Time-domain Studies of M31- Through the eye of Pan-STARRS 1 李見修 (Lee, Chien-Hsiu)
Subaru Telescope, NAOJ
EAYAM2017, Nov. 16 @ Ishigaki, Japan

1. Project overview: Lee et al. 2012, AJ, 143, 89
2. Cepheids: Kodric et al. 2013, AJ, 145, 106
3. Beat Cepheids: Lee et al. 2013, ApJ, 777, 35
4. Luminous blue variables: Lee et al. 2014, ApJ, 785, 11
5. Eclipsing binaries: Lee et al. 2014, ApJ, 797, 22
6. PS1 + PHAT = Cepheid IR PL: Kodric et al. 2015, ApJ, 799, 144… and many more! All summarized in:Lee, 2016, “Time-domain Studies of M31”,
Astronomical Review, 12, 1 (open access)M31 - the closest spiral galaxy
1. Complete view of M31 vs. partial/limited sight-lines of Milky Way
2. Simple geometry, all sources at same distance (770 kpc)
3. Variables and transients bright enough/to be resolved
4. Metal rich (compared to LMC and SMC)
1st wave: Distance indicator surveys

2nd wave: Microlensing surveys

Lee (2017)2

3rd wave: ultra-wide CCD surveys

The PAndromeda TeamPIs: Ralf BenderStella Seitz

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PAndromeda in a nutshell
Scientific drivers- Constraining the compact matter fraction in theM31/MW halos- Inventory of variables in M31, including Cepheids, binaries,
long-period variables

Observation strategy- Observed M31 in 2010-2012, from July to Dec.
- rPS and iPS : up to 2 visits per night- gPS, zPS, yPS : sparse obs. in 3 yrs

5How to tackle crowded fields?
—Image Subtraction!!!
Epoch 1

Epoch 2Difference

Wozniak (2011)6

Result 1: Microlensing

Lee et al. (2012)
More about microlensing in:Lee, 2017, “Microlensing and Its Degeneracy Breakers: Parallax, Finite Source,
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High-Resolution Imaging, and Astrometry”, Universe, 3, 53 (open access)Result 2: 2009 Cepheids– Largest published sample to-date
PS1 optical photometry

Kodric et al. (2013)

Pan-chromatic Hubble
Andromeda Treasury (PHAT)

Dalcanton et al. (2012)
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Cepheids– PL relation
PS1 optical photometry

Kodric et al. (2013)

HST IR photometry

Kodric et al. (2015)
9Cepheids– Age distribution

t>70 Myr
70>t>40Myr
t<40 Myr

Gordon et al. 2006

Star formation ring at 10 kpc
Kodric et al. (2013)
10Result 3: 298 Eclipsing BinariesLee et al. 201411

Eclipsing binary- M31 as a distance anchor
H0 error budget (Riess et al. 2011)
3 Anchors:- MW Cepheids- LMC- NGC4258- M31?

Credit: NASA, ESA, and A. Feild (STScI)Eclipsing binary- M31 as a distance anchor● H0 error budget (2.4%, Riess et al. 2016)

3 Anchors:- MW Cepheids- LMC- NGC4258- M31?
Riess et al. 2016

Making data public!
The only way to realize the fullscientific benefit of ourobservation is to share the datawith our competition.

—Bohdan Paczynski14Public time-series data of M31
PS1

PTF
30:00.0

PHAT
CFHT-N

Declination

42:00:00.0

INT-N

30:00.0
INT-S
CFHT-S
41:00:00.0

30:00.0

40:00:00.0
48:00.0 46:00.0 44:00.0 42:00.0 0:40:00.0 38:00.0 36:00.0
Right ascension

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Content includes:
1. Concept of stellar pulsation
2. Variable star classification
3. Transients
4. Difference imaging analysis

http://iopscience.iop.org/bookListInfo/aas-iop-astronomy

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Prospect: going redder
LMC (OGLE) variables at the distance of M3118

Prospects 2: Going Deeper

Flare starNiikura+ (2017)

Eclipsing binary with 10-min eclipses

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RR Lyrae

Sarajedini (2011)21