Volume 387, Number 3, June I 2002
|Page(s)||993 - 1002|
|Section||Interstellar and circumstellar matter|
|Published online||17 May 2002|
Re-examining the X-ray versus spin-down luminosity correlation of rotation powered pulsars
Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: firstname.lastname@example.org
2 Dipartimento di Fisica, Università di Milano , via Celoria 16, 20133 Milano, Italy e-mail: email@example.com
3 Dipartimento di Fisica, Università di Milano Bicocca, Piazza della Scienza 3, 20126 Milano, Italy e-mail: firstname.lastname@example.org
4 Istituto di Astrofisica Spaziale e Fisica Cosmica, Sezione di Milano “G.Occhialini”, CNR, via Bassini 15, 20133 Milano, Italy e-mail: email@example.com
Corresponding author: M. Colpi, firstname.lastname@example.org
Accepted: 22 March 2002
The empirical relation between the X-ray luminosity (in the 2–10 keV band) and the rate of spin-down energy loss of a sample of 39 pulsars is re-examined considering recent data from ASCA, RXTE, BeppoSAX, Chandra, and XMM-Newton and including statistical and systematic errors. The data show a significant scatter around an average correlation between Lx, (2-10) and . By fitting a dependence of Lx, (2-10) on the period P and period derivative of the type , we obtain and (i.e. ). This translates into the relation with a normalization . However, the reduced is large (=7.2) making the fit unacceptable on statistical ground. All the X-ray luminosities lie below a critical line Lx,crit: the corresponding efficiency of conversion of rotational energy into 2–10 keV X-rays is and varies, within the sample, between 0.1 and 80%. The large dispersion of Lx below Lx,crit indicates that other physical parameters uncorrelated with P and need to be included to account for the observed emission at X-ray energies. We indicate a few possibilities that all conspire to reduce Lx, (2-10).
Key words: radiation mechanisms: non-thermal / star: neutron / stars: pulsar: general / X-rays: general / γ-rays: observations
© ESO, 2002
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