RX1856-3754 NEUTRON STAR

represented by: Ayşe Banu BİRLİK Uludağ University Physics Departmant ; researching Jan, 2001-preparing May,2005
Supervisors; Neşever BALTACI-2001-2005 and M.Ali ALPAR 2001

Title:: AN ISOLATED and PROPELLER NEUTRON STAR RX J1856-3754
ABSTRACT

Comparing on RX J185635-3754 Neutron Star on optical and X-ray for 1° view with other rays taken from satallites and researching on where it borns calculating excess flux of RX J1856 optical flux (49eV) to x-ray blacbody flux (57eV) discussing AXPs ,SGRs, DNTs and RQNSs models for propeller neutron star.Comparing on datas which are taken from the satalites RASS-Cnt Broad,PSPC 2.0 Deg-Inten, Digitized Sky Survey, 1420 MHz (Bonn), GB6 (4850 Mhz), Old PSPC (2 deg), COBE DIRBE, IRAS 12 micron and 100 micron.Where the target (neutron star) was born?Why is the neutron star’s closest to earth and lack of a companion so important to astronomers?Explaning the models for the target in AXP and SGR.Calculation about the difference flux of the target to the x-ray blackbody flux.This is a main question for us; Is this target a magnetar or a propeller neutron star?
INTRODUCTION
DATAS FROM SATALLITES:*RASS-Cnt Broad, PSPC 2.0 Deg-Inten, Old PSPC (2 deg), COBE DIRBE, IRAS 12 micron, IRAS 100 micron,1420 Mhz (Bonn) and GB6 (4850 MHz) are taken at 1° view. RASS-Cnt Broad: X-rays datas from ROSAT satallite. PSPC 2.0 Deg-Inten: X-ray data from ROSAT satallite but the spectrum is diffErent.Old PSPC (2 Deg): X-rays data but Old PSPC’s spectrum is bigger than PSPC 2.0 Digitized Sky Survey: Optical view.COBE DIRBE: Infrared rays.IRAS 12 micron: Toward infrared rays of region which IRAS 100 micron ray parted in 12 and 100 view.420 MHz (BONN): Radio waves.GB6 (4850 MHz): Radio waves but the frequency is different. *RASS-Cnt Broad, PSPC 2.0 Deg-Inten, Old PSPC (2 deg), COBE DIRBE, IRAS 12 micron, IRAS 100 micron,1420 Mhz (Bonn) and GB6 (4850 MHz) are taken at 1° view. *Where does it come from?*(preprint Walter 2000);X J185635-3754 is confirmed to be an isolated neutron star. At a of 61+9 pc, with a heliocentric space velocity of 108+16 km s-1. ıt appears to have left the upper Sco OB association between 0,9 and 1,0 million years ago. It may have been the binary companion of the runaway O star z Oph, which left Upper Sco at the same time. If so, the neutron star suffered a kick velocity of about 200 km s-1 amplitude at birth.Rexamination of the space motions of z Oph and Sco-Cen OB association casts some doubt on van Rensenbergen et al.’s conclusion that z Oph orginated in the Upper-Cen-Lup association. It is not clear how to reconcile their binary evolutionary scenarios with these geometric constaints.The existence of an old, isolated neutron star of known age permits one to place another point on the cooling curve, a point not contaminated by possible non-thermal emission. The exact temperature depends on the choice of atmospheric model, but in any event the luminosity lies near the FP (Friedman & Pandharipande 1981) cooling curve at an age near 1 Myr.The infarred radius of the neutron star depends on the angular diameter, which is model-dependent. The smallest angular diameter for a given temperature is given by a black body. For a temperature kT=49 eV the lower bound on the radius R¥ is 6,0+1,2 km, and preliminary atmospheric models yield R¥ =11.2+3,4 kmRX J185635-3754 will make its closest approach to the Earth in about 280,000 years, at a distance of 52+9 pc, in the constellation Grus Resalba:AXPs sources of pulsed X-ray emission with persitent luminodities Lx ~ 1035-1036 erg/s ans soft spectra.Periods lie a very narrow range,between 6 and 12s.Their charecteristic ages of order 103-105 yr.Corpared to binary X-ray pulsars,AXPs have lower luminosities and exhisits narrow distiribution of periods.Unlike young radio pulsars ,AXPs have rather long periods and appear to be radio quiet.To understanding there differences is to try and identfy the energy source that powers the x-ray emmision. It is quite clear that this energy can’t be provided by rotation (as it is in radio pulsars)For values P* and P that are charecteristics of AXPs the rate of lots of rotational energy is E= 4p2IP/P3 » 1032,5 erg s-1 orders of magnitude smaller than the observed X-ray luminosities.
Researching on its condition ,excess flux ,either it has a companion or not , its age and comparing with
AXPs and SGRs Models of the target - RX J1856-3754
.First One AXPs Models (X-ray emmision)Isolated ultramagnetized with field strengths in the range 1014-105 G.Lose rotational energy similar radio pulsars field strengths consistend for soft gamma repeaters. Magnetars: X-ray luminosities could be powered by magnetic field.Residual thermal energy (if it is correct the envolope of the star must consist light elements such as hyrdogen and helium).The emission is powered by magnetic field deray then a value of B ³ 1016 G is requried unlies nonstandart deray processes are invoked.Second One AXPs Model:X-ray emission is powered by accetion, high values of the magnetic field are not required.Accetion can occur from binary companions of very low mass OR from the interstellar medium.If the emission is powered by accetion from a disrupted binary companion, it is not clear why AXPs should be associated with young supernovea remnats.X-ray luminosity can be explained by cooling without requiring that this neutron star be old and have experienced magnetic field decay.Another accetion model, in which neutron stars accerete from disks that formed from fallback material after a supernovae explossion (by Alpar 1999 and Marsolen at al 1999). The possibility that material might fall back onto a neutron star following a supernovae explosion and settle in a disk is not now (e.g Woosley 1998) suggested that this process might account for the presence of planets around some radio pulsars.Subsequent accretion can occur only under specific circumstencesDepending on relative locations of the magnetospheric radius.The light cylinder radius. Corotation radius related there conditions to physical parametres ,Mitial mass of the disk (Md) İntial period of the neutron star (Po)The strength of the magnetic field B. As to SGR Models: (soft gamma Repetars) The neutron stars are accepted as a magnetar. They are formed like the other neutron stars remain of the explosion of giant stars becoming supernovae.Magnetar stars are special in their high velocities. Their rotating speed is too more, after the explosion the conductive liquid matter inside the star causes 1*1012 Gauss Magnetic Field that makes the star like a dynamo
Rotating Dynamos’s Kınetic Energy:KE=1/2*I*W2(dipolradiation)I*W*W=2/3*B2*R6/c3W4(erg/s) W(rad/s2)=(2/3*R2/c3*I)B2*W3 Rotating dynoma’s energy speed.As to magnetar model; the high magnetic field damages iron crust so in high velocity elemantar particles produces high energy luminosity.On of the SGR identicially observation on a neutron star; while the rotating of the star it gets slow in velocity as 1/1000 ratio in a few years.“Magnetic Breaking” causes the star to be rotating in slowly with producing 8*1011 Gauss in Magnetic Field. As to that model there is a star quake on the extraordinary strength of magnetic field.As to AXP Model (Anomalous X-ray Pulsars):Their brightness of the neutron star is because of the observation of the gass around in gravitational force.That means; while mass is transferring disk around of the star it gets heating and that produces energy.They are alone; have no companion so the disk around of the star is the gass remnant of the supernovae explosion.There is an other AXP model in last years; that is the existance of the rotating heated gass of the mass transffering disk is not necessary for brightness.The getting slow in rotating that is ; slow rotating energy produces lumonisity.For the angular momentum of the small neutron star; it is not enough effective equal mass but big radius stars it can be.Both of the SGR abd AXP common properties:They are the remain of a supernovae.They are alone, they have no companion for transfferring mass.Their rotating period is 5-12 second.Their rotating speed is getting slowly apperantly.They are approximately 20 km. in diameter with dense center after supernovae explosion.As to Duncan; the stars are in different two phase of the same process in AXP and SGR observations.The Age of The Neutron Star In AXP and In SGR:Magnetars can be 104 year in age. At the end of that age temperature decrease the level where the mecanism produces extraordinary magnetic energy. So there is no quake on the crust and no soft gamma ray explosion. After 105 year the star cares the magnetic field that produces regularly X-ray radiation. The end of that age magnetic field gets weak and the star can not be observed.In Milkyway, every 1000 year a magnetar can be observed. So now in Milkyway there must be 107 died magnetar travelling in space.The age of the magnetar is @ W/2W Rotating dynoma energy speed W(rad/s2) = (2/3* R2/c3*I)B2*W3 For radio pulsar which is only known magnetic filed B ~ 1012 Gauss (W,W) B ~ 1012 Gauss There are approximately 1000 radio pulsars. W»10-13 W»10-100 rad/s 1012 Gauss For RX J1856 neutron star W=? W= 2p/P = 2p/8,4 second @ 1 W=? Not known ( age t @ W/2W) can be found(W , t) , B (magnetic field) ,rotation, age,speed dP= dP/dt P~10-15 s.s-1 P=2p/W P= dP/dt = -2p/W2*WSlow W and high W (breaking) B ~ 1015 gauss (magnetic field) Slow W and young age t B ~ 1015 gauss
CALCULATIONS;In mathematically operations by using engtral we can calculate the areas under graphics.The upper line (observed) in between l1-l2 wavelength bands shows total flux from the target (erg/cm2s).= ò A/l4*dl = A/3* (1/l3) = A/3* (1/l3 – 1/l3)The upper line (X-rays for black body line continues) in between l1-l2 wavelength bands shows total flux from a black body. = ò B/l4*dl = B/3* (1/l3 – 1/l3) The difference flux=(observed flux) – (x-rays for black body line continues)The difference flux = (1/l3 – 1/l3)* (A/3 – B/3) = 1/3* (1/l3 – 1/l3)*(l4f1 - l4f1) The difference flux = erg/cm2 s cm Using logaritmic rules for graphics;Excess flux of optical spectral energy distribution flux to x-ray for blackbody energy distribution flux (57eV) [Between F303 HSTU and F606 HSTV] Excess flux= åflux(upper) - åflux(lower)
-15 -15 -15 2 -15 2
Excess flux= 1,56*10 – 0,67*10 Excess flux= 0,89*10 erg/cm.s.cm Excess flux= 0,9*10 erg/cm.scm
CONCLUSIONS: Keywords; equilibrium periods magnetic fields and mass age.Properties of (DNTs) (dim isolated thermal neutron stars)Common mechanism with an asymptotic spindown phase extending through the propeller and early accretion stage.They are interpreted as sources in the propeller stage.Their luminosities arise from frictional heating in the neutron star. Rotation period is close to its rotational equilibrium period. Propeller torque indicates a magnetic field in the 1012 Gauss range . The mass inflow rate onto the propeller is of the order of the accretion rates of the AXPs (by Chatterkee,Hernquist&Narayan 1999)The limited range of rotation periods. Taken to be close to equilibrium periods, and conventional magnetic fields in the range 5*1011 – 5*1012 Gauss.Range of mass inflow rates3,2*1014 g/s < M < 4,2*1017 g/s.Those neutron stars do not become radio pulsars.Highest mass inflow rates the propeller action may support enough circumstellar material so that the optical thickness to electron scattering destroys the X-ray beaming, and the rotation period is not observable. These are radio quiet neutron stars (RQNSs) at the centers of supernovae remnants. RQNSs are at the highest mass inflow rate, these are propellers whose pulse periods are not observable because of accumulated circumstellar material that is optically thick to electron scattering.DNTs fits to balckbody with tempeature 57eV and 79eV and luminosities in the Lx ~1031-32 erg/s range and similiar blackbody tempeatures flux values and limits on the radio of x-ray flux to optical flux and ages ~106 years are or longer.Thermal luminosity which takes over at ~105~106 years after the intial cooling and losts longer than the cooling luminosity. There will be energy dissipation (frictional heating) in a neutron star being spun down by some external torque. The rate of energy dissiptaion is given by (Alpar at al.1984, Alpar, Nandkumar&Pines 1985)Ediss will supply the termal luminosity of a non-accreting nutron star at ages greater than ~106 years.Between DNTs,AXPs and SGRs, AXP spindown takes actually sugsut that the DTN spindown rate may be closer to W~W-12 rad/sn-2. are there spindown mechanisms that will give high spindown rates, larger than 10-12 rad s-2with 1012 G magnetic fields typical of the canonical radio pulsars and of the accreting neutron stars wth observed cyclotron lines? Propeller spindown with high spindown rates larger than 10-12 rad/s2 can indeed be expected for neutron stars eith conventinal 1012 Gauss fields under the typical spindown torques for certain phases of accreting sources Propeller torques depend on the magnetic moment of the neutron star and on the rate of mass in flow
SOURCES: 1)Alpar Ali.M, preprint astro-ph/0005211“The lives of the neutron stars2)Ögalman H. ed. Alpar Ali.M, Kızıloğlu Ü. and Paradijs Van.J. Publishing House: Kluwer 1995Page: 101”3).Neuhäuser R. preprint astroa-ph/0102004 1 Feb. 2000 4).Perna R. , Hemquist L. and Narayan R. Review name: astrophysical JournelBinding: 541:344-350 Pages: 344-501 October 2000 5)Walter Frederich M. preprint astroa-ph/0009031“The proper motion, parallax and origin of the isolated neutron star RX J1856-3754” 6). Web Adress;Legacy.gsfc.nasa.gov Astroa.physics.metu.edu.tr.html Copernic 2000 (search RX J1856-3754). 7)Sabancı University in Istanbul. Alpar Ali.M.–2001 8)Yerli Sinan.K.- Middle East Technical University 9)Supervisor Physics Teacher, Baltacı Neşever-2001-2005