Quasiperiodic X-ray eruptions in galactiv nuclei Potential topics for BSc. and MSc. theses Michal Zajaček Faculty of Science, Masaryk University February 24, 2023 What are Quasiperiodic Eruptions (QPEs)? a new class of short-duration, large-amplitude X-ray flares duration ranges from an hour to several days recurrence timescale (periodicity) ranges from a few hours to tens of days first source: GSN 069 (Miniutti et al. 2019): flares last one hour, repeat every 9 hours → duty cycle of ∼ 0.1 Soft X-ray light curves (0.4-2 keV) M. Zajaček ·QPEs ·February 24, 2023 2 / 13 What are Quasiperiodic Eruptions (QPEs)? the X-ray spectrum is soft temperature at the flare peak (100-200 keV: 1.2-2.3×106 K) during the flare, spectrum hardens and becomes soft again at the end soft X-ray luminosity reaches LX ≈ 1042 − 1044 erg s−1 representative source: GSN 069 (Miniutti et al. 2019) Folded X-ray flares in different X-ray energy bands M. Zajaček ·QPEs ·February 24, 2023 3 / 13 What are Quasiperiodic Eruptions (QPEs)? the X-ray spectrum is soft temperature at the flare peak (100-200 keV: 1.2-2.3×106 K) during the flare, spectrum hardens and becomes soft again at the end soft X-ray luminosity reaches LX ≈ 1042 − 1044 erg s−1 representative source: GSN 069 (Miniutti et al. 2019) Folded X-ray light curve (0.2-2 keV), and phase-resolved spectra during flare rise and decay M. Zajaček ·QPEs ·February 24, 2023 4 / 13 More sources: RX J1301.9+2747 analysis by Giustini et al. 2020 active galaxy recurrence times: 5.6 and 3.6 hours (long-short alternation) flare duration: 0.5 hour, duty cycle: ∼ 0.1 M. Zajaček ·QPEs ·February 24, 2023 5 / 13 More sources: eRO-QPE1 and eRO-QPE2 analysis by Arcodia et al. (2021) quiescent galaxies recurrence times and flare duration: 18.5 hours and 7.6 hours (eRO-QPE1); and 2.4 hours and 27 minutes (eRO-QPE2) duty cycles: 0.4 (eRO-QPE1) and 0.2 (eRO-QPE2) M. Zajaček ·QPEs ·February 24, 2023 6 / 13 1st Thesis topic: QPE properties what are the relations between the flare duration and period? evaluation of periodicity significance/irregularity level flare amplitude: dependence of peak luminosity vs. temperature estimation of the emission area/length-scale spectral properties M. Zajaček ·QPEs ·February 24, 2023 7 / 13 2nd Thesis topic: Model interpretations 1. disc instabilities: radiative instability of the inner disc M. Zajaček ·QPEs ·February 24, 2023 8 / 13 2nd Thesis topic: Model interpretations 1. disc instabilities: radiative instability of the inner disc 2. disc/Lense-Thirring precession M. Zajaček ·QPEs ·February 24, 2023 8 / 13 2nd Thesis topic: Model interpretations 1. disc instabilities: radiative instability of the inner disc 2. disc/Lense-Thirring precession 3. orbiting body interacting with the accretion disc (secondary massive black hole, star, neutron star) M. Zajaček ·QPEs ·February 24, 2023 8 / 13 2nd Thesis topic: Model interpretations 1. disc instabilities: radiative instability of the inner disc 2. disc/Lense-Thirring precession 3. orbiting body interacting with the accretion disc (secondary massive black hole, star, neutron star) 4. Roche-lobe overflow from an orbiting star M. Zajaček ·QPEs ·February 24, 2023 8 / 13 2nd Thesis topic: Model interpretations 1. disc instabilities: radiative instability of the inner disc 2. disc/Lense-Thirring precession 3. orbiting body interacting with the accretion disc (secondary massive black hole, star, neutron star) 4. Roche-lobe overflow from an orbiting star 5. lensing of two orbiting massive black holes (now rather disfavoured) M. Zajaček ·QPEs ·February 24, 2023 8 / 13 2nd Thesis topic: Model interpretations 1. disc instabilities: radiative instability of the inner disc 2. disc/Lense-Thirring precession 3. orbiting body interacting with the accretion disc (secondary massive black hole, star, neutron star) 4. Roche-lobe overflow from an orbiting star 5. lensing of two orbiting massive black holes (now rather disfavoured) 6. own, unique model (best option) M. Zajaček ·QPEs ·February 24, 2023 8 / 13 2nd Thesis topic: Model interpretations 1. disc instabilities: radiative instability of the inner disc 2. disc/Lense-Thirring precession 3. orbiting body interacting with the accretion disc (secondary massive black hole, star, neutron star) 4. Roche-lobe overflow from an orbiting star 5. lensing of two orbiting massive black holes (now rather disfavoured) 6. own, unique model (best option) 7. (Bayesian) fitting routine → application to real data and new QPE sources M. Zajaček ·QPEs ·February 24, 2023 8 / 13 QPE model 1: Accretion disc instability Regular increase of the accretion rate due to radiation-pressure instability operating in a narrow zone (Sniegowska et al., 2020) M. Zajaček ·QPEs ·February 24, 2023 9 / 13 QPE model 2: Roche-lobe overflow from an orbiting star See e.g. Krolik & Linial (2022) M. Zajaček ·QPEs ·February 24, 2023 10 / 13 QPE model 3: Two orbiting stars See Metzger, Stone, & Gilbaum (2022) M. Zajaček ·QPEs ·February 24, 2023 11 / 13 New QPE source: “Crazy Swift source” To be submitted to Nature Astronomy, Guolo, ..., Zajaček et al. (2023) mean flare periodicity: 20 days (longest) flare duration: 3-8 hours; duty cycle: 0.3 0 5 10 15 20 25 0.3-2.0keVFlux [1013ergcm2s1] Swift/XRT 0 2 4 6 8 0.3-2.0keVLuminosity [1042ergs1] Modified Julian Date 0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 0.3-0.8keVFlux [1013ergcm2s1] NICER/XTI 0 1 2 3 4 5 6 7 0.3-0.8keVLuminosity [1042ergs1] 59750 59775 59800 59825 59850 59875 59900 59925 59950 59975 17 18 ABmag U UV W1 1000 750 500 250 0 250 500 x[rg] 800 600 400 200 0 200 400 600 y[rg] e=0.0 e=0.3 e=0.5 e=0.7 e=0.9 5 10 15 20 25 30 35 RRL[R] M. Zajaček ·QPEs ·February 24, 2023 12 / 13 Thank You for Your Attention! Figure: Image credit: Jack Ciurlo