New Results from Four Elusive Binary Pulsars in 47 Tucanae

Transcription

1 Max-Planck-Institut für Radioastronomie New Results from Four Elusive Binary Pulsars in 47 Tucanae Alessandro Ridolfi and P. Freire, P. Torne, C. O. Heinke, M. van den Berg, C. Jordan, M. Kramer, C. G. Bassa, J. Sarkissian, N. D Amico, D. Lorimer, F. Camilo, R. N. Manchester, A. Lyne Bonn NS Workshop 9-20/06/2016

2 The pulsars in 47 Tuc We know 23 pulsars residing in this cluster Pulsar Offset (arcmin) Period (ms) DM (cm!3 pc) Pb (days) x (ls) Ecc C i i i i D i i i i mc (M ) E F i i i i G i i i i Notes H (i) mildly eccentric I < low-mass J < eclipsing, low-mass L i i i i M i i i i N i i i i O < eclipsing, low-mass P * low-mass Q R * eclipsing, low-mass S T U V * ? eclipsing? W eclipsing X * * * * * Y * Z * i i i i Manchester et al. 1990; Manchester et al. 1991; Robinson et al. 1995

3 The pulsars in 47 Tuc 25 We know 23 pulsars residing in this cluster Pulsar Offset (arcmin) Period (ms) DM (cm!3 pc) Pb (days) x (ls) Ecc C i i i i D i i i i mc (M ) E F i i i i G i i i i Notes H (i) mildly eccentric I < low-mass J < eclipsing, low-mass L i i i i M i i i i N i i i i O < eclipsing, low-mass P * low-mass Q R * eclipsing, low-mass S T U V * ? eclipsing? W eclipsing X * * * * * Y * Z * i i i i aa? i i i i NEW! ab i i i i NEW! Manchester et al. 1990; Manchester et al. 1991; Robinson et al Pan et al. (2016)

4 The pulsars in 47 Tuc 25 We know 23 pulsars residing in this cluster Pulsar Offset (arcmin) Period (ms) DM (cm!3 pc) Pb (days) x (ls) Ecc C i i i i D i i i i mc (M ) E F i i i i G i i i i Notes H (i) mildly eccentric I < low-mass J < eclipsing, low-mass L i i i i M i i i i N i i i i O < eclipsing, low-mass P * low-mass Q R * eclipsing, low-mass S T U V * ? eclipsing? W eclipsing X * * * * * Y * Z * i i i i aa? i i i i NEW! ab i i i i NEW! Manchester et al. 1990; Manchester et al. 1991; Robinson et al Pan et al. (2016)

5 The problem of scintillation The majority of the 47 Tuc pulsars are very faint and are not detected in normal conditions. MJD:

6 Redetecting the pulsars in 47 Tuc We have used a PRESTO-based search pipeline devised by P. Torne to redetect the 47 Tuc pulsars in ~16 years data taken at the Parkes radio telescope. We divided the observations in 1-h chunks and we looked for the known periodicities of pulsars: 47 Tuc P (P=3.6ms, Pb=3.5 h) 47 Tuc V (P=4.8ms, Pb=5.1 h) 47 Tuc W (P=2.3ms, Pb=3.1 h) 47 Tuc X (P=4.7ms, Pb=10.9 days) 47 Tuc Z (P=4.5ms, isolated) never detected never detected detected (once) detected detected

7 T0-search for 47 Tuc P, V and W discovery Pb = Pb_true + Pb

8 Pb = Pb_true + Pb T0-search for 47 Tuc P, V and W discovery

9 Pb = Pb_true + Pb T0-search for 47 Tuc P, V and W discovery

10 Pb = Pb_true + Pb T0-search for 47 Tuc P, V and W discovery

11 Pb = Pb_true + Pb T0-search for 47 Tuc P, V and W

12 T0-search for 47 Tuc P, V and W Solution: search in T0 T0

13 Many more detections Good Pb Detections obtained with the different search methods: Pulsar PRESTO (20-min) PRESTO (60-min) T 0 -search 47 Tuc P Tuc V Tuc W Tuc X 12 16

14 Refining the orbits of P, V and W Now, from one T0 and another, there MUST be an integer number of orbits. N1 orbits N2 orbits N3 orbits Pb = T0_2 - T0_1 N1 Pb = T0_3 - T0_2 N2 Pb = T0_4 - T0_3 N3 T0_1 T0_2 T0_3 T0_4

15 47 Tuc P 47 Tuc P is a 3.64-ms binary pulsar in a 3.5-h orbit We redetected it only 4 times (!) in over 400 epochs 0.97% detection rate, lowest among all the 47 Tuc pulsars 47 Tuc P pulse profile Mc 0.02 M (for a pulsar mass of 1.4 M and an orbital inclination i = 60, Black-Widow type pulsar) No phase-connected timing solution

16 47 Tuc V and W: strong orbital variability Pulsars V and W are Redback binary systems that show a very strong orbital variability. To model the orbits, we had to use a BTX binary model, which allows for multiple orbital period derivatives. 5 orbital frequency derivatives needed No phase-connected timing solution 9 orbital frequency derivatives needed Phase-connected timing solution!

17 47 Tuc V: a transitional MSP? In our 16-year data, 47 Tuc remains undetectable during two ~6-year time intervals. The disappearance of the pulsations during long gaps, the strong orbital variability, its persistent and irregular eclipses, and the mass of the companion of the order of 0.3!0.4 M, are typical characteristics of tmsps. Is 47 Tuc V a transitional MSP? Probably not! tmsps, during their active LMXB states, have X-ray luminosities in the range of 10 33! erg/s. We have looked into four, widely separated, groups of Chandra data of 47 Tuc. No new Chandra sources significantly brighter than erg/s were seen in these data. No signals were detected in satellite and ground-based optical data.

18 47 Tuc X is by far the farthest (~3.8 arcmin) pulsar from the globular cluster center, 3 times the distance of 47 Tuc C. Formation: likely an unrecycled NS interacted with a wide MS-MS binary. In the recoil, the new system was put in an eccentric orbit about the cluster, and it has had yet no time to settle back to the core. The mass function implies a minimum companion mass of 0.36 M for a pulsar mass of 1.4 M - very likely a MSP-WD binary system. 47 Tuc X Phase-connected timing solution! No optical counterparts were detected in archival HST data.

19 Summary of the new 47 Tuc results Pulsar P: refined orbital solution Black Widow-type binary Ridolfi et al. (submitted) Pulsar V: refined orbital solution Redback-type binary Ridolfi et al. (submitted) Pulsar W: coherent timing solution Redback showing strong orbital variability Ridolfi et al. (submitted) Pulsar X: coherent timing solution Wide binary MSP, far from GC center Ridolfi et al. (submitted) Pulsar Z: coherent timing solution Normal isolated MSP. Freire et al. (in prep) Pulsar AA: no solution yet Isolated, fastest MSP with highest DM in 47 Tuc Pan et al. (2016) Pulsar AB: coherent timing solution Normal isolated MSP. Pan et al. (2016)

20 Thank you for your attention! Pan et al. (2016) Ridolfi et al. (submitted) Freire et al. (in prep.)