1. Longterm X-ray observation of Blazars with MAXI Naoki Isobe (Kyoto University; n-isobe@kusastro.kyoto-u.ac.jp), & MAXI teamn-isobe@kusastro.kyoto-u.ac.jp 5.MAXI Lightcurve of other blazars/Radio Galaxies 1.Introduction to MAXI (Matsuoka et al. 2009, Poster by Kawai et al.) 2.Longterm X-ray lightcurve of Mrk 421 with MAXI Longterm continuous X-ray observations of blazars with MAXI are reported. Thanks to its unprecedentedly high sensitivity as an all-sky X-ray monitor, MAXI is the ideal observatory to investigate variability of blazars. Since it started its operation in 2009 August, MAXI has successfully alerted two strong X-ray flares from the BL Lac object Mrk 421. In one of these flares, the object was found to become the brightest (164±17 mCrab in 2 – 10 keV) in history. By close examination on the MAXI lightcurve, physical quantities of the flares are estimated. These results clearly demonstrates the potential of MAXI for the blazar variability. 3.Spectral variation of Mrk 421 All sky X-ray monitor on the Japanese Experiment Module of the International Space Station (ISS) Successful observation from 2009 August 2 X-ray slit cameras Gas Slit Camera (GSC): 2 – 10 keV Large area gas proportional counters Solid-state Slit Camera (SSC): 0.5 – 10 keV 32 X-ray CCD chips High sky coverage : about 95 %/day High Sensitivity : higher than 10 mCrab/day 1 mCrab = 2 x 10 -11 ergs cm -2 s -1 in 2 – 10 keV. Daily lightcurve of about 200 sources available from the MAXI web : http://maxi.riken.jp/top/ Fig. 1 MAXI on the ISS Fig.2 All sky X-ray Image with the MAXI GSC Ideal observatory for longterm X-ray variability of blazars. 2-4 keV 4-10 keV 10 – 20 keV Fig. 3 Daily MAXI lightcurve of Mrk 421 in (a) 2 – 4 keV and (b) 4 – 10 keV from 2009 August to 2010 August, compared with (c) Swift/BAT lightcurve in 15- 50 keV Mrk 421 The High-energy Peaked BL Lac object (HBL) at z = 0.031. Brightest extragalactic source at VHE  -rays (>100 GeV) The 1 year MAXI lightcurve reveals that the object is highly variable. MAXI successfully alerted 2 strong X- ray flares from the object A)2009 January 1 (MJD=55197; Atel 2368) B)February 17 (MJD=55243; Atel 2444) Fig. 4, 2 – 10 keV MAXI lightcurve in a time resolution of 6 hours and daily hardness (HR1 and HR2), associated with the 2 strong X-ray flares (Epochs A and B in Fig. 3). MAXI 2- 10 keV HR1 F 4- 10keV /F 2-4keV HR2 F 14-50keV /F 2-4keV Maximum 2 – 10 keV flux with MAXI Epoch A : 120±10 mCrab (MJD = 55197.4) Epoch B : 164±17 mCrab (MJD = 55243.6) cf. The highest flux reported before this MAXI results; 130 mCrab in the flare of 2008 June (Donnarumma et al. 2009) MAXI detected the strongest X-ray flare from Mrk 421 4.The physical parameters, associated the flares 10 months VHE  -ray flare with VERITAS (Rene et al. Atel 2443) Hard X-ray Flare with Swift/BAT (Atel 2292, Krimm et al.) Strong X-ray flares with MAXI (Atel 2368,2444 Isobe et al.) Fig. 5 Relation between HR1 and HR2 during Epochs A and B, averaged over 3 days. The color definition (A, B1, B2 ) is shown with the arrows in Fig. 4. The hardness for some representative value of the photon index  (2.0, 2.5, 3.0) is indicated by dashed lines. If the X-ray spectrum is a simple PL in the MAXI-Swift/BAT energy range, the data is expected to be distributed on the solid line. If a simple power-law (PL) is assumed, the value of HR1 corresponds to a photon index of  = 2 – 2.5, in the MAXI band pass. (The current systematic uncertainties of MAXI response corresponds to  = 0.1.) A comparison between HR1 and HR2 indicates a spectral softening toward the hard X-ray band. Fig. 6. An example of the spectral energy distribution of Mrk 421, from radio to  -ray frequencies. (Donnarumma et al. 2009) MAXI is observing around the synchrotron peak frequency. Synchrotron Inverse Compton MAXI bandpass (2-20 keV) MAXI GSC SSC Japanese Experiment Module ISS motion Exposed Facility Pressurized module Horizontal FoV Zenith FoV Horizontal FoV (a) F 2-4keV (MAXI) (b) F 4-10keV (MAXI) 100 mCrab Crab-like Crab-like (  = 2.08) (http://heasarc.gsfc.nasa.gov/docs/swift/results/transients/BAT_detected.html). A B1 B2 A B Fig. 7. HR2 plotted against the 2 – 10 keV flux. A (MJD=55190-55210) B1 (MJD=55232-55245) B2 (MJD=55246-55275) A (MJD=55190-55210) B1 (MJD=55232-55245) B2 (MJD=55246-55275) No significant spectral change was observed, associated with the flare in Epoch A. A spectral softening was suggested in the decay phase of the flare in Epoch B1. During Epoch B2 (after the decay of the B1 flare) HR2 was variable. HR2 was higher than that at the peak of the B1 flare (in spite of the flux lower than the peak flux be a factor of 3). These spectral behavior is diffent from those in the previous observations, which revealed a positive correlation between the synchrotron peak frequency and luminosity (e.g., Tanihata et al. 2004), equivalent to the positive correlation between HR2 and the 2-10 keV MAXI flux. Hard Decay phase A challenge to the simple one-zone synchrotron-self Compton model In HBLs, the timescale of flare is controlled by an interplay between the cooling time  cool, the acceleration time  acc, and the light crossing time  crs (e.g. Kataoka 2000). In the flares of Epochs A and B1, asymmetrical lightcurves were observed, where the rise time t rise is shorter than the decay time t decay (See Fig. 4). ⇒ t decay ～  cool, t rise >  crs In HBLs, the synchrotron radiation usually dominates other cooling process.  cool = 1.5 x 10 3 s B -3/2 E keV -1/2  -1/2 (Takahashi et al. 1996) B : magnetic field in Gauss, E kev : synchrotron photon energy in keV,  : beaming factor of the jet t rise t decay t rise < 2.5 x 10 4 s ～  crs ⇒ Region size R< c t crs  /(1+z) ～ 6 x 10 15 cm (  /10) t decay = 2 x 10 4 s ～  cool ⇒ B = 0.045 Gauss (  /10) -1/3 Flare in Epoch A Flare in Epoch B1 Consistent with the previous studies; B = 0.036 – 0.44 G (Kino et al. 2002) t rise < 1.3 x 10 5 s ～  crs ⇒ R< 4 x 10 16 cm (  /10) t decay = 1.4 x 10 5 s ～  cool ⇒ B = 0.015 Gauss (  /10) -1/3 The magnetic field was found to be weaker than that in the previous flares. The flare could not be a single event. (Isobe et al. PASJ submitted) Mrk 501 (HBL) 3C 273 (FSRQ) 3C 454 (FSRQ) Centaurus A (Radio Galaxy, SyII) GeV  -ray Flare with Fermi (Atel 2200) GeV  -ray Flare with AGILE (Atel 2326) and Fermi (Atel 2328) GeV  -ray Flare with Fermi (Atel 2168) GeV  -ray Flare with AGILE (Atel 2376) GeV  -ray Flare with Fermi (Atel 2200) 2 – 4 keV 4 – 10 keV 10 mCrab 20 mCrab 10 mCrab 50 mCrab (The MAXI lightcurve of more than 10 blazars are available from http://maxi.riken.jp/top/) CentaurusA 3C 273 Mrk 501 3C 454.3 (3 day average)