Skip to main content

Table 1 Reference values for different types of stars

From: On the origin of jets from disc-accreting magnetized stars

 

Protostar

CTTS

Brown dwarf

White dwarf

Neutron star

M ( M )

0.8

0.8

0.056

1

1.4

R

2 R

2 R

0.1 R

5,000 km

10 km

R 0 (cm)

2.81011

2.81011

1.41010

109

2106

v 0 (cm s−1)

1.95107

1.95107

1.6107

3.6108

9.7109

P

1.04 days

5.6 days

0.13 days

89 s

6.7 ms

P 0

1.04 days

1.04 days

0.05 days

17.2 s

1.3 ms

B (G)

3.0103

103

2103

106

109

B 0 (G)

37.5

12.5

25.0

1.2104

1.2107

ρ 0 (g cm−3)

3.710−12

4.110−13

1.410−12

1.210−9

1.710−6

n 0 (cm−3)

2.21012

2.41011

8.51011

71014

1018

M ˙ 0 ( M yr 1 )

1.810−7

210−8

1.810−10

1.310−8

210−9

E ˙ 0 (erg s−1)

2.11033

2.41032

2.51030

5.71034

61036

L ˙ 0 (erg s−1)

3.11037

3.41036

1.71033

1.61035

1.21033

T d (K)

2,290

4,590

5,270

1.6106

1.1109

T c (K)

2.3106

4.6106

5.3106

8108

5.61011

  1. We choose the mass M, radius R , equatorial magnetic field B and the period P of the star and derive the other reference values. The reference mass M 0 is taken to be the mass M of the star. The reference radius is taken to be twice the radius of the star, R 0 =2 R . The surface magnetic field B is different for different types of stars. The reference velocity is v 0 = ( G M / R 0 ) 1 / 2 . The reference time-scale t 0 = R 0 / v 0 , and the reference angular velocity Ω 0 =1/ t 0 . We measure time in units of P 0 =2π t 0 (which is the Keplerian rotation period at r= R 0 ). In the plots we use the dimensionless time T=t/ P 0 . The reference magnetic field is B 0 = B ( R / R 0 ) 3 / μ ˜ , where μ ˜ is the dimensionless magnetic moment which has a numerical value of 10 in the simulations discussed here. The reference density is taken to be ρ 0 = B 0 2 / v 0 2 . The reference pressure is p 0 = B 0 2 . The reference temperature is T 0 = p 0 /R ρ 0 = v 0 2 /R, where is the gas constant. The reference accretion rate is M ˙ 0 = ρ 0 v 0 R 0 2 . The reference energy flux is E ˙ 0 = M ˙ 0 v 0 2 . The reference angular momentum flux is L ˙ 0 = M ˙ 0 v 0 R 0 . The poloidal magnetic field of the star (in the absence of external plasma) is an aligned dipole field.