Swift BAT blazars with NICER Sergio Mundo Richard Mushotzky University of Maryland College Park MARLAM 9 JHU Baltimore MD Blazar characteristics Radioloud AGN with jet aligned close to line of sight ID: 1012727
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1. Investigating the variability of Swift-BAT blazars with NICERSergio Mundo, Richard MushotzkyUniversity of Maryland, College ParkMARLAM 9, JHU, Baltimore, MD
2. Blazar characteristicsRadio-loud AGN with jet aligned close to line of sightBlazars have been known to be highly luminous & variable objects due to extreme non-thremal processes in the jetSED double hump structureTwo flavors:BL Lacs: SED Compton hump due to SSCFSRQs: SED Compton hump due to ECX-ray spectra: power law, or curvatureCurvature intrinsic? External origin?Sample FSRQ SED (PKS 2149-306) Sample BL Lac SED (Mrk 421) SSCSyncBATLATPaliya et al. 2019
3. Non-variable blazars?Time-domain variability analysis of 117 blazars in Swift-BAT 105-month catalog (Mundo et al. in prep) shows significant fraction (~30%) of blazars with little to no variability on monthly timescalesDeeply at odds with previous studies showing blazars are highly variable in the X-rays on wide range of timescalesNature of variability:Relatively constant emission?Mostly constant with flares?Sensitivity/systematic issues of BAT?Confirmation of results could change our understanding of the properties of blazars and beamed AGN“Constant” BAT light curves according to 𝛘2-test
4. INVESTIGATION WITH NICERNICER has >100 times sensitivity per unit time compared to BAT; requested data on a subset of 4 faint, “quiescent” blazars as seen by BAT2021 monitoring campaign (500s x 8 visits per month for 5 months per source) allows us to estimate variability on wide range of timescalesPrimary goals:Determine whether sources are variableDescribe the nature of the variabilityFind a physical interpretation if they indeed exhibit little or no variability
5. NICER Time-domain analysisMundo et al. (submitted)
6. Spectral analysis𝝘 varies by no more than ~10% at 1-𝝈 from observation to observation; co-add spectra2 sources well-described by simple power law, but we observe curvature in the remaining 2BATPaliya et al. 2019SyncSSCLATMundo et al. (submitted)
7. Spectral analysis (cont.)BATPaliya et al. 2019SSCSyncECLATMundo et al. (submitted)
8. Implications of our AnalysisSeveral blazars show flares + ~year-long quiescent states in gamma raysPossibly seeing a rare case of this behavior occurring in X-rays, maybe with much longer quiescent statesCooling timescale vs. variability timescale:Maximum cooling time ~1 week; observe low-amplitude variability on similar timescalesNear-constant source of electrons could provide tight balance with effects of energetic losses, resulting in close to constant fluxHigher minute-timescale variability:Possibly due to multi-region X-ray emission scenario in jet, with effects “smoothing” out on longer timescales
9. SUMMARY and future workIn our sample, we do NOT observe high-amplitude variability expected of blazars (in both flux and spectra)We observe curvature in two sources:Source 1: likely intrinsic, due to synchrotron peak/emissionSource 2: Possible absorption due to IGM; would like to fit with models that directly represent IGMPremature to draw strong conclusions given small sample sizeFollow-up multi-cycle NICER campaign underway to characterize nature of variability on longer timescales; increased sample size
10. Additional plots: PKS 2126-15