Insight-HXMT observations on type-I &type-II X-ray bursts Chen Yu-Peng On behalf of Insight-HXMT team IHEP, CAS, China chenyp@ihep.ac.cn

outline Introduction Insight-HXMT observations on type-I X-ray bursts type-II X-ray burst Insight-HXMT observations on type-I X-ray bursts 4U 1636-536 4U 1728-34 Insight-HXMT& Swift/XRT observations on type-II X-ray bursts Rapid Burster

type-I X-ray burst Burst energy thermonuclear Persistent flux gravitational energy (much more energy) Chen Y.-P. et al. 2010, A&A, 510, A81

Type-I X-ray burst

Rapid burster (MXB 1730-335 ）Bursting Pulsar （GRO J1744-28 ） type-II X-ray burst Younes et al. 2015 Rapid burster (MXB 1730-335 ）Bursting Pulsar （GRO J1744-28 ）

spectral softening in decay X-ray bursters Frequent Outbursts of 10-100s duration with lower, persistent X-ray flux inbetween Type I bursts (~111 sources) Thermonuclear By far most of the bursters Type II bursts (2 sources) sudden increases accretion rate Rapid burster (MXB 1730-335 ） Bursting Pulsar （GRO J1744-28 ） Use as handout and maybe project on second screen spectral softening in decay a>30 ( the ration between outburst fluence and burst fluence)

type-I X-ray burst as a evidence for Disk corona not sphere corona Chen et al. 2013, ApJL, 777,9 Ji et al. …..

Insight-HXMT observations on type-I &type-II X-ray bursts sources Name OBSID No ks Tyep-I X-ray bursts Type-II X-ray bursts 4U 1636-536 P0114654 17 170 3 4U 1728-34 P0101303 70 1 Rapid Burster ~360 Aql X-1 P0114668 30 Cyg X-2 P0101300 11 320 GS 1826-238 P0101320 40 GX 17+2 P0101306 5 150

4U 1636-536 LMXB Atoll source 6 kpc The orbit and spin periods are about 3.8 h and 581 Hz Type-I X-ray burst

4U 1636-536

HE > 25 keV

LE&ME &HE top 2 seconds spectra Soft X-ray excess Hard X-ray excess T=2.64 +/-0.13 keV

LE&ME&HE effective area

Exposure Time: 2 sec 5.291e+02 +/- 1.756e+01 (86.0 % total) 5.482e+02 +/- 2.085e+01 (63.5 % total) 1.829e+02 +/- 2.362e+01 (16.7 % total) 1 1 constant factor 1.00000 frozen 2 2 wabs nH 10^22 0.410000 frozen 3 3 bbodyrad kT keV 2.64389 +/- 7.67614E-02 4 3 bbodyrad norm 105.415 +/- 8.18331 Data group: 2 5 1 constant factor 0.857767 +/- 7.13610E-02 6 2 wabs nH 10^22 0.410000 = p2 7 3 bbodyrad kT keV 2.64389 = p3 8 3 bbodyrad norm 105.415 = p4 Data group: 3 9 1 constant factor 1.22433 +/- 0.294047

s 6.4*108 ergs/cm2/s Mean peak PRE (photospheric radius-expansion) burst (Galloway 2008 , ApJS,179,360) 4.7 *108 ergs/cm2/s 

Hard X-ray excess Photon from type-I X-ray burst As seed photon for comptonization of corona ?

Type-I X-ray burst spectra of LE

Exposure Time: 40 sec Net count rate (cts/s) for Spectrum:1 1.642e+02 +/- 3.240e+00 (65.8 % total) Model wabs<1>*bbodyrad<2> Source No.: 1 Active/On Model Model Component Parameter Unit Value par comp 1 1 wabs nH 10^22 4.40643E-07 +/- 6.14539E-02 2 2 bbodyrad kT keV 1.64949 +/- 3.04777E-02 3 2 bbodyrad norm 118.574 +/- 7.09533 _______________________________________________________ Test statistic : Chi-Squared = 342.46 using 318 PHA bins. Reduced chi-squared = 1.0872 for 315 degrees of freedom Null hypothesis probability = 1.378211e-01

4U 1728-34 (slow burster)

angular distance~0.5 degree

HXMT/LE & swift/XRT lightcurve

4U 1728-34 type-I X-ray burst

Burst spectra ~20 sec xposure Time: 23 sec Net count rate (cts/s) for Spectrum:1 1.490e+02 +/- 5.259e+00 (50.2 % total) Exposure Time: 23 sec Net count rate (cts/s) for Spectrum:2 1.337e+02 +/- 7.429e+00 (28.0 % total) 1 1 constant factor 1.00000 frozen 2 2 wabs nH 10^22 0.584162 +/- 0.0 3 3 bbodyrad kT keV 2.17015 +/- 0.0 4 3 bbodyrad norm 58.2681 +/- 0.0 Data group: 2 5 1 constant factor 0.857467 +/- 0.0 Test statistic : Chi-Squared = 414.89 using 346 PHA bins. Reduced chi-squared = 1.2131 for 342 degrees of freedom Null hypothesis probability = 4.198035e-03

MXB 1730-335 NS XRB Rapid Burster 8 kpc B ~4*108 G Type-I X-ray burst & Type-II X-ray burst

HXMT/LE lightcurve (~360 bursts)

Swift/XRT type-I X-ray burst Lightcurve shape Hardness Tbb

XRT&LE spectra of type-II X-ray bursts

Effective area XRT&LE(small FoV)

Exposure Time: 325.5 sec Net count rate (cts/s) for Spectrum:1 3.001e+01 +/- 3.177e-01 (94.6 % total) Exposure Time: 2458 sec Net count rate (cts/s) for Spectrum:2 4.394e+01 +/- 3.525e-01 (23.6 % total) Model constant<1>*wabs<2>*nthComp<3> Source No.: 1 Active/On 1 1 constant factor 1.00000 frozen 2 2 wabs nH 10^22 3.16549 +/- 0.0 3 3 nthComp Gamma 1.45630 +/- 0.0 4 3 nthComp kT_e keV 2.28118 +/- 0.0 5 3 nthComp kT_bb keV 0.100000 frozen 6 3 nthComp inp_type 0/1 0.0 frozen 7 3 nthComp Redshift 0.0 frozen 8 3 nthComp norm 0.402748 +/- 0.0 Data group: 2 9 1 constant factor 0.978463 +/- 0.0 Reduced chi-squared = 1.05979 for 1114 degrees of freedom Null hypothesis probability = 8.106641e-02

propeller effect N. Masetti et al. 2001. A&A. 363 188 Type-I x-ray burst Large fraction of accretion drop on the NS surface after propeller effect 4E+35 erg/s

type-I & type-II X-ray bursts 2012,ApJ,752,158 123 type I and 8458 type II bursts from the RB Type-II bursts are from disk type-I & type-II X-ray bursts happened simultaneously Nthcomp can fit the burst spectra well

outline Introduction Insight-HXMT observations on type-I X-ray bursts type-II X-ray burst Insight-HXMT observations on type-I X-ray bursts 4U 1636-536 Hard X-ray excess: busrt as seed photon for comptonization of corona 4U 1728-34 Soft X-ray excess? Insight-HXMT& Swift/XRT observations on type-II X-ray bursts Rapid Burster Large fraction of accretion drop on the NS surface after propeller effect Type-II X-ray burst from disk not the NS surface

193179195.5303