Thiên văn học và vật lý thiên thể học

It is designed 1» measure positions, paallates eal proper motions for about 1 Bilton ubjets Ate focusing asirametry: the spectrophutomster and the spectrometer on board will allow the de

Ñ ASTRONOMY AND ASTROPHYSICS

hi Minh ity University o{ Pedagogy, Viet Nam, ` Wber 2011) PROCEEDINGS

= IAU - VIETNAM WORKSHOP

I Em ON ASTRONOMY AND ASTROPHYSICS

Ho Chi Minh City University of Pedagogy, Viet Nam

21 - 25 November, 2011

` —==:

THU VIEN

KỈ YẾU HỘI THẢO QUỐC TẾ

THIÊN VĂN HỌC VÀ VẬT LÝ THIÊN THỂ HỌC

Hội tháo được tài trợ bởi

Hội Thiên văn Quốc tế (IAU)

Trường Đại học Sư phạm TP Hỗ Chỉ Minh

'Quỹ Phát triển khoa học và Công nghệ Quốc gia (Nafosted)

Trường Đại học Quốc tế - Đại học Quốc gia TP HCM

ĐẠI HỌC SƯ PHẠM THÀNH PHÓ HỖ CHÍ MINH

21-25 tháng 1! năm 2011

SS

MUCLUC

1 Michdle Gorbaldi

Physical characterization of the stars in the light ofthe the gaia space mission

"Nghiên cứu đặc trưng vật lì của các sao hằng tầu thăm dõ vừ trụ Gaia 2

2 Pierre Darriulat

‘Cosmic rays: an introduction Giới thiệu vỶ tia vũ trụ 2 3.M B N (Thijs) Kouwenhoven

The fornation and evolution of iar clusters and planetary s

Sw ôn: hành và tê hỏ của es inh nn sas rà nổ vấn hành nh 38

ts Xenslyieesnerelabirlee]

ime, cosmology and the evolution of the universe

5 Phan Bao Ngọc

Molecular outflows in the substllar domain: new constraint on trown dwarf formation

(Qu trình giải phòng kỉ phủn tế: Những chỉ dẫn mỗi v nguẫn gắc sao lùn nân TÔ

6 Nguyen Quynh Lan, Le Cong Tuor

Pham Khanh Hoi, Nguyen Anh Vinh, Nguyen Van Khanh

Dark matter

80

Nguyen Van Khanh, Mathews G., Suh |

Cosmic formation and decaying dark matter

Sichinh thimh của vũ tru ủa với

8 Dinh Van Trung

Molecules in the circumstellar environment around evolved stars Phân tử trong mỗi trường Vỏ sáo già

9 Vo Hong Hai, Nguyen Quoc Hut

Develop the detection system for cosmic ray measurements using plastic scintillation HoChiMinh

Phat triển hệ đo bức xạ vũ tụ sử dụng deleclar nhấp nhúy planic và hệ thống gải nhận Flash-ADC/FPGA tiển hành tại Trường Đại học Khoa học Tự nhiên Thành,

Hỗ Chỉ Minh

10.Nguyen Van Hiep

The Vatly radi

Kinh thiên van v6 tuyén Vatly

11 Do Thi Moai

Gravitational lensing and eistein rings

Thaw kinh hap dan vũ các vòng Einstein

los

us 13

TAU - VIETNAM WORKSHOP

ON ASTRONOMY AND ASTROPHYSICS

Ho Chi Minh City University of Pedagogy Viet Nam 21-25 November, 2011

o ere

Tis [0b = Vii Wana oa Ase, a in 2011 Em

‘lly (a ee Teaching Asmonors) tx Devilowman (VAI progam of be International Astronomical Union (AU) This program aims at promoting the cing

#9 le Sự All E esintet wierd selec Naot been yell escloped As pat ofthe TAD prugrat ie IAU ~ Vien Workshop on Asvonoey Sapportunity fr aioncmers asrophyicis, aronomy Adhơn and studens and also from other countries to update their knowledge in tronomy and related sclonors to discuss thir rescurch in etronomy The

is also an important step in developing astronomy and the teaching of this science in Vietnam

'eeiptertdditteerboliaeigoiragTiar-Trrsdirslubemr Tel

In Vietnam, workshops have been organized in Hanoi Vinh, Danang The [AU ~ Thoem Wogahgpot airman) wn mle 2011 is hosted by Ho Chi Minh City Unhenly of Pefagony in cooperation with Intemational University - Viewam National University at Ho Chi Minh Cit ported by the National Foundation for Since and Teshnslogy Developer rom Nowcfter 2 0 November 25,201)

‘The workshop covers contemporary research topics in astronomy and astrophysics including:

‘* Sun and Climate, Exoplanets! Solar

| Characterization of the Stars: Understanding Dynamics, Chemical Composition and Age

săn from Vietnam and other count Farle! with rapons fom ober verti, Move oi sin krlie tê bit: He vetoes so Has im and three students trom the Sepulsh Nopember Insitute of Teta Indonesia participated in the workshop

The workshop is made a success by the great effort of the organizers and the participation of the participants We are thankful to our co-organizers sponsors, and thank the editors for theit work in making this proceeding

+ International Astronomi

4 Chi Minh City University of Pedagogy, Vietnam I Union (IAC)

~ VNL = HCMC, Vietnam

c for Astronomy and Astrophysics Beijing

* Thijs Kouwenhoven (Kavli Insti University China

+ Nguyen Quynh Lan (Hanoi National University of Education, Vietnam)

* Phan Bao Ngoc (Intemational University-VNU, HCMC, Vietnam) + Dinh Van Trung (Institute of Physics, Vietnamese Academy of Science and Technology Vietnam)

‘Scientific Organizing Committee

+ Michele Gerbaldi (Paris Institute of astrophysics, France)

* Edward Guinan (Villanova University USA), Chair

* _ Nguyen Quynh Lan (Hanoi National University of Education, Vietnam)

* Phan Bao Ngoc (Intemational University-VNU, HCMC, Vietnam)

Local Organizing Committee

* Le Van Hoang (HCMC University of Pedagogy), Co-chair Phan Bao Ngoc (International University-VNU, HCMC), Co-chair + Nguyen Lam Duy (HCMC University of Pedagogy)

+ Tran Quoc Ha (HCMC University of Pedagogy)

+ Tran Hoang (1ICMC University of Pedagogy)

+ Bui Minh Tam (HCMC University of Pedagogy)

Secretariat

* Hoang Ngoc Duy (International University-VNU HCMC) + Nguyen Vinh Khuong (HCMC University of Pedagogy) + Nguyen Ngoe Linh (Intemational University-VNU, HCMC)

* Le Hai My Ngan (HCMC University of Pedagogy)

* Hoang Do Ngoc Tram (HCMC University of Pedagogy)

Prof Michele Gerbaldi (Paris Institute of astrophysics, France)

‘The Dynamics of Star Clusters and Planetary Systems 1 13:30-15:00 py Thijs Kouwenhoven (Kavli Institute for Astronomy and Astrophysics (KIAA) Beijing University China)

08:30-10-00 Ass Prof Dinh Van Trung (lasttute of Physics Viemames

of Science and Technology Vietnam)

Academy

‘The Dynamics of Star Clusters and Planetary Systems II 10:30-12:00 Dr Thijs Kouwenhoven (Kavli Institute far Astronomy and Astrophysies (KIAA) Beijing University China)

13:30-15:09 Molecules in Space

Ass Prof Dinh Van Trung (Institute of Physics, Vietnamese Academy

Sun and Climate, Exoplanets/ Solar IT

Prot Hdward Guinan (Villanova University USA)

‘The Cosmic Rays (part!)

Prof Pierre Dariulate (Institute

‘The Cosmic Rays It

Prof Pierre Dariulate (Institute for Nuclear Science and Technique, Vietnam)

Develop the detection system for cosmic ray measurements using Plastic Scintillation Detectors and Fla CIFPGA-Based Readout performed at University of Science-Ho Chi Minh City

Dr Vo Hong Hai (HCMC University of Science)

Dr Phan Bao Ngoe (International University

NU, HCMC, Vietnam) Dark Matter IL

Ass, Prof Nguyen Quynh Lan (Hanoi National Univer Education, Vietnam)

Concluding Remarks

Prof, Edward Guinan (Villanova University, USA)

Dr Hugnh Thanh Triểu (

(CMC Vietnam }

rector of the University of Pedagogy

No | Full name | Institution

h = MSs Ho Thi Thanh Van, MSc , ¬ Tình University

1 ÏNn Hang lh Thạnh

9 Mr fran Thanh Bình MSc, 1 Hue University

10 Me Hoang Cong Phuong, MSc Dong Nai University

-_ Mr, Nguyen Thanh Dụng, Mộc —— Sai Gon Universit

| Ms Bui Thi Cam Hue MSc,

Mr Nguyen Dang Thanh MSc ——

Pre University College

36 | Ms Nguyen Thi Thuy Dung — |

37 |Ms.Nguyen Tran Ngoc Anh

38° | Ms Do Thi Thanh Hai |

40 | Mr Nguyen Le Hoang B _

41 | Mr Ngo Thanh Liem, BSe

42 | Mr Pham Quoe Trung BSc |

43_| Ms Nguyen Thi My Da |

44 — | Ms Tran Thi Huong |

46 — [Me Nguyen Nhat Minh ]

47 | Mr Phan Ngoc Hung, MSc _|

50_| Mr Le Anh Duc, BSe

SE — | Ms Nguyen Thi Kiew Thu, BSe

$3 — |MSLeThiCamTu.BSc

$3 — ME NguyenHuuMam HCMC University of Pedagogy S4 | Mr Le Bin Ho, BSc

35 _| Mr Tran Hong Nghia

36 —_ | Mr Mai Hoang Phuong MSc

ST | Ms Vu Thi Lan Anh

38 | Mr Le Tan Phuc

59 —_ | Mr Chau Hong Thang MSe

œ {Me Tran Sper Thien Ta 867 |

6A Ms Nguyen Vinh Hong Tran

64 Ms Nguyen Thi Tham

6S — Ì Me Nguyen Cao Minh, BSe,

| Ms Nguyen Thi Thu Trang BS

71 | Ms Ha Nguyen Minh Phuong Bi |

21-25 November, 2011 PHYSICAL CHARACTERIZATION OF THE STARS

IN THE LIGHT OF THE THE GAIA SPACE MISSION

MICHELE GERBALDI ABSTRACT

The Guia space mission will be launched in 2013 It is designed 1» measure positions, paallates eal proper motions for about 1 Bilton ubjets Ate focusing asirametry: the spectrophutomster and the spectrometer on board will allow the determination of stellar fundan imeters, in particular effective temperature

‘metallicity und the line-of-sight inwerstellar extinction The methods used to derive such parameters are presented

eds: Gaia mission, stars: Tundamental parameters, astromet TOM TAT

Nghiên cứu đặc trưng vặt lí của các sao bằng tàu thăm dò vũ trụ Gaia thăm dỗ vũ trụ Cala về đưc pl xảo năm 3013 Tàu thâm đủ Guảa được thất đc in vị trí, đơ tị sai vã chuyên đồng riêng của khoong một tí tiên the Mac

nã 4L ào: vông xài vực do mia bang ak

(European Space Age i 1) cesta itis lA A Ae clmcraional mop of our Unley within = TOkpe Boot te Sunt (sabe designed tạ dynamics and intrinsic properties of a wide range of star

Over its S-year mission, Gaia will measure positions parallaxes and jbo Ri ns bile pijons #ự Odnmy mưì dmgfeul oe Local Came, brighter than about the 20" magnitude

Michote Gerbaldi Besides the positional and kinematics information Gaia will provide astrophysical information using two instruments A spectrophotometric instrument, operating in the spectral domain 330 ~ 1000nm, will provide low-resolution spectra, in the range 20 to stars, quasars .) a challenging task For the stars the astrophysical parameters effeive emperaure, sfece groviy and metaiciy, will Be derived using

‘consortium in charge presently of this aspect comprises more than 400 scientists from more than 25 European institutes

In these lecture I will describe the principal methods used to determine the itusmareal yal paramer ofthe sare og Tef, malic, gravity, as well as the interstellar reddening and how it will be applied to the Gaia

of a course

2, The physical characterization of the stars

Even if the stars represent only 0.4% of the Universe in term of energy, the stars

‘are the main constituent of the observable Universe

+ are the source of its chemical evolution

+ content the memory of the history of the Universe

+ are tremendous laboratories for the physicists

All out knowledge is based 0 sheon- aberrations confonaion at we cox

Bi logic fen Wit te tte, The ests SẼ Bi dødsemagnsie mm femperane, gral chemical compostion ua wil dled obrerion# the ris and the mass parameters can be obtained directly and others require 2 model of the: star radiation in such a way thot porametcrs are deduced frm the cd©loöi Eem the Sorgen oft stor comopere mel, The cay ermine parameters were use to check the validity of the star models

S presentation will be cotended to the determination of the star age, using evolutionary racks or sochones ‘computed from stellar interior models

21-25 November, 2011

3 Fundamental stellar parameters

SL Luminosity

‘The luminosity oF the absolute magni

eel sel a Ths al any tee by Si an be eed comining

‘ground and space data have 10 be calibrated into ters dtc Ta mar brghtea, a obrorved fom the Earth [2] Abe OF cme convert the raw data into flux Vega is sill the primary fundamental calibrator, even if cannot be considered as a “normal” AOV star being a rapidly rotator scen pole-on [3, 4] A set of new primary standard stars tor the determination of the SED is under

‘construction [5]

For the calibration of the Gaia low resolution spectra into SED, a grid of about

Bi oesrophetemeesnnd ss Lxpeesenly esti Absa syer he sky This set of standard stars is much larger and more homogeneous than any set star distance as well as the amount of the interstellar absorption along the line of sight

As only afew thousand of sas ve aur dsunces sheretod methods were developed (0 derive the luminosity Th sed om the measurement of the intensity

of omme apacial (teres which are, prod iiicators of the luis, These cthods

Ch two sie have sillr lonley Ue He oF both as we laingnhble i tie spectrum,

ipsing binary: the total brightness of the system is varying when the stars periodically cm ‘each other,

In the case of a visual binary if the distance of the system is measured the mass

of each star ean be computed, 23 such systems have mass with accuracy better than 3°

H

wry systems for which accurate masses can be determined are used for detailed tess of stellar structure and evolutionary models

the Gaia mission f combining images and spire fe Steen of aaa illic, binaries i ores is 3/4 of the ne fer than 20 mags and about 15% of thm i located a! 1 hpe, The Gal ae nisl cae could be more than:

© 10" resolved binaries within 250 pe,

+ and 10.000 stars with masses within 156,

33 Radius

Two methods are presently used to measure the stellar angular diameter from Which the radii can be obtained if the distance of the star is known These are the high method to mẹ: ‘angular diameter; the lunar occult thod is hased on a measure of the time needed for the star to be hidden behind the Moon Two few interferometer exist to able to use it routinely to determine the stellar angular diameter Actually’ the determination of accurate radii trom interferometry is limited by the direct measurements of the radius

A small theoretical impact is present in all these methods through the limb darkening which has to be considered either for the interferometric data or the light

Is

21-25 November, 2011

‘curve analysis An indirect method can be used to determine the star angular diameter itis based on the comparison of the SED to a theoretical spectral energy distribution Radii of a few thousands of stars have been determined up to-now, CHARM? caaloge is complain of dist messuremects by high agus reeolion methods

as vel ines exons ofr lamer This clog comdees 3238 nique se5 [8] The Gaia mission will expand drastically our knowledge on the stellar

PIG re mice a sem effective temperature imerous, A semi-empirical method using the flux in the infrared was initially proposed by Blackwell and Skalls [10] es eae dhe lnfa Red Flux Method (IRFM)

Tr uses the ratio between the bolometric flux of the star and the monochromatic flux at some IR wavelength bth measured on Ean, This observed quantity is then compared determination of the Tey The IRFM method provides this tim angular atmosphere model can be compute which implies the knowledge of more parameters t0 the star surface

The indirect methods are mainly based on on the use of photometric or spectroscopic data, The indirect spectroscopic method is based on the “best” fitting

te mean difference between Tay computed with various methods is of the order of 100-200 Kelvin

hy mae cio es conret chev nie tlie aici

Sa pea oo emson aera different wavelength The Colour Indes ave compare lacie values cealoed run soocrosSened mai

16

Michele Gerbaldi

‘observed and the” intrinsic” colour is called the colour excess (eg E (B-V) Vir ~ (B*V)ute for the UBV photometry) and

Another method to estimate the interstellar absorption is based on the SI

‘compared to a “theoretical” SED computed from a stellar atmosphere model

% Modeling

Stellar modelling is a fundamental wil Reversing of irs parameters such as their chemical comy cannot be measured đượnhg, All of she lnforyaion chen about ats Iz provided by clecromegnete radiation The photons we detect originate in the outermost layers, or atmosphere of the star In order to interpret stellar spectra itis necessary to construct models which accurately represent the structure of a sta

‘A star model depicts the nucleosynthesis in the core and the transfer of radiation

‘most of the cases Equations have to be solved taken into account which are the observable quantities Two distinct models are onan Hệ”) interior model and a stellar atmosphere mode!

SL Stellar interior modet

stellar interior model represents the solution to the equations of stellar structure describing:

the conservation and continuity of mass,

* the hydrostatic equilibrium,

the energy generation through nucleosynthesis,

* the eneray transport (radiation, convection and conduction) input parameters to build such a model are simply the mass of gas and its chemical commponton According to the Vog-Remsel theorem te saton |s vnque From the solution values of many different parameters can be derived in particular the first nuclear reactions which are taking place are those transforming H into He ~ the hydrogen burning After some the nuclear reactions are taking place in the core its chemical composition

Ter pros Soe model aso be bulk wich deacrie ace wae fr tear The equations are solved as many times as necessary follow i ofthe

the fundamental parameters These successive models represent the life ofa star and its changing properties during its lite

ta a set i evolutionary tracks for different masses isochrones can be

‘computed An isochrone represents the locatio IR diagram of stars of various

‘mass but having the same age This is the definition of a star cluster, open or globular

By comparing the HR diagram of a star cluster to a set of isochrones its age can be sel urat Nots ta i cate conection fla stansuctiex no edie bonus there is no large motion of matter bringing to surface matter from the core, during most ofthe life ofa sar {12}

5.2, Stellar atmosphere model

A stellar atmosphere model describes the properties e.g density temperature of the external layers of a star This region has a density much less than deeper in the star See ie wires oben i epi mi be debe I uel aking ts account how the photons en “re-emitted” by the matter this being eeccd by ie opacay eollsiat qed cocklebur quien" Goold yen flux constancy at any dey

Ate the chetrical comnpoiion of the ga, the ey a te sure (neaded for the hydronic shih) a isa ses (nde the flux constancy) or the effective temperature In the atmosphere, the — is constant as the mass of the Keo) is negligible compared to that of the star which, atmosphere having a depth of a few hundred to a few thousand of kilometres

In the atmosphere, the gas is in Local Thermodynamic Equilibrium (LTE) for most of the stars, LTE means that the components of the gas (atoms, electrons, form: the collisions dominate, There is a unique temperature to describe, locally, all the varies with the depth inside the star atmosphere, The effective temperature is not the

‘at the surface but the temperature at some depth from where the photons can leave the atmosphere “freely” that is without any more interactions This result is valid outside any strong lines

Large grids of stellar atmosphere models have been computed, in LTE, for a variety of chemical composition, gravity and Tạ [13] From a stellar atmosphere model

in order to be compared to the observations The best fit between the observed and the

jon of the fundamental parameters by adjusting the computed spectra to the observed one More parameters can be derived such as the rotational velocity of the star, and its radial velocity

Michele Gerbaldi

The stellar atmosphere models are widely used to calibrate the photometric systems in order to derive the fundamental properties of a star through a combination

of clour ines: such heretical approach iy Presently stellar model atmospheres form the basis for any element abundance is checked wt fundamental data oie

<ktcrinaion and hence are eneial ingreiees for sadn OF wll, glace and cosmic evolution

¢ dominant source of uncertainty today’ originates with the assumptions and approximations in the analyses emphasizing the great need for continuing efforts in three complementary types of model atmospheres: line-blanketed non-L.TE models of al models odes of cool stars including the formation of polyatomic molecules and dust

6 Physical characterization of the stars with the Gaia mi sign, THU VIEN

rom the BPIRP calibrated spectrophotometre data compared to

in folloving Keene permis wl be termed re apes, Te surface gravity log g the metallicity [Fe/H], and the interstellar reddening Combined with the parallax the radi and the mass can be obtained

‘The radial velocity is the Fundamental parameter obtained from these spectra and combined to the parallax and proper motion it will give the velocity ofthe star The apparent magnitude Fora BIV sar wih V=12, (RV) = kms fora G2V sar wth V=13.0 (RV)

calibration in wavelength and the radial velocity measurements will be done set

of “radial velocity standard stars” This seer ol ae "se HÌ ote te and their characterization is under way

7 ‘The challenge for the fundamental parameters determination with Gaia Toe dermintion ofthe sells praetersaconsiderble challenge beeae É will have to rely on totally automated methods based or

‘The capabilities of Gaia is to have about 20 mllien stars with their distance determined to better than 1%, If their Tạy is obtained from the SED with an accuracy of

19 jeoreticat ones —

21-25 November, 2011

visual binaries for which masses should be computed to wit

The age not findemeal parameter, can be qutied fom the evohlnary models, a8 Ter luminosity and m known, When trying to determine several parameters from a data set ki problem of degeneracy exists, This is the case

The overall procedure will be the following: object identification, coarse parametrization (determination of Teif, log g [Fe/H] AGA) and if possible, [a/H] RV

in addition to the spectroscopic data, The whole procedure will be iteratively repeated

of data to improve the the parameter

Over the Sẽ misslon on the average 70-80 observations per star will be

‘bie For perce onan 9 C-t2mikg tm, sitet better than 0.1% at 250pe, 1% within 2700pe and 10% espe a bare od

cd proper motion a are expected to be better than 10has for stars brighter ‘han 1Omag in C-band, for G15 and 300 pas for G=20

Độ 0y Meier sisi be determination of not only the tangential tieton tw ales He Cmyaieat alo, Gt Rac of sah Sat ste rad voc Tas

opi

the spectroscopic radial velocities may provide information on these phenomena, 20

Michéte Gerbalét

-¢ methouls can be used: the changing of the annual parallay over the time, he

if Proper motion over the time and the changing of the angular extent cf a

‘moving group of stars Aecuracies needed for such determination will be obtained with the 5-year Gaia mission [15]

9, Thestellar ages with Gaia

Stellar interior models produce evolutionary tracks or isochrones which are used lợi mm l0 Hàn s ra lệ em x is mr[16,Ti doe ater inaccurately for a single star but in a much better way for a star cluster using the cluster sequence iting inthe HR dagram with an isochvon

Solar uses (GC) are cong he cle oes fa he Caley be dense field in the sky and a “clean” HR diagram (or tude diagram) is oni dehy teed abe đan he Kệ 0948p a bi Tan 100 GC wil be observed by Gaia, The availability of parallayes, prope radial velocities

VI AR9% ii n9ÈĐ HS clhdr mnöenllp tHỸ hehe pri "EN diagram

The most classical clock provided by stellar evolution theory for dating the metal- poor GC is the luminosity of the tum-off stars (TO), Actually the age of a GC is Titing giving access to 3 parameters: the distance the reddening and the bas of the cluster Gaia mission data will allow the determination of the distance e reddening of the stars cluster independently of such fitting and the

— ‘observations will give an estimate of the metallicity of the cluster The the absolute age of the GC will be determined Absolute age is expected to determined to vel discussions on the input physics in the model could

be started through the discrepancies between the fits from various models,

10 Conclusion

The main strength of Gaia lies in asưometry Moreover its impact on stellar atmosphere research is likely to be large not only from the foreseen results but also stellar research from binary stars to 3-D stellar models,

To conclude, let me quote a statement made by D.J Crawford in a lecture at the Intemational Union General Assembly in 1970 “In many cases, theory can help us

us However, I must be extremely careful not to force-fit or to pr ve ideas mess

us up, We are measuring observed parameters and these we relate or calibrate to physical parameters.”

"

l5

21-25 November, 2011 REFERENCES:

ESA http://www rssd exa.int and then follow the links

Tig H., White N M., Lockwood G W (1977) Asironomy & Astrophysics 61, 679, Aufienberg J.P, t al (2006), Ap 648, 664,

Engelke C.W., etal (2010), AJ, 140, 1919

Moon T-T and Dworetsky, M.M (1985), MVRAS 217, 305 Torres G., Andersen J., Giménez A, (2010), Astronomy & Astrophysics Review: 18,

Fitzpatrick E and Massa D (1999) ApJ, $25, 1011

Schaller G., Schaerer D., Meynet G., Maeder A (1992), Astronomy & Astrophysics Sup, 96, 269

Kurucz R (1979), ApJ, 40,

Bailer-Jones C.A.L (2010), MNRAS 403, 96

Dravins D., Lindegren L., Madsen S (1999), Astronomy & Astrophysics 348, 1040 'Kochukhov O., et al (2004), Astronomy & Astrophysics 414, 613 Grundah F., et al (2000), AJ, 120, 1884

Pierre Darriulat COSMIC RAYS: AN INTRODUCTION

PIERRE DARRIULAT’ ABSTRACT

A bref and elementary inroducton tthe poses cam rap x presi, wth particular emphasis on the mechanism of accelerat

Keywords: cosmic rays diffusive shock sedesi extensive air showers

1927 the dependence on nina an the east-west asymmetry establi unambiguously that cosmic rays were charged particles, not photons In 1938, Peme understood that they were produced by very high energy (up to 10!’eV) primaries interacting with the earth atmosphere

In the thirties and forties, when accelerators were not yet dominating the scene, cosmic rays became the laboratory for the study of particle physics Anderson discovered the posivon in 1932 nd the muon fn 1938, Powell and Occhi discovered the pion in 1947 Then strange particles such as kaons, hyperons and many Prolesor a former deator of CERN, Curent instutons,VATLYINST and Hanoi Univerty of

‘Sciences, 178, Hoang Quoc Veet, Cau Gay, Ha Noi, Vit

In the past 20 years, spectacular progress in astrophysics and long time scales implied in the construction of very high energy accelerators have caused a renaissance

Of interest in cosmic ray physics per se under the name of astroparticle physics TeV derwna ry dees have bee snr sil opened ls rales hưng the ability to the sources without suffering deflections {rom magnetic fields At the same time, a new generation of ground detectors was bom,

Plans to use the whole Earth atmosphere as a radiator observed from space are being implemented and neutrino astronomy is currently being pioneered

Pierre Darriulat

2 ‘The main features

Cosmic rays [5] are ionized nuclei that travel in space up to extremely high energies of the order of 10°'eV=16 Joules! There are very few of them but they carry as much energy as the CMB or the visible light or the magnet that is —1eV em’ They have a power law energy spectrum (Figure 3, left) spanning 32 decades (12 decades in energy), of

hhenever they have been measured, cosmic ray abundances are similar to Jbundances observed in their environment, Suge

‘medium typically ~7 gem

fe ray during its journey in the interstel

low energy part of the cosmic ray spectrum is of solar origin, it

etic Shield, Which results in a low While the ve

does not reach the’ earth hecause of the geomagr

‘energy threshold (around the Earth poles it manifest itself in the form of auroras), The

21-25 November, 2011

variable solar activ

important magnetic fields induces variations of this threshold that are transferred vwsicg of te cosmic roy flex caching the Exh It has been Flaed a sich the Earth climate Cosmic rays are indeed the main cause of ionization in the role in the evolution of species

Most cosmic rays reaching the Earth are therefore of galactic origin, From the

‘energy spectrum, one evaluates an energy density ~10°' erg/cm’, Magnetic trapping in the Milky Way disk corresponds to a galactic escape time of ~3 10° y The cosmic ray power amounts pecs to some ~10™* ergicm's which can be compared with the power delivered by sa explosions, ~10"' erg/SN giving for three SN explosions per conury inthe dik, ~10-> er/cns Namely eoomie ras-cary some ~10% of the power delivered by SN explosions

It is only in the higher energy part of the spectrum that an extra gal

‘component can be found, Estimates of its energy content give ~2 10 cee implying a power of ~ 1.3 10” ergfMpc'⁄ In comparison, a density of 10°” Active Galactic Nuclei (AGN) per Mpc’ implies >10™ erg/s/AGN in order to reach the same er/ORB, Both active galactic mole and garoma roy bursts sand theefne, oem the

Pierre Darriulat Ihe differential spectral index of the energy specirum changes at - 3 10'eV from 2.7 w 30 this is referred to as the knee It changes again back to 3 at the upper end of the spectrum: this is referred to as the ankle, These deviations from a pure power spectrum are related with the composition and the origin of the cosmic rays in the energy intervals of relevance (galactic or extra-galactic) and are not understood in

Figure 6, Left: the High Energy Stereoscopic

resolution X ray: images of SNRs (Chandray: Cassop

and Tycho (SN 15

System (HESS), Right: Very high A, the Crab, Kepler (SN 1604)

3

ed point back to ther Ti Tes revealing the high energy (nề tong cohfeg: Bi acusd ples predacel tthe ieeasion of bay Bi, ery cosmic 1s vHh nerty Tmenielirmater(ISMI

2) gamma rays from the Cherenkov light huvers induced by thei

wma ray astronomy detects high en

— by electrons and positrons in the

the upper atmosphere Such showers are simi

by cosmic rays but significantly shorter be

shorter than the interaction length Main sources of high et

scaticring (bremsstrahlung) and synchrotron radiation at lower energies and a” decays,

‘or inverse Compton on the CMB at higher energies

Accurate observations in the TeV range have been made by the High Energy Stereoscopic System (HESS, Figure 6 et in Namibia It includes four telescopes [10]

at the corners of a 120x120 m? square operating above 100 GeV Its field of view is $° land its resolution a few arc minutes HESS has shown that many sources have an

‘counterpart identified as SNR (Figure 6, right)

1m 200, othe wake of erler es secure sbneraions 11), HESS made 8 33h live time observation [12] of SNR RX 1713 which, when ci with an À image taken by Rosat in 1996 [13] established that the SN shell 14 ite source of revealed the presence of important turbulences (Figure 8) in the region of the shock wit tant variations from one year to the next Many such observations followed, With improved resolution, establishing this way that galactic cosmic rays originate from SNRs

4 Diffusive shock acceleration

The identification of SNRs as sources of galactic cosmic rays has suggested an acceleration mechanism called ditfusive shock acceleration (DSA) which is now accepted as the most likely candidate for accelerating cosmic rays [16] As in a (equivalent of the gap between the eyelotron dees) and is guided by magnetic fields on

”

21-25 November, 2011 field of the cyclotron) However both the acceleration and guiding processes are very sitter inherited from the parent star, now strongly dilt dan by stochasic colons cclotron case Guiding is provided hy the remnant magnetic field scattering on magnetic turbulences Indeed, the se path is so large in the much Zit TEM tet ellen cas he aediece vel ec tn media can So an 94 carrying nothing else than magnetic fields

Figure 7 Comparison of raueal ints sured 19 X-ravs (ASCA) and

1 rays (HESS) in separate octans of SNR RX JI13 The ovcrall eurreltion coefcient berween the two radtul distributions is 80°,

hell of RX JI713 Acceleration is best described in the frame where the particle happens to be an where the magnetic fields are at rest: while bending the panicle trajectories, they do not very low density of the ISM in which the pa making the occurrence of collisions negligible Eventually, the particle returns to the shock and crosses it The

sith profi

Figure 8 Evidence for time varying turbulences int

Pierre Darriulat stars inpies aceeraion as ban nia sa exch oiher with selaivehocy At shock traversal, the energy E of the particle increases by AE such that 1B

‘Aer shock averse reaches Ey= Ball

AL Some point, however the particle drifts too far from the shock to have a chance to return 10 it and escapes, Indeed, in a uniform magnetic esote lcgikelcaszogn em enegr/lunesre

Model: ơi Ty Í

đc Là me Maei Ko

‘must be commensurate with the Larmor radius of the particle being accelerated

i hpstiene, te tine btunen sucsesaite conten di HE,

‘ith A conta, and de ese marking the end of the acceleration pres heal (of (esis ABE), Calg ‘ie shock compression ratio (the ratio between upstream and downstream densities) the energy spectrum takes the form aNaE ME" with ate ye-I) Foe monatomic r=4 and dNidE =E*, The prediction of a power spectrum with an index not too different from that observed, is a major success of the model

‘Quantitatively good results have been obtained after it had been realized that the fngoete kt in We shock region oe much sronger tan as oigaly chai There exists indeed copious evidence in favour of strong magnetic turbulences and ene Ge mien in the shock region of young SNRs For example, RX JI713 shows, shock structure implying strong turbulences (Figure 8) and magnetic field amplification [17] Important varations sre detected as ‘Ancton of

me zones of turbulence becoming quiet and conversely on a few years time scale, Evidence for magnetic field amplification is obtained from the ratio of radio to TeV emission and from the compression of the shock front Magnetic fields are enhanced by factors of up to hundred, much larger than the factor of 4 associated with front compression (Figure 10 right) implies a magnetic field of $00 wG instead of the 100G expected otherwise [18]

Ta hợp ote Yen ies sea inane you Si (Keser Can A Tach, SN1006) dence Indeed, shock front compression is a revelator of Field amplification, Sharply peaked Xcrays al forward shock are evidence that the eld efficient and nonlinear at SNR outer blast wave shocks Older remnants do not show such field amplification: the excitation of turbulences decreases with shock velocity

‘while damping (by non-linear wave interactions and jon-neutral collisions) does not the stellar debris are only half a light-year behind the outer shock instead of (wo

21-25 November, 2011 expected suggeing tha «large rath ofthe energy ofthe oawardmoving shack ave is going into the acceleration of atomie nuclei (in addition 10 the electrons Teveaed fy ado and X ray observations, Comparison witha simulation gives again evidence for strong magnetic field amplification

Figure 9 Left: schematic drawing of a cxelotron: right: energy doubling when

‘crossing a shock in a uniform magnetic field

Pierre Darriulat Extragalactic sources

The mow energetic UHECK ane enpced wo pit hr sours wi a fe

is expectation ess onthe asumgion tha extragalactic magnet eld ‘a microgauss which is a priori by no means certain, Their tunitorm distri ie da Gould Hien bể EiAvkt Ee ck oreguactié ign: therrie ey would shir sound the dn 6f the Milky Way) general arguments limit the possible UHECR acceleration avery few The argument is that whatever the acceleration mechanism (itis obviously true in the case of ditfusive shock acceleration) the product of the size of the site by ils mean magnetic field must exceed some value to contain the orbits This is illustrated in

‘GRBs and magnetars (neutron stars having extremely high magnetic fields) For the

in quasars and colliding galaxies (Figure 12

8 of ea galaxies and merging galaxy clusters suggest that these were common phenomena in the ay denser Universe, Suc leved to have played an important role in the process of galaxy formation Galaxy collisions usually do not imply direct star collisions but the strongly ased gravity field enhances the collapse of hydrogen clouds and the fection of

Unt eecey it had not been posible o do cos ay astronomy becuse the images of the sources were blurred by magnetic fields The coming into operation of correlation wth meaty gaaces (1, OF reevence to this sudy I the fc ha the universe (100 Mpe radius), in which detected UHECRs are confined by the GZK cil is My inhomogeneous (Figure 13) Selecting UHECR having an ergy in excess of 6 10'° eV and comparing the direction in the sky where they come

‘observed correlation and were in agreement with reasonable expectations based on favoured entmatesof he galactic and entra galactic magnetic ls for the former, nd horizon for the latter There was an even better correlation with nearby AGNs (of which, however, there Sis mceeen og) The correlation disappeared when including lower energy cosmic rays (pointing accuracy) of farther away galaxies (GZK cut-off)

Figure 12 Left: Radio image of a quasar Right: Centaurus A, merging of an elliptical galaxy with a smaller spiral hes an AGN in its centre (the AGN closest 10 us) and is te site of large shocks

34

However, recent updates [9] including data collected through 31st March, 2009 and corresponding to an exposure of 17°040 km se yr (+3%) nearly twice the former decreased with the accumulation of new data yet, possible biases have been carefully explored and discarded and the observed correlation remains significant While an accumulation of showers point to nearby galaxies, in particular to the Centaurus A region, others point to voids, far away from any matter, Present statistics abundance of massive primaries as a function of energy may suggest that showers that iron nuclei, but much more statisties will have t0 be collected before being able to conclude

Finally it should be noted that much improved limits on photon and neutrino uxes now disfavour exotic top-down models

‘These results have established the ability to point to sources in the sky typically within 1°, which was not a priori obvious because of uncertainties in magnetic fields met by UHECR during their journey to the earth (typically 3G in the disk mean 6 10” eV), Itremains to be understood why such and such a galaxy AGN or else, is a source

‘now: only photons could be used

For now 40 years astrophysics has made fascinating and spectacular progress The whole of physics is invited to the banquet: particle, nuclear, atomic, molecular privileged countries can afford to launch space missions or to build giant

‘observatories But any country can, in principle, access the data This is an opportunity Auger Observatory is such an example The sky belongs to all of us We are all made

of the same star dust

21-25 November, 2011

Figure 13 The nearby Universe

Figure 14 Correlations between nearby AGN’s (left) and nearby galaxies (right)

‘and the direction where the highest energy UHECRs observed by the PAO appear to come from

REFERENCES,

Hess V (1912), Phys Z 13, 1084-1088

‘Auger P etal, (1938), Comptes renudus Ae Se., 206, 1721-1725, Linsley J (1963), Phys Rev: Lett 10, 146-149

Pisma Zh Eksp, Teor Fiz 4 114-118

Piere Auger Coll, The cosmic ray energy spectrum and related measurements with

Fela fly 20) X00 6WvAe srg HE: Ababa 11 Coll) (2010), Phys Rev Let, 101 061101 Abbas! Ret al Hikes cat tô) Phos few Ler ÂN 10110: Sex aso (at lower energies) Nag 12000), Ker Mad Ps T3 689-603, Antoni T etal (2002), Asropar Phys

‘measurements with the Pierre Auger Observatory Contribution to the 31" Int Cosmic Ray Conf, (Lodz Poland, July 2009), aXiv:0906.2347s2 [astro-ph HE] Hino etal (HESS Collaboration) (2008), Nature, 432, 75-79 JA (HESS Cll) 2004), New sronamy Review, 8, 331-336; Absronian

i Muraishi er af (CANGAROO Coll.) (2000), Astron & Astrophys 384, LS7: R Enomoto er al (CANGAROO Coll.) (2002), Nature, 416, 823-829 Aharonian F et al (HESS Coll.) (2004), Nature, 432, 75+

fete Aschenbach B (1996), ROSAT observation of a new SNR in constellation Scorpius, ROntgenstrahlung from the Universe, 267-272 Ellison D.C Decourchelle A, and Ballet J (2004) Astron & Astrophys , 413, 189-

193

+ Zatsepin G1 and Kuzmin V.A

Uchiyama Y er al (2007), Nature, 449, 576-582 and references there Bide Rt Eee (1987) be Rea 154, 1-10 Astrophys J 401.115.381: lang Ý coi G009) mKh: (5044011; Bedio EO oR SP (1998), and Ellison D.C (1999), 4sirophys J 389; Bererhko 6 and Valk (2006), Astron & Astrophys ASI 981 O86 Flison DC eval (2007) Asirophys J (661 pp.879-885, Vladimirov A.E (2008), Asirophys, J, 688, 1084-1084

‘Schure KM et al (2009), Adv: Space Res, 44/4, 433-436 and references therein

21-25 November, 2011 THE FORMATION AND EVOLUTION OF STAR CLUSTERS AND PLANETARY SYSTEMS

M.B.N (THIJS) KOUWENHOVEN” ABSTRACT

For many: centuries the Solar Siem was the only place where theories of formation

‘and evoluion of planetary systems could be studied Nowadays hundreds are exoplanets orbiting other stars are known Most stars and their planets are horn in star clusters where sar encounters cam pra lana orbs Tes a ters wally dove

cvervcw of the formation, evoltion rat detection ofboth star elisters and planetary Tương lệ nen, 1 Wl provide © short berpaction on coopster agai

‘focusing on N-body simulations in particular

Keywords: Star clusters, exoplanets N-body simulations, star formation, Solar System

TOM TAT

Sự hình thành và tiền hóa của hệ các tình vân sao và tình vân hành tỉnh Trải qua nhiều thể kỉ Hệ Mặt Trời của chúng ta vẫn chí là một nơi mà cóc lỉ thn hình thành và tiền hóa của các hệ hành tính không thể nghiên cửu được Ngày nay đã hàng trăm hành nh choến động xưng anh cúc ngi sao Mhúc được phẩt hận Phủn lớn các ngồi sao và cúc hành tình của chủng được sinh ro trong các tỉnh vẫn sao ở đó cúc

họ thường (hực ch ra (hàn cức Tên lẻ rụng Moing vài mi nữm Trong bài lúc này tôi muôn cung cấp tổng quan vẻ sự hình thành tiện hỏa v sự phát hiện của có tỉnh

ân sao và hệ hành tính Hơn nữa ti sẽ giới thiệu ngắn gọn về s nữ í hiển vôn nh tan tập trưng vào phương pháp mô phỏng Nhột thể

Từ khóa: tình vân sao hành tình ngoải hệ mật trời mô phỏng N-vật thể, hình thánh sao Hệ Mặt Trời

1 Introduction

Astronomy i the since tha temps a arawer many of he “Ble Questions” of

‘mankind: Where do we come from? What is the origin and destiny of our world? Are astronomers have studied the heavens for many centuries It should therefore not come

* De, Kavi Institute for Astronomy and Astrophysics, Peking University i He Yuan Lu 5, Haidian Cu, Beÿng 100871, P R Chung 38