Detecting radio afterglows and host emissions of Gamma-Ray Bursts with FAST Speaker: Longbiao Li Collaborators: Yongfeng Huang, Zhibin Zhang, Di Li, Xuefeng Wu, Siwei Kong, Heonyoung Chang and Chulsung Choi Guizhou University

Contents 1 Observations of GRB radio afterglows 2 Dynamical Model and FAST Sensitivity 2 Detecting Radio Afterglows of GRBs with FAST 3 Radio Afterglows and Host Galaxies of GRBs 4 LOGO www.themegallery.com

1. Observations of GRB radio afterglows Fig.1. GRB 970508: First burst with an observed radio afterglow. 8.46 GHz LOGO www.themegallery.com Frail et al., 1997, Nature, 389, 261

A Radio-selected sample of GRB afterglows (Frail & Chandra, 2012) Fig.2. Histogram summarizing the distribution of the radio-selected sample. In left panel, more than fifty percent measurements are taken in eight point five GHz band, and in right panel, radio afterglows can continue until one thousand days. LOGO Frail & Chandra, 2012, ApJ, 746, 156 www.themegallery.com

Table 1. Multi-waveband Statistics of the GRB Afterglow Sample. LOGO Frail & Chandra, 2012, ApJ, 746, 156 www.themegallery.com

2. Dynamical Model and FAST Sensitivity Huang, Dai & Lu , 1998, A&A, 336, L69 Huang, Dai & Lu, 1999a, Chin. Phys. Lett., 16, 775 Huang, Dai & Lu, 1999b, MNRAS, 309, 513 Huang, Dai & Lu, 2000a, MNRAS, 316, 943 Huang, Gou, Dai & Lu 2000b, ApJ, 543, 90 LOGO www.themegallery.com

the system temperatures of FAST How to estimate the detect limiting sensitivity of FAST ? the effective area. the system temperatures of FAST ηA=0.65 (yue et al . 2013) Ag=pi (300/2)^2 m^2 LOGO www.themegallery.com

Table 2. Parameters describing the Nine Sets of Receivers that are Part of FAST. Nan et al., 2011, IJMPD, 20, 989 Zhang et al., 2015, RAA, 15, 237 LOGO www.themegallery.com

3. Detecting Radio Afterglows of GRBs with FAST LOGO www.themegallery.com

We calculate the radio afterglow light curves of standard, failed, high-luminosity, and low- luminosity GRBs in different observational bands of FAST. Table 3. Initial physical parameters of these four types of GRBs. LOGO www.themegallery.com

The GRBs are assumed to be located at different distances from us. Notices: The GRBs are assumed to be located at different distances from us. Contributions of host galaxies have been neglected for simplification. LOGO www.themegallery.com

The peak emissions of standard bursts at Fig.3. Radio afterglow light curves at a redshift z = 0.5 in the observer frame within the FAST’s observational bands. The peak emissions of standard bursts at ν > 0.4 GHz can be easily detected. FAST can hardly detect radio emissions from low-luminosity GRBs. LOGO www.themegallery.com Zhang et al., 2015, RAA, 15, 237

Fig.4. Radio afterglow light curves at a redshift z = 1.0. FAST can detect the radio emission of standard bursts at ν> 0.6 GHz. LOGO www.themegallery.com Zhang et al., 2015, RAA, 15, 237

Fig.5. Radio afterglow light curves at a redshift z = 5.0. Radio afterglows of standard GRBs under 0.8 GHz are undetectable by FAST. LOGO www.themegallery.com Zhang et al., 2015, RAA, 15, 237

Fig.6. Radio afterglow light curves at a redshift z = 10.0. Only standard GRBs’ radio afterglows above 1.4 GHz can be marginally detected. LOGO www.themegallery.com Zhang et al., 2015, RAA, 15, 237

Radio afterglows of high- luminosity GRBs can be detected at Fig.7. Radio afterglow light curves at a redshift z = 15.0. Radio afterglows of high- luminosity GRBs can be detected at 0.4–2.5 GHz. LOGO www.themegallery.com Zhang et al., 2015, RAA, 15, 237

4. Radio Afterglows and Host Galaxies of GRBs LOGO www.themegallery.com

How to consider the contribution from the host galaxy? The observed radio emission the GRB afterglow component the contribution from the host galaxy Meanwhile, the host flux density should be a constant at all stages of the afterglow. LOGO www.themegallery.com

There’s a constant component in the observed emission, Fig.8. Radio afterglow light curves of GRB 980703. There’s a constant component in the observed emission, which is interpreted as the contribution from the host. LOGO Berger, Kulkarni & Frail, 2001, ApJ, 560, 652 www.themegallery.com

The sample of radio afterglows： 50 GRBs whose radio afterglows are detected 10 GRBs associated with supernova (SN), 6 GRBs without known redshifts. Three types of GRBs according to isotropic energy: 5 low-luminosity GRBs, 18 standard GRBs, 21 high-luminosity GRBs. Radio observational bands: 1.4 – 9.0 GHz. 47 data points @8.46 GHz, 25 data points @4.86 GHz, 10 data points @1.43 GHz, … LOGO www.themegallery.com

Table 4. Observational properties of 50 GRBs and their host galaxies in radio bands. LOGO For more detailed data, please see Li L.B. et al., 2015, MNRAS, 451, 1815 www.themegallery.com

RRF -- the Ratio of the radio fluxes of the host to the peak emission A new parameter: RRF -- the Ratio of the radio fluxes of the host to the peak emission the observed peak flux density the peak flux density of the pure radio afterglow component the host flux density

The linear fitting method The correlation between RRF and observational frequency ? The linear fitting method www.themegallery.com

Fig.9. The best linear fits to RRF versus ν for the low-luminosity, standard, high-luminosity GRBs and all GRBs. LOGO www.themegallery.com Li et al., 2015, MNRAS, 451,1815

Table 5. Best-fitting parameters for the linear RRF–ν correlation. LOGO

Using the fitting function, one can easily derive and LOGO www.themegallery.com

According to the relation, observed radio emission is dominated by the host component at lower frequencies. It may explain why the low-frequency radio afterglows are usually difficult to be detected, in contrast with the high-frequency case. LOGO www.themegallery.com

The RRF-predicted host fluxes are included. Fig. 10. Predicted radio light curves for four kinds of GRBs lying at z = 1.0. The RRF-predicted host fluxes are included. LOGO Li L.B. et al., 2015, MNRAS, 451, 1815 www.themegallery.com

Thank You !