Radio-to-Gamma Ray Monitoring of Mkn 421 and Mkn 501: Source Variability › science › mtgs › fermi_jansky › ... · 2012-01-06 · Radio-to-Gamma Ray Monitoring of Mkn 421 and

Radio-to-Gamma Ray Monitoring of Mkn 421 and Mkn 501: Source Variability

N. Nowak, D. Paneque, U. Barres de Almeida, N. Strah, D. Tescaro

On behalf of the Fermi-LAT, MAGIC, VERITAS and other collaborations and groups involved in the multiwavelength campaigns

Outline

• Introduction

• 2009 MWL campaigns on Mrk 421 and Mrk 501:

- SEDs

- Lightcurves

- Variability

- Correlations

• Conclusions & Outlook

Motivation

Blazars: - AGN with relativistic jet pointing directly towards us

- highly variable at all wavelengths

- SEDs dominated by jet emission, two non-thermal bumps at low (radio-optical-Xray) and high (X/γ-rays) energies respectively. Origin of high-energy

bump not yet identified unambiguously.

➡ simultaneous observations of blazars over the whole wavelength range (Radio - TeV) over a long time period needed (mostly in low state).

Mrk 421 and Mrk 501:- luminous gamma ray sources

- nearby blazars (z~0.03) which implies a low EBL absorption

➡ ideal candidates for multiwavelength studies

2009 MWL campaigns on Mrk421 and Mrk501

4.5 months long multiwavelength campaigns in 2009 (PI: David Paneque):

• Mrk421: Jan 19, 2009 (MJD 54850) - June 1st, 2009 (MJD 54983)

• Mrk501: Mar 15, 2009 (MJD 54905) - Aug 1st, 2009 (MJD 55044)

• monitored regardless of activity. However, both sources were in a relatively low state throughout the campaigns

• participating collaborations/telescopes/instruments:

MAGIC, Whipple, VERITAS, Fermi-LAT, Swift/BAT, RXTE/PCA, Swift/XRT, Swift/UVOT, GASP-WEBT, GRT, ROVOR, New Mexico Skies, MITSuME, OAGH, WIRO, SMA, VLBA, Noto, Metsähovi, OVRO, Medicina, UMRAO, RATAN-600, Effelsberg

2009 MWL campaigns on Mrk421 and Mrk501

[Hz])log10(10 15 20 25

Tim

e [M

JD]

54850

54900

54950

55000Radio IR O-UV X-rays -raysHE -raysVHE

Mrk421 [Hz])log10(

10 15 20 25

Tim

e [M

JD]

54900

54950

55000

55050 Radio IR O-UV X-rays -raysHE -raysVHE Mrk501

Excellent time and energy coverage for both sources

Abdo et al., 2011, ApJ, 736, 131

Abdo et al., 2011, ApJ, 727, 129

Spectral Energy Distribution of Mrk 421

[Hz]1010 1210 1410 1610 1810 2010 2210 2410 2610 2810

]-1

s-2

[erg

cm

F

-1410

-1310

-1210

-1110

-1010

-910

MAGIC

Fermi

Swift/BAT

RXTE/PCA

Swift/XRT

Swift/UVOT

ROVOR

NewMexicoSkies

MITSuME

GRT

GASP

WIRO

OAGH

SMA

VLBA_core(BP143)

VLBA(BP143)

VLBA(BK150)

Metsahovi

Noto

VLBA_core(MOJAVE)

VLBA(MOJAVE)

OVRO

RATAN

Medicina

Effelsberg

Abdo et al., 2011, ApJ, 736, 131

high-energy bump of the SED well covered by Fermi-LAT + MAGIC

Spectral Energy Distribution of Mrk 501

[Hz]1010 1210 1410 1610 1810 2010 2210 2410 2610 2810

]-1

s-2

[erg

cm

F

-1410

-1310

-1210

-1110

-1010

-910

MAGICVERITASVERITAS_flare

Fermi

Swift/BATRXTE/PCASwift/XRT

Swift/UVOTBradfordRoboticTelescopeGASPGRTMITSuMEROVORWIROOAGHCampoImperatore

SMAVLBA(BP143)

VLBA_core(BP143)VLBA_core_ellipsefit(BP143)VLBA(BK150)VLBA_core(BK150)Noto

MetsahoviMedicinaVLBA(MOJAVE)VLBA_Core(MOJAVE)

OVRORATANUMRAOEffelsberg

Abdo et al., 2011, ApJ, 727, 129

host galaxy

3-day spectrum of a flare seen by

VERITAS

low-state spectrum (flare excluded)

high-energy bump of the SED well covered by Fermi-LAT + MAGIC + VERITAS

Modelling the Mrk 421 and Mrk 501 SEDs

• can be well described by standard one-zone synchrotron self-Compton model with 2 breaks in the electron spectrum

• model parameters (e.g. Doppler factor, size of emitting blob, magnetic field, properties of the electron population, ...) are very similar for both objects

➡ common properties of jets and acceleration mechanisms in blazars

108 1011 1014 1017 1020 1023 1026 1029

[Hz]

10-14

10-13

10-12

10-11

10-10

10-9

10-8

F [e

rg s-1

cm

-2]

Mrk 421 SED with SSC model fits

Abdo et al., 2011, ApJ, 736, 131!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!

!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!

!!!!!!!!

!

!!!!!!!!!!!!

10101010 10121012 10141014 10161016 10181018 10201020 10221022 10241024 10261026 102810!1410!14

10!1310!13

10!1210!12

10!1110!11

10!1010!10

10!9

" !Hz"

"F"!ergc

m!2s!

1 " Mrk 501 SED with SSC model fits

Mrk 421 SED with SSC model fitsMrk 421 SED with SSC model fits

host galaxy

Abdo et al., 2011, ApJ, 727, 129

PRELIMINARY

Lightcurves for Mrk 421 − Radio

MJD54800 54840 54880 54920 54960 55000

Flux [

Jy]

Effelsberg 110mm

Effelsberg 13mm

Effelsberg 20mmEffelsberg 28mmEffelsberg 36mm

Effelsberg 60mm

Effelsberg 9mmMetsähovi 37GHz

Medicina 8GHz

Noto 22GHz

Noto 8GHz

OVRO 15GHz

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

• Radio observations at different frequencies

• single-dish instruments• flux ~const., no strong variability

Effelsberg

Metsähovi

Noto

OVROMedicina

PRELIMINARY

PRELIMINARY

Lightcurves for Mrk 421 − NIR and Optical

I

R

V

B

MJD54800 54840 54880 54920 54960 55000

Flux [

mJy]

10

15

20

25

30

35

40

45 ROVOR BMITSuME IcMITSuME RcMITSuME gGRT BGRT IGRT RGRT VGASPSteward V

MJD54800 54840 54880 54920 54960 55000

Flux [

mJy]

25

30

35

40

45

50 OAGH HOAGH JOAGH KWiro JWiro K

• good coverage of optical-NIR wavelengths provided by many telescopes around the world

• flux increases with time• significant variability

PRELIMINARY

PRELIMINARY

PRELIMINARY

Lightcurves for Mrk 421 − UV and X-rays

Swift

RXTE

MJD54800 54840 54880 54920 54960 55000

Flux [

mJy]

6

8

10

12

14 UVOT M2UVOT W1UVOT W2

• UV: flux increases with time, significant variability

• X-rays: large variability amplitudes of ~factor 2

Flux [

coun

ts/s

]-1 s-2

Flux [

ergs

cm

0.10.20.30.40.50.60.70.8

-910!

RXTE/PCA (2 - 10 keV)Swift/XRT (0.3 - 2 keV)Swift/XRT (2 - 10 keV)

0.20.40.60.8

11.21.41.61.8

2RXTE/ASM

MJD54800 54840 54880 54920 54960 55000

0

0.0005

0.001

0.0015

0.002

0.0025Swift/BAT

] ]Flu

x [co

unts/

s

PRELIMINARY

PRELIMINARY

PRELIMINARY

Lightcurves for Mrk 421 − γ-rays and VHE

]-1 s-2

Flux [

phot

ons c

m

0.04

0.06

0.08

0.1

0.12

0.14-910!

MAGIC

MJD54800 54840 54880 54920 54960 55000

]-1

Flux [

phot

ons m

inute

0

0.2

0.4

0.6

0.8

1

1.2 WhippleMJD54800 54840 54880 54920 54960 55000

]-1 s

-2Flu

x [ph

oton

s cm

0

0.04

0.08

0.12

0.16

-610!

Fermi-LAT

• γ-rays and VHE: some level of

variability• no significant flaring activity

Fermi MAGIC Whipple

E>300MeV, 2 day bins E>300GeV

E>400GeV

PRELIMINARY

Lightcurves for Mrk 501 − Radio

MJD54900 54940 54980 55020 55060

Flux [

Jy]

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2Effelsberg 110mm

Effelsberg 13mm

Effelsberg 20mmEffelsberg 28mmEffelsberg 36mm

Effelsberg 60mm

Effelsberg 7mm

Effelsberg 9mm

Medicina 22GHz

Medicina 8GHz

Metsähovi 37GHz

GASP 14GHz

GASP 5GHzGASP 8GHz

Noto 43GHz

Noto 8GHz

SMA 225GHz

OVRO

• Radio observations at many different frequencies

• no strong variability

Effelsberg

Metsähovi

Noto

OVROMedicina

PRELIMINARYPR

ELIMINARY

Lightcurves for Mrk 501 − NIR and Optical

I

R

V

B

MJD54900 54940 54980 55020 55060

Flux [

mJy]

5

10

15

20

25

30ROVOR B

ROVOR I

ROVOR R

ROVOR V

GASP R

GRT B

GRT R

GRT V

MITSuME Ic

MITSuME Rc

MITSuME g

Steward V

MJD54900 54940 54980 55020 55060

Flux [

mJy]

3035404550556065 GASP H

GASP JGASP KOAGH HOAGH JOAGH KsWiro JWiro K

• good coverage of optical-NIR wavelengths provided by many telescopes around the world

• flux ~const. with time• little variability

PRELIMINARY

PRELIMINARY

PRELIMINARY

Lightcurves for Mrk 501 − UV and X-rays

Swift

RXTE

• UV and X-rays: significant variability

MJD54900 54940 54980 55020 55060

1.41.61.8

22.22.42.62.8

UVOT M2UVOT W1UVOT W2

Flux [

mJy] ]

-1 s-2

Flux [

ergs

cm

0.020.040.060.08

0.10.120.140.160.18

0.2

-910!

MJD54900 54940 54980 55020 55060

]Flu

x [co

unts/

s

0

0.1

0.2

0.3

0.4

]Flu

x [co

unts/

s

-0.000200.00020.00040.00060.00080.0010.0012

RXTE/PCA (2 - 10 keV)Swift/XRT (0.3 - 2 keV)Swift/XRT (2 - 10 keV)

RXTE/ASMSwift/BAT

Swift/XRT PC mode (0.3 - 2 keV)Swift/XRT PC mode (2 - 10 keV)

PRELIMINARY

PRELIMINARY

PRELIMINARY

Lightcurves Mrk 501 − γ-rays and VHE

Large flare in VHE around MJD 54952 (May 1st, 2009). No obvious correlation with other wavelengths.

54900 54940 54980 55020 55060

]-1 s

- 2Flu

x [ph

oton

s cm

10

20

30

40

50

-910!

Fermi (15 day bins)Fermi (30 day bins) ]-1 s

-2Flu

x [ph

oton

s cm

0

0.05

0.1

0.15

0.2-910!

MAGICVERITAS

MJD54900 54940 54980 55020 55060

]Flu

x [ph

oton

s/minu

te

0

0.5

1

1.5

2 WhippleMJD

Fermi MAGIC Whipple

E>300MeV E>300GeV

E>400GeV

PRELIMINARY

PRELIMINARY

PRELIMINARY


Large flare in VHE around MJD 54952 (May 1st, 2009). No obvious correlation with other wavelengths.

Flarewithout X-ray counterpart

54900 54940 54980 55020 55060

]-1 s

- 2Flu

x [ph

oton

s cm

10

20

30

40

50

-910!

Fermi (15 day bins)Fermi (30 day bins) ]-1 s

-2Flu

x [ph

oton

s cm

0

0.05

0.1

0.15

0.2-910!

MAGICVERITAS

MJD54900 54940 54980 55020 55060

]Flu

x [ph

oton

s/minu

te

0

0.5

1

1.5

2 WhippleMJD

Fermi MAGIC Whipple

E>300MeV E>300GeV

E>400GeV

PRELIMINARY


PRELIMINARY

PRELIMINARY


optical linear polarisation: -steady and then drops by ~15% after flare-much larger than in March 2009

EVPA:-continuous increase from ~15o to ~30o

in 3 days before flare- rotation stops when flare occurs

➡ indicates common origin for optical and γ-ray emission (e.g., Marscher et al. 2010)

]-1 s-2

Flux [

phot

ons c

m

0

0.05

0.1

0.15

0.2-910!

MAGICVERITAS

MJD54900 54940 54980 55020 55060

]Flu

x [ph

oton

s/minu

te

0

0.5

1

1.5

2 Whipple

P (%

)

123456

54900 54940 54980 55020 55060

°EV

PA( )

1520253035

MJD

Steward Observatory

PRELIMINARY


PRELIMINARY

PRELIMINARY


optical linear polarisation: -steady and then drops by ~15% after flare-much larger than in March 2009

EVPA:-continuous increase from ~15o to ~30o

in 3 days before flare- rotation stops when flare occurs

➡ indicates common origin for optical and γ-ray emission (e.g., Marscher et al. 2010)

]-1 s-2

Flux [

phot

ons c

m

0

0.05

0.1

0.15

0.2-910!

MAGICVERITAS

MJD54900 54940 54980 55020 55060

]Flu

x [ph

oton

s/minu

te

0

0.5

1

1.5

2 Whipple

P (%

)

123456

54900 54940 54980 55020 55060

°EV

PA( )

1520253035

MJDFurther details on this flaring event can be found inPichel & Paneque, Proc. ICRC 2011, arXiv:1110.2549v1

Steward Observatory

log(frequency [Hz])10 12 14 16 18 20 22 24 26 28

var

F

0

0.2

0.4

0.6

0.8

1

Fermi

ROVOR NMSkies

MITSuME

GRT

GASPOAGH

UVOT

WiroEffelsberg

Metsähovi

Medicina

OVRO

Whipple

MAGIC

PCAASM

BAT

XRTa

XRTb

Steward V

Variability of Mrk 421 and Mrk 501

Largest variability in X-rays

PRELIMINARY

Low but significant variability at all wavelengths

Mrk 421Fvar =

!

S2! < !2

err >

< F! >2

Fractional variability Fvar (Vaughan et al. 2003)

open circles:host galaxy subtracted(R band; Nilsson et al. 2007)

log(frequency [Hz])10 12 14 16 18 20 22 24 26 28

0

0.2

0.4

0.6

0.8

1

Fermi (15 day)Fermi (30 day)

ROVOR

GASP

GRT

MITSuMEOAGH

UVOTWiroMetsähoviGASP

SMA

OVRO

MAGIC

PCAASM

BAT

XRTaXRTb

Steward V

VERITAS

Whipple

Whipple(flare removed)

VERITAS (flare removed)va

rF

PRELIMINARY Largest variability in VHE due to flare in May

2009

Mrk 501

Variability increases with frequency

Variability of Mrk 421 and Mrk 501

open circles:host galaxy subtracted(R band; Nilsson et al. 2007)

Fermi-LAT: dominated by

variability at 30 day timescales

• unevenly sampled lightcurves, gaps• each lightcurve has a different sampling, different number of data points

What is the error in Fvar introduced by this? How many flux measurements are needed to obtain a reliable Fvar estimate?

Unequally & unevenly sampled lightcurves




log(frequency [Hz])10 12 14 16 18 20 22 24 26 28

var

F

0

0.2

0.4

0.6

0.8

1varF and its uncertainty calculated using Vaughan et al. 2003

delete-d jackknife estimate and variance, d=sqrt(n)

Fermi

UVOTMetsähovi

OVRO

Whipple

MAGIC

PCA

ASM

BAT

XRTa

XRTb

PRELIMINARY

d randomly selected flux measurements removed from eachlightcurve without replacement (Jackknife)

Mrk 421




log(frequency [Hz])10 12 14 16 18 20 22 24 26 28

var

F

0

0.2

0.4

0.6

0.8

1varF and its uncertainty calculated using Vaughan et al. 2003

delete-d jackknife estimate and variance, d=sqrt(n)

Fermi

UVOTMetsähovi

OVRO

Whipple

MAGIC

PCA

ASM

BAT

XRTa

XRTb

PRELIMINARY


Mrk 421

➡no significant change in the Fvar values


What is the error in Fvar introduced by this? How many flux measurement are needed to obtain a reliable Fvar estimate?

PRELIMINARY


log(frequency [Hz])10 12 14 16 18 20 22 24 26 28

0

0.2

0.4

0.6

0.8

1va

rF

varF and its uncertainty calculated using Vaughan et al. 2003delete-d jackknife estimate and variance, d=sqrt(n)

Fermi

UVOTMetsähoviOVRO

MAGIC

PCAASM

BAT

XRTa

XRTb

VERITAS

Whipple

Mrk 501


➡no significant change in the Fvar values

PRELIMINARY

• d = 1 ... n-2 flux values removed from each lightcurve

• Fvar measurements reliable for all but the smallest (n 10) samples

nn-d

0.2 0.4 0.6 0.8 1

Fvar

-0.1

0

0.1

0.2

0.3

0.4

0.5 ASM

nn-d

0 0.2 0.4 0.6 0.8 1

Fvar

0

0.1

0.2

0.3

0.4

0.5 PCAn

n-d0 0.2 0.4 0.6 0.8 1

Fvar

0

0.05

0.1

0.15

0.2

0.25

0.3 GASP

nn-d

0 0.2 0.4 0.6 0.8 1

Fvar

0.2

0.25

0.3

0.35

0.4 UVOT W2n

n-d0 0.2 0.4 0.6 0.8 1

Fvar

00.05

0.10.15

0.20.25

0.30.35

0.40.45 Whipple

nn-d

0 0.2 0.4 0.6 0.8 1

Fvar

0

0.1

0.2

0.3

0.4

0.5

0.6 Metsähovi

!

Mrk

421


PRELIMINARY

• d = 1 ... n-2 flux values removed from each lightcurve

• Fvar measurements reliable for all but the smallest (n 10) samples!

ASM

PCA

GASP

UVOT W2

Whipple

Metsähovi

nn-d

0 0.2 0.4 0.6 0.8 1

Fvar

0.050.060.070.080.09

0.10.110.120.13

nn-d

0 0.2 0.4 0.6 0.8 1

Fvar

00.020.040.060.08

0.10.120.140.160.18

nn-d

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Fvar

-0.3-0.2-0.1

00.10.20.30.4

nn-d

0 0.2 0.4 0.6 0.8 1

Fvar

-0.05

0

0.05

0.1

0.15

0.2

0.25

nn-d

0 0.2 0.4 0.6 0.8 1

Fvar

0.2

0.4

0.6

0.8

1

1.2

nn-d

0 0.2 0.4 0.6 0.8 1

Fvar

0

0.05

0.1

Mrk

501


P R E L I M I N A R Y

P R E L I M I N A R Y

Correlations

Mrk 421: clear correlation between VHE and X-raysDiscrete correlation function (Edelson & Krolik 1988)

Mrk 501: no correlation between VHE and X-rays

Mkn 421MAGIC – Whipple

–200 –100 0 100 200–1.0

0.5

–0.0

–0.5

1.0

!! [d]

DC

F

Mkn 421ASM – PCA

–200 –100 0 100 200–1.0

0.5

–0.0

–0.5

1.0

!! [d]

DC

F

Mkn 421MAGIC – PCA

–200 –100 0 100 200–1.0

0.5

–0.0

–0.5

1.0

!! [d]

DC

FMkn 501

Whipple – PCA

–200 –100 0 100 200–1.0

0.5

–0.0

–0.5

1.0

!! [d]

DC

FMkn 501

XRT – PCA

–200 –100 0 100 200–1.0

0.5

–0.0

–0.5

1.0

!! [d]

DC

F

Mkn 501VERITAS – Whipple

–200 –100 0 100 200–1.0

0.5

–0.0

–0.5

1.0

!! [d]

DC

F Mrk 501

Mrk 421

Conclusions & Outlook• 2009 MWL campaings on Mrk 421 and Mrk 501

• preliminary results on variability:

- both sources in low activity state

- Mrk 421: - Fractional variability Fvar low but significant at all frequencies, largest in

X-rays

- Mrk 501: - flare in VHE in May 2009, accompanied by changes in optical

polarisation and EVPA- Mrk 501: Fractional variability Fvar increases with frequency, largest in

VHE due to flare

• Problem of unevenly and unequally sampled lightcurves: first quick test shows that Fvar is not significantly affected by sampling, gaps and different number of flux measurements

• more detailed analysis of the variability and correlation studies (discrete correlation functions) under way

SED fitting parameters

Mrk 501: Stawarz’s codeAbdo et al., 2011, ApJ, 727, 129

Mrk 421: Finke’s codeAbdo et al., 2011, ApJ, 736, 131

log(frequency [Hz])10 12 14 16 18 20 22 24 26 28

0

0.2

0.4

0.6

0.8

1 and its uncertainty calculated using Vaughan et al. 2003varF

moving block jackknife estimate and variance

var

F

Fermi

UVOTMetsähovi

OVRO

Whipple

MAGIC

PCA

ASM

BAT

XRTa

XRTb

• removed block of m consecutive flux measurements, m=n1/3

• somewhat larger errors

PRELIMINARY

Mrk 421


PRELIMINARY

log(frequency [Hz])10 12 14 16 18 20 22 24 26 28

0

0.2

0.4

0.6

0.8

1 and its uncertainty calculated using Vaughan et al. 2003varF

moving block jackknife estimate and variance

var

F

Fermi

UVOTMetsähovi

OVRO

MAGIC

PCA

ASM

BAT

XRTa

XRTb

VERITAS

WhippleMrk 501


• removed block of m consecutive flux measurements, m=n1/3

• somewhat larger errors

Documents

Radio-to-Gamma Ray Monitoring of Mkn 421 and Mkn 501: Source Variability › science › mtgs › fermi_jansky › ... · 2012-01-06 · Radio-to-Gamma Ray Monitoring of Mkn 421 and