VERITAS: Status and Highlights

Transcription

1 VERITAS: Status and Highlights Jamie Holder 1 for the VERITAS Collaboration 2 1. Bartol Research Institute/ University of Delaware nd ICRC Beijing, August 2011

2 1 Smithsonian Astrophysical Observatory Purdue University Iowa State University Washington University in St. Louis University of Chicago University of Utah University of California, Los Angeles McGill University, Montreal University College Dublin University of Leeds Adler Planetarium Argonne National Laboratory Barnard College DePauw University Bartol Research Institute/ University of Delaware Grinnell College University of California, Santa Cruz University of Iowa University of Massachusetts Cork Institute of Technology Galway-Mayo Institute of Technology National University of Ireland Galway DESY/Potsdam Pennsylvania State University ~95 Members +35 Associate Members

3 2 VERITAS: Fall 2009 Smithsonian Astrophysical Observatory Purdue University Iowa State University Washington University in St. Louis University of Chicago University of Utah University of California, Los Angeles McGill University, Montreal University College Dublin University of Leeds Adler Planetarium Argonne National Laboratory Barnard College DePauw University Bartol Research Institute/ University of Delaware Grinnell College University of California, Santa Cruz University of Iowa University of Massachusetts Cork Institute of Technology Galway-Mayo Institute of Technology National University of Ireland Galway DESY/Potsdam Pennsylvania State University ~95 Members +35 Associate Members

4 3 VERITAS Situated at 1250m altitude at the Whipple Observatory in Arizona 111m 2 tessellated mirrors Recoated every ~2 years 499 PMTs 12m MSPS sampling FADCs 3-level trigger

5 4 The Whipple 10-meter Mrk501, May minute bins In operation since 1968 Used to detect the first TeV source, the Crab Nebula, in 1989 (Weekes et al.) Established AGN as TeV sources in the 90 s Useful extension into the Fermi era as an AGN monitor Pichel et al., this meeting Mothballed, summer 2011

6 5 VERITAS Technical Performance Sensitive to 1% Crab in ~25 hours Angular resolution ~0.1 (68% containment) Energy resolution ~15-20% above 300GeV Energy threshold ~150 GeV Spectral performance strongly depends on choice of analysis cuts

7 6 The VERITAS Sky tevcat.uchicago.edu A pulsar, many blazars, a radio galaxy, a starburst galaxy, gamma-ray binaries, pulsar wind nebulae, supernova remnants, unidentified objects

8 7 At this meeting Benbow et al., Highlights of the VERITAS Blazar Observation Program, OG 2.3 Benbow et al., VHE Blazar Discoveries with VERITAS, OG 2.3 Pichel et al., Multi-wavelength observations during a VHE flare of Mrk 501 in May 2009, OG 2.3 Errando et al., Target of opportunity observations of flaring blazars with VERITAS, OG 2.3 Majumdar et al., Observations of selected IBLs and LBLs with VERITAS, OG 2.3 Orr et al., EBL Studies Using VERITAS Observations of Distant Blazars, OG 2.3 Senturk et al., VERITAS Discovery of the Blazar RBS 0413, OG 2.3 Galante et al., VERITAS observation of Mrk421 flaring: variability and spectral evolution, OG 2.3 Galante et al., The VERITAS extragalactic non-blazar program, OG 2.3 Aune et al., VHE follow-up observations of GRBs detected by Fermi and Swift, OG 2.4 Vivier et al., VERITAS observations of the SEGUE 1 dwarf spheroidal galaxy, HE 3.4 Maier et al., Long-term γ-ray observations of the binary candidate HESS J , OG 2.2 Maier et al., VHE Observations of Galactic binary systems with VERITAS, OG 2.2 McCann et al., VERITAS observations of the Crab pulsar, OG 2.2 Aliu et al., VERITAS observations in the vicinity of the Cygnus OB1 region & PWN, OG 2.2 Weinstein et al., Recent observations of Supernova Remnants with VERITAS, OG 2.2 Kieda et al., Status of the VERITAS Upgrade, OG 2.5 Otte et al., Upgrade of VERITAS with high efficiency photomultipliers, OG 2.5 Kieda et al., Orbit Mode observations of Crab and Mrk 421 Senturk et al., Disp Method for Large Zenith Angle VERITAS Observations

9 8 Extragalactic Sources: Blazars 22 AGN detected (10 VERITAS discoveries) Fermi-LAT guidance helps to increase and broaden the population HBL: 1ES IBL: B IBL: W Comae PRELIMINARY Benbow et al., Highlights of the VERITAS Blazar Observation Program, OG 2.3

10 9 Blazars 22 AGN detected (10 VERITAS discoveries) Fermi-LAT guidance helps to increase and broaden the population HBL: 1ES IBL: B IBL: W Comae PRELIMINARY Benbow et al., Highlights of the VERITAS Blazar Observation Program, OG 2.3

11 10 Blazars Extreme flare of Markarian 421 in February times Crab Nebula flux (>10σ per 2 minute bin) Rapid variability (~5 minute timescale) Galante et al., VERITAS observation of Mrk421 flaring: variability and spectral evolution, OG 2.3

12 11 Blazars Now have exposures on over 100 blazars (most >7 hours) Detected sources generally well described by inverse-compton leptonic models An external-compton component is often required, particularly for flaring IBLs Recent detection of a flare from the eponymous LBL BL Lacertae 50% Crab Nebula flux, with 4 minute-scale variability BL Lac Synchrotron self-compton + External Compton model for 3C66A BL Lac flare: Majumdar et al., Observations of selected IBLs and LBLs with VERITAS, OG 2.3

13 12 Other Extragalactic Sources: M82 & M87 M82: nearby starburst galaxy (4 Mpc) Star-formation rate = 10xMilky Way Supernova rate = per yr High cosmic ray and gas density 137-hour exposure, ~0.9% Crab The starburst Galaxy M82 M87: nearby radio galaxy (16Mpc) Resolved jet at optical, X-ray and radio (jet angle deg) VERITAS, H.E.S.S. & MAGIC observations in 2008 linked a TeV flare to increased radio (VLBA) & X-ray (Chandra) activity in the nucleus flare best sampled at TeV MWL correlation less clear; X-ray core brightening, but no radio M87 day-scale flare in April 2010 Galante et al., The VERITAS extragalactic non-blazar program, OG 2.3

14 13 Dark Matter Candidates Dwarf spheroidal galaxies are gravitationally-bound, DM-dominated objects (by > 1000), with low astrophysical backgrounds VERITAS published limits on Draco, Ursa Minor, Boötes 1, and Willman 1 Acciari et al, ApJ 2010 Based on stellar kinematics, Segue 1 is the most DM-dominated Belokurov et al. (2007) Vivier et al., VERITAS observations of the SEGUE 1 dwarf spheroidal galaxy, HE 3.4

15 14 Dark Matter Candidates Dwarf spheroidal galaxies are gravitationally-bound, DM-dominated objects (by > 1000), with low astrophysical backgrounds VERITAS published limits on Draco, Ursa Minor, Boötes 1, and Willman 1 Acciari et al, ApJ 2010 Based on stellar kinematics, Segue 1 is the most DM-dominated New 48 hour VERITAS exposure provides deepest limits to date ~0.5% Crab Nebula Flux Limits on the annihilation cross-section for different channels 95% Confidence Limits for different assumed power-law spectra Typical range Vivier et al., VERITAS observations of the SEGUE 1 dwarf spheroidal galaxy, HE 3.4

16 15 Galactic Sources VERITAS (latitude N) primarily observes the outer Galaxy Cygnus arm provides a region of particular interest

17 15 Galactic Sources VERITAS (latitude N) primarily observes the outer Galaxy Cygnus arm provides a region of particular interest

18 16 HESS J Point source coincident with a B0pe star (MWC 148) Detected by H.E.S.S., and earmarked as a possible binary Variability measured by VERITAS, also variable radio and X-ray source 3 years of Swift XRT observations identified a 321-day period, and an X-ray flare in Feb 2011 (Bongiorno et al., 2011) VERITAS exposure of 110 hr, 50 hr since December 2010 Maier, Skilton et al., Long-term γ-ray observations of the binary candidate HESS J , OG

19 17 HESS J Point source coincident with a B0pe star (MWC 148) Detected by H.E.S.S., and earmarked as a possible binary Variability measured by VERITAS, also variable radio and X-ray source 3 years of Swift XRT observations identified a 321-day period, and an X-ray flare in Feb 2011 (Bongiorno et al., 2011) VERITAS exposure of 110 hr, 50 hr since December 2010 Maier et al., Long-term γ-ray observations of the binary candidate HESS J , OG 2.2

20 18 The Crab Pulsar One of the most powerful gamma-ray pulsars. Spin-down energy= 4.6 x erg s -1. Fermi-LAT measures spectral break at E c = (5.8 ± 0.5 ± 1.2) GeV MAGIC detected the pulsar at 25 GeV using dedicated hardware. Hint of higher energies (60 GeV) VERITAS observations Total exposure=107 hours. Standard configuration Crab pulsar phaseogram. H-test value =50 (~6σ) Pulses above 120 GeV are aligned with radio; 2-3 times narrower than Fermi-LAT Ratio of pulse amplitudes flips

21 19 The Crab Pulsar Pulsar flux ~1% of Nebula flux at 150 GeV Highest energy point at 280 GeV Overall spectrum favours a broken power-law fit Detection at 280 GeV implies emission region > 10 stellar radii. Absence of exponential cutoff makes curvature radiation unlikely as the dominant mechanism at these energies Narrowing of pulses may probe geometry; e.g. tapered acceleration region? An alternative (and competitive) test of Lorentz invariance violation (Otte, this meeting) Fermi-LAT MAGIC TeVCat picture will go here McCann et al., VERITAS observations of the Crab pulsar, OG 2.2

22 20 Cygnus OB1 region Cygnus OB 1 association contains many potential TeV sources, including PSR J MGRO J : Brightest new source in Milagro survey, ~80% Crab, E>15 TeV b Abdo et al., ApJL 2007 Aliu et al., VERITAS observations in the vicinity of the Cygnus OB1 region & PWN, OG 2.2 l

23 21 Cygnus OB1 region VERITAS observations (75 hours) resolve two distinct regions: A point-like source, co-located with PWN CTB 87 (excludes blazar B , likely associated with variable LAT source 1FGL J ) An extended asymmetric source, co-located with the centre of MGRO J and probably comprised of multiple components ARGO-YBJ non-detection is intriguing; could be spectral, spatial or temporal differences? VERITAS Excess Map Preliminary VER J (CTB 87) PSR J Aliu et al., VERITAS observations in the vicinity of the Cygnus OB1 region & PWN, OG 2.2

24 22 The Galactic Center Complex region. : strong H.E.S.S. detection, Hard spectrum: E -2.1 with cutoff ~15 TeV. Source location consistent with Sgr A* Diffuse emission component along the Galactic ridge Declination -29 : culminates much lower than traditional VERITAS sources High energy threshold, but large zenith angle increases effective area 25 hours, 65 zenith angle: 14σ detection using LZA-optimized analysis Emission is stable, source location consistent with H.E.S.S. Future constraining measurement of the high-energy cutoff could help to resolve emission mechanism.

25 23 The Galactic Center Complex region. : strong H.E.S.S. detection, Hard spectrum: E -2.1 with cutoff ~15 TeV. Source location consistent with Sgr A* Diffuse emission component along the Galactic ridge Declination -29 : culminates much lower than traditional VERITAS sources High energy threshold, but large zenith angle increases effective area 25 hours, 65 zenith angle: 14σ detection using LZA-optimized analysis Emission is stable, source location consistent with H.E.S.S. Future constraining measurement of the high-energy cutoff could help to resolve emission mechanism.

26 24 Tycho s SNR Historical SNR: Type Ia, observed in Strong limits from HEGRA & MAGIC Good candidate for smoking gun of hadronic acceleration Clean environment X-ray morphology provides evidence for hadronic acceleration (Warren et al, 2005) VERITAS discovered TeV emission in 2010 (Acciari et al, 2011) 68 hour exposure, 0.9% Crab flux, Γ = 1.95 ± 0.51 ± σ detection, peaking on north-east rim though not significantly offset from centre.

27 VERITAS observations alone can be described by leptonic or hadronic emission processes (although in both cases, hadrons carry the majority of the particle kinetic energy) VERITAS plus Fermi-LAT seems to require hadron-dominated emission Compelling, but weak detections, and various unknowns (Distance, possible molecular cloud interaction) Acciari et al, 2011 Giordano et al., arxiv: Morlino & Caprioli (arxiv: )

28 26 The VERITAS Upgrade: Plans Fully funded New telescope-level trigger (faster, more flexible, with better diagnostics) Additional instrumentation on central pixel for optical studies Major component: Replace PMTs with higher-qe (super-bialkali) devices. At least 35% improvement in Cherenkov-photon collection efficiency Faster pulses. Expected hardware trigger threshold of 75 GeV Effective Area PRELIMINARY Differential Trigger rate PRELIMINARY Kieda et al., Status of the VERITAS Upgrade, OG 2.5 Otte et al., Upgrade of VERITAS with high efficiency photomultipliers, OG 2.5

29 27 The VERITAS Upgrade: Status 14 test pixels installed and operating since September 2010 Pixel assembly as close to existing design as possible (minimal re-engineering) Trigger systems complete installation ongoing 2200 PMTs arriving at 250/month final delivery January 2012 Installation during regular summer shutdown in 2012 (no loss of observing time) Pulse Shapes Photonis XP2970 Hamamatsu R10560 Kieda et al., Status of the VERITAS Upgrade, OG 2.5 Otte et al., Upgrade of VERITAS with high efficiency photomultipliers, OG 2.5

30 28 Summary The VERITAS Array has been operating smoothly since Prototype telescope relocation in 2009 significantly improved sensitivity The VERITAS source catalog continues to grow Source diversity allows us to address many topics in astrophysics and astroparticle physics. A few simple VERITAS upgrades promise further improvement in Continued operation is foreseen throughout the Fermi mission

31

32 Backup Slides

33 New Result on Segue 1 Preliminary Preliminary <σv> min cm 3 s -1 Limits are factor of 4-5 better than our previous dsph results and best on dsph reported so far.

34 Current IACT bounds on the annihilation cross-section VERITAS HESS dsph Draco Ursa Minor Distance (kpc) DM profile Log 10 <J> (GeV 2 cm -5 ) Bootes I Willman Segue I Sgr Carina Sculptor Canis Major NFW NFW NFW NFW Einasto NFW/Cor e / 20.8 NFW NFW NFW T obs (h) Ann. channel <σv> 95% (cm 3 s -1 ) τ + τ -, bbar τ + τ -, bbar τ + τ -, bbar τ + τ -, bbar τ + τ -, bbar W + W - W + W - W + W - W + W / Reminder: typical WIMP annihilation cross-section <σv> cm 3 s -1. IACTs are at least 2 orders of magnitude higher τ + τ -,bbar and W+W- ann. channels are pretty similar 34

35 Photon Detection Efficiency Afterpulsing rate 35

36 A Gamma-ray Candidate Arrival direction from the sky Core position on the ground T4 T1 T3 T2

37 VERITAS Technical Performance Energy resolution ~15-20% >300GeV Energy threshold ~150 GeV