سمینار این هفته را خانم نجمه شیخی از دانشکده فیزیک دنشگاه تحصیلات تکمیلی علوم پایه زنجان ارائه خواهند کرد. عنوان و چکیدهٔ سمینار ایشان به شرح زیر است:

کسر دوتایی ها و تفکیک جرمی در خوشه ی باز آلفا برساووش

The binary fraction and mass segregation in Alpha Persei open cluster

Abstract: We have obtained membership probabilities of stars within a field  of :3^o  from the center of the open cluster Alpha Persei using proper motions and photometry from the PPMXL  and Wide-field Infrared Survey Explorer catalogues. We have identified 810 possible stellar members of Alpha Persei. We derived the global and radial present day mass function of the cluster and found that they are well matched by two stage power law relations with different slopes at different radii. The global MF of Alpha Persei shows a turnover at 0.62M_e  with low and high mass slopes of α_low =0.50 ±0.09  and  α_high = 2.23 ±0.14, respectively. The high mass slope of the cluster increases from 2.01 inside 1^o.10 to 2.63 outside 2^o .2, whereas the mean stellar mass decreases from 0.95 to 0.57M_e  in the same regions, signifying clear evidence of mass segregation in the cluster. From performing a series of Monte Carlo simulations,  we  obtained a binary fraction of f_bin= 34±12 per cent for stars with 0.70<m/M_e<4.68. This is significantly larger than the observed binary fraction, indicating that this open cluster contains a large population of unresolved binaries. Finally, we corrected the MF slopes for the effect of unresolved binaries and found low and high mass slopes of α_low= 0.89 ± 0.11 and α_high = 2.37 ± 0.09 and a total cluster mass of 352M_e  for Alpha Persei.

این سمینار در روز یکشنبه ۲۵ بهمن ۱۳۹۴، ساعت ۱۵ در اتاق ۵۱۷ در طبقهٔ پنجم دانشکدهٔ فیزیک برگزار خواهد شد.