Identification of X-ray Point Sources and Study on the Nature of 62 X-ray Globular Cluster Candidates in M31

Zhou Fan, Jun Ma, Xu Zhou, Jiansheng Chen, Zhaoji Jiang, Zhenyu Wu

Our work contains 2 parts:

1. Identify the 8 unknown X-ray Sources.

2.Study the optical nature of 62 GC X-ray sources.

The Data of X-ray Point Sources in M31

1. Trinchieri & Fabbiano(1991) presented the positions of 108 Einstein X-ray sources

2. Primini, Forman & Jones(1993) listed the positions of 86 ROSAT HRI X-ray sources.

3. Supper et al. (2001) 2nd ROSAT detection of M31, 7 GC X-ray sources.

4. Kong et al. (2002) (Chandra ACIS)204 X-ray point sources.

5. Kaaret (2002) (Chandra HRC)143 X-ray point sources.

6. Williams et al. (2004) (Chandra HRC)166 X-ray point sources.

7. Trudolyubov & Priedhorsky (2004), (XMM-Newton & Chandra ) 43 GC X-ray sources.

The BATC Optical Observation of M31

Using 60/90cm f/3 Schmidt telescope in XINGLONG Station of NAOC, CAS.

2048 X 2048(pixels) CCD. Field of view ~ 58’X 58’ , 1 pixel ~ 1.67”. Using 13 intermediate-band filters

(BATC03 - BATC15) covering from 4,000~10,000 Å.

The observation of M31 was from Nov. 15th, 1995 to Dec. 16th, 1999.

Obtained 8 new X-ray sources

We compared the BATC data and the X-ray data of M31 in 3 pixels(~5”) and found 8 new X-ray sources unidentified.

Identification of 8 New GC X-ray Sources

Using the 49 GC X-ray sources’ SEDs as templates, we compared them with the 8 SEDs. Combined the FWHMs, we have identified 4 new GC X-ray sources.

Criterion:χ2 <18.1(DOF=12,Q > 10%) & FWHM source > FWHM star 4 new GC X-ray sources.

49 GC X-ray

sources (circles)

and 4 new GC X-ray sources (boxes)

and 9 are out the BATC

M31 Field.

V distribution(58~353) (KMM fit)KMM test: the distribution is bimodal with peaks at 15.65 and 17.89,and p value ~ 0.094.

KS test: D max = 0.354 ， P=4.829E-06

B-V distribution(58~353)

KS test: Dmax = 0.181 ， P=0.068

Color (B-V) ~ V(58)

The Correlation between LX (0.3-10keV) and Lopt (41)

Log (L /1035ergs-

1) = a V + ba = 0.26± 0.11; b = 6.17± 1.76, and the linear correlation coefficient r = 0.36 at the confidence level of 98.0%.

Thank you !