Capabilities of GROND

Jochen Greiner
LOFAR TKP Meeting, Amsterdam, June 2011

Transcript

1. Amsterdam, 27-29.6.2011 Jochen Greiner - 1 GROND an optical/NIR 7-channel imager: Capabilities for transient follow-up Jochen Greiner Max-Planck Institut für extraterrestrische Physik Garching, Germany
2. ~48 hrs ~12 hrs 2 GROND Afterglow emission at radio, optical, and NIR wavelengths GRB Afterglow and Light Curve ~2 hrs
3. 3 Due to characteristic spectrum of GRB Afterglow: Photometry in 7 filters simultaneously, from that derive redshift If redshift >5, then follow-up spectroscopy in the same night at 8m-class telescopes and with satellites (VLT, LBT, Spitzer, XMM, …) Quickly finding high-redshift GRBs
4. Amsterdam, 27-29.6.2011 Jochen Greiner - 4 GROND=GRB Optical/NIR Detector K J H g r i z Imaging in 7 channels simultaneously
5. Amsterdam, 27-29.6.2011 Jochen Greiner - 5 GROND: General Design  7 bands: Sloan g’, r’, i’, z’ and J, H, K One detector for one filter band (no movable filters!) 3 HAWAII 1K*1K Arrays + 4 E2V 2K*2K CCDs  Field- of- view: Visual: 5.4´x5.4´ (0.16´´/pixel) NIR: 10´x10´ (0.59´´/pixel)  Dichroics tuned to minimize intrinsic polarization effects  2 shutters, i.e. g’r’ and i’z’ pairs of CCDs have same exposure  Combined telescope and intrinsic mirror (K- band) dithering  Sensitivity: 4 min 1 hr gr 22.0 mag 25.0 mag (AB) iz 21.5 mag 24.5 mag (AB) J/H/K 20/19.5/19 mag 23/22.5/22 mag (AB)
6. Amsterdam, 27-29.6.2011 Jochen Greiner - 6 Example of GROND sensitivity Advantage of separate detector per filter: can add sensibilization for spectral band:  GROND@2.2m detector/filter is 4x more sensitive than FORS2@VLT  total efficiency only 4x less than FORS2, not 16 (8.22/2.22) • 7 filter bands cover Lyman- α for large z- range: 3<z<13 • GROND has proper z- band sensitivity to define drop- out for z~ 8
7. Amsterdam, 27-29.6.2011 Jochen Greiner - 7 GROND @ 2.2m MPI/ESO telescope GROND History: First light: Apr 30, 2007 First GRB: May 21, 2007 Photometric calibration: Jul 2007 Routine observations: since Sep 2007 fastest response time: 2 min Electronics cryostat cryostat M3 δ-twister J H K
8. Jochen Greiner Milano, 22.4.2009 • First image: 4 min after GRB onset, ~ 80 sec after trigger 1st night: 6 hrs continuous exposure; 350 data points ß- evolution (instead of one for all AG) GRB 071031 Krühler et al. 2008
9. Amsterdam, 27-29.6.2011 Jochen Greiner - 9 Show-case: GRB 081029 Nardini, Greiner et al. 2011 (subm) K H J z’ i’ r’ g’ No spectral evolution after jump
10. Jochen Greiner Milano, 22.4.2009 GRB 080913 at redshift 6.7 1st exposure starts T 0 +6 min T 0 +15 min: XRT position T 0 +35 min: first SED (Σ of 3 OBs = 16 min expo) T 0 +90 min: VLT starts taking spectrum with proper grism (5 mag fainter than 050904) Greiner et al. 2009, ApJ 693, 1610
11. Amsterdam, 27-29.6.2011 GRB 080710 Only 7 GRBs with X-ray and optical/NIR on same powl ß ox sensitive to extinction A V AND SED shape GRB 070802 GRB 080129 XRT-GROND SEDs 1 keV R band KHJ zirg ß ox
12. 12 Extinction curve GROND GRB 070802: first 2200 A bump at z=2.45 Krühler et al. 2008 SED at 2000 sec after GRB
13. Amsterdam, 27-29.6.2011 Recognize ‘thermal’ transients • With 7 filter bands you always get an SED • Transient classification according to SED: allows to distinguish other types of transients, e.g. accretion-disk dominated galactic transients “GRB” 100331A  likely galactic transient
14. 14 LOFAR-transient follow-up possible  GROND is built for rapid (min), automatic response  Broad-band coverage helpful for identification  Swift GRB rate declining: leaves time for transients; amount for LOFAR TBD  Guaranteed telescope access until 2016