane et al. 2017). For a compact object inspiralling into a 10⁴-class IMBH, matched-filter parameter estimation delivers fractional precisions of order 10⁻³–10⁻⁴ on mass and 10⁻³ on spin (Babak et al. 2017; Amaro-Seoane 2018). At 5.49 kpc — versus the Gpc distances over which LISA expects to detect its EMRI population — any ω Cen inspiral in band during the mission would be loud (signal-to-noise in the hundreds to thousands), making the limiting factor occurrence probability, not sensitivity.

6.2 Rates, honestly

Cluster-dynamics simulations imply IMRI formation rates per cluster of order 10⁻⁸–10⁻⁶ yr⁻¹ depending on IMBH mass, binary fraction, and core density; over a 4–10-year mission this yields an in-band inspiral probability for ω Cen of order 10⁻² or below — possibly enhanced by the cluster's unusually dense remnant population, but not to order unity. The forecast must therefore be stated in three tiers. Tier 1 (probable): no ω Cen source; LISA still constrains the stochastic foreground from the core remnant population, directly testing H₁'s extended-component density profile. Tier 2 (plausible): a quasi-monochromatic source — a compact object orbiting the IMBH well outside plunge — detectable over the mission as a continuous-wave source; this measures M_• through the orbital frequency and its drift, to precision intermediate between timing and a full inspiral. Tier 3 (lucky): a genuine inspiral; per-mille mass and spin. The campaign's structure ensures that even Tier 1 is decisive when combined with the pulsar acceleration map (Section 4): a stochastic-foreground non-detection plus a point-mass timing profile isolates H₀.

6.3 The spin measurement as the H₂ adjudicator

Paper A dependence (labelled): under H₂ the single sharpest residue is near-extremal spin (a_★ ≳ 0.9) on a hole that has demonstrably accreted nothing for Gyr; under H₀ natural formation channels for cluster IMBHs span low-to-moderate spin. A Tier 3 spin measurement therefore adjudicates H₂ at the same instant it completes the H₀/H₁ question — the entire reason this campaign's electromagnetic and dynamical groundwork must precede LISA rather than follow it. The full decision tree, including this branch, is assembled in Section 13.

6.4 Deliverables before launch

Between now and the mid-2030s the program's work is preparatory but concrete: (i) maintain the dynamical model of the inner parsec (timing + astrometry) so that any LISA source has an immediate host context; (ii) publish the ω Cen-specific EMRI/IMRI rate forecast with the post-2026 mass constraints folded in; (iii) ensure the cluster's barycentric ephemeris and distance (±0.06 kpc; Häberle et al. 2025) are maintained at the precision LISA parameter estimation will assume.

7. Program 5: KM3NeT/ARCA neutrino monitoring

7.1 Science case and geometry

ω Cen at declination −47.5° is an up-going source for the Mediterranean: KM3NeT/ARCA observes it through the Earth, with atmospheric muons filtered out and sub-0.2° angular resolution for track events at ≳10 TeV (Adrián-Martínez et al. 2016). For IceCube the same source is down-going (degraded but usable above ~100 TeV; IceCube Collaboration 2020); the combined ANTARES+IceCube southern-sky analysis (Albert et al. 2020) defines the archival baseline. ARCA stood at 51 of 230 detection units in early 2026, with real-time alert distribution entering commissioning; sensitivity grows roughly linearly with instrumented volume through the decade. The conventional science driver is a deep point-source limit on a dense old stellar system; the technosignature driver (Paper A dependence, labelled) is the burst-mode prediction of black-hole-based computation models (Dvali & Osmanov 2023; Lacki & DiKerby 2025), for which a cluster like ω Cen is the natural test bed and which the existing point-source pipelines do not target: their time-integrated statistics dilute rare short multiplets.

7.2 Implementation

Steady-state search (archival + ongoing). Standard unbinned-likelihood point-source analysis (Braun et al. 2008) at the ω Cen coordinates in (i) the ANTARES+IceCube combined dataset, (ii) the growing ARCA exposure. Full-array ARCA reaches E²Φ ~ few ×10⁻¹²–10⁻¹¹ TeV cm⁻² s⁻¹ at this declination over multi-year integrations — the deepest neutrino limit ever placed on a globular cluster.

Burst pipeline (new, the campaign's contribution). A pre-registered transient search in sliding windows of 10², 10³, and 10⁴ s within 1° of the cluster centre, E ≳ 10 TeV, on ARCA data plus IceCube alerts. The detection criterion — ≥3 tracks in one window, ≥5σ post-trials, no plausible astrophysical counterpart — is calibrated by the background expectation: the atmospheric-neutrino rate above 10 TeV within a 1° cone is of order 10⁻⁷ s⁻¹, so a 10³-s window expects ~10⁻⁴ events and a triplet is intrinsically far beyond 5σ before trials; the design problem is the trials budget over a decade of monitoring (~3×10⁶ windows), which the post-trials threshold absorbs (Figure 3). Any KM3NeT or IceCube real-time alert within 1° triggers the electromagnetic protocol of Section 11 — the alert system's first ω Cen-relevant cycle begins in late 2026.

7.3 Decision criteria

A decade-scale null at full-array sensitivity closes the burst-mode channel of Dvali & Osmanov (2023) for this system at its predicted strength — a publishable falsification regardless of H₂ (the underlying micro-black-hole physics is itself contested; Álvarez-Domínguez et al. 2024; Loeb 2024). One confirmed multiplet with no counterpart, repeated at the same location, would be among the most significant anomalies in high-energy astrophysics independent of any ETI interpretation; the protocol deliberately treats it as an astrophysical discovery first.

8. Program 6: Gamma rays — Fermi-LAT archival and CTAO-South

8.1 Science case

ω Cen is a GeV source: 4FGL J1326.7−4729 coincides with the core, and its emission is attributed to the MSP ensemble after deep searches found no individual pulsations (Dai et al. 2020, 2023). This is both foreground and opportunity: the steady MSP emission is a calibration source against which transient or spectrally anomalous excesses can be sought with high contrast. The technosignature channel shares the burst phenomenology of Program 5 (the Dvali & Osmanov 2023 spectrum is "democratic" across species, implying γ-ray counterparts to any neutrino burst); the conventional channel is a TeV detection or limit on the cluster, of independent interest for MSP magnetospheric and inverse-Compton physics.

8.2 Implementation

Fermi-LAT (archival, immediate). Re-analysis of the now >17-year LAT exposure at the cluster position: (i) refit of the steady source with current diffuse models; (ii) a sliding-window transient search (Δt = 10²–10⁴ s, matched to Program 5's windows) over the full mission, with the steady MSP flux as null model; (iii) spectral-cutoff analysis — MSP ensembles cut off at a few GeV, so any significant emission above ~30 GeV flags a non-MSP component. All three are pure archival analyses.

CTAO-South (2027+). The first Paranal telescopes arrive through late 2026 (CTA Consortium 2019); intermediate arrays operate while construction proceeds. We propose (i) a 50-h deep exposure reaching ~10⁻¹³ erg cm⁻² s⁻¹ at 1 TeV — the first meaningful TeV limit on any globular cluster core at this depth — and (ii) a standing target-of-opportunity trigger: any Program-5 alert within 1° pre-authorizes prompt CTAO follow-up, the latency being minutes for a source that transits Paranal ~23° from zenith.

8.3 Decision criteria

A LAT transient coincident with a neutrino window elevates any Program-5 candidate to the campaign's highest tier. A TeV detection of steady emission is conventional astrophysics (and would be the first for a globular cluster); its absence at CTAO depth tightens the inverse-Compton budget of the MSP population. Spectral excess above 30 GeV without transient behaviour prompts a dark-matter-versus-exotica analysis before any H₂ language is entertained.

9. Program 7: Optical/IR time domain — Rubin/LSST and archival anomalies

9.1 Science case

Two distinct searches share this program. First, transients: tidal disruption of a star by an IMBH is the one natural event that would announce the central object unambiguously (Hills 1988; Gezari 2021); rates are low (~10⁻⁷–10⁻⁶ yr⁻¹ per cluster for full disruptions, higher for partial-disruption flares of the dense remnant environment) but the cost of monitoring is now effectively zero, because LSST began surveying in early 2026 and ω Cen sits in the survey footprint (Ivezić et al. 2019). Second, archival photometric anomalies: the oMEGACat HST archive — 500+ epochs over 20+ years for 10⁶ stars (Häberle et al. 2024b; Nitschai et al. 2023) — is an essentially unmined time-domain dataset in which periodic dimmings, secular fades, or statistically anomalous variability classes (the photometric residues conjectured for megastructures; Wright et al. 2014; Hsiao et al. 2021; Socas-Navarro et al. 2021) can be sought with two decades of baseline for free.

9.2 Implementation

LSST stream. The cluster core saturates LSST, but the half-light region and outskirts do not: a standing broker filter on the ω Cen field flags (i) any nuclear transient brighter than r ~ 16 (TDE flares at 5.49 kpc would reach naked-eye-adjacent magnitudes; even heavily extincted or partial events are unmissable), and (ii) anomalous variables among ~10⁵ measurable members. Difference-imaging in the crowded annulus is handled with the oMEGACat reference catalogue.

Archival mining. A systematic variability census of the oMEGACat photometric archive: period search to ~0.05 mag depth across 10⁶ stars, secular-trend extraction, and an explicitly pre-registered anomaly statistic (population-level excess of non-physical light-curve classes) with human vetting of survivors. Conventional yield: the deepest variable-star census of any globular cluster, eclipsing-binary distance cross-checks, and stellar-rotation demographics — publishable regardless of anomalies.

Core-depletion statistic (joint with Program 3). Paper A dependence (labelled): H₂'s P4c predicts secular depletion of the loosely bound core population beyond N-body expectations. The measurement — star counts by binding-energy quantile against matched N-body models (González Prieto et al. 2025) — is identical to standard mass-segregation analysis and is conventional dynamics on its face; we simply pre-register the depletion direction as a tracked statistic.

9.3 Decision criteria

A nuclear TDE settles the IMBH question electromagnetically (and its decay light curve constrains M_•; Gezari 2021); the campaign's role is to guarantee the multi-wavelength response is pre-arranged. Archival anomalies are population statistics: no single weird star means anything (the false-positive history of photometric SETI is long); only a ≥3σ class-level excess, surviving vetting, enters the coordination protocol.

10. Program 8: Supplementary archival channels

Two channels are cheap enough to run as graduate-student archival projects and complete the messenger coverage.

Continuous gravitational waves (LIGO–Virgo–KAGRA). Narrowband searches at twice the spin frequencies of the eighteen known MSPs, using public O4/O5 data and the MeerKAT ephemerides, following the known-pulsar methodology of Abbott et al. (2022). Expected upper limits h₀ ≲ 10⁻²⁶ translate to ellipticity limits ε ≲ few ×10⁻⁸ at 5.49 kpc for the faster spinners — conventional neutron-star physics in an environment (a dense old cluster) where the recycled-pulsar population is dynamically distinctive. The technosignature reading (structured masses in MSP orbits) is not separately funded; it shares the identical data product.

Ultra-high-energy cosmic rays (Pierre Auger). ω Cen sits well inside Auger's southern acceptance. A stacked directional analysis around the cluster position in the public E > 8 EeV dataset (Pierre Auger Collaboration 2017), with 1° and 3° apertures bracketing magnetic deflection, either contributes an upper limit on hadronic acceleration in the core — of conventional interest given the MSP wind population — or flags an anisotropy for which the Galactic-Centre region (18° away) is the obvious confounder to exclude first.

11. Coordination, joint statistics, and data policy

11.1 The two-messenger rule, operationalized

Table 3 pre-registers the campaign's trigger and confirmation matrix. Each row names a primary trigger, the channels that can confirm it, and the joint-significance requirement. Combined significances across independent channels use Fisher's method on the per-channel p-values, with the global claim threshold set at p < 5×10⁻⁷ post-trials — deliberately at discovery convention, because the base rate of true technosignatures is unknown and plausibly zero, so the loss function is asymmetric: a false positive damages the field's credibility far more than a delayed true positive damages the discovery (Wright et al. 2022).

11.2 Alert latency and standing authorizations

The latency-critical path is neutrino → gamma/optical: KM3NeT real-time alerts (commissioning through 2026) distribute within seconds–minutes; the CTAO ToO and LSST-broker hooks are standing authorizations requiring no human decision for the first response hour. Slow-path coordination (JWST DDT requests, radio re-pointing) is pre-drafted as template proposals with trigger criteria attached, cutting submission latency to <24 h.

11.3 Data policy

All pipelines, thresholds, and analysis code are public from the start (the pre-registration is itself the methods paper); all derived catalogues are released with their papers; raw data inherit host-facility policies. Negative results are published on a fixed cadence — the field's credibility problem is survivorship bias, and a campaign explicitly designed around falsification should model the cure.

11.4 Program summary

Table 4 assembles the eight programs with sensitivities, requests, and timelines.

12. Cost and timeline

12.1 Costing

Table 5 presents full-cost estimates (salaries, computing, travel, publication; US academic rates) for each program. Facility time is excluded — it is competitively allocated and carries no cash cost to the campaign — as is LISA, which is mission science. The total, ≲ US$7M over a decade, is calibrated against the per-program budgets developed in the precursor proposal studies for this campaign and is small by every relevant comparison: a single mid-scale NASA Explorer instrument, one JWST cycle's archival-funding pool, or the marginal cost of a few nights of ELT operations.

12.2 Timeline

Figure 4 lays the programs against the facility schedule. The structure is deliberate: the 2026–2028 window is dominated by archival work and standing-pipeline construction (cheap, immediate); 2029–2034 by the new-facility harvest (ELT, SKA-Mid, CTAO completion, Roman mid-mission); 2035+ by LISA. Decision points D1–D4 are marked and defined in Section 13.

13. The decision structure through 2040

Figure 5 assembles the campaign into a single decision tree, extending the gravitational-wave branch of Paper A's falsification framework backward into the electromagnetic-and-timing era. Rough branch weights are stated where the inputs exist to estimate them; they are planning priors, not forecasts, and we expect D1/D2 to revise them substantially.

14. Conclusion

Omega Centauri in 2026 presents a configuration that observational astronomy rarely supplies: a contested discovery (the Galaxy's best IMBH candidate) whose two strongest constraints formally contradict each other; an electromagnetic silence deep enough to be a result in itself; an essentially untouched technosignature parameter space; and a fleet of new southern and all-sky instruments — Rubin, Roman, Gaia DR4, KM3NeT, CTAO, SKA-Mid, ELT, and ultimately LISA — arriving on exactly the timescale needed to resolve all of it. The campaign presented here is, at bottom, an exercise in not wasting that conjunction.

Its architecture reflects three commitments. First, dual use: every program stands as conventional astrophysics — the mass tension, the quiescent-accretion frontier, the MSP dynamical laboratory, the first deep TeV and neutrino limits on a globular cluster — so that no null result is a loss. Second, honesty about sensitivity: where the obvious measurement fails (direct fast-star acceleration before ~2040), we demonstrate the failure quantitatively and redesign around it, because a program that oversells its tests invites the credibility collapse that has repeatedly damaged this field. Third, pre-registration: hypotheses H₀/H₁/H₂, thresholds, confirmation rules, and decision points are fixed in advance, so that whatever the sky delivers — a remnant swarm, a quiet heavy hole, or a genuine anomaly — the inference chain was written down before anyone knew the answer.

The cost is under US$7M across a decade, most of it salaries for archival analysis riding on facilities that are funded regardless. The payoff structure is asymmetric in the campaign's favour: the probable outcomes (a resolved mass tension, a characterized central object, the first technosignature limits on 10⁷ old stars) are solid science at modest cost, and the improbable outcome — the green branch of Figure 5 — would justify the program many thousands of times over. We commit, symmetrically, to the red branches: if the timing profile confirms an extended remnant component, or LISA delivers a light or slowly spinning hole, the anomaly hypotheses retire here without special pleading, and what remains is what was always underneath: the most interesting stellar system in the southern sky, finally measured properly.

Acknowledgements and disclosure

The author thanks the maintainers of the NASA Astrophysics Data System and arXiv, on which the citation verification for this work relied. AI assistance disclosure: drafting, citation verification, derivation checking, and figure preparation for this manuscript were performed with substantial assistance from a large language model (Claude, Anthropic), under the author's direction; the author reviewed and takes full responsibility for all claims, derivations, and references. Interactive calculators implementing the quantitative material in this paper, together with the underlying per-instrument proposal studies, are available at omegacentauri.me.

Data availability

No new observational data were generated for this work. All quantitative claims derive from the cited literature; analysis conventions for the proposed programs will be released with the respective pipeline papers.