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Astrophysics 1

by: Stephan Kuvalis

Astrophysics 1 ASTR 3730

Stephan Kuvalis

GPA 3.89

Philip Armitage

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Philip Armitage
Class Notes
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This 10 page Class Notes was uploaded by Stephan Kuvalis on Thursday October 29, 2015. The Class Notes belongs to ASTR 3730 at University of Colorado at Boulder taught by Philip Armitage in Fall. Since its upload, it has received 29 views. For similar materials see /class/231954/astr-3730-university-of-colorado-at-boulder in Astronomy at University of Colorado at Boulder.


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Date Created: 10/29/15
Distribution of radio pulsars Can detect pulsars that are much older than the oldest distinct supernova remnants So most pulsars are not in supernova remnants More interestingly not all supernova remnants have pulsars at their center 3 55 a 9 1 9 29 00 ac 39 5 b3 on Q o 3 o O I 1 s v t g d 0 I179 00 a 9 4 31 v 4 b4 w V V 39 39 I1so oo 25 0039 4 39 a 1311 81130 395 12 5h48m 5h44m 5h40m 5h36m 5h32m RA Jzoon Off ce nte r Righl Ascension 12000 ASTR 3730 Fall 2003 Together with observations of the distribution and proper motion of radio pulsars across the sky this suggests that pulsars have velocities that can be as large as 103 km s1 b9039 1180 1715039 b Qo39 Much larger than the space velocities of massive stars suggests neutron stars receive a kick at time of formation ASTR 3730 Fall 2003 Producing neutron star kicks 2 GM Binding energy of a neutron star Is 5gtlt1053 erg Kinetic energy of a neutron star moving at 1000 km s1 is Mtz 15 gtlt1049 erg No energetic problem small asymmetry in the emission of neutrinos or mass from the supernova would be enough to give the neutron star enough kick energy Can repeat exercise for momentum as well as energy Seems plausible but no definite mechanism is known asymmetry in the supernova explosion o irregularities in the progenitor star ASTR 3730 Fall 2003 m pulse arrival time Glitches mm lm39l In some pulsars the steady spin down is sometimes interrupted by a sudden almost instantaneous spin up a glitch Thought to arise because the neutron star has a fluid interior which is only weakly coupled to the crust As the crust is braked a mismatch in angular velocity develops which is suddenly corrected ASTR 3730 Fall2003 Binary pulsar In 1974 Russell Hulse and Joe Taylor discovered a pulsar in a close binary system From analysis of the arrival time of the pulses they determined that the orbit was eccentric e 062 with a period of 78 hours mum VELOCITY km 4 wuss FIG 12 The complete velocity curve for PSR 1913 16 from y paper lled with it Kepleriun Oxbltixl solution The orbital pm is the fraction of a binary orbital period of 7 4539n from R A Hills and l H Taylor 1975M ASTFl 3730 Fall 2003 Observations of this system provide very accurate masses for the stars M1 1442 i 039003Msun double neutron M2 1386 t 0003MW Star binary To a very good approximation this is a system of two point masses in orbit around each other Expect that energy is being lost from the binary in the form of gravitational radiation As energy is lost stars should be spiralling together toward collision ASTR 3730 Fall 2003 Observed change in time of closest approach matches the General Relativity prediction Orbit shrinks by 3 mm per orbit of the binary system GR prediction Accumuiuted Shi or or39m39mi phase 5 1 S i 14 1975 1950 1985 1990 Year FIG 10 Accumulated shift of the times or penastron in the PSR 191316 system xeimive m an assum orbit with cone stam period The parabolic curve represents the general relatiw islic prediction for energy losses from gravitational radiation AS TR 3730 Fall 2003 Pulsar planets Timing of the pulsar B125712 showed periodic changes in the arrival times of pulses PSR B125712 Arecibo 430 MHz 2000 0 2000 1 39 E f 214 35 m ff 13932 mi 57 j fi 522 L 25 3 gaff 2 3 39 21 3 Tb 2 rp 32 We 2 I W 23gt 9 I n I I n I 1990 1992 1994 1995 1998 2000 I I I I I cf the radial velocity curve of the multiple planet system Ups Andromeda Velocity Residuals m squot 45day Planet 150 Removed 1992 1994 1996 1998 2000 2002 Time yr A S TR 3730 Fall 2003 Data suggests at least three possibly four planetary mass companions Orbital Planet mass radius au Earth masses Eccentricity A 019 002 00 B 036 43 00186 C 046 39 00252 Phenomenon appears to be rare 48 similar pulsars show no sign of planets at similar levels of sensitivity Formation mechanism uncertain planets almost certainly formed after the supernova explosion that created the neutron star ASTR 3730 Fall 2003


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