Gamma-Rays and BlazarsGamma-Rays and BlazarsMore Work for Variable Star ObserversMore Work for Variable Star Observers

Gordon G. SpearGordon G. Spear

Sonoma State UniversitySonoma State University

What are Gamma-rays?What are Gamma-rays?

Just photons, but with very high Just photons, but with very high energiesenergies

Photons with energies billions of times Photons with energies billions of times greater than visible light photonsgreater than visible light photons

Natural sources of Gamma-raysNatural sources of Gamma-rays Man made sources of Gamma-raysMan made sources of Gamma-rays Gamma-rays from spaceGamma-rays from space

How are Gamma-rays How are Gamma-rays characterized?characterized?

Gamma-rays are characterized by the Gamma-rays are characterized by the energy of individual photons.energy of individual photons.

Energies generally measured in MeV and Energies generally measured in MeV and GeV (millions and billions of eV).GeV (millions and billions of eV).

Infrared photons have energies on the Infrared photons have energies on the order of eV.order of eV.

One erg is about 600 billion eV.One erg is about 600 billion eV. The erg and the mosquito?The erg and the mosquito?

Different Types of EMRDifferent Types of EMRTYPE(TYPICAL)

WAVEL ENGTH

(CM)

FREQUENCY

(HZ)

ENERGY

(MEV)

Radio(21 cm, 1.4 GHz)

21 1.42E+09 5.90E-12

Visible(5500 A, green)

5.50E-05 5.45E+14 2.25E-06

X-ray(1 KeV)

1.24E-07 2.42E+17 1.00E-03

Gamma-ray(100 MeV)

1.24E-12 2.42E+22 100

(1 GeV) 1.24E-13 2.42E+23 1.00E+03

(1 TeV) 1.24E-16 2.42E+26 1.00E+06

Compton GRO and EGRETCompton GRO and EGRET

Compton Gamma Ray Observatory Compton Gamma Ray Observatory (CGRO)(CGRO)

Launched in 1991Launched in 1991 Re-entered Earth atmosphere in 2000Re-entered Earth atmosphere in 2000 Energetic Gamma Ray Experiment Energetic Gamma Ray Experiment

Telescope (EGRET)Telescope (EGRET) First all-sky survey in energy range 30 First all-sky survey in energy range 30

MeV to 10 GeVMeV to 10 GeV

Deployment of CGRO from the Deployment of CGRO from the Space ShuttleSpace Shuttle

The Objects in the Gamma-Ray SkyThe Objects in the Gamma-Ray Sky

Milky Way glow from cosmic ray Milky Way glow from cosmic ray interactions with dustinteractions with dust

Point sources in the Milky Way are Point sources in the Milky Way are Gamma-ray pulsars (SNRs)Gamma-ray pulsars (SNRs)

Point sources outside the Milky Way are Point sources outside the Milky Way are AGNsAGNs

Some point sources remain unidentifiedSome point sources remain unidentified

The EGRET Gamma-Ray SourcesThe EGRET Gamma-Ray Sources

GLAST and the LATGLAST and the LAT Gamma-ray Large Area Space Telescope (GLAST)Gamma-ray Large Area Space Telescope (GLAST) Substantial increases in sensitivity, energy range, Substantial increases in sensitivity, energy range,

and resolution over GROand resolution over GRO GLAST Burst Monitor (GBM)GLAST Burst Monitor (GBM) Large Area Telescope (LAT)Large Area Telescope (LAT) Scheduled for launch in 2006Scheduled for launch in 2006 5 year mission design, expected5 year mission design, expected 10 year useful 10 year useful

lifetimelifetime One year all-sky survey followed by pointed One year all-sky survey followed by pointed

observationsobservations

GLAST Specifications ComparisonGLAST Specifications Comparison

Representation of GLAST in OrbitRepresentation of GLAST in Orbit

AGNsAGNs

Active Galactic NucleiActive Galactic Nuclei Extragalactic objects that are more Extragalactic objects that are more

luminous than normal galaxiesluminous than normal galaxies The nucleus can be 10 to 100 times The nucleus can be 10 to 100 times

brighter than an entire normal galaxybrighter than an entire normal galaxy The underlying galaxy can appear The underlying galaxy can appear

relatively normal (when it can be seen)relatively normal (when it can be seen) Many different types or sub-classesMany different types or sub-classes

Some Categories of AGNsSome Categories of AGNs

Seyfert GalaxiesSeyfert Galaxies– Sy 1, Sy2Sy 1, Sy2

Radio GalaxiesRadio Galaxies– Narrow Line Radio Narrow Line Radio

Galaxies (NLRG... Galaxies (NLRG... FR I, FR II)FR I, FR II)

– Broad Line Radio Broad Line Radio Galaxies (BLRG)Galaxies (BLRG)

QuasarsQuasars– Broad Absorption Line Broad Absorption Line

Quasars (BALQ)Quasars (BALQ)– Steep Spectrum Radio Steep Spectrum Radio

Quasars (SSRQ)Quasars (SSRQ)– Flat Spectrum Radio Flat Spectrum Radio

Quasars (FSRQ)Quasars (FSRQ) BlazarsBlazars Optically Violent Optically Violent

Variables (OVV)Variables (OVV)

A Typical QuasarA Typical QuasarPKS 1117-248PKS 1117-248

General Characteristics of General Characteristics of AGNsAGNs

ExtragalacticExtragalactic More luminous than normal galaxiesMore luminous than normal galaxies Generally point sources (stellar Generally point sources (stellar

appearance)appearance) Some exhibit jetsSome exhibit jets Bright in X-rays and Gamma-raysBright in X-rays and Gamma-rays All exhibit variability at some level!All exhibit variability at some level!

AGN UnificationAGN Unification

All AGN are manifestations of the same All AGN are manifestations of the same physical phenomenonphysical phenomenon

This phenomenon is the accretion disk This phenomenon is the accretion disk and jets associated with a and jets associated with a supermassive black holesupermassive black hole

The different appearances are simply The different appearances are simply due to the orientation of the jets and due to the orientation of the jets and disk to our line of sightdisk to our line of sight

Artistic Impression of an AGNArtistic Impression of an AGN

Voyage into an AGNVoyage into an AGNA SimulationA Simulation

Starts 100s of Mpc Starts 100s of Mpc away from AGNaway from AGN

Underlying galaxy is a Underlying galaxy is a spiral (20000 stars)spiral (20000 stars)

The AGN engine has The AGN engine has been switched offbeen switched off

Size scale changes by Size scale changes by 10 orders of magnitude10 orders of magnitude

QuickTime™ and aGIF decompressor

are needed to see this picture.

AGN Unification TaxonomyAGN Unification Taxonomy

Some Typical Optical SpectraSome Typical Optical Spectra

The BlazarsThe Blazars The blazars appear to be AGN for which the The blazars appear to be AGN for which the

jets are pointing directly at us.jets are pointing directly at us. We are looking directly down the throat of the We are looking directly down the throat of the

dragon!dragon! Spectra (SEDs) have bright compton peak in Spectra (SEDs) have bright compton peak in

addition to the typical AGN synchrotron peak.addition to the typical AGN synchrotron peak. These are the only prominent point sources in These are the only prominent point sources in

the Gamma-ray sky. (Gamma loud)the Gamma-ray sky. (Gamma loud) Beams of particles moving at relativistic Beams of particles moving at relativistic

speeds produce intense beams of Gamma-speeds produce intense beams of Gamma-rays.rays.

These are the most variable of the AGNs.These are the most variable of the AGNs.

AGN Variability?AGN Variability?

All AGNs appear to be variable at some All AGNs appear to be variable at some levellevel

The emission lines vary in strengthThe emission lines vary in strength The continuum levels vary in brightnessThe continuum levels vary in brightness Variability has been documented over Variability has been documented over

decades, years, months, weeks, days, decades, years, months, weeks, days, and even hoursand even hours

Characteristics of AGN VariabilityCharacteristics of AGN Variability

Periodicity has NOT been convincingly Periodicity has NOT been convincingly demonstrated!demonstrated!

Slow, longterm irregular changesSlow, longterm irregular changes Outbursts (flares) and declinesOutbursts (flares) and declines General increase in variability for shorter General increase in variability for shorter

wavelengths (higher energy photons)wavelengths (higher energy photons) General increase in variability for longer time General increase in variability for longer time

scalesscales Apparent increase in variability with luminosityApparent increase in variability with luminosity Apparent increase in variability with redshiftApparent increase in variability with redshift

AGN Variability DataAGN Variability Data

Available observationsAvailable observations– Longterm (few per year)Longterm (few per year)– Intraday (few per week)Intraday (few per week)– Microvariability (many Microvariability (many

per hour)per hour)

Lightcurve classificationLightcurve classification– OutburstsOutbursts– DeclinesDeclines– Outbursts and declinesOutbursts and declines

The blazarsThe blazars– Most variable of the Most variable of the

AGNsAGNs– Amplitudes to 4 Amplitudes to 4

magnitudes or moremagnitudes or more– Can exhibit detectable Can exhibit detectable

variations from night-to-variations from night-to-night and within a nightnight and within a night

A Blazar with a Long History of Observation

B2 1308+326outbursts

B2 1215+303declines

B2 1215+303outbursts and

declines

PG 0804+762non-blazar AGN

Intraday Variability

Mrk 5010.1 mag miniflare

BL Lac0.4 mag in 30 minutes

The AAVSO has blazar data!The AAVSO has blazar data!

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

Observing Techniques for Observing Techniques for AGNsAGNs

Just like variable stars!Just like variable stars! Visual observations can detect outbursts Visual observations can detect outbursts

and declines.and declines. CCD images which include a photometric CCD images which include a photometric

sequence can be measured. (BVRI filters sequence can be measured. (BVRI filters preferred)preferred)

Robotic telescope systems can be Robotic telescope systems can be extremely efficient, consistent, and extremely efficient, consistent, and productive.productive.

Opportunities Provided by Opportunities Provided by GLASTGLAST

Detect the Gamma-rays that are directly Detect the Gamma-rays that are directly produced by the supermassive black hole produced by the supermassive black hole engine.engine.

Provide data to evaluate various theories of Provide data to evaluate various theories of jet production.jet production.

Detect and measure several thousand new Detect and measure several thousand new Gamma-loud blazars.Gamma-loud blazars.

Provide for true multi-wavelength blazar and Provide for true multi-wavelength blazar and AGN surveillance.AGN surveillance.

Enter the GTNEnter the GTN GLAST Telescope Network (GTN)GLAST Telescope Network (GTN) Collaboration of observatories and observers Collaboration of observatories and observers

to obtain observations of AGNsto obtain observations of AGNs Professional astronomers, amateur Professional astronomers, amateur

astronomers, studentsastronomers, students Establish base line variability and coordinate Establish base line variability and coordinate

multi-wavelength campaignsmulti-wavelength campaigns Provide fundamental scientific data that will Provide fundamental scientific data that will

support and complement the GLAST missionsupport and complement the GLAST mission

The Goals for the GTNThe Goals for the GTN

Establish base-line activity levels and behavior for Establish base-line activity levels and behavior for gamma-loud blazarsgamma-loud blazars

Coordinate multi-wavelength campaigns (eventually Coordinate multi-wavelength campaigns (eventually include GLAST)include GLAST)

Establish and maintain data archive of blazar imagesEstablish and maintain data archive of blazar images Establish and maintain database of brightness data Establish and maintain database of brightness data

(like the AAVSO database?)(like the AAVSO database?) Distribute announcements about blazar activity (a Distribute announcements about blazar activity (a

GCN for blazars?)GCN for blazars?) Encourage participation by professionals, amateurs, Encourage participation by professionals, amateurs,

and students; establish mentoring relationshipsand students; establish mentoring relationships

Participants in the GTN will...Participants in the GTN will...

Contribute a minimum of 1-2 observations each Contribute a minimum of 1-2 observations each monthmonth

Participate in coordinated campaigns 1-2 times each Participate in coordinated campaigns 1-2 times each yearyear– intraday campaignsintraday campaigns– microvariability campaignsmicrovariability campaigns

Have access to data in the GTN archivesHave access to data in the GTN archives Contribute to improved understanding of blazar Contribute to improved understanding of blazar

energy production (supermassive black holes, energy production (supermassive black holes, relativistic jets)relativistic jets)

Contribute to the success of the GLAST missionContribute to the success of the GLAST mission

http://glast.sonoma.edu/gtnhttp://glast.sonoma.edu/gtn

AAVSO ContributionsAAVSO Contributions GTN partnerGTN partner Add bright Gamma-loud AGNs (blazars) to Add bright Gamma-loud AGNs (blazars) to

AAVSO object listAAVSO object list Monitor program AGNs for outbursts and Monitor program AGNs for outbursts and

other activity and provide notification to other activity and provide notification to interested partiesinterested parties

Introduce and mentor new observers to the Introduce and mentor new observers to the process of variable star observationprocess of variable star observation

Establish robotic observatories for use by Establish robotic observatories for use by AAVSO members, students, and schoolsAAVSO members, students, and schools

http://glast.sonoma.edu/gtnhttp://glast.sonoma.edu/gtn