Optical (counterparts of radio) transients

Teo Muñoz-Darias
LOFAR Transients Key Project Meeting, Meudon, December 2011

Transcript

1. Optical Transients (counterparts of Radio Transients) Teo Muñoz Darias University of Southampton 4-PI-SKY
2. Motivation Optical/Infrared counterparts can provide key inputs to identify the nature of the radio transient • Optical/Infrared colors • Radio/optical spectral slopes Optical transient is an old field, but • with ambitious ongoing programs (Catalina survey...LSST) • Expertise • Smart methods for removing artifacts
3. Optical Astronomy Optical magnitudes • Logarithmic scale (as the human eye) • M = -2.5 Log (Flux) + Constant (the bigger the fainter) • Several bands (UBVRI / u’g’r’i’z’) Orders of magnitude (300 seconds exposure) • V ~ 26 ( 0.2 µJy ) 10 m Telescopes (Keck/GTC) • V ~ 24 ( 1 µJy ) 4m telescopes (WHT) • V ~ 23 ( 2 µJy ) 2m telescopes (Liverpool Telescope) • V ~ 6 ( 15 Jy ) Human eye 3 x 108 -- 109 GHz 300 nm -- 1µm
4. Catalina Survey ~4000 transients in 4 years • 20 % supernovae • 15 % CVs • 8 % Flaring stars/Asteroids • 3-4 % Blazars X-ray binaries, GRBs ... 19-21 < V; 33000 deg2 Mahabal et al. 2011
5. Usual suspects Supernovae • SN can be detected in radio at Z=0.01-0.1 • Well defined time scales (weeks - years) . • Associated with host galaxies AGNs: • They can be strong radio sources (~Jy) • R~23 we should reach Z~2 ( Z=5 requires V~26) • R-K color ~3 between Z=0--3 CVs (e.g. dwarf Novae) • Much brighter in the optical • Spectroscopy FRadio/FOptical ~ 0.001 Körding et al. 2008
6. Rates for optical transients The Deep Lens Survey (DLS) 1.1 deg-2 days; 1000s time scales • Rate ~ 6.5 events deg-2 day-1 (18.6<B<23.8) Becker et al. 2004 • Three detections in B but Zero detections en R band (very blue) • M dwarf stars Kulkarni & Rau 2006 • 106 events per year 6000 in a 10 deg2 survey MPG/ESO survey 0.24 deg-2 days Rau et al. 2004 • Rate ~ 10-15 events deg-2 day-1 (3sigma <28; 16<R<23) • R band: 1 M dwarf; 2 CV/dwarf nova; Maybe one extragalactic Gudel et al. 2002
7. Isolated neutron stars Proposed as the origin of the Bower et al. (Kida et al.) long duration radio transients Ofek et al. 2010 In general they are faint optical sources (V~25) Rotating radio transients (XTE J1819-1458) • Flux(1.4 GHz) = 3.6 Jy burst McLaughlin et al. 2006 • g’ band (6.2x108 GHz) < 17.4 (0.4 mJy) Dhillon et al. 2006 • FRadio/FOptical > 104 Anomalous X-ray pulsars (XTE J1810-197) • Flux(1.4 GHz) = 1-10 mJy Camilo et al. 2006 • K band (1.4x108 GHz) < 21.9 (1.7 µJy) Camilo et al. 2007 • FRadio/FIR > 103--104
8. Summary and future goals • We will search for optical counterparts of LOFAR transients. • LOFAR is going to discover MANY interesting TRANSIENTS: • It is going to be difficult to perform the follow up of all of them • An a priori characterization of some of the expected populations can help to take real time decision • Optical colors • Luminosity ratios • Nearby objects (host galaxies)