Search for X-ray Transients with MAXI

Transcription

1 Search for X-ray Transients with MAXI Nobuyuki Kawai (Tokyo Tech) M. Serino (RIKEN), H. Negoro (Nihon U.) on behalf of the MAXI Team MAXI Instrumentation and operation Observations for GW and results in context Observations for GW

2 Monitor of All-Sky X-ray Image Mission started August 2009 Ops approved until ~ March 2018 Matsuoka et al. 2009

3 Instruments and Observation 6 x 2 GSC (Gas Slit Camera) 2-20 kev, Time Resolution 50 µs Mihara+ 2011, Sugizaki x SSC (Solid-state Slit Camera) kev, Time Resolution s Tsunemi+ 2010, Tomida SSC (slit) collimator Proportional Counter slit

4 Nova-Alert System Negoro+ 2016, PASJ TKSC/JAXA RIKEN & MAXI MLs (& ATel/GCN) Nova Alert System < 10 sec (Real) ~ 1.5 h (Stored)

5 2.5 Blackholes MAXI Transients : 17 sources in 6 years J J (GRB A) J J J (Swift J ) J J (Swift J ?) J J GRB A (Swift J ) J J MAXI J J White Dwarf, 6 Neutron Stars, 6 Black Hole Candidates, and 1 unknown

6 6 Black holes discovered by MAXI (out of 12 BHCs discovered since Aug 2009) 2.5 Blackholes Negoro et al. (2014) MAXI J (GRB A) 500 days MAXI MAXI MAXI MAXI J (Swift J ) MAXI J

7 MAXI watches through the whole Galaxy. 12 kpc 8.5 kpc F = al Edd /4pd Blackholes a = (Maccarone 2003) Soft-to-Hard Transition J1828 (l, b) = (8.1, -6.5) d > 12 kpc!? J1543 (l, b) = (325.1, -1.1) d > 12 kpc? (Stiele+ 2012) J1305 (l, b) = (304.2, -7.6) Negoro 2008

8 MAXI J : unique soft X-ray transient 8 MAXI GSC Allsky Image Galactic Coordinate :05:59 (UT) GRB A Soft X-ray transient ( < 5 kev) Swift follow-up lead to identification to a star near SMC (Be star at 60 kpc) Morii et al. 2013

9 MAXI J X-ray Flux MAXI GSC X-ray light curve days MAXI SSC Morii et al Swift XRT 1 10 Duration hour (1300 s <ΔT< 1.1 x 10 4 s) Extremely luminous erg / s x100 solar mass Eddington luminosity supersoft X-ray source at late phase à white dwarf classical/recurrent nova? but x10 4 more luminous than known nova X-ray emission (shocked ISM? Li et al. 2012) 9

10 Nova (nuclear fusion) explosion Morii et al. (2013) rare WD-Be binary system (MAXI J ) Be star Circumstellar disk Very massive O-Ne white dwarf Nova ignited with a less accumulation Luminous (100L E ) and Exploded out quickly Thermal Ne line Press Release from RIKEN ( ) 10 Credit: Takuya Ohkawa

11 Tidal Disruption Events - A star approaching to a giant black hole in the center of a galaxy is torn into pieces by the tidal force. The debris accretes to the black hole. - Long time monitoring of MAXI guarantees a single event, not one of the AGN activities. - MAXI detected three TDE during Swift J with Swift/BAT and MAXI/GSC 8 Burrows et al. Nature 2011 Swift J with MAXI/GSC n T =-1.92 (-0.73/+0.58) /5/ /3/28 MAXI 2-10 kev Flux (mcrab) MJD (DAY)

12 GRB Reports to GCN Alert issued 12 sec GRB A MAXI Trigger: XRT follow-up ToO: A (+13.2 ks, afterglow detection) A(+46.2 ks, 2 candidates) C (+11.1 ks, No), A (+10.8 ks, No) No ToO: A, B, A (Fermi, CALET) Swift/BAT (faster) Trigger: detection: A (BAT +36 s), A (BAT +185 s) no detection: A Swift-BAT Fermi INTEGRAL CALET + others MAXI 2-4 kev 4-10 kev kev MAXI/All % % % % % % note: these numbers are not complete.

13 MAXI GRBs and transients (2 20 kev) : only MAXI (43) : MAXI + other (39 prompt + 7 afterglows) Serino et al. (2014) 13

14 GRB localization with MAXI 14

15 MAXI Short Transient with no XRT counterparts GRB C MAXI J MAXI J GRB A MAXI J GRB A MAXI J (l, b) = (139.1, +11.3) (354.6, +46.8) (351.6, +30.6) (139.9, +66.4) (201.1, -12.6) (26.4, +35.6) ( ) 2-4 kev 4-10 kev kev No flux in high energy flux 0.16 Crab 0.44 Crab band 0.1 Crab 0.23 Crab 0.2 Crab 0.17Crab 0.12 Crab GCN #17772 Atel #7954 GCN #17568 GCN #16686 ATel #6066 GCN #14359 ATel # FOV MAXI light curves not corrected for collimator transmission 15

16 GW (T0+4~92 min) Sun 2-20 kev 3-s upper limit: 0.1 counts s 1 cm mcrab erg s 1 cm (Serino et al. GCN 19013)

17 GW (T0+0~1 day) kev 3-s upper limit: 8 mcrab erg s 1 cm -2

18 MAXI on GW scan ( 92 min) 5 min ~ 1 day Where there is no will, there might be a way to a GW star!?

19 MAXI observations for GW Timescale (s) Flux (erg s 1 cm -2 ) Luminosity* (erg s 1 ) Radiated Energy (erg) E X /E GW 1 orbit 1000 < < < < day < < < < days < < < < * Distance 410 Mpc assumed Eddington luminosity for 62 M BH erg s 1 Radiated energy in GW: E GW = DMc erg

20 10-4 MAXI on GW Flux (erg/s/cm^2) Time since Trigger (sec)

21 10-4 MAXI on GW Fermi GBM possible detection (extrapolated to 2 20 kev flux averaged over 1 second assuming photon index 1.4) 10-8 MAXI could have marginally detected GBM SGRB if it was in the field of view Flux (erg/s/cm^2) Time since Trigger (sec)

22 Short GRB The only short GRB observed in soft X-ray HETE-2 Short hard pulse Villasenor et al HST Fox et al HETE kev Chandra Soft extended emission z=0.160 Dwarf irregular galaxy SFR = 0.2 M sun /yr

23 MAXI sensitivity for SGRB in GRB Short pulse GRB Extended emission GW range 10-8 MAXI could easily detect short pulse and soft extended emission of GRB Flux (erg/s/cm^2) Time since Trigger (sec) GRB Afterglow (Chandra)

24 MAXI sensitivity for GRB scaled to 100 Mpc SGRB in 10-7 GW range 10-8 Soft extended emission or X-ray afterglow of a short GRB at O2 BNS range may be detected by MAXI in the following scan Flux (erg/s/cm^2) Time since Trigger (sec)

25 Summary MAXI scans about 60-80% of the sky in one orbit (92 min), and more than 90% in a day. We can provide a fast (<30 sec) alert for bright bursts. MAXI is detecting ~10 short transients per year. About half of them are confirmed as GRBs simultaneously detected by other satellites. There can be other class(es) of objects yet to be identified. MAXI discovered 17 new sources in 7 years including 6 black hole binaries and a white dwarf/be system. The latter exhibited a ultra-luminous explosion at ignition of a nova. A large fraction of GW region was covered in 1000s, yielding a flux upper limit ~10 10 erg s 1 cm 2. MAXI can constrain the short GRB scenarios for DNS merger at <100 Mpc (O2 range) Instantaneous field of view of MAXI is 2% of the sky. iwf-maxi (FoV >10% sky) has been proposed.