Multiwavelength emission of the gamma-ray binary LS I

Multiwavelength emission of the gamma-ray binary LS I +61 303 Benito Marcote Joint Institute for VLBI ERIC (JIVE, The Netherlands) 14 June 2017 Multifrequency Behavior of High Energy Cosmic Sources

High-energy binary systems High-Energy (above 1 GeV) sky from Fermi/LAT Binary systems: High-Mass X-ray binaries, Colliding Wind Binaries, Gamma-Ray Binaries 2

High-energy binary systems Pulsar Wind Nebula Blazar/AGN Isolated Pulsar Unidentified Starburst Galaxy Star Forming Region Supernova Remnant Binary System Globular Cluster Very High-Energy ( TeV) sky from Cherenkov Telescopes High-Mass X-ray binaries, Colliding Wind Binaries, Gamma-Ray Binaries 2

Gamma-ray binaries Massive star and compact object Non-thermal SED dominated by γ-rays Only six systems are known to date: System Main star P/ days LS 5039 O6.5 V 3.9 LMC P3 O5 III 10.3 1FGL J1018.6 5856 O6 V 16.6 LS I +61 303 B0 Ve 26.5 HESS J0632+057 B0 Vpe 315.0 PSR B1259 63 O9.5 Ve 1236.7 Only in PSR B1259 63 we know the nature of the compact object: NS Orbital motion Wind standoff Star Pulsar Zabalza et al. (2012) V. Zabalza et al.: GeV-TeV emiss Coriolis turnover Shocked pulsar wind Shocked stellar wind Fig. 1. Sketch of the proposed scenario at the periastron of a close-orbit system similar to LS5039. The region of the CD where significant turbulence, and therefore wind mixing, are expected to take place is indicated with a wavy line. The red regions indicate the two proposed emitter locations. off tio wh em 200 an pro rea de em sta the the em orb mo thi the et a of wh bu ity ave lin ula bu 3

The Gamma-Ray Binary LS I +61 303 300 B0 Ve star (12.5 ± 2.5 M ) d = 2.0 ± 0.2 kpc e = 0.72 ± 0.15 S 2.2 GHz/ mjy 200 100 0 Radio P orb = 26.496 ± 0.003 d P super = 1667 ± 8 d Frail & Hjellming (1991), Casares et al. (2005), Gregory (2002) F0.3 10 kev 10 12 erg cm 2 s 1 20 15 10 5 1.1 X-rays F0.1 1 GeV 10 6 cm 2 s 1 1.0 0.9 0.8 GeV 0.7 20 F>1 TeV 10 12 cm 2 s 1 15 10 5 TeV 0 0.0 0.5 1.0 1.5 2.0 φorb (P = 26.4960 d, JD0 = 2 433 366.775) 4

Superorbital modulation Superorbital modulation of the amplitude & phases of these outbursts with P so 1 667 d ( 4.4 yr) 432 GREGORY 1990A&A...232..377P Paredes et al. (1990) Orbital Phase Orbital Phase 1 0.8 0.6 0.4 0.2 0 3.6 3.8 4 4.2 4.4 4.6 4.8 5 P 2 Cycles 1 0.8 0.6 0.4 0.2 Gregory (2002) Observed from radio to TeV 0 3.6 3.8 4 4.2 4.4 4.6 4.8 5 a b 250 0 mjy 280 0 mjy ( tru res pr tro in th an ac sec pr sa or ta th tio me JD th as 5 th is

Microquasar or non-accreting pulsar wind? Orbital motion Wind standoff Star Pulsar V. Zabalza et al.: GeV-TeV emissio Coriolis turnover Shocked pulsar wind Shocked stellar wind Fig. 1. Sketch of the proposed scenario at the periastron of a close-orbit system similar to LS5039. The region of the CD where significant turbulence, and therefore wind mixing, are expected to take place is indicated with a wavy line. The red regions indicate the two proposed emitter locations. T off lo tion whic emis 2006 and c prod reach detec emit stand the s the c emis orbit mod this e the c et al. of 0.1 whic but i ity of avera lineulati bulk T locat 6 stella

Presence of a precessing jet? The two observed periods can be explained as a beat frequency due to a precessing jet and the orbital motion Massi & Jaron (2013); Massi & Torricelli-Ciamponi (2016) Anti-correlation between X-ray luminosity and photon-index consistent with BH X-ray Binaries (Massi et al. 2017) Jet velocities of β 0.006 0.5 (Jaron et al. 2017) Requires the presence of a black-hole 7

Non-accreting pulsar evidences? X-ray spectrum and spectral variability consistent with a rotation-powered pulsar (Chernyakova et al. 2006) Estimation of the mass of the compact object to be: 1.3 M < M < 2.0 M, likely a Neutron Star (Zamanov et al. 2017) Absorption profile derived at X-rays as a function of orbital and superorbital phases. Circumstellar disk disrupted at Φ 0.6 and slowly regenerated (Chernyakova et al. 2017) 8

Optical and radio campaigns

Optical observations Observations with the robotic Telescope Fabra-ROA Montsec (TFRM): Orbital and superorbital modulation also observed in the optical band Paredes-Fortuny et al. (2015; 2017 in prep) 9

Optical observations Coupling between the thermal and non-thermal superorbital variability Periodic changes in the circumstellar disk (Paredes-Fortuny et al. 2015; 2017 in prep) Similar evidences observed at TeV (Ackermann et al. 2013) 10

Profile of a single radio outburst Focusing on a single outburst (Strickman et al. 1998): No. 1, 1998 RELATIONSHIP BETWEEN 424 2CG 135]1 AND LSI ]61 303 STRICKMAN ET AL. 423 Vol. 49 1.5 23 GHz FIG. 4.ÈMultifrequency radio light curves of LSI ]61 303 observed with the VLA corresponding to the radio outburst of 1994 JuneÈJuly. Error bars not shown are smaller than the symbol size. from two observations (radio phase 0.2 and 0.42) into the OSSE energy range. Observations by Goldoni & Meregh- OSSE range than was observed. The OSSE integral Ñux from 100 50È300 kev during VP 325 is (4.3 ^ 1.1) ] 10~4 photons cm~2 s~1, while the integral of the ASCA best-ðt power-law 10 9 June 94 (0.97) 26 June 94 (0.62) models extrapolated to the same energy range are (1.0 ^ 0.4) ] 10~4 and (0.5 ^ 0.2) ] 10~4 photons 100 cm~2 s~1 for radio phases 0.2 and 0.42 respectively. These are inconsistent at the 2.8 p and 3.4 p levels, assuming that 10 11 June 94 (0.06) 28 June 94 (0.70) the spectrum does not change (in particular, does not harden100 signiðcantly) from 10 to 300 kev. Since the relatively large OSSE Ðeld of view does not exclude 10 the nearby 12 June QSO 94 (0.09) 0241]622 as a possible 1 July 94 source (0.79) of emission, we have also plotted the result of EXOSAT (2È10 kev) observations 100 of the QSO (Turner & Pounds 1989), corrected for its position in the OSSE collimator response. Note that 10 the15 1.7June photon 94 (0.19) index power-law spectrum 2 July 94 (0.84) used to model the EXOSAT data is consistent with the OSSE result. 100 When we look at an overall view of the spectra from this region, 10 no clear 17 June picture 94 (0.28) emerges. However, 3 July the94 fact (0.88) that OSSE and COMPTEL results fall signiðcantly above an extrapolation 100 of the ASCA spectra and that the OSSE and COMPTEL spectra are consistent with the X-ray spectrum of QSO10 18 June 94 (0.31) 5 July 94 (0.95) 0241]622, lead to the likelihood that at least some, and perhaps a signiðcant amount, of the Ñux observed by 100 both OSSE and COMPTEL might come from the QSO rather than LSI ]61 303. Cycle-to-cycle variations in the 10 19 June 94 (0.35) 7 July 94 (0.02) X-ray emission may also contribute to the observed discrepancy. More contemporaneous X-ray and c-ray data are 100 required to test for the existence of cycle to cycle variability of the LSI ]61 303 system and to better study the X-ray 10 21 June 94 (0.42) 8 July 94 (0.07) period recently reported by Paredes et al. (1997a). Similarly, 0.1 the low 1.0signiÐcance 10.0 of the0.1 OSSE light 1.0 curves10.0 shown in Figure 2 does not allow us to use temporal signatures to associate LSI ]61 303 Frequency with the (GHz) OSSE source. We note that the Ñux detected by OSSE is relatively higher during the 1994 April observation, in apparent coincidence with a prominent onset and slow decay of a radio Ñare. 1994 Flux Density (mjy) FIG. 5.ÈTime evolution of the LSI ]61 303 nonthermal radio spectrum during the outburst of 1994 JuneÈJuly. Spectra are labeled according to the dat and radio phase of the observation. 11

Low-frequency radio emission of LS I +61 303 GMRT and LOFAR observations contemporaneous with 15-GHz RT and OVRO ones 160 140 LOFAR 150 MHz GMRT 150 MHz OVRO 15 GHz S ν/mjy 120 100 80 60 40 20 0 0.0 0.5 1.0 1.5 2.0 φorb (Porb = 26.4960 d, JD0 = 2 443 366.775) Marcote et al. (2016) Both campaigns at different superorbital phase. Cannot be compared! 12

Low-frequency radio emission of LS I +61 303 Absorption process? Free-free abs: v FFA = 700 ± 200 km s 1 Synchrotron self-absorption: v SSA = 1 000 ± 140 km s 1 Wind velocity 1 500 ± 500 km s 1 Marcote et al. (2016) 13

Conclusions LS I +61 303 remains as a challenging gamma-ray binary Many clues suggest the presence of a neutron star The optical and non-thermal correlation suggest a common origin Superorbital modulation dominated by perturbations of the circumstellar disk? The low-frequency turnover constrains the conditions on the region A more detailed low-frequency radio campaign is ongoing (spectrum, variability along the orbit) 14

Thank you! 14