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HADS in the Large Magellanic Cloud : Initial findings from the SuperMACHO Project. Arti Garg Lawrence Livermore National Laboratory, Institute of Geophysics and Planetary Physics. Stellar Pulsation, Santa Fe, NM June 4, 2009 LLNL-PRES-413511. - PowerPoint PPT Presentation
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HADS in the Large Magellanic Cloud:Initial findings from the SuperMACHO Project
Arti GargLawrence Livermore National Laboratory,
Institute of Geophysics and Planetary Physics
This work work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Stellar Pulsation, Santa Fe, NMJune 4, 2009LLNL-PRES-413511
Microlensing to Detect MACHOs
• In 1986, B. Paczynski suggested using gravitational microlensing toward the Magellanic Clouds to detect MACHOs
Large Magellanic Cloud
Milky Way Halo
Us
MACHOs
Light PathMW illustration: Mark Garlick (Space-art) Earth Image: Apollo 17
Anglo-Australian Observatory/Royal Observatory Edinburgh
SuperMACHO ProjectLLNL/IGPP: A. Garg, K.H. Cook, S.Nikolaev, Harvard: A. Rest, C.W. Stubbs (P.I.), P. Challis, W.M.
Wood-Vasey, G. Narayan, NOAO: R.C. Smith, K. Olsen, A. Zenteno, JHU: M.E. Huber, UW: A. Becker, A. Miceli, FNAL: G. Miknaitis, McMaster: D.L. Welch, Catolica: A. Clocchiati, D. Minniti,
Padova: L. Morelli, OSU: J.L. Prieto, UT-Austin: N.B. Suntzeff
• CTIO 4m• Mosaic Imager: big FOV• Monitor 68 LMC fields
– 23 deg2 and ~50 million sources
• 150 half-nights• 5 years (2001-2006)
– Blocks of ~3 months/year
• Near real-time detection• Single filter: custom VR• Difference imaging
SuperMACHO fields
Primary field setPrimary field set
Secondary field setSecondary field set
Image: Gregory Bothun
Difference Imaging
Detection Imageflux(timage)
Difference Imageflux(timage) – flux(ttempl)
Reference Imageflux(ttempl)
RR Lyrae from MACHO (black) and SuperMACHO (red)
Periodic Variables
High Amplitude δ-Scuti1580 candidates
Garg 2009
Selection based on:• P-L diagram• Color (B-I)• Amplitude (> 0.2mag)
Light Curves
Garg et al., in prep.
VR
Phase
Phase
VR
VR
Phase
Phase
VR
Color-Magnitude Diagram
MACHO low amplitude variability limit
Garg et al., in prep.
Period-Luminosity Diagram
Garg et al., in prep.
VR = −3.49±0.313 log10P + 16.94±0.357
Median Mode
VR = −3.65±0.07 log10P + 16.72±0.146(Poretti et al. 2008)
VR
log10P
VR-intercept
Garg et al., in prep.
VRint,-3.49 = 3.49 log10P + VRVRint,-3.65 = 3.65 log10P + VR
Overtone Pulsators?
r 41
VRint,-3.49
r 31
VRint,-3.49
r 21
VRint,-3.49
0.07742 days, 1.85808 hours
0.07035 days, 1.68840 hours
0.07283 days, 1.74792 hours
0.06804 days, 1.63296 hours
Light Curve Shape
Garg et al., in prep.
0.0909 days, 2.1816 hours
Garg et al., in prep.
VRint,-3.49
Amplitude
(mag
)
0.06735 days, 1.1640 hours
Fornax
Cole et al. (2005) find evidence for lower metallicity population in LMC
• Not enough to explain the position of peak assuming metallicity dependence of McNamara et al (2004)
Amplitude of Pulsation
Distance to the LMCMv = – 3.65(±0.07) log10 P – 1.83(±0.08) – 0.19 [Fe/H]
(Poretti et al. 2008; McNamara et al. 2004)
Distance = 18.58±0.184
Mv = – 3.49(±0.313) log10 P – 1.83(±0.08) – 0.19 [Fe/H](This work; McNamara et al. 2004)
Distance = 18.80±0.374
[Fe/H] = – 0.37(±0.15)(Cole et al. 2005)
MV = MVR+ 0.10(±0.074)(From RR Lyrae in MACHO and SuperMACHO)
Armin Rest, 02/13/08, UCSD
The SuperMACHO survey was undertaken as part of the NOAO Survey Program.
SM-2004-LMC-821
VR≈21
Spectral classification: Broad Absorption Line AGN
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