The BAT Hard X-ray Monitor and Survey: 10+ years running Hans A. Krimm NASA Goddard Space Flight Center Greenbelt, MD USA USRA / CRESST
Swift/BAT overview 14-195 kev energy range FOV: 1.94 sr (> 10% coding) Location resolution ~1.5 arcmin Detector area: 5200 cm 2 Similar to IBIS but Swift observing plan leads to more uniform sky coverage
The X-ray astronomy community uses the BAT monitor & survey. 48 refereed references to monitor paper (2013) 109 refereed references to 70-month survey paper (2013) 132 refereed references to 22-month survey paper (2010) 177 refereed references to 9-month survey paper (2008) 90 refereed references to 3-month survey paper (2005) Talks at this meeting referring to BAT monitor or survey Monday: Koss, Ricci, Ghisellini, Bassani, Esposito Wednesday: Klochkov, Chenevez, Walter, Sidoli Probably missed several
Exposure Source Types Swift/BAT survey Ecliptic poles Most sensitive to steady sources 14-195 kev 8 energy bands Built from survey intervals, typically 300 sec. Lengthy processing time; not pipeline 1210 sources ~60% AGN (Seyfert and beamed) Results from 70-mon survey paper: Baumgartner et al, ApJSS 19, 2013 104-month now processed Sensitivity ~ 1.34 X 10-11 erg s -1 cm -2
Palermo BAT Survey Cusumano et al, A&A 524, 2010 Cusumano et al, A&A 510, 2010 Segreto et al, A&A 510, 2010 Somewhat different methodology; complementary results.
Swift/BAT hard X-ray transient monitor IGR J17391-3021 Orange=flaring Green=outburst Very sensitive to variable sources 15-50 kev (single energy range) Built from on-board scaled maps from 64 to >1000 seconds duration. Rapid, near real-time pipeline processing 269 detected sources: 146 persistent and 123 in outburst Red=steady Blue=variable GX 9+1 1A 0535+262 GRS 1915+105 Results from monitor paper: Krimm et al, ApJSS 209, 2013
Survey/Monitor web sites Links to >1000 source lights curves Basic information Optical images Mission, past year, orbit light curves Monthly light curve Integrated spectrum Download spectra, response, light curves Download ASCII or FITS light curve files
Survey Highlights I: X-ray background Seyfert population is local shows no evolution FSRQ can account for entire CXB up to 10 MeV FSRQ population shows strong evolution modeled with modified pure luminosity evolution model + double power law From Ajello et al, ApJ 699, 2009; based on 36 months Seyfert: gray Blazars: open
Survey Highlights II: Galaxy Morphology Larger fraction of BAT AGNs with disturbed morphologies or in close physical pairs (<30 kpc) compared to matched control galaxies or optically selected AGNs. The high rate of apparent mergers (25%) suggests that AGN activity and merging are critically linked for the moderate luminosity AGN in the BAT sample. From Koss et al, ApJL 716, 2010
Survey Highlights III: Spectroscopy First study of global X-ray properties of an unbiased toward absorption (n H < 3X 10 25 cm -2 ),local(<z> = 0.03),AGN sample. young Red: broad line Blue: narrow line Lower Eddington limit for dusty gas (blue curve). Outflow sources High column Intermediate/old Blue Sy1 Green Sy1.2 Red Sy1.5 Most BAT-selected galaxies are from intermediate to old (2.5-10 Gy) stellar populations. Low column From Winter et al, ApJL 745, 2012; based on XMM-Newton observations of 48 AGN and Winter et al, ApJL 710, 2010; based on optical spectroscopy of 64 AGN.
Monitor Highlights I: New Sources 18 new discoveries: 6 neutron stars 5 black hole candidates 2 tidal disruption flares (extragalactic) 4 XRB (compact object unknown) 1 unknown Swift J1756.9-2508 Accretion-powered msec pulsar with < 0.03 M companion; Krimm et al, ApJL 668, 2007. Swift J1357.2-0933 Swift J2058.4+0516 Tidal disruption flare in z=1.1853 galaxy; Cenko et al, ApJ 753, 2012. LMXB/dynamically confirmed black hole viewed edge-on through torus; short eclipses from accretion disk show considerable structure. Corall-Santana et al, Sci 339, 2013; Armas Padilla et al, MNRAS 428, 2013
Monitor Highlights II: Known Sources IGR J17091-3624 GRO J1655-40 Hard X-rays Soft X-rays IGR J17091-3624 is a black hole candidate detected in outburst at high luminosity in 2011 by BAT monitor; RXTE observations show complex heartbeat variability similar to GRS 1915+105 and likely due to disk instabilities. (Altamirano et al, 2011) MJD-50000 GRO J1655-40 is a black hole transient, last in outburst in 2005; spectral evolution studied in both hard (top) and soft (bottom) X rays by Brocksopp et al, 2006.
Swift/BAT studies of Supergiant Fast X-ray Transients (monitor) SFXT (Sidoli talk) are high-mass X-ray binaries defined by their hard X-ray flaring activity. Peak luminosity 10 36 10 37 erg s -1 for a few hours. Major, multi-year (100-month) effort to characterize >1000 flares from 11 SFXTs using BAT transient monitor data. BAT triggers Daily monitor Orbital monitor Onboard non-trigger 4.926±0.001 d orbital period Romano et al., A&A 562, 2014 IGR J17544-2619 is SFXT class prototype.
Superorbital periods of wind-accretion high mass X-ray binaries (monitor) IGR J16418 4532 BAT monitor data led to discovery of super-orbital periods in 3 wind-driven systems. Corbet & Krimm, ApJ 778, 2013
Long-term variability of AGN (survey) Low variability (Mrk 79) Study of 110 AGN from BAT survey 80% exhibit variability on month-year time scale Variability not compatible with changes in absorbing column. High variability (QSO B0033 ) Soldi et al, A&A 563, 2014
Un-beamed tidal disruption events at hard X rays Use BAT survey data to search for flares in the light curves. Rejected galactic objects and other objects near GRB s, which produced artifacts in the light curves. Find nine TDE candidates near cataloged galaxies leading to an estimated upper limit on the rate of TDE s of 2.1 X 10-5 yr -1 galaxy -1. Hryniewicz & Walter, arxiv:1505.06612, 2015
Decreased specific star-formation rate in AGN host galaxies (survey) Comparison of star-forming rate in BAT AGN host galaxies shows a deficit relative to non-agn galaxies from Herschel survey. BAT sample Shimizu et al, MNRAS 452, 2015
New Initiative: BAT and MAXI broadband transient monitor GX 339-4 Combines BAT 14-195 kev (4 bands) with MAXI/GSC 2-20 kev (3 bands) Updates 3X daily using Swift Quicklook data and MAXI public light curves. 106 sources currently monitored. Will be available on a public web site. MAXI BAT 2-4 kev 4-10 kev 10-20 kev 14-24 kev 24-50 kev 50-100 kev Sakamoto et al, submitted to PASJ, 2015 100-195 kev
New initiative: BAT monitor triggers to HAWC telescope Arrangement with team of the High Altitude Water Cerenkov gamma-ray A observatory to share triggers. Will r go live in the next few months. r HAWC covers 2/3 of the sky in 24 hours and operates between 100 GeV and 100 TeV at 4100 meters elevation on the slopes of Pico de Orizaba in Mexico.
Summary BAT monitor operates in near real-time in 50-150 kev with light curves available for > 1000 sources BAT survey is complete to 70 months with catalog of >1200 sources BAT survey/monitor contributes to science of Black hole transients High-mass X-ray binaries Active galactic nuclei Neutron stars etc