STUDY OF ORPHAN (OFF-AXIS) AND PARENT (ON-AXIS) GAMMA-RAY BURSTS WITH LSST (A SMALL DROP IN THE TRANSIENT SKY)

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1 SERGIO CAMPANA GIANCARLO GHIRLANDA PAOLO D AVANZO ANDREA MELANDRI GIANPIERO TAGLIAFERRI GABRIELE GHISELLINI STUDY OF ORPHAN (OFF-AXIS) AND PARENT (ON-AXIS) GAMMA-RAY BURSTS WITH LSST (A SMALL DROP IN THE TRANSIENT SKY)

2 WHAT ARE GRBS? Intense (brightest in the sky), short (<10 3 s) emission of gamma-rays FOLLOWED by the afterglow

3 GRB STANDARD MODEL

4 AFTERGLOW EMISSION IS COLLIMATED Jet effect Jet half opening angle Log(F) Γ >> 1/ϑ Γ 1/ϑ Jet break Log(t)

5 JETS Achromatic breaks

6 GRB OPENING ANGLE DISTRIBUTION Ghirlanda et al Mean angle ~ 3 deg Correction factor (1-cos ) -1 ~730

7 ORPHAN AFTERGLOW Off-axis orphan afterglows are much dimmer than on-axis afterglows at all wavelengths Urata et al. 2015

8 PREDICTIONS FOR LSST. Spectral energy distribution of the OA that can be detected bythelsst(pinkfilledregion).thesedofthelowpowerblazarbllac (open s), of the FSRQ 3C454.3 (asterisks) and of two supernovae SN1978K (open squares) and the GRB SN associated GRB980425/SN1998bw stars) are shown by different symbols. The solid lines provide an interpolation of the data points and do not represent any physical model. e two blazars we also show (dashed grey line for 3C454.3 and dashed orange line for BLLac) how their spectra would appear if they at z Ghirlanda = 2(typicalet ofgrbs).the(5σ) al limitsfora12hcontinuumobservationwiththeskaisshownby the yellow shaded region.

9 (CONSERVATIVE) NUMBERS Survey FOV Cadence F lim Coverage Lifetime R OA T #OA (deg 2 ) (mjy) (deg 2 night 1 ) days (deg 2 yr 1 ) days yr 1 PTF 7.8 1m 5d [ ] 1.5 ROTSE II 3.4 1d [ ] 0.1 CIDA QUEST 5.4 2d 1yr [ ] 0.1 Palomar Quest h 1d [ ] 0.8 SDSS II SS 1.5 2d [ ] 0.8 Catilina m 1yr [ ] 0.6 SLS 1.0 3d 5yr [0.8-11] 0.03 SkyMapper d 1yr [ ] 0.3 Pan STARRS d [ ] 12 LSST 9.6 3d [0.8-11] 50 Gaia 0.5x2 20d [0.5-5] 2 ZTF d [ ] 20 RASS months [ ] 10 erosita months years [ ] 26 Early LSST prediction ~1,000 /yr

10 WHY? (LONG GRBS) study of the collimation of GRBs: the number of orphan vs. on-axis GRBs is a unique tool to assess the energy distribution along the jet true rate of GRBs and connections with SN Ic (and magnetars, and superluminous-sn, etc.) spectroscopic studies of pristine ISM (even at high redshift) with no photoionisation effects

11 WHY? (SHORT GRBS) collimation angle NS-NS merger events (do all mergers give rise to an afterglow?) true rate and predictions for GW events relations with kilonovae GW searches

12 CONCLUSIONS (AND POINTS FOR THE DISCUSSION) Large SYNOPTIC Survey Telescope is a TRANSIENT searching machine (time-domain) need for a SPECTROSCOPIC follow-up (SOXS)

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