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Gamma-Rays and Blazars More Work for Variable Star Observers Gordon G. Spear Sonoma State University.

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Presentation on theme: "Gamma-Rays and Blazars More Work for Variable Star Observers Gordon G. Spear Sonoma State University."— Presentation transcript:

1 Gamma-Rays and Blazars More Work for Variable Star Observers Gordon G. Spear Sonoma State University

2 What are Gamma-rays? n Just photons, but with very high energies n Photons with energies billions of times greater than visible light photons n Natural sources of Gamma-rays n Man made sources of Gamma-rays n Gamma-rays from space


4 How are Gamma-rays characterized? n Gamma-rays are characterized by the energy of individual photons. n Energies generally measured in MeV and GeV (millions and billions of eV). n Infrared photons have energies on the order of eV. n One erg is about 600 billion eV. n The erg and the mosquito?

5 Different Types of EMR

6 Compton GRO and EGRET n Compton Gamma Ray Observatory (CGRO) n Launched in 1991 n Re-entered Earth atmosphere in 2000 n Energetic Gamma Ray Experiment Telescope (EGRET) n First all-sky survey in energy range 30 MeV to 10 GeV

7 Deployment of CGRO from the Space Shuttle


9 The Objects in the Gamma-Ray Sky n Milky Way glow from cosmic ray interactions with dust n Point sources in the Milky Way are Gamma-ray pulsars (SNRs) n Point sources outside the Milky Way are AGNs n Some point sources remain unidentified

10 The EGRET Gamma-Ray Sources

11 GLAST and the LAT n Gamma-ray Large Area Space Telescope (GLAST) n Substantial increases in sensitivity, energy range, and resolution over GRO n GLAST Burst Monitor (GBM) n Large Area Telescope (LAT) n Scheduled for launch in 2006 n 5 year mission design, expected 10 year useful lifetime n One year all-sky survey followed by pointed observations

12 GLAST Specifications Comparison

13 Representation of GLAST in Orbit

14 AGNs n Active Galactic Nuclei n Extragalactic objects that are more luminous than normal galaxies n The nucleus can be 10 to 100 times brighter than an entire normal galaxy n The underlying galaxy can appear relatively normal (when it can be seen) n Many different types or sub-classes

15 Some Categories of AGNs n Seyfert Galaxies –Sy 1, Sy2 n Radio Galaxies –Narrow Line Radio Galaxies (NLRG... FR I, FR II) –Broad Line Radio Galaxies (BLRG) n Quasars –Broad Absorption Line Quasars (BALQ) –Steep Spectrum Radio Quasars (SSRQ) –Flat Spectrum Radio Quasars (FSRQ) n Blazars n Optically Violent Variables (OVV)



18 A Typical Quasar PKS 1117-248

19 General Characteristics of AGNs n Extragalactic n More luminous than normal galaxies n Generally point sources (stellar appearance) n Some exhibit jets n Bright in X-rays and Gamma-rays n All exhibit variability at some level!

20 AGN Unification n All AGN are manifestations of the same physical phenomenon n This phenomenon is the accretion disk and jets associated with a supermassive black hole n The different appearances are simply due to the orientation of the jets and disk to our line of sight

21 Artistic Impression of an AGN

22 Voyage into an AGN A Simulation n Starts 100s of Mpc away from AGN n Underlying galaxy is a spiral (20000 stars) n The AGN engine has been switched off n Size scale changes by 10 orders of magnitude

23 AGN Unification Taxonomy

24 Some Typical Optical Spectra

25 The Blazars n The blazars appear to be AGN for which the jets are pointing directly at us. n We are looking directly down the throat of the dragon! n Spectra (SEDs) have bright compton peak in addition to the typical AGN synchrotron peak. n These are the only prominent point sources in the Gamma-ray sky. (Gamma loud) n Beams of particles moving at relativistic speeds produce intense beams of Gamma- rays. n These are the most variable of the AGNs.


27 AGN Variability? n All AGNs appear to be variable at some level n The emission lines vary in strength n The continuum levels vary in brightness n Variability has been documented over decades, years, months, weeks, days, and even hours

28 Characteristics of AGN Variability n Periodicity has NOT been convincingly demonstrated! n Slow, longterm irregular changes n Outbursts (flares) and declines n General increase in variability for shorter wavelengths (higher energy photons) n General increase in variability for longer time scales n Apparent increase in variability with luminosity n Apparent increase in variability with redshift

29 AGN Variability Data n Available observations –Longterm (few per year) –Intraday (few per week) –Microvariability (many per hour) n Lightcurve classification –Outbursts –Declines –Outbursts and declines n The blazars –Most variable of the AGNs –Amplitudes to 4 magnitudes or more –Can exhibit detectable variations from night-to- night and within a night

30 A Blazar with a Long History of Observation

31 B2 1308+326 outbursts B2 1215+303 declines

32 B2 1215+303 outbursts and declines PG 0804+762 non-blazar AGN

33 Intraday Variability

34 Mrk 501 0.1 mag miniflare BL Lac 0.4 mag in 30 minutes

35 The AAVSO has blazar data!

36 SSUO data for 3C 66A (2002-2002)

37 Observing Techniques for AGNs n Just like variable stars! n Visual observations can detect outbursts and declines. n CCD images which include a photometric sequence can be measured. (BVRI filters preferred) n Robotic telescope systems can be extremely efficient, consistent, and productive.

38 Opportunities Provided by GLAST n Detect the Gamma-rays that are directly produced by the supermassive black hole engine. n Provide data to evaluate various theories of jet production. n Detect and measure several thousand new Gamma-loud blazars. n Provide for true multi-wavelength blazar and AGN surveillance.

39 Enter the GTN n GLAST Telescope Network (GTN) n Collaboration of observatories and observers to obtain observations of AGNs n Professional astronomers, amateur astronomers, students n Establish base line variability and coordinate multi-wavelength campaigns n Provide fundamental scientific data that will support and complement the GLAST mission

40 The Goals for the GTN n Establish base-line activity levels and behavior for gamma-loud blazars n Coordinate multi-wavelength campaigns (eventually include GLAST) n Establish and maintain data archive of blazar images n Establish and maintain database of brightness data (like the AAVSO database?) n Distribute announcements about blazar activity (a GCN for blazars?) n Encourage participation by professionals, amateurs, and students; establish mentoring relationships

41 Participants in the GTN will... n Contribute a minimum of 1-2 observations each month n Participate in coordinated campaigns 1-2 times each year –intraday campaigns –microvariability campaigns n Have access to data in the GTN archives n Contribute to improved understanding of blazar energy production (supermassive black holes, relativistic jets) n Contribute to the success of the GLAST mission


43 AAVSO Contributions n GTN partner n Add bright Gamma-loud AGNs (blazars) to AAVSO object list n Monitor program AGNs for outbursts and other activity and provide notification to interested parties n Introduce and mentor new observers to the process of variable star observation n Establish robotic observatories for use by AAVSO members, students, and schools


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