Stellar variability monitoring in open clusters with mini-SONG

X.B. ZhangNational Astronomical

Observatories,Chinese Academy of Sciences

contents

Mini-SONG Overview

Main Science goals

Interesting subjects concerned

Predicted results

Mini-SONG Overview A global photometry

system;

Shares the sites and operation net-work with the North SONG.

Instruments & parameters:

Double-tube 50 cm reflector;

F/9.5

equatorial mount;

2k×2k CCD;

SDSS or Johnson filters

Capability & utilities: FOV: 20’×20’ ; image scale of 0.6”/pixel; Photometry precision:

0.008 mag for V=15 and 0.011mag for V=16 ( 1 single exposure);

0.003, 0.005 mag for V=15, 16 respectively (10 exposures combined).

Time-resolution: 1 min.; Duty-cycle: > 40%; Two-color simultaneously.

Main Science goals

Multi-color photometric survey of open clusters; To obtain the unique multi-color CMDs of about 300 nearby

open clusters and determine the basic parameters by isochrone fitting, by single site.

Stellar variability monitoring in open clusters; Long-term, time-series photometry on about 20-30 selected

clusters, each with a time span longer than 1 month.

Follow-up photometry of ToOs such as GRB, SN etc.

Why open clusters? More effective for

denser stars; The same evolution

history and environment of member stars;

Definite parameters known from other ways;

The probable mini-SONG OC targets

337 OCs collected as the

initial candidates, each with the

modest coordinates, distance

modulus (brightness) and

diameters

(http://www.univie.ac.at/webda/webda.html),

Interesting subjects concerned

Eclipsing binaries

Basic data: fraction & distributions in mass ratio,

orbital period etc.;

Test the theory of stellar evolution;

Effects of mass transfer and angular momentum

loss, constraints to the model of binary evolution.

Example. 1V12 in NGC188, a detached

binary discovered by Zhang

et al. (2002, 2004)

Zhang, et al., 2002, 2004

Meibom et al., 2009

Zhang, Deng & Lu, 2009

Example. 2TX Cnc, a W UMa star

In the praesepe cluster

Pulsating stars:

Detect and compile the complete sample of

several types of pulsating stars, SPB, Cephei,

Scuti etc.;

Blue & red edges of the instability stripe for each

types of variables based on large-sample study.

Comparison asteroseismic study with known

physical parameters.

Example. 312 Scuti variables in NGC6811

Luo & Zhang et al., 2009

Example. 4:18 SPBs in NGC7654

Luo, Zhang & Han, 2011

Transit searching for Jupiter-like planets;

Detailed by Prof. Zhou

Stellar eruptive events.

CVs, flares of late-type stars

Predicted results

Unique, high-precision CMDs and basic physical parameters will be determined for about 300 nearby open clusters,;

Light variability of tens of thousands of stars be monitored by continuous, long-term photometry, a discovery of hundreds to thousands of variables in various types is expected;

Transits and some other unexpected events

Thanks!

xzhang@nao.cas.cn