Spectroscopy of the short GRB B The host galaxy and environment of a compact object merger

Transcription

1 Spectroscopy of the short GRB B The host galaxy and environment of a compact object merger Antonio de Ugarte Postigo Instituto de Astrofísica de Andalucía (IAA-CSIC) Dark Cosmology Centre (DARK/NBI)

2 Thanks to a lot of people! A. de Ugarte Postigo 1,2,, C.C. Thöne 1, A. Rowlinson 3, R. García-Benito 1, A.J. Levan 4, J. Gorosabel 1,5,6, P. Goldoni 7, S. Schulze 8,9, T. Zafar 10, K. Wiersema 11, R. Sánchez-Ramírez 1, A. Melandri 12, P. D Avanzo 12, S. Oates 13, V. D Elia 14, M. De Pasquale 13, T. Krühler 2, A. J. van der Horst 3, D. Xu 2, D. Watson 2, S. Piranomonte 15, S. Vergani 16,12, B. Milvang-Jensen 2, L. Kaper 3, D. Malesani 2, J.P.U. Fynbo 2, Z. Cano 17, S. Covino 12, H. Flores 16, S. Greiss 4, F. Hammer 16, O.E. Hartoog 3, S. Hellmich 18, C. Heuser 19, J. Hjorth 2, P. Jakobsson 17, S. Mottola 18, M. Sparre 2, J. Sollerman 20,21, G. Tagliaferri 12, N.R. Tanvir 11, M. Vestergaard 2,22, R.A.M.J. Wijers 3 1 Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, Granada, Spain

3 Gamma-ray bursts Most energetic explosions in the Universe Isotropical distribution Last from a fraction of a second tohundreds of seconds Short / Long Counterparts in all wavelengths

4 Gamma-ray bursts Most energetic explosions in the Universe Isotropical distribution Last from a fraction of a second tohundreds of seconds Short / Long Counterparts in all wavelengths

5 Gamma-ray bursts Most energetic explosions in the Universe Isotropical distribution Last from a fraction of a second tohundreds of seconds Short / Long Counterparts in all wavelengths

6 Gamma-ray bursts Most energetic explosions in the Universe Isotropical distribution Last from a fraction of a second tohundreds of seconds Short / Long Counterparts in all wavelengths

7 Gamma-ray bursts Most energetic explosions in the Universe Isotropical distribution Last from a fraction of a second tohundreds of seconds Short / Long Counterparts in all wavelengths

8 Long GRBs First counterparts in 1997 (BeppoSAX) Spectroscopy of ~200 Redshifts SN components Star-forming hosts Collapse of massive stars

9 Long GRBs First counterparts in 1997 (BeppoSAX) 2.0 Spectroscopy of ~200 Redshifts Normalised flux Ly OVI Ly NV SII SiII* CI OI** SiII* NiII CII* NiII SiIV SiIV SiII* CIV FeII CI FeII Fe** Fe** AlII NiII NiII SiII AlIII AlIII ZnII ZnII SN components Star-forming hosts Collapse of massive stars Observed wavelength (Å)

10 Long GRBs First counterparts in 1997 (BeppoSAX) Spectroscopy of ~200 Redshifts SN components Star-forming hosts Collapse of massive stars

11 Long GRBs First counterparts in 1997 (BeppoSAX) Spectroscopy of ~200 Redshifts SN components Star-forming hosts Collapse of massive stars

12 Short GRBs First counterparts in 2005 (Swift) Very faint afterglows No supernova component Diverse host galaxies, often older populations Compact object mergers?

13 Discovery of GRB B Discovered by Swift = 0.18+/-0.2s T90 Hard spectrum Negligible lags No extended emission

14 Discovery of GRB B Discovered by Swift = 0.18+/-0.2s T90 Hard spectrum Negligible lags No extended emission

15 Discovery of GRB B Discovered by Swift = 0.18+/-0.2s T90 Hard spectrum Negligible lags No extended emission A prototypical short GRB

16 Discovery of the optical counterpart Afterglow discovered from La Palma: WHT: Levan et al. GCN NOT: de Ugarte Postigo et al. GCN 14743

17 Discovery of the optical counterpart Afterglow discovered from La Palma: WHT: Levan et al. GCN NOT: de Ugarte Postigo et al. GCN 14743

18 First spectrum obtained at 10.4m GTC Object was r=21.30 at the time of the spectrum (7.4hr after GRB) Both GRB and host galaxy in the slit A second spectrum, 5 days later, to subtract the host Thöne et al. GCN 14744

19 First spectrum obtained at 10.4m GTC

20 First spectrum obtained at 10.4m GTC z=0.3565

21 Further spectroscopy FORS2 (8.4 hr): Like GTC but better seeing X-shooter (8.6 hr): Intermediate resolution Different slit angles FO RS 2 Xsh WHT (8.2 hr): Low S/N OS IR IS

22 Host galaxy dynamics with X-shooter Absorption of MgII, MgI CaII with broad profiles: km/s Absorption of NaI unresolved (30 km/s) Emission lines of [OII], [OIII], HII, [NII], [SII] with components at 100 km/s

23 SED fitting of the afterglow

24 SED fitting of the afterglow NIR/optical

25 SED fitting of the afterglow NIR/optical X-rays

26 SED fitting of the afterglow NIR/optical X-rays AV=0.86+/-0.15

27 SED fitting of the afterglow NIR/optical Obscured afterglow X-rays AV=0.86+/-0.15

28 SED fitting of the afterglow NIR/optical Obscured afterglow NH,X/AV similar to MW X-rays AV=0.86+/-0.15

29 Light curve Early X-rays and optical strongly differ Break at 0.3 days Late evolution is consistent between bands SN component <0.01 SN1998bw Evolution consistent with magnetar X-ray tail (Fong et al. 2013)

30 Light curve Early X-rays and optical strongly differ Break at 0.3 days Late evolution is consistent between bands SN component <0.01 SN1998bw Evolution consistent with magnetar X-ray tail (Fong et al. 2013)

31 1 t Light jet curve Radio Time after Burst (d) Early X-rays and optical strongly differ Break at 0.3 days 2006aj Late evolution is consistent between bands SN component <0.01 SN1998bw Evolution consistent with Time after Burst (d) magnetar t jet Optical r band host A =1 mag V 1998bw H band Flux 1 kev Flux Density (µjy) Time after Burst (d) Swift/XRT XMM Newton t jet X ray Time after burst (d). Radio through X-ray afterglow light curves of GRB B. Error bars correspond to 1σ confidence, and triangles denote 3σ upper limits. The model is shown as a black line, while the jet break time of t j 0.47 d is marked by a vertical grey dashed line. Also shown is a model with energy (dark grey dashed line) that fits the X-ray excess but violates the detections and limits in the optical, NIR, and radio bands. Top left: 6.7 GHz observations VLA (red). X-ray Top right: tail H-band (Fong observations et (green; al. Berger 2013) et al. 2013; de Ugarte Postigo et al. 2013; Tanvir et al. 2013), where JK-band observations polated to H-band using β opt = 2. The observed values (open green squares) are corrected for AV host =1mag(filledgreensymbols). Thecircled t δt 9 d is the kilonova associated with GRB B(Berger et al. 2013; Tanvir et al. 2013). Bottom left: Optical r-band observations (orange; t jet

32 Host galaxy: photometric analysis UV/optical/nIR spectral energy distribution Fitted with LePhare 10 9 yr log (M/Msol) = 9.8 SFR = 5.6 Msol/yr

33 Host galaxy: resolved analysis Spectrum extracted in 3 regions Stellar population fitting with STARLIGHT

34 Host galaxy: resolved analysis Spectrum extracted in 3 regions Stellar population fitting with STARLIGHT

35 Host galaxy: resolved analysis

36 Host galaxy: resolved analysis Emission line analysis AV= log(O/H) (R23) = 8.6 (80% solar) SFR = 4.85 Msol/yr M/Msol=1.7x10 9

37 Host galaxy: resolved analysis Emission line analysis AV= log(O/H) (R23) = 8.6 (80% solar) SFR = 4.85 Msol/yr M/Msol=1.7x10 9

38 Host galaxy: resolved analysis Emission line analysis AV= log(O/H) (R23) = 8.6 (80% solar) SFR = 4.85 Msol/yr M/Msol=1.7x10 9

39 Host galaxy: resolved analysis Emission line analysis AV= log(O/H) (R23) = 8.6 (80% solar) SFR = 4.85 Msol/yr M/Msol=1.7x10 9

40 Discovery of a kilonova Compact object mergers produce neutron-rich radioactive species Their decay produce a very extinguished transient called kilonova days after the burst This could be the predominant of stable r-process elements in the Universe At z=0.36, GRB B was a good candidate to look for it

41 Tanvir et al Berger et al Discovery of a kilonova

42 Tanvir et al Berger et al Discovery of a kilonova

43 Discovery of a kilonova SGRBs are produced in the merger of compact objects (at least some) Tanvir et al Berger et al. 2013

44 Conclusions For the first time we have detected a kilonova-like emission associated with a SGRB --> compact object merger! For the first time we obtain spectroscopy of a SGRB Produced in an arm of a disrupted galaxy: Almost solar metallicity, star forming with rich dynamics X-ray absorption and dust absorption similar to the MW (unlike long GRBs) The environment points towards a rapid merger and/or a low natal kick

45 Thanks!