The current status of the Fermi/Gamma ray Burst Monitor (GBM) and the Magnetar Key Project

C. Kouveliotou (NASA/MSFC) on behalf of the GBM and the Magnetar teams The Fermi Observatory Launched 2008 June 11 Large AreaTelescope (LAT) 20 MeV ->300 GeV

Gamma-ray Burst Monitor (GBM) NaI and BGO Detectors 8 keV - 40 MeV

KEY FEATURES

Spacecra Partner: General Dynamics • Large field of view LAT: 20% of the sky at any instant; in sky survey mode, expose all parts of sky for ~30 minutes every 3 hours. GBM: whole unocculted sky at any time. • Over 7 decades energy range largely unexplored band 10 GeV - 100 GeV GBM • 4 x 3 NaI Detectors with different orientations. • 2 x 1 BGO Detector either side of spacecraft. • View entire sky while maximizing sensitivity to events seen in common with the LAT

The Large Area Telescope (LAT)

GBM BGO detector. 200 keV -- 40 MeV 126 cm2, 12.7 cm Spectroscopy Bridges gap between NaI and LAT.

GBM NaI detector. 8 keV -- 1000 keV 126 cm2, 1.27 cm Triggering, localization, spectroscopy. • GBM Triggered sources – Gamma-ray bursts (GRBs) – Soft gamma repeaters (SGRs) aka magnetars – Terrestrial gamma flashes (TGFs) – Short transients detected by on-board trigger algorithm – Solar Flares • Non-triggered sources – Pulsed sources detected by power spectral analysis and/or epoch folding – Longer-term transients and persistent sources detected by Earth occultation Paciesas et al. 2010 – Locations Trigger Summary (July 12, 2008 - • RA, Dec July 11, 2009) – Durations Gamma-Ray Bursts 258 • (t50, t90) in 50–300 keV – Peak flux (ph/cm2-s) Soft Gamma Repeaters 168 • 64 ms, 256 ms, 1024 ms Terrestrial Gamma 12 • 50–300 keV, 10–1000 keV Flashes – Fluence (erg/cm2) Solar Flares 1 • 50– 300 keV, 10–1000 keV – Light curves Particles (local or distant) 17 Commanded tests 62 Will be accessible on-line through FSSC Others (sources, accidentals, 35 unclassifiable) Total 553

Current total number of GRBs detected: 448 Goldstein et al. 2010, Preece et al. 2010

1. The “Peak Flux and Fluence” Spectral Catalog: Two Spectra from all but the weakest GRBs: 2.048 s Peak Flux Spectrum > 3.5 sigma integrated Fluence Spectrum Approximately 200 bursts per year (BATSE Heritage: Mallozzi et al. 1995; Goldstein et al. 2010) 2. The “Time-Resolved” Spectral Catalog for Bright Bursts: At least two spectra for each burst, fit as a time sequence: > 15 sigma integration for each spectrum Approximately 50 bursts per year (BATSE Heritage: Preece et al. 2000; Kaneko et al. 2006)

Four Spectral Models Fit to each spectrum: – Power Law: A & α

– Exponentially-attenuated Power Law (“Comptonized”): A, α & Epeak

– Band function: A, α, β & Epeak

– Smoothly-Broken Power Law: A, α, β, Δ & Ebreak

Will be accessible on-line through FSSC

Band (Cstat: 699/607 dof) Cutoff PL + PL (Cstat: 689/606 dof)

10000 10000

1000 α β 1000

100 100 PL Cutoff PL

10 10 Epeak

6 6

0 0

‐6 ‐6 10 100 1000 10000 10 100 1000 10000 Energy (keV) Energy (keV)

Cutoff PL+PL prefered over the Band function => Additional component ?

Guiriec et al. 2010 Guiriec et al. 2010

100 8 to 200 keV 1600 80 1200 60 800 40

20 400

0 0 9 1600 8 1 to 38 MeV 7 1200 6 5 4 800 3 2 400 1 0 0 0.05 0.1 0.15 0.2 0 Time since GBM trigger in seconds Fermi/GBM Accreting Pulsars GBM Key Project PI: M. Finger

Persistent Sources Her X-1 1.24 1.70 Eclipsing LMXB Cen X-3 4.80 2.09 Eclipsing Disk-fed HMXB 4U 1626-67* 7.63 0.023 Super-Compact LMXB OAO 1657-415 37.1 10.4 Eclipsing Wind-fed HMXB GX 1+4 158 1161 Symbiotic Binary (red giant+ns) Vela X-1 283 8.96 Eclipsing Wind-fed HMXB 4U 1538-52 525 3.73 Eclipsing Wind-fed HMXB GX 301-2 686 41.5 Wind-fed HMXB Transient Sources V 0332+53 4.37 34.2 Be/X-ray Binary 2S 1417-624 17.5 42.1 Likely Be/X-ray Binary Swift J0513.4-6547 27.3 ? Likely Be/X-ray Binary in LMC EXO 2030+375 41.3 46.0 Be/X-ray Binary Cep X-4 66.3 ? Be/X-ray Binary GRO J1008-57 93.7 248 Be/X-ray Binary A 0535+26 103 111 Be/X-ray Binary MXB 0656-072 160 ? Be/X-ray Binary LS V +44 17 205 ? Persistent Be/X-ray Binary? GX 304-1 275 132 Be/X-ray Binary A 1118-615 407 ? Be/X-ray Binary

*Camero-Arranz et al. 2009 Times of Transient Outbursts

October 2008

http://gammaray.msfc.nasa.gov/gbm/science/pulsars/ • Twelve TGFs in year 1 Fishman et al. 2010 – Rate is higher now by ~8X, due to inclusion of BGO detectors in trigger algorithm – Over 50 to date • Duration < ~1 ms, maximum energy > ~40 MeV – High instantaneous rates imply significant deadtime & pulse pile-up • Associated with thunderstorms: – “Runaway electron” process produces gamma-rays – Sometimes GBM detects electrons  & positrons directly Briggs et al 2010 WWLLN sferics  others

Connaughton et al. 2010 Two Well-separated, Double-Pulse TGFs seen with GBM, All Detectors – Time Profiles

Narrowest Pulse seen with GBM, ~0.08 ms

Weakest Pulse

Fishman et al. 2010, TGF Catalog • Using the EOT we are currently monitoring 70 sources, including the Sun.

• To date, we detect 8 of these sources above 100 keV: 1E 1740-29, Cen A, Crab, Cyg X-1, GRS 1915+105, Swift J1753.5-0127, XTE J1752-223, and GX339-4 (Case et al. 2010).

• Preliminary detections for 55 sources below 100 keV (either > 10 sigma long-term average or activity coincident with other observatories) including Mrk 421 (Wilson-Hodge et al. 2010).

• This is our “bright source” catalog and consists primarily of X- ray binaries, the Crab, and a few AGN (currently active transients and sources added by request).

http://gammaray.msfc.nasa.gov/gbm/science/occultation/ PI: Chryssa Kouveliotou SGR Source Active Period Triggers Comments

J0501+4516 08/22/08-09/03 26 New source at Perseus /08 arm 1806-20 11/29/08 1 Old source - reactivation J1550-5418 10/03/08-10/20 7 Known source – first time /08 117 exhibiting burst active 01/22/09-02/24 14 episodes /09 03/22/09-04/17 /09 J0418+5729 06/05/09 2 New source at Perseus arm SGR 1833-0832 discovered 10/03/19 with Swift and RXTE – no GBM detection http://gammaray.nsstc.nasa.gov/gbm/science/magnetars Magnetars are magnetically powered neutron stars

~17 are discovered to date – three in 2008-2010 – Only 2 extragalactic sources

Discovered in X/γ-rays; radio, optical and IR observations: Short, soft repeated bursts . P = [2-11] s, P ~[10-11- 10-13]s/s . τspindown(P/2 P)= 2-220 kyrs . B~[1-10]x1014 G (mean surface dipole field: 3.2x1019√PP)

Bright sources, L~1033–36 erg/s , >> rotational E-loss

No evidence for binarity so far (fallback disks?)

SNe associations? Neutron star populations which may comprise Magnetars:

Soft Gamma Repeaters (SGRs)

Anomalous X-ray Pulsars (AXPs)

Dim Isolated Neutron Stars (DINs)

Compact Central X-ray Objects (CCOs)

Rotation Powered PSRs?! PSR J1846−0258 PSR J1846−0258

SGR 0418+5729 SGR 1833-0832 2008-2010: Good years for Magnetars!

Fermi

IPN

Swift

RXTE SGR 0501+4516

Swift triggered on 4 bursts on 22 August 2008

RXTE ToO program triggered ~4 hours after the first Swift trigger for 600 s

P = 5.7620 s was reported ~ 9 hours after the first Swift trigger! . P = 7.4980x10-12 and B = 2.1 x 1014 G

CXO HRC location: RA = 05h 01m 06.756s DEC = +45d 16m 33.92s (0.1” error)

IR Counterpart with UKIRT, K~18.6 (Tanvir & Varricatt 2008)

GBM triggered on 26 events from the source – total of 56 events in ~ 3.5 days BURSTS

Suzaku data for 080826_136: Integrated spectrum best fit by 2 BB: kT1 = 3.3 keV, kT2 = 15.1 keV

Enoto et al. 2009 GBM data for 080826_136 (common with Suzaku):

Integrated spectrum can be fitted with two BB or one BB + PL kT1 = 8 keV, kT2 = 18 keV or kT = 11 keV, γ = -2.4

Watts et al. 2010 Lin Lin et al. 2010 PRE in thermonuclear bursts

• Luminosity reaches Eddington limit, triggering Photospheric Radius Expansion (PRE). • Expanding layers cool, leading to a multi-peaked light curve. • Standard candle to measure a neutron star distance or mass/radius and hence equation of state.

Watts et al 2010 PRE in thermonuclear bursts

>10 keV

5-10 keV Counts/s 2-5 keV

Time PRE in magnetar bursts

• Identifying PRE during a magnetar burst would give us the magnetic Eddington limit. If the magnetic field is known (e.g. from timing) this would again constrain distance/equation of state.

Miller 1995

• PRE can only occur under certain burst emission scenarios. A PRE burst will therefore also constrain the burst trigger mechanism, a major unknown. The first magnetar candidate PRE burst

Other candidate PRE bursts being investigated!

Watts et al. 2010

• Distance and field strength known.

• Predicted critical flux matches that recorded by GBM!

• Emission becomes softer during the dip in the lightcurve. SGR 1550-5418 formerly known as AXP 1E1547.0-5408 formerly known as an ASCA CCO in G327.0-0.13

Three episodes detected with GBM: Oct. 2008, Jan. & Mar. 2009

P = 2.069s . P = 2.318 x 10-11 s/s and B = 2.2 x 1014 G

Near IR detection, Ks = 18.5±0.3

GBM triggered on 131 events from the source; many more in the data SGR 1550–5418 Bursting Activity

Von Kienlin et al. 2010 Van der Horst et al. 2010 Van der Horst et al. 2010 450 bursts on one day…

…even when the Earth is in the way! Adopting a distance to the SGR of 5 kpc, we estimate a total isotropic- equivalent energy release of 1042 ergs during this activation. Magnetar twist and shake…

Kaneko et al. 2010 Spectral Analysis Time Integrated Spectrum [T0 + 72 – 248 s]

8 – 909 keV Burst Free

Power Law

Total Energy Additional Blackbody (kT = 18 keV) : 40 4.3 × 10 ergs DCstat = 13.5 (for 2 DOF)

Kaneko et al. 2010 Time Resolved Spectra (n Fn) [T0 + 72 – 117, 122 – 169, 173 – 223 s] 74 – 117 s Power Law only (Blackbody is not needed)

122 –169 s 173 –223 s

Power Law Power Law Blackbody Blackbody

FBB/FTOTAL = 26% 25% Kaneko et al. 2010 Temporal Properties Spectral Properties • Pulsations most significant • Blackbody required in in 120 – 210 s 122 – 223 s

• Pulse fraction peaks in • Blackbody kT ~ 17 keV 50 – 74 keV (Wien peak ~50 keV)

• Pulsations not seen above • FBB  25% 110 keV FPWRL  75%

Kaneko et al. 2010 Assuming a hot spot of radius RHS on the neutron star surface

For D = 5 kpc, kT = 17 keV :

2 2 Hot AHS ≈ 0.044 (D/5 kpc) km Spot  RHS ≈ 120 m which is the size of the magnetically- confined hot plasma and is << 1% of

the NS surface area Kaneko et al. 2010 SGR 0418+5729

GBM triggered on 5 June 2009 – new source confirmed with IPN

RXTE ToO program triggered ~ 4 days after the GBM triggers

P = 9.0783(1) sec . ν ~ 2 x 10-14 Hz/s at 3σ and B < 1014 G

CXO location: RA = 04h 18m 33.867s, Dec = +57d 32' 22.91"

No IR (Ks > 21.3, Wachter et al 2009) or optical (R > 24, Ratti, Steeghs & Jonker 2009) counterpart detected

GBM triggered on 2 events from the source Magnetar Candidates SGR burst time history with Fermi/GBM

(2)

SGR 1550-5418 (7/131)

SGR 0501+4516 (26)

SGR 0418+5729 (2) CONCLUSIONS I • GBM Triggered sources – Gamma-ray bursts (GRBs): ~ 450 – Soft gamma repeaters (SGRs) aka magnetars: 4 – Terrestrial gamma flashes (TGFs): 50 – Short transients detected by on-board trigger algorithm: 1-2 – Solar Flares: 2-3 • Non-triggered sources – Pulsed sources detected by power spectral analysis and/or epoch folding: ~ 20 – Longer-term transients and persistent sources detected by Earth occultation: 8 CONCLUSIONS II

We still do not understand the differences – if any – between AXPs, SGRs and rotationally powered pulsars, in: persistent emission spectra glitching properties magnetic field strengths burst fluences and spectra

The associations of magnetars with SNRs, and their environments and track possible proper motions, now with two best candidates

The progenitor properties of magnetars, such as mass and cluster memberships

Could we identify PRE in magnetar flares and probe the neutron star EOS?