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