The Fermi Large Area Telescope Science highlights and prospects for the extended mission Luca Baldini Universit` a and INFN–Pisa luca.baldini@pi.infn.it on behalf of the Fermi LAT collaboration Astroparticle Physics 2014, Amsterdam June 25, 2014
Fermi at Astroparticle Physics 2014 (1/2) Cast of characters (in strict alphabetical order) ◮ Markus Ackermann: “The intensity and origin of the isotropic gamma-ray background” [24 Jun @ 16:30] ◮ Keith Bechtol: “Gamma-ray Observations of Galaxy Clusters and Implications for Cosmic Rays” [23 Jun @ 16:30] ◮ Rolf Buehler: “Galactic particle accelerators” [25 Jun @ 11:00] ◮ Anna Franckowiak: “The Spectrum and Morphology of the Fermi Bubbles” [25 Jun @ 17:00] ◮ Marie-Helene Grondin: “Gamma-ray observations of the pulsar wind nebula 3C58 with the Fermi-LAT” [25 Jun @ 14:20] ◮ Lucas Guillemot: “Fermi LAT observations of gamma-ray pulsars” [25 Jun @ 14:50] ◮ Marianne Lemoine-Goumard: “Constraints on Cosmic-Ray Origin from Gamma-Ray observations of Supernova Remnants” [24 Jun @ 17:00] Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 2 / 25
Fermi at Astroparticle Physics 2014 (2/2) Cast of characters (in strict alphabetical order) ◮ Melissa Pesce-Rollins: “Fermi Large Area Telescope observations of high-energy gamma-ray emission from solar flares” [23 Jun @ 15:10] ◮ Gabrijela Zaharijas: “Recent results on dark matter search with the Fermi LAT” [23 Jun @ 14:30] ◮ Stephan Zimmer: “Search for DM-induced gamma-rays from Galaxy Clusters with the LAT” [23 Jun @ 14:55] And broader talks, e.g., ◮ Valerie Connaughton: “Prospects for detecting Gamma-Ray Bursts at the highest energies” [23 Jun @ 17:20] ◮ Luigi Tibaldo: “Galactic interstellar gamma-ray emission” [25 Jun @ 15:30] And probably as many others by the Community analyzing Fermi data. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 3 / 25
Fermi: a remarkably large dynamic range (Fermi LAT and GBM combined) SNR CRE EGB GRB -2 -1 2 3 4 5 6 10 10 1 10 10 10 10 10 10 Energy [MeV] GRB extended GRB prompt TGF Solar flares Pulsar periods AGN flares Pulsar substr. Binary systems -5 -4 -3 -2 -1 2 3 4 5 6 7 8 10 10 10 10 10 1 10 10 10 10 10 10 10 10 Time [s] Sun GRB Moon AGN Earth limb Galactic TGF CRE 6 8 10 16 18 20 26 12 14 22 24 10 10 10 10 10 10 10 10 10 10 10 Distance [m] Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 4 / 25
Outline For the next 20 minutes ◮ My three favorite. ◮ (Among the Fermi -LAT publications coming out in the short term.) ◮ Why, after 6 years in orbit, are we excited about the Fermi extended mission? ◮ Time-domain astronomy; ◮ Pass 8. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 5 / 25
The IGRB and EGB Earlier talks by Markus Ackermann and Gabrijela Zaharijas ◮ Updated LAT measurement of IGRB spectrum. ◮ 50 months of data, dedicated event selection(s). ◮ Extended energy range: 200 MeV–100 GeV → 100 MeV–820 GeV. ◮ Roughly ∼ 1 / 2 of total EGB intensity above 100 GeV now resolved into individual sources. ◮ Significant high-energy cutoff feature around ∼ 250 GeV. ◮ Consistent with simple source populations attenuated by EBL. ◮ Reality might more complex, with multiple populations contributing. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 6 / 25
The Fermi bubbles Talk by Anna Franckowiak later today—can’t miss that! ◮ First discovered by Su, Finkbeiner & Slatyer in 2010. ◮ First Fermi -LAT publication. ◮ Based on 50 months of data. ◮ Modeling of the diffuse emission is the foremost challenge. ◮ Hard spectrum with cutoff at ∼ 110 GeV. ◮ No spectral variations in latitude stripes. ◮ No energy dependence of the overall morphology. ◮ Excess emission in the the South-East; no evidence for a jet. ◮ Leptonic and hadronic interpretation of gamma-ray data possible. ◮ Assuming association with microwave haze prefers leptonic models. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 7 / 25
The 3FGL Heading toward ∼ 3000 sources ◮ 4 years of Pass 7 reprocessed LAT data above 100 MeV: ◮ vs. 2 years of (un-reprocessed) Pass 7 data for the 2FGL. ◮ Front/Back handled separately (different isotropic and Earth limb). ◮ More data and improved performance (due to reprocessing): ◮ Better localization on average (error radius ∼ 15% smaller outside the Galactic plane). ◮ Improved interstellar model of Galactic diffuse (e.g., Fermi bubbles): ◮ Lower overall detection threshold. ◮ Association process improved. ◮ Dedicated multiwavelength follow-up, new surveys. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 8 / 25
Fermi and the Galactic center ◮ A topic of discussion that stirred the interested of the community over the last few months. ◮ The Fermi -LAT collaboration is fully engaged in studying the sources of gamma-ray emission in the inner Galaxy: ◮ Modeling of the Galactic diffuse emission is (again) the foremost challenge. ◮ “Diffuse emission around the Galactic center” is one of the top three for the next few years in L. Tibaldo’s review on GDE this afternoon. ◮ Fermi transitioned to a new observing profile emphasizing coverage of the Galactic center (more on this later). ◮ Dedicated session on the “Galactic center GeV excess” tomorrow afternoon. ◮ Including presentations and ∼ 1 / 2 hour of panel discussion. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 9 / 25
Extended mission and timeline SR 2012 SR 2014 Prime phase Extended phase 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 Year # orbits 0 10000 20000 30000 × 6 10 Distance traveled [km] 0 500 1000 × 9 10 # triggers 0 50 100 150 200 250 300 350 × 9 10 # events downlinked 0 10 20 30 40 50 60 70 × 6 10 # events @ FSSC 0 500 1000 1500 2000 × 6 10 γ # -ray candidates 0 50 100 150 200 250 300 0 5 0 5 0 5 0 5 5 0 5 0 2 5 7 0 2 5 7 0 2 5 7 1 1 1 1 2 2 2 2 # ATELs 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 # GCNs Full SR reports @ http://science.nasa.gov/astrophysics/documents/ Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 10 / 25
Faster than the √ t : time-domain astronomy ◮ Laundry list of source classes: ◮ GRB, AGN, Solar Flares, TGFs, novae. . . ◮ Large acceptance and FOV, all-sky coverage and long integration time are key. ◮ Fermi surely plays a prominent role—in synergy with other instruments and observatories. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 11 / 25
GRB 130427A A nearby monster! ◮ Highest γ -ray fluence: ◮ Highest γ -ray energy in the LAT frame: ◮ 95 GeV @ T 0 + 244 s; ◮ 32 GeV @ T 0 + 34 . 4 ks; ◮ Longest-lived γ -ray emission: ◮ 19 hours. ◮ Second brightest optical flash: ◮ 7-th magnitude. ◮ Within closest 5% of GRBs: ◮ z = 0 . 34. ◮ A rapid localization by the Fermi LAT and GBM is crucial to enable this kind of science. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 12 / 25
Faster than the √ t : steady sources —Low energy —High energy Bkg. dominated Photon counting ∝ √ t nearly ∝ t ◮ Envelope of the minimum detectable power-law spectra over the full band, varying the spectral index. ◮ (i.e, not a differential sensitivity plot .) ◮ High-energy limiting sensitivity comes from photon counting statistics (rather than the background). ◮ Increase nearly linear with time, rather than √ t . Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 13 / 25
Faster than the √ t : external inputs ◮ Specific LAT analyses rely on external inputs. ◮ And our knowledge of these inputs advances independently. ◮ Galactic diffuse model and Planck maps. ◮ This impacts (to different extents) pretty much all the analyses of Fermi data. ◮ Radio timing solutions for pulsar searches. ◮ The rate of discovery for pulsars has been ∼ constant through the prime phase of the mission. ◮ Note this goes in the other direction, too: searches for radio pulsation in LAT unassociated sources. ◮ Targets for indirect DM searches. ◮ e.g., dwarf spheroidal galaxies. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 14 / 25
The role of the observing strategy ◮ Two basic observation modes: ◮ Survey mode: tilt z -axis perpendicular to orbit plane ( ± 50 ◦ ). ◮ Pointing mode: point z -axis to a specific location in the sky. ◮ Nearly all pointed observations interrupted by Earth occultation. ◮ Survey mode provides ∼ uniform sky exposure. ◮ Coverage of specific parts of the sky can be enhanced by pointed observations. ◮ ARRs and TOOs (e.g., PSR B1259-63, 3C279, the Crab, the Sun. . . ) ◮ Fermi transitioned to a new default observing mode with emphasis on the GC in December 2013. ◮ Community actively involved in the decision. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 15 / 25
Long-baseline measurements ◮ Binary system PSR B1259-63: a radio pulsar in a highly-eccentric orbit (period 3.4 years) around a main sequence star. ◮ Large increase of the flux at GeV energies one month after the last periastron passage in 2011. ◮ No corresponding variability observed in radio, X-rays and VHE γ . ◮ Current periastron passage on May 4, 2014. ◮ Recurrent nature of the flaring activity seems to be confirmed. ◮ 6 ATELs over the last three weeks. Luca Baldini (UNIPI and INFN) Amsterdam, June 25, 2014 16 / 25
Recommend
More recommend
