The Chinese SONG proposal: scientific concerns Jianning Fu (Beijing Normal University) and Chinese SONG team Beijing ─ March 29, 2010 The third workshop of SONG

Contents  Scientific goal of Chinese SONG proposal  Criteria of target selection  Process and results of target selection  Test observations  Summary and discussion

1. Scientific goal of Chinese SONG proposal

The SONG project

Optical path of the SONG 1-m telescope

Scientific goals of the SONG project 1 ） Make high-precision time-series radial-velocity observations for individual stars brighter than 6th magnitude, to do asterseismological study. 2 ） Make high-precision high-speed photometric observations for selected fields of the bulge of the Milky Way, to search for exoplanets by means of the micro-lensing effects.

Scientific goal of the Chinese SONG proposal  The Chinese-initiated scientific goal ： 1) For the selected bright target stars of SONG: Make Johnson BVR simultaneous photometrical observations for the 15′×15′ fields around the target stars, when radial-velocity observations are being made for the target stars 2) For the bright stars selected by Chinese SONG team: Select bright stars in the fields of open clusters  Aim ： 1) to search for and study in detail the variable objects 2) to make asteroseismology for the pulsating stars

Modifications of the optical paths 1)Move the lucky image module to the secondary Nasmyth focus; 2)Place a mirror before the primary Nasmyth focus, to reflect light of a 15′×15′ FOV to a Wide-Field-Imager Module (WFIM); 3)Make a hole of 12-mm diameter (92  × 92  FOV) at the center of the reflection mirror, to allow the light of the bright target star to go to M4 then to the Coudé train.

1) Two Dichroic beam-splitters lead light to three CCD cameras equipped with Johnson B 、 V 、 R filters after a focal reducer; 2) Time-series data of the objects in the 15′×15′ FOV are collected simultaneously with the Coudé train. WFIM composition

(Light from the telescope) WFIM

2. Criteria of target selection

 Targets selected by Chinese SONG team ： Stars brighter than 7 magnitudes in V in the fields of open clusters  Using long-term networked observation data of SONG, one may do, 1 ） asteroseismology of pulsating stars in the open clusters; 2 ） exoplanet detection in the open clusters by transit events; 3 ） study of binary stars in open clusters.

Potential target stars of SONG Number of targets: 813 (From the talk of JCD in Beijing in Dec. 2009) B - V V

 For bright stars: Field and parameter search limits: V magnitude: Min -2, Max 7 B-V: Min 0.4, Max 1.3  For open clusters: close enough to the potential bright stars

3. Process and results of target selection

Step 1: for bright stars  6477 candidate stars found in Hipparcos Main Catalogue (epoch J ) with the Multi-parameter search tool;  PARCOS&page=multisearch2

RA DISTRIBUTION

DEC DISTRIBUTION

V MAG DISTRIBUTION

B-V DISTRIBUTION

Step 2: for open clusters Download catalog of open clusters from: Dias W. S., Alessi B. S., Moitinho A. and Lépine J. R. D., 2002, A&A, 389, 871

Number of clusters: 1787 Clusters with Diameter: 1782 (99.72%) Clusters with Distance: 1114 (62.34%) Clusters with Reddening: 1093 (61.16%) Clusters with Age: 982 (54.95%) Clusters with Distance, Reddening. and Age: 969 (54.22%) Clusters with Proper Motion (PM): 890 (49.80%) Clusters with Radial Velocity (RV): 502 (28.09%) Clusters with PM + RV: 482 (26.97%) Clusters with Distance, Age, PM and RV: 430 (24.06%) Clusters with Abundance: 178 ( 9.96%)

RA DISTRIBUTION

DEC DISTRIBUTION

APPARENT DIAMETER DISTRIBUTION Apparent Diameter (Degree)

Step 3: bright stars in open cluster fields  Take the bright stars at the center of the fields, and the edges of the open clusters (OC) located just at the edges of the fields, as the critical situation of targets  Separation in RA ≤ (Diameter of OC + Diameter of the field)/2 Separation in DEC ≤ (Diameter of OC + Diameter of the field)/2

SELECTED CANDIDATES  254 PAIRS  BRIGHT STARS ： 243 (3.75%) OPEN CLUSTERS ： 121 (6.77%)

RA DISTRIBUTION OF OPEN CLUSTERS

DEC DISTRIBUTION OF OPEN CLUSTERS

APPARENT DIAMETER OF OPEN CLUSTERS Apparent Diameter (arc minute)

RA-DEC GRAPH OF OPEN CLUSTERS

RA DIATRIBUTION OF BRIGHT STARS

DEC DISTRIBUTION OF BRIGHT STARS

V MAG DISTRIBUTION

B-V DISTRIBUTION

RA-DEC GRAPH OF BRIGHT STARS

NUMBER OF BRIGHT STARS WITHIN THE OPEN CLUSTER FIELDS

Separation in RA from the bright star to the open cluster center

Separation in Dec from the bright star to the open cluster center

NoName of Open ClusterRA (h)DEC (degree)Number of bright stars 1'Platais 2' 'NGC 457' 'NGC 752' 'NGC 869' 'NGC 884' 'Alessi 13' 'Melotte 20' 'Melotte 25' 'Melotte 31' 'Collinder 65' 'Collinder 70' 'Platais 5' 'Platais 6' 'Collinder 89' 'NGC 2451A' 'Collinder 173' 'Ruprecht 64' 'NGC 2632' 'Platais 8' 'Platais 9' 'Turner 5' 'Platais 10' 'Collinder 285' 'Collinder 302' 'Alessi 24' 'NGC 6475' 'Collinder 359' 'IC 4725' 'ASCC 100' 'ASCC 123' 'Alessi 22'

4. Test observations

 March 2 and 6, 2010: Run I The 80-cm telescope at Xinglong station  March 10 and 12, 2010: Run II The 100-cm telescope at Xinglong station Attention: Light of the bright star masked at the center of the window of the CCD camer

 The 80-cm telescope  Mounting: equatorial  Made by AstroOptik company of Germany  Equipped with a PI CCD camera of 1340×1300  Cooling: liquid nitrogen  FOV: 11.5′×11.5′

 The 1-m telescope  Mounting: altazimuth  Made by EOS company of Australia  Equipped with a PI CCD camera of 1340×1300  Cooling: electronic  FOV: 12′×12′

 Targets: HIP 29860: RA=06:17:16; DEC=05:06:00; V=5.71; B-V=0.61; Open cluster: Platais 6; RA=06:15:26; DEC=03:50:42; Diameter=4.2°; Sep in RA=27.6′; Sep in DEC=75.3′ HIP 69107: RA=14:08:46; DEC=59:20:16; V=6.47; B-V=1.023; Open cluster: Collinder 285; RA=14:41:06; DEC=69:34:00; Diameter=23.33°; Sep in RA=8°5′; Sep in DEC=10°14′

Test observations: Run I /80cm/Hip 29860

238 frames in 3.86 h Light curves example

Photometry precision

Test observations: /80cm/Hip 69107

108 frames in 4.13 h Light curves example

Photometry precision

Date: Telescope: 100cm Target: Hip Data: 136 frames for 3.68 hours Test observations : Run II

Date: Telescope: 100cm Target: Hip Data: 127 frames for 4.13 hours Test observations

5. Summary and discussion  ― the Coudé path for RV observations and the Nasmyth instruments for micro-lensing effect detection will never work simultaneously; ― the M3 can rotate 180°; ― the 3-color 15′×15′ photometer allows the light of the bright star to go to the Coudé path; the proposed modifications will not harm the original scientific work of SONG.

 However, one may get scientific benefits with these modifications.  Long-term 3-color networked data will be collected for the objects in the fields. This kind of data will be unique and very important in science.  We estimate the price of these modifications around 300,000 euros for each node.

 Bright stars matching the requirements of SONG are found in the fields of open clusters.  In the test observations with the 80-cm telescope, no variable stars discovered. Possible reasons: 1) photometry precision relatively low and few data collected; 2) the ages of the open clusters should be concerned in the target selection.

 Test observations with the 100-cm telescope: 1) field rotation is visible; 2) a specific photometry code is needed to do photometry for the objects in the rotating frames.  We plan to make more test observations for more bright stars in the selected open clusters with the ages concerned.  Discussion and collaboration are welcome.

Thanks for your attention!