HE and VHE Galactic Highlights Marc Rib OUTLINE 1. Introduction - - PowerPoint PPT Presentation
High Energy Phenomena in Relativistic Outflows III Barcelona, 27 June-1 July 2011 HE and VHE Galactic Highlights Marc Rib OUTLINE 1. Introduction 2. HE and VHE Galactic sources 3. Pulsars 4. Globular clusters 5. Pulsar Wind Nebulae
Barcelona, 27 June-1 July 2011
1. Introduction 2. HE and VHE Galactic sources 3. Pulsars 4. Globular clusters 5. Pulsar Wind Nebulae 6. X-ray binaries 7. Gamma-ray binaries 8. Conclusions
Two year of Fermi satellite image of the sky (Vandenbroucke et al. 2010).
http://www.mppmu.mpg.de/~rwagner/sources/ http://tevcat.uchicago.edu/ Known VHE sources As of 2011 May, there are ~115 sources known! ~50 extragalactic, ~65 galactic.
HE Galactic sources Supernova Remnants (~10) Pulsars (>60) Globular clusters (~10) Pulsar Wind Nebulae (5) Colliding wind binaries: Eta Carinae (1) Nova in symbiotic binary: V407 Cyg (1) X-ray binaries: Cyg X-3 + Cyg X-1 (1+1?) Gamma-ray binaries (4) VHE Galactic sources Galactic Center and Galactic ridge (1+1) Supernova Remnants and SNR/MC (15) Open clusters and stellar assoc. (2+2?) Pulsars: Crab (1) Globular clusters: Terzan 5 (1?) Pulsar Wind Nebulae (20) X-ray binaries: Cyg X-1 (1?) Gamma-ray binaries (4)
HE/VHE Galactic sources with relativistic outflows HE VHE Pulsars > 80 1 Globular clusters ~ 10 1? Pulsar Wind Nebulae ~ 5 ~ 20 X-ray binaries 1+1? 1? Gamma-ray binaries 4 4 (5 in total)
Fermi/LAT has detected (Abdo et al. 2010):
Most important results of the Fermi/LAT pulsar catalog (Abdo et al. 2010):
the outer magnetosphere, while polar-cap emission remains plausible for a few.
the radio-selected ones. The birthrate of all young gamma-ray-detected pulsars is a substantial fraction of the expected Galactic supernova rate.
Most important results of the Fermi/LAT pulsar catalog (Abdo et al. 2010):
the outer magnetosphere, while polar-cap emission remains plausible for a few.
the radio-selected ones. The birthrate of all young gamma-ray-detected pulsars is a substantial fraction of the expected Galactic supernova rate.
Pulses from the Crab at tens of GeV! MAGIC detected a pulsed signal from the Crab at E > 25 GeV (Aliu et
Cherenkov Telescope. The pulsed signal occurs at the same spin phases as those observed with EGRET (E> 100 MeV) and simultaneous MAGIC/optical data (central pixel). This has been possible thanks to a new trigger system (sum-trigger). Conclusion: The energy cut-off in the phase-averaged spectrum is relatively
happens far out in the
the polar cap model and challenge the slot gap model.
Pulses from the Crab at tens of GeV! MAGIC detected a pulsed signal from the Crab at E > 25 GeV (Aliu et
Cherenkov Telescope. The pulsed signal occurs at the same spin phases as those observed with EGRET (E> 100 MeV) and simultaneous MAGIC/optical data (central pixel). This has been possible thanks to a new trigger system (sum-trigger). Conclusion: The energy cut-off in the phase-averaged spectrum is relatively
happens far out in the
the polar cap model and challenge the slot gap model.
GeV emitting globular clusters as seen by Fermi/LAT (Abdo et al. 2010):
indices (0.7 < Γ < 1.4) and clear evidence for an exponential cut-off in the range 1.0−2.6 GeV, which is the characteristic signature of magnetospheric emission from MSPs.
properties.
expected to be present in these globular clusters can be estimated.
See also Tam et al. (2011) and Hui et al. (2011) for recent updates.
HESS J1747-248, overlapping with Terzan 5, detected at TeV energies by HESS (Abramowski et al. 2011). Terzan 5 has the largest population of identified millisecond pulsars, a very high core stellar density and the brightest GeV range flux as measured by Fermi/LAT. The nature of HESS J1747-248 is uncertain, since no counterpart or model can fully explain the observed
Terzan 5 is tantalizing, but the available data do not firmly prove this scenario.
Young (<105 year old) pulsars produce relativistic winds of electron/positron pairs. In the presence
magnetic fields, these pairs produce synchrotron radiation from radio to keV-MeV energies, and inverse Compton radiation from MeV to TeV energies. The extended morphologies of these radio, X-ray and TeV emissions are often trailing the motion of the pulsar in the ISM.
Funk et al. (2007).
The Pulsar Wind Nebula MSH 15-52 as been detected as an extended source by Fermi/LAT (Abdo et al. 2010). The extended GeV emission is coincident with the HESS extended emission (contours in the figure). E > 1 GeV E > 10 GeV
HESS J1825–137 (PSR J1826–1334). Offset position from radio to X-rays. First evidence of energy-dependent morphology at TeV gamma-rays: softening with distance synchrotron cooling. X-ray emitting particles cool faster than TeV emitting ones, hence the smaller X-ray size. Spectral evolution favors leptonic IC scenario, but not sufficient. The high γ-ray luminosity of the source cannot be explained on the basis of constant spin-down power of the pulsar and requires higher injection power in past. Trace the history of the spin- down luminosity (Aharonian et al. 2006).
keV image TeV image red – below 0.8 TeV yellow – 0.8-2.5 TeV blue – above 2.5 TeV
The standard candle that does not behave as such! The Crab Nebula is powered by the Crab pulsar, which has a rotational energy loss of 5×1038 erg s−1, and a period of 33 ms. Four GeV flares have been detected up to now. Nothing remarkable in the
but no enhancement seen by VERITAS and MAGIC. Everything in ATels still. From Tavani (2011, Texas Symposium).
September 2010, October 2007 flares seen by AGILE (Tavani et al. 2011). The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from PeV electrons in a region smaller than 1.4 × 10−2 pc. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory (Abdo et al. 2011). February 2009, September 2010 flares seen by Fermi/LAT (Abdo et al. 2011).
The spectrum flattens significantly during the 2010 flare as seen by Fermi/LAT (Abdo et al. 2011).
Conclusions by Bednarek & Idec (2011):
be extension of the broadband synchrotron spectrum from the Crab Nebula.
before reaching the shock.
baseline emission.
GeV energies.
April 2011 flare as seen by Fermi/LAT (Buehler et al. 2011, Fermi Symposium). New spectral component
power law of index 1.6 and exponential cutoff at 580 MeV (pulsar like, but no sign of pulsation in flare photons).
Mirabel 2006, (Perspective) Science 312, 1759
Cygnus X-3, Cygnus X-1 LS 5039 ? LS I +61 303 ? PSR B1259−63 HESS J0632+057 ? 1FGL J1018.6−5856 ? Models are not so simple…
Several X-ray binaries with relativistic outflows, aka microquasars, have been observed at HE and VHE:
et al. 2009) and upper limits by MAGIC (Aleksic et al. 2010).
detected by MAGIC (Albert et al. 2007). Not detected by Fermi/LAT.
ICRC; Acero et al. 2009).
Several X-ray binaries with relativistic outflows, aka microquasars, have been observed at HE and VHE:
et al. 2009) and upper limits by MAGIC (Aleksic et al. 2010).
detected by MAGIC (Albert et al. 2007). Not detected by Fermi/LAT.
ICRC; Acero et al. 2009).
Review by W. Bednarek
Microquasars as HE/VHE gamma-ray sources from the theoretical point of view. Leptonic models: Inverse Compton Synchrotron Self Compton (SSC) Atoyan & Aharonian 1999, MNRAS, 302, 253 Latham et al. 2005, AIP CP, 745, 323 External Compton (EC) Paredes et al. 2000, Science, 288, 2340 Kaufman Bernadó et al. 2002, A&A, 385, L10 Georganopoulos et al. 2002, A&A, 388, L25 SSC+EC Bosch-Ramon et al. 2004, A&A, 417, 1075 Dermer & Böttcher 2006, 643, 1081 Synchrotron jet emission Markoff et al. 2003, A&A 397, 645 Hadronic models: Pion decay Romero et al. 2003, A&A, 410, L1 Bosch-Ramon et al. 2005, A&A, 432, 609 Wind of the companion. Interstellar medium.
Cygnus X-3, containing a WR donor and an accreting compact object
detected >100 MeV by AGILE and Fermi/LAT (Tavani et al. 2009, Abdo et al. 2009). Active periods span 50-70 d, with several GeV flares correlated with radio flares that lag 5±7 d (Abdo et al. 2009).
Cygnus X-3. Fermi/LAT data reveal orbital periodicity during active periods, which in turn take place during high/soft states of the source as seen from RXTE/ASM and Swift/BAT data.
Cygnus X-3. Application of an old idea: GeV emission is produced when relativistic electrons in the jet up-scatter photons emitted by the Wolf– Rayet star. The GeV orbital variability is naturally explained. Modelling shows that the jet must be inclined and oriented close to the line of sight, and that the gamma-ray emitting electrons cannot be located within the system (Dubus et al. 2010). See also Bednarek (2010) for predictions in the sub-TeV regime.
Cygnus X-3. It has been extensively observed with MAGIC, providing upper limits in different spectral states, including observations contemporaneous to GeV detections by Fermi/LAT (Aleksic et al. 2010).
Cygnus X-1, containing an O9.7Iab donor and an accreting black hole of at least 10 solar masses orbiting it every 5.6 days, in a circular orbit. It has been detected >100 MeV by AGILE (Sabatini et al. 2010, ApJ and ATel) but not by Fermi/LAT (Abdo et al. 2010, ATels and Fermi/LAT blog). The detection spans 1 d in about 2 years of observations, and has a 5.3σ pre- trial significance, which is 4σ post-trial. It occurred during a low luminosity low/hard state (Sabatini et al. 2010).
Cygnus X-1.
24h] flaring episode discovered by MAGIC on 24-09-2006.
(Albert et al. 2007, ApJ, 665, L51).
5 gamma-ray binaries (SED peak at MeV-GeV) detected at HE and/or VHE:
2005).
All of them are found in HMXBs, were:
decay.
Parameters PSR B1259-63 LS I +61 303 LS 5039 HESS J0632+057 1FGL J1018.6-5856 Components O9.5Ve + NS B0Ve + ? O6.5V((f)) + ? B0Vpe + ? O6V((f)) + ? Distance (kpc) 2.3 2.0 2.5 ~1.5 ~5 Orbital Period (d) 1237 26.5 3.9 320 16.6 Eccentricity 0.87 0.72 0.35 ? ? Inclination (º) 23 30 ± 20 10–75 ? ? Periastron-apastron (AU) 0.9–13.4 0.1–0.7 0.1–0.2 ~3 ~0.4 Radio emission Periodic (48ms and 3.4yr) Periodic (26.5d and 4yr) Persistent Variable Periodic Radio structure (AU) ~Cometary tail 120 ~Cometary tail 10–700 ~Cometary 10–1000 ~Jet-like? 60 ? X-ray emission Periodic ~Periodic Periodic ~Periodic Periodic GeV emission Transient ~Periodic Periodic ? Periodic TeV emission Periodic ~Periodic Periodic Periodic? ? Pulsations Radio ? ? ? ?
General properties of gamma-ray binaries:
separations (0.1-10 AU).
next).
X-ray flux is modulated with the
period, but with maximum≠periastron. No clear accretion signatures, no X-ray pulsations.
pulsar magnetospheres, but the emission is variable(!) and periodic.
Parameters PSR B1259-63 LS I +61 303 LS 5039 HESS J0632+057 1FGL J1018.6-5856 Components O9.5Ve + NS B0Ve + ? O6.5V((f)) + ? B0Vpe + ? O6V((f)) + ? Distance (kpc) 2.3 2.0 2.5 ~1.5 ~5 Orbital Period (d) 1237 26.5 3.9 320 16.6 Eccentricity 0.87 0.72 0.35 ? ? Inclination (º) 23 30 ± 20 10–75 ? ? Periastron-apastron (AU) 0.9–13.4 0.1–0.7 0.1–0.2 ~3 ~0.4 Radio emission Periodic (48ms and 3.4yr) Periodic (26.5d and 4yr) Persistent Variable Periodic Radio structure (AU) ~Cometary tail 120 ~Cometary tail 10–700 ~Cometary 10–1000 ~Jet-like? 60 ? X-ray emission Periodic ~Periodic Periodic ~Periodic Periodic GeV emission Transient ~Periodic Periodic ? Periodic TeV emission Periodic ~Periodic Periodic Periodic? ? Pulsations Radio ? ? ? ?
D.F. Torres, V. Zabalza
Review by G. Dubus This talk This talk This talk This talk This talk
Binary pulsars as HE/VHE γ-ray sources from the theoretical point of view. A possible scenario comes from the application of the pulsar wind nebulae formed with the interaction of a relativistic pulsar wind with the ISM… but where the wind of the companion plays the role of the ISM. The stagnation point, where the pressure from the two winds is balanced, is within the binary system. Particles are accelerated at the termination shock and produce the non-thermal synchrotron emission (Maraschi & Treves 1981, Dubus 2006).
UV photons from the companion star suffer inverse Compton scattering by the same population of non-thermal particles, leading to emission in the GeV-TeV energy range. Particles move downstream away from the pulsar at a speed v (initially ≈c/3). A cometary nebula of radio emitting particles is formed. It rotates with the
2006). PSR B1259−63 at 5 GHz.
UV photons from the companion star suffer inverse Compton scattering by the same population of non-thermal particles, leading to emission in the GeV-TeV energy range. Particles move downstream away from the pulsar at a speed v (initially ≈c/3). A cometary nebula of radio emitting particles is formed. It rotates with the
2006). PSR B1259−63 at 5 GHz. Problem: to explain the SED, the spin-down luminosity of the pulsar has to be very high, and the wind of the companion cannot confine the accelerated particles behind the pulsar (Romero et al. 2007). Detailed RHD simulations reveal non-trivial effects, with extreme Lorentz factors downstream of the flows (Bogovalov et al. 2008).
LS I +61 303. Jet-like features have been reported several times, but show a puzzling behavior (Massi et al. 2001, 2004). Later VLBI observations show a rotating jet-like structure (Dhawan et al. 2006). Orbital phase: 3.6cm images, ~3d apart, beam 1.5x1.1mas
Discovery of extended and variable radio emission from PSR B1259-63 with LBA observations conducted around the 2007 periastron passage (Moldón et al. 2011). The peak of the radio emission is detected
This is the first observational evidence that non- accreting pulsars orbiting massive stars can produce variable extended radio emission at AU scales. (Dubus 2006) The red crosses mark the region where the pulsar should be located at each epoch. (Moldón et al. 2011)
(1999) (2007) (2000)
Orbital Phase
0.0 1.0 0.5
0.98 0.10 0.23 0.44 0.49 0.72 0.75 0.00
Orbital morphological variability of LS 5039. Images at the same phase have similar morphology. Images between adjacent runs show a hybrid morphology of the two runs. (Moldón et al., in prep).
Orbital astrometric variability of LS 5039. The modeling by Dubus (2006) predicts orbital astrometric variability at mas scales in the non- accreting pulsar scenario. We have just measured a displacement after the periastron passage in the VLBA images
is not compatible with the predicted
The origin of LS 5039 (see poster by Moldón et al. outside). Updated proper motion of LS 5039 suggests an origin in SNR G016.8-01.1 about 105 yr ago. However, PSR J1825-1446 also appears to come from the same SNR about 2x104 yr ago, although the characteristic age is one order of magnitude bigger (Moldón et al., in preparation).
HESS J0632+057 EVN observations during the February 2011 X-ray and TeV
with the Be star (astrometry).
nature of the radio source (compactness).
extended emission one month after the outburst. (Moldón et al., in prep.).
PSR B1259-63. Recent VLT/UVES spectroscopy, photometry, and atmosphere model fitting strongly supports LS 2883 as a member of Cen OB1, located at 2.3±0.4 kpc. The new spectral type is O9.5 Ve (although with a very fast rotation of v·sin(i)≈260 km s-1), Teff= 27500-34000 K, Lopt ≈ 2.3×1038 erg s-1, Mopt ≈ 30 Msun and iorb≈23º (Negueruela et al. 2011). Atmosphere model fitting to the photospheric lines with FASTWIND. Distance estimate based on the edges of IS absorption lines and a Galactic rotation curve.
PSR B1259-63. Expected GeV emission from inverse Compton scattering of stellar photons by the unshocked pulsar wind electrons during the periastron passage (Khangulyan et al. 2011a, subm.; see also poster outside).
PSR B1259-63. 2010 periastron passage by Fermi/LAT (Abdo et al. 2011). (Khangulyan et al. 2011a, subm.)
PSR B1259-63. 2010 periastron passage by Fermi/LAT (Tam et al. 2011).
PSR B1259-63. Interaction with the Be disk to explain the GeV flares (Khangulyan et al. 2011b, subm.; see poster outside). At periastron During the GeV flares:
Courtesy of Javier Moldón LS 5039 Porb = 3.9 day O6.5 V + ? LS I +61 303 Porb = 26.5 day B0Ve + ? PSR B1259-63 Porb = 3.4 yr O8.5Ve + pulsar On the lack of pulsations in LS 5039 and LS I +61 303
Courtesy of Javier Moldón LS 5039 Porb = 3.9 day O6.5 V + ? LS I +61 303 Porb = 26.5 day B0Ve + ? PSR B1259-63 Porb = 3.4 yr O8.5Ve + pulsar Radio pulses disappear On the lack of pulsations in LS 5039 and LS I +61 303
Courtesy of Javier Moldón LS 5039 Porb = 3.9 day O6.5 V + ? LS I +61 303 Porb = 26.5 day B0Ve + ? PSR B1259-63 Porb = 3.4 yr O8.5Ve + pulsar Radio pulses disappear On the lack of pulsations in LS 5039 and LS I +61 303 Radio pulses disappear ? Radio pulses disappear ?
LS I +61 303. We have conducted a search for radio pulsations in LS I +61 303 with the Giant Metrewave Radio Telescope (GMRT) at 1.28 GHz. Observations were conducted at orbital phase ~0.55, ~when free-free absorption is expected to be less important. Averaged flux density upper limits of the order of 1 mJy have been obtained (PSR B1259-63 displays ~5 mJy) (Cañellas et al., in prep.).
Our GMRT upper limit on the pulsed emission of LS I +61 303 in the context
pulsations or more constraining upper limits. Several spectral indexes and absorption have been considered (Cañellas et al., in prep.). Searches by other groups using the Green Bank Telescope at 2 and 5 GHz have been conducted, with negative results (unpublished so far). Searches in X rays have also been performed with Chandra (Rea et al. 2010).
Timing analysis of Fermi/LAT data, as the one that has lead to the discovery of 1FGL J1018.6-5856, can provide lots of new gamma-ray binaries. We are just seeing the tip of the iceberg! (Corbet 2011, Fermi Symposium).
MAGIC and VERITAS are providing a new view of the Galactic sky.
sources: young isolated pulsars, recycled ms pulsars, pulsar wind nebula, globular clusters containing several ms pulsars.
binary pulsar scenario (but see next talk for caveats). New sources found.