Multipoint Detection of GRB221009A's Propagation through the Heliosphere

GRB221009A was a bright and long-lasting gamma-ray burst (GRB) detected by the spaceborne telescopes such as the Burst Alarm Telescope (BAT) on board Swift (Dichiara et al. 2022; afterglow), Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (FGST) (Veres et al. 2022; Lesage et al. 2022; Pillera et al. 2022), AGILE (Piano et al. 2022; Ursi et al. 2022), INTEGRAL SPI-ACS (Gotz et al. 2022), Solar Orbiter (Xiao et al. 2022), SRG/ART-XC (Lapshov et al. 2022), Konus-Wind (Frederiks et al. 2022), GRBAlpha (Ripa et al. 2022), and STPSat-6 (Mitchell et al. 2022), High Energy Burst Searcher (HEBS) on SATech-01 (Liu et al. 2022), BepiColombo (Kozyrev et al. 2022), and by the ground observatories such as the Large High Altitude Air Shower Observatory (LHAASO; Brdar & Li 2023). The GRB221009A started with a precursor at T₀ = 2022 October 9 13:16:59 UTC (Pulse 1), followed by a set of pulses at ∼ T₀ + 225 s (Pulse 2), ∼ T₀ + 256 s (Pulse 3), and ∼T₀ + 509s (Pulse 4) (GRB Coordinates Network; GCN Veres et al. 2022; Liu et al. 2022; Rodi & Ubertini 2023). The afterglow of the burst outshone all other GRBs seen before (Sahu et al. 2023) in a very-high-energy (VHE) band. The water Cherenkov detector array and the larger air shower kilometer square area detector at LHAASO observed more than 5000 VHE photons in the 500 GeV–18 TeV energy range within 2000 s from the trigger, making them the most energetic photons ever observed from a GRB (Baktash et al. 2022). The multiwavelength afterglow and comparative brightness of the GRB221009A were studied in Laskar et al. (2023) and Kann et al. (2023). The event was so long and intense that the increased ionization by X- and gamma-ray emission caused sudden global ionospheric disturbances in the D region of Earth's ionosphere (Hayes & Gallagher 2022; Pal et al. 2023).

The source location of the GRB has been derived to be centered at R.A. = 288282 and decl. = 19495 (J2000) with a 90% containment radius of 0027 (Pillera et al. 2022) and its redshift was estimated to be z = 0.15 (Veres et al. 2022; de Ugarte Postigo et al. 2022). The relatively small value of the redshift indicates that this is one of the closest observed long-duration GRBs (Rastinejad et al. 2022; Troja et al. 2022; Mei et al. 2022; Gompertz et al. 2023) as its luminosity distance is ≈ 720 Mpc (O'Connor et al. 2023) based on the ΛCDM cosmological model (Freedman 2021). Even after taking into account the proximity, the GRB221009A remains one of the most luminous explosions to date (O'Connor et al. 2023), with lower limits of isotropic-equivalent gamma-ray energy ≳3 × 10⁵⁴ erg measured over the energy range from 20 keV to 10 MeV (Frederiks et al. 2022; de Ugarte Postigo et al. 2022; Kann & Agui Fernandez 2022) and the more precise value of ≳1.2 × 10⁵⁵ (Frederiks et al. 2023; Lesage et al. 2023).

In this article, we present the analysis of observations of GRB221009A by the charged particle detectors on board various spacecraft located at different points across the heliosphere on 2022 October 9. Data from charged particle detectors on board heliosphere spacecraft can provide an additional perspective on the GRB that complements observations from the gamma-ray telescopes (Schwartz et al. 2005; Terasawa et al. 2005). Charged particle detectors, despite not being designed to detect high-energy gamma-ray photons, can measure the flux of secondary particles produced within the material of the spacecraft (Pisacane 2005) or the detector itself (Battiston et al. 2023). GRB221009A has been previously studied using data from the electrostatic analyzer and solid-state telescopes on board the THEMIS mission (Agapitov et al. 2023), the HEPP-L charged particle detector on board the low Earth orbit (LEO) China Seismo-Electromagnetic Satellite (Battiston et al. 2023), and MEPED on board POES/MetOp (Vitale et al. 2023). It was shown that the high-time resolution of the electron and proton flux measurements (up to 8 measurements per second Agapitov et al. 2023) reveal the structure of the intense bursts (Pulses 2, 3, and 4) and were shown to follow quite well the fine inner structure of the Pulses 2 and 3 of the GRB221009A signal recorded by HEBS with 0.05 s resolution (Liu et al. 2022). Here we present observations of the GRB221009A by the charged particle detectors of STEREO-A, Solar Orbiter (SolO), Wind, THEMIS, POES/MetOp, and MAVEN spacecraft. STEREO-A (Kaiser et al. 2008) and SolO (Müller et al. 2020) are Sun observing missions. Wind (Wilson et al. 2021) and THEMIS (Sibeck & Angelopoulos 2008) are the missions dedicated to studying processes in the solar wind and Earth's magnetosphere. POES (Rodger et al. 2010) and MetOp (Selesnick et al. 2020) are a constellation of polar-orbiting weather satellites. MAVEN (Jakosky et al. 2015) is the NASA mission to study atmospheric losses at Mars. The spacecraft locations are shown in Figure 1. The description of the missions' particle flux measurements is in Section 2. The multipoint observations of the GRB221009A effects and the results of timing processing are in Sections 3 and 4. The conclusion section contains a short description of the obtained results.

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2.1. SolO Data

2.2. STEREO-A Data

2.3. Wind Data

2.4. THEMIS Data

2.5. POES and MetOp Data

2.6. MAVEN Data

Figure 1 shows the locations of the spacecraft during the GRB221009A. Panel (a) provides a general view of the spacecraft's location in the Heliocentric coordinate (HCI) system (Fränz & Harper 2002). Relative to the Sun, SolO was the closest, at the heliocentric distance of ∼0.30 au (1 au ∼ 499 lt-s), followed by STEREO-A (∼0.96 au), Earth, and MAVEN (∼1.46 au). During the event, SolO was below the ecliptic plane (shown as a blue surface). Panels (b) and (c) show a zoomed view of the configuration of the spacecraft in the vicinity of the Earth in the Geocentric Solar Ecliptic (GSE) coordinate system (Fränz & Harper 2002). The THEMIS mission (Sibeck & Angelopoulos 2008) consists of five identically equipped satellites (probes THA, THB, THC, THD, and THE). In 2011, two of the probes (THB and THC) were repurposed for the ARTEMIS mission and moved first to a Lissajous orbit around a lunar Lagrange point and a year later into highly eccentric, near-equatorial lunar orbit (Angelopoulos 2014). During the event, THB and THC were located near the Moon in the tail of Earth's magnetosphere at geocentric distances of 58 and 61 R_E (1 R_E [Earth radius] ∼ 0.021 lt-s), while the inner THEMIS probes were at the geocentric distances of ∼9–10 R_E . Wind was further from the Earth to the sunward direction (x-axis) at the geocentric distance of ∼203.26 R_E from the Earth. POES/MetOp spacecraft are on polar LEO orbits (panel (c) in Figure 1). The propagation of the GRB221009A in the heliosphere is schematically illustrated by the set of planar surfaces in Figure 1.

Xiao et al. (2022) reported the detection of GRB221009A by the Spectrometer/Telescope for Imaging X-rays (STIX; Krucker et al. 2020) on board SolO (panel (a) in Figure 2). In addition, Pulses 2, 3, and 4 were captured by the EPT electron and proton detectors (they are shown in Figures 2(b) and (c), respectively). The electron and proton apparent flux enhancements associated with GRB221009A are observed at energies up to 0.5 MeV. Figures 2(e) and (f) show the integrated electron and proton counts in EPT 2 and the antisunward detector on EPT 1. For comparison, the shifted by −13 s temporal profile measured by SST on THEMIS is shown in gray. The temporal profiles recorded by EPD follow quite well the profiles recorded on THEMIS (Agapitov et al. 2023) and HEPP-L (Battiston et al. 2023) but EPD detected GRB221009A ∼13 s earlier: the start of the main peak of Pulse 2 at ∼T₀+212s, and the start of Pulse 3 at ∼T₀+243 s, compared to T₀ + 225 s and T₀+256s reported in Agapitov et al. (2023; T₀ = 13:16:59.000, Veres et al. 2022). Data from STE on board STEREO-A are shown in Figure 2(d). GRB221009A-related signals were detected in the energy range from 20 to 100 keV at 13:19:06 (Pulse 2) and 13:19:36 (Pulse 3) almost 100 s earlier than they were detected by THEMIS (Agapitov et al. 2023). The STE time revolution of 10 s, is not sufficient to resolve details like shoulders (Liu et al. 2022) on the temporal profile of the burst (Figure 2(g)).

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KONUS on board Wind detected the first Pulse of the GRB221009A at 13:17:01.648 (Frederiks et al. 2022; also shown in Figure 3(a)). Figures 3(b) and (c) show electron and ion flux measured by the Wind SST with 12 s resolution. The GRB221009A-related signals (Pulses 2 and 3) are visible in the lower-energy channels: 25–40 keV for electrons and 70–130 keV for ions. The related signal was also found in the α-particle density calculated on board from the PESA measurements. Comparing the temporal profile with the THEMIS measurements (Figure 3(d)) shows a time delay of ∼1.5 s.

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The GRB221009A was detected by THEMIS ESA and SST on board the four THEMIS probes (THA, THB, THC, and THE). The signal appears as two very intense bursts at 13:20:36–13:21:30 and a subsequent less intense burst at around 13:25:30 (Figure 3(e)). The event was studied in detail by Agapitov et al. (2023). It was shown that the temporal profile of the burst with 0.25 s resolution can be obtained by combining the spin-resolved data from THB and THC Agapitov et al. (2023). Here we use the light curve of the combined THB and THC SST counts with 1 s resolution for comparison with the profiles detected by the other spacecraft used in this study.

Figure 3(f) shows electron flux measured by the POES 19 MEPED detector. The effects of the GRB221009A are visible as two relatively intense bursts detected within an energy range of 40 keV–1 MeV at 13:20:30–13:21:30. The temporal profiles of the GRB221009A-related signals recorded on POES 15, 19, and MetOp are shown in panel (g). The profile of Pulse 2 is very similar to that detected by THC, while the profile of Pulse 3 is much less prominent. The event was studied in detail by Vitale et al. (2023).

Figure 4 shows the observations of the GRB221009A made by the particle instruments on board MAVEN. The two very intense bursts—Pulses 2 and 3—were detected by all of the MAVEN particle instruments between 13:24:30 and 13:25:30, almost 4 minutes later than they were detected in the vicinity of the Earth (Earth–Mars distance at that time was ∼0.73 au or ∼364 lt-s). STATIC (Figure 4(d)) detected the third burst—Pulse 4—at 13:29:30. Measurements by the electrostatic analyzers are consistent, and the GRB221009A-related signal is visible in the ion data (SWIA and STATIC) through the entire energy range (up to 30 keV). In the electron measurements by SWEA, the signal was detected at the energies above ∼1 keV. Electron measurements by SEP show the effects of the GRB within the energy range from 20 to 200 keV. Comparison of the temporal profiles measured by MAVEN with the THEMIS observation (Figures 4(e)–(h)) shows a time delay of about 237.5 s.

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High-energy gamma-ray photons mainly interact with the spacecraft and detector material via the electron–positron pair production process. The flux and energies of these secondaries are determined by the initial photons energy and flux as well as the thickness and density of the passive material of the spacecraft and detector itself. For this GRB, the spacecraft particle detectors mainly encountered energy deposition from the secondary charged particles (electrons and positrons). The simulation performed for the parameters of the HEPP-L telescope (Battiston et al. 2023) showed that 83% of the detected secondaries originate in the passive material around the silicon detector and about 17% were directly generated within the detector. The secondary electrons also produce the signal recorded by the proton telescopes (and electrostatic analyzers; Agapitov et al. 2023), as was shown by the comparison of the electron fluxes measured by the electron and proton MEPED telescopes on board POES/MetOp (Vitale et al. 2023). The dilated study of the signal detected by SolO and MAVEN will be a subject of the upcoming publications.

The multipoint observations of the GRB221009A signal propagation by the spacecraft at different locations enable estimation of the normal to the signal front (Paschmann & Daly 1998) and thus can be used to determine the direction to its source in the sky. Using THC spacecraft as a reference and assuming that the burst propagated as a planar front, one can find a normal n to the front by solving a system of linear equations:

$$\begin{eqnarray*}&&\displaystyle \sum _{\beta =1}^{3}\left({r}_{\beta }^{\alpha }-{r}_{\beta }^{\mathrm{THC}}\right){n}_{\beta }=v\left({T}^{\alpha }-{T}^{\mathrm{THC}}\right),\end{eqnarray*}$$

where r is a position vector of the spacecraft, T is a time of observation, v is the speed of the front, and α is the spacecraft: STEREO, SolO, and MAVEN. Positions of the spacecraft in the HCI coordinate system are listed in the legend of Figure 5. Using the start of the Pulse 2 detected at T₀ +126 ± 5 s at STEREO-A, +212 ± 0.5 s at SolO, +225 ± 0.5 s at THEMIS, and +462.5 ± 1 s at MAVEN, we estimated normal vector n = [−0.6033, −0.3775, 0.7025] and the v = 1.01c. The normal vector gives the GRB221009A source location at R.A. 2885, decl. 185 in J2000 a cone of uncertainty (95% confidence level) δ θ = 2°. Start times of the Pulse 2 were determined by comparing the temporal profiles with the profiles captured on THC (Agapitov et al. 2023; shown as gray dashed lines in Figures 2–4). In the case of MAVEN, the start of Pulse 2 was found to be at T₀+262s (STATIC) and T₀+263s (SWEA and SEP). In order to estimate the accuracy of the obtained values, we used the approach described in Vogt et al. (2011), which is based on the reciprocal vector formalism and takes into account uncertainties both in the crossing times and in the spacecraft positions. ^{10 , 11}

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The obtained results are consistent with the previously reported values of R.A. = 288282, decl. = 19495 ± 0027 (Pillera et al. 2022), R.A. = 2882643, decl. = 197712 (Dichiara et al. 2022) and R.A. = 287761, decl. = 20670 (center; Kozyrev et al. 2022).

Figure 5 summarizes the observations of GRB221009A by the spacecraft across the heliosphere sorted along the normal to the GRB221009A signal front (the y-axis) on 2022 October 9. It shows the temporal profiles of the GRB signal recorded on STEREO-A, SolO, THEMIS, Wind, and MAVEN, starting at T₀ = 13:16:59.000—time of the detection of the triggering signal (Pulse 1) of the GRB near the Earth (Veres et al. 2022). All of the listed spacecraft have detected the effects of Pulses 2 and 3, seen as two intense bursts. SolO, THEMIS, and MAVEN have also captured Pulse 4. The speed-of-light signal propagation is marked by the light-gray lines.

We report the effects of the powerful gamma-ray burst GRB221009A recorded by the charged particle detectors on board the spacecraft probes at different locations across the heliosphere: Sun and solar wind observatories—STEREO-A, Solar Orbiter, and Wind; the magnetosphere multiprobe mission THEMIS; space weather probes at LEO orbits—POES/MetOp; and the planetary Martian mission MAVEN. GRB221009A had a structure of four bursts: the first triggering impulse was detected by the gamma-ray observatories near the Earth at T₀ = 13:16:59 UT, the most intense Pulses 2 and 3, and less intense Pulse 4 were detected in the charged particle detector records (Pulse 4 in more than 500 s after the triggering Pulse 1). The effects of the GRB were detected at times corresponding to the spacecraft locations: STEREO-A detected the signal of Pulse 2 almost 100 s before it was detected in the vicinity of the Earth, and it took another ∼237 s for the signal to reach MAVEN. Assuming that the burst propagated as a planar front across the heliosphere, we have determined the direction toward the source region of the GRB221009A at R.A. 2885, decl. 185 with a 95% containment radius of 2°, for the first time, from multipoint observations of spacecraft-based particle detectors.

The work was supported by NSF grant No. 1914670, NASA's Living with a Star (LWS) program (contract 80NSSC20K0218), and NASA grants contracts 80NNSC19K0848, 80NSSC22K0433, 80NSSC22K0522, 80NSSC20K0697, and 80NSSC21K177. We acknowledge NASA contract NAS5-02099 for the use of data from the THEMIS Mission and J. P. McFadden for the use of THEMIS ESA data and MAVEN STATIC data; J. Luhman for the use of STEREO-A data; Samuel Krucker for the use of SolO STIX data. STEREO-A data were processed at SSL under NASA grant 80NSSC22K1359.