New limits on the orbital parameters of 1E 1048.1–5937 and 1E 2259+586 from RXTE observations |
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| Authors: | S Mereghetti G L Israel & L Stella |
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| Institution: | Istituto di Fisica Cosmica del CNR, Via Bassini 15, I-20133 Milano, Italy,;Osservatorio Astronomico di Roma, Via dell'Osservatorio 2, I-00040 Monteporzio Catone, Roma, Italy |
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| Abstract: | We report on two Rossi X-ray Timing Explorer ( RXTE ) observations of the anomalous X-ray pulsars 1E 1048.1–5937 and 1E 2259+586. Both sources have continued their almost constant spin-down during 1995/96. We carried out a search for orbital Doppler shifts, in their observed spin frequencies, deriving stringent limits on the projected semi-axis. Unless these systems have unlikely small inclinations, main-sequence companions can be excluded. If 1E 1048.1–5937 and 1E 2259+586 are indeed binary systems, their companion stars must be either white dwarfs, or helium-burning stars with M ? 0.8 M⊙, possibly underfilling their Roche lobe. |
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| Keywords: | binaries: close pulsars: individual: 1E 1048 1–5937 pulsars: individual: 1E 2259+586 X-rays: stars |
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