Ultrahigh-energy neutrino follow-up of gravitational wave events GW150914 and GW151226 with the Pierre Auger Observatory

On September 14, 2015 the Advanced LIGO detectors observed their first gravitational wave (GW) transient GW150914. This was followed by a second GW event observed on December 26, 2015. Both events were inferred to have arisen from the merger of black holes in binary systems. Such a system may emit neutrinos if there are magnetic fields and disk debris remaining from the formation of the two black holes. With the surface detector array of the Pierre Auger Observatory we can search for neutrinos with energy $E_{\nu }$ above 100 PeV from pointlike sources across the sky with equatorial declination from about $-65°$ to $+60°$, and, in particular, from a fraction of the 90% confidence-level inferred positions in the sky of GW150914 and GW151226. A targeted search for highly inclined extensive air showers, produced either by interactions of downward-going neutrinos of all flavors in the atmosphere or by the decays of tau leptons originating from tau-neutrino interactions in the Earth’s crust (Earth-skimming neutrinos), yielded no candidates in the Auger data collected within $\pm 500\mathrm{s}$ around or 1 day after the coordinated universal time (UTC) of GW150914 and GW151226, as well as in the same search periods relative to the UTC time of the GW candidate event LVT151012. From the nonobservation we constrain the amount of energy radiated in ultrahigh-energy neutrinos from such remarkable events.

Figure 1

Sky map in equatorial coordinates where the color scale indicates the fraction of one sidereal day for which a pointlike source at declination $\delta$ is visible to the SD of the Auger Observatory (latitude $\lambda =-35.2°$) at zenith angle $90°<\theta <95°$ (top panel), and $75°<\theta <90°$ (bottom panel). The white solid lines indicate the 90% C.L. contour position of GW150914 [1, 2] and the dashed white lines indicate the corresponding 90% C.L. contour position of GW151226 [3, 4]. The white star indicates the best-fit position of the GW150914 event obtained in combination with data from the Fermi-GBM instrument (see Fig. 10 in [7]).

Figure 2

Instantaneous field of view of the ES (red band) and DGH (blue band) channels at the moment of coalescence of GW150914 (top panel) and of GW151226 (bottom panel). The black spots represent the 90% C.L. contour enclosing the positions of the corresponding GW events. Note that by chance the instantaneous field of view of Auger is approximately the same at the instants of occurrence of both GW events.

Figure 3

Top panel: Upper limits to the UHE neutrino spectral fluence per flavor [see Eq. (4)] from the source of GW150914 as a function of equatorial declination $\delta$. Fluences above the black solid line are excluded at 90% C.L. from the nonobservation of UHE neutrino events in Auger. The 90% C.L. declination bands of the GW150914 are indicated in the plot by the shaded rectangles. Bottom panel: Same as the top panel for the GW event GW151226.

Figure 4

Top panel: Constraints on $E_{\nu ,\text{tot}}$ the energy radiated in UHE neutrinos (per flavor) from the source of GW150914 as a function of equatorial declination $\delta$. Energies above the black solid line, assuming the luminosity distance to the source is $D_s=410\mathrm{Mpc}$, are excluded at the 90% C.L. from the nonobservation of UHE neutrinos in Auger. The long-dashed line represents the constraints if the source is farther away at $D_s=410+160\mathrm{Mpc}$, and the short-dashed line if the source is closer to Earth at $D_s=410–180\mathrm{Mpc}$ corresponding to the 90% C.L. interval of possible distances to the source. For reference the dot-dashed black horizontal line represents $E_{\mathrm{GW}}\simeq 5.4\times 10^{54}\mathrm{erg}$, the inferred energy radiated in gravitational waves from GW150914 [1, 2]. The 90% C.L. declination bands of the GW150914 are indicated in the plot by the shaded rectangles. Bottom panel: Same as the top panel for GW151226 but in this case $D_s=440_{-190}^{+180}\mathrm{Mpc}$ and the energy released in the form of GW is $E_{\mathrm{GW}}\simeq 1.8\times 10^{54}\mathrm{erg}$.