OGLE-2003-BLG-235/MOA-2003-BLG-53: A Definitive Planetary Microlensing

Event

David BennettUniversity of Notre Dame

Author List:I.A. Bond, A. Udalski, M. Jaroszynski, N.J. Rattenbury, B. Paczynski, I. Soszynski, L. Wyrzykowski, M.K. Szymanski, M. Kubiak, O. Szewczyk, K. Zebrun, G. Pietrzynski, F.Abe, D.P. Bennett, S. Eguchi, Y. Furuta, J.B. Hearnshaw, K. Kamiya, P.M. Kilmartin, Y. Kurata, K. Masuda, Y. Matsubara, Y. Muraki, S. Noda, K. Okajima, T. Sako, T. Sekiguchi, D.J. Sullivan, T. Sumi, P.J. Tristram, T. Yanagisawa, and P.C.M. Yock

(the MOA and OGLE collaborations)

Real-Time Lightcurve Monitoring is Critical!

• Ian Bond (IFA, Edinburgh) noticed a caustic crossing for this event on July 23, 2003.

• He contacted the telescope and requested additional images

• The requested images caught the caustic crossing endpoint.

• This caustic endpoint data is critical to the conclusion that a planet is required.

Lightcurve

OGLEalert

Definition of a Planet• Formed by core accretion? (with a rocky core)

– But we don’t know that this is how planets form!

– We aren’t even sure about Jupiter’s rocky core!

• Secondary Mass < 13 Mjupiter?– This is the Deuterium burning threshold for solar

metalicity, but why is that important?

– What if binary is a 0.08 M?• Mass ratio may only be 0.16!

– In the brown dwarf desert

• Planetary mass fraction < 0.03– In the brown dwarf desert

– Easily measured in a microlensing lightcurve!!

Lightcurve close-up & fit• Cyan curve is the

best fit single lens model 2 = 651

• Magenta curve is the best fit model w/ mass fraction 0.03 2 = 323

• 7 days inside caustic = 0.12 tE

– Long for a planet,– but mag = only

20-25%– as expected for a

planet near the Einstein Ring

Caustic Structure & Magnification PatternBlue and red dots indicate times of observations

Parameters:tE = 61.6 1.8 days

t0 = 2848.06 0.13 MJD

umin = 0.133 0.003

ap = 1.120 0.007 = 0.0039 0.007

q = /(1+ ) = 223.8 1.4t* = 0.059 0.007 days

or */E = 0.00096

0.00011

Alternative Models: ap < 1

2 = 110.4

tE = 75.3 days

t0 = 2850.64 MJD

umin = 0.098

ap = 0.926

= 0.0117

= -6.1t* = 0.036 days

Also planetary!

Alternative Models: ap < 1

2 = 110.4

tE = 75.3 days

t0 = 2850.64 MJD

umin = 0.098

ap = 0.926

= 0.0117

= -6.1t* = 0.036 days

Also planetary!

Alternative Models: ~ 180

2 = 40.15

tE = 76.0 days

t0 = 2847.09 MJD

umin = 0.100

ap = 1.064

= 0.0127

= 185.6t* = 0.034 days

Also planetary!

Alternative Models: ~ 180

2 = 40.15

tE = 76.0 days

t0 = 2847.09 MJD

umin = 0.100

ap = 1.064

= 0.0127

= 185.6t* = 0.034 days

Also planetary!

Alternative Models: Early 1st Caustic Crossing

2 = 7.37

tE = 58.5 days

t0 = 2847.90 MJD

umin = 0.140

ap = 1.121 = 0.0069 = 218.9t* = 0.061 days

Excluded by 2.7Adjust = 0.0039 0.007

to = 0.0039 0.011

Lens Star ConstraintsUsing Isource = 19.7

and V-I = 1.58,we conclude that the source is a bulge G dwarf of radius:

* = 520 80 as

Iblend= 20.7 0.4

Gives likelihood curve

Planetary Parameters in Physical Units

• Best fit lens distance = 5.2 kpc– 90% c.l. range is 2.3-5.4 kpc

• Best fit separation = 3.0 AU– 90% c.l. range is 1.3-3.1 AU

• Best fit stellar mass = 0.36 M

– 90% c.l. range is 0.08-0.39 M

• Best fit planet mass = 1.5 Mjup

– 90% c.l. range is 0.3-1.6 Mjup

• If lens star is a 0.6 M white dwarf– Dlens = 6.1 kpc– ap = 1.8 AU– Mp = 2.5 Mjup

Conclusions

1st definitive lensing planetary discovery

- complete coverage not required for characterization

Real-time data monitoring was critical!

S. Gaudi video