1. Radio Emitting Magnetars Jason Hessels, Feb. 22, 2007 Anton Pannekoek Institute - Pizza Seminar

2. Outline 1.Magnetars: Anomalous X-ray Pulsars (AXPs) and Soft Gamma Repeaters (SGRs) 2.XTE J1810-197: A New (Transient!) AXP 3.Radio Emission from Magnetars 4.XTE J1810-197 is a Radio Point Source! 5.XTE J1810-197 is a Radio Pulsar!!! 6.Further Radio Monitoring of XTE J1810-197 7.Where are the other New Kids on the Block?

3. MAGNETARS: AXPS & SGRs 5(8) known All but 1 in Galactic Plane (|b| < 1 deg), exception in SMC; some in SNRs young sources periods from 6-12 s, all spinning down X-ray luminosities 10^33 – 10^36 erg/s Soft X-ray spectra: thermal and non-thermal components “ anomalous ” as energy source unclear: X-ray luminosity much too high to be rotation-powered AXPs

4. MAGNETARS: AXPS & SGRs SGRs 4(5) known not confined to plane (one in SMC) Repeating Gamma-Ray bursts periods from 5-8 s Some giant bursts 10 41 -10 43 ergs/s Last burst of 1806-20 HYPER! inspired Magnetar model (Duncan & Thompson 1992)

5. MAGNETARS: AXPS & SGRs AXP X-ray luminosity requires energy source B-field implied by P, dP/dt is magnetar-strength Similar X-ray spectra to SGRs Can exhibit X-ray bursts (Gavriil et al. 2002) – Seen in 2 sources – Quantitatively similar to SGR bursts Why are they the same?

6. XTE J1810-197: A New (Transient!) Magnetar Serendipitously found by RXTE while observing SGR 1806-20 Soft spectrum  4) X-ray pulsations at a period of 5.54 s. High spin down: Pdot ~ 10 -11 s/s No evidence of binary companion. B ~ 3 x 10 14 G T ~ 7600 yr Ibrahim et al. 2004

7. XTE J1810-197: A New (Transient!) Magnetar Source went into outburst sometime between 2002 Nov 17 and 2003 Jan 23. Increase in brightness by ~100 x compared with archival ASCA & ROSAT data. First clearly transient magnetar. Could be on average much dimmer than the other AXPs. Implies a much larger population of such sources! Ibrahim et al. 2004 e-fold: 269±25d “more turn-on than SGR-like outburst”

8. Radio Emission from Magnetars Absence of radio emission was a defining characteristic of AXPs. Radio emission only seen from two SGRs, following very large  -ray bursts: SGR 1900+14, 1998 Aug 27, faint radio source faded within a month of burst (Frail et al. 1999) SGR 1806-20, 2004 Dec 27, radio source with complex decay (Cameron et al. 2005, Gaensler et al. 2005) No transient radio emission observed after, say, burst of AXP 1E 2259+586 (Kaspi et al. 2003) No persistent radio emission detected from either the AXPs or SGRs.

9. XTE J1810-197 is a Radio Point Source! Magnetars thought to be radio quiet. First ever detection of radio emission from a magnetar. Found (2004 Jan) serendipitously in VLA MAGPIS survey one year after original X-ray outburst. 4.5 ± 0.5 mJy at 1.4 GHz. Radio lum. is energetically insignificant. Halpern et al. 2005 Coords match those from Chandra (Gotthelf et al. 2004) and IR counterpart (Israel et al. 2004).

10. XTE J1810-197 is a Radio Point Source! Only weak upper limits on radio flux at other epochs (var. unknown). Can neither support or rule out a decaying radio afterglow following the X- ray turn-on. Radio source is unresolved at ~ 3’’. Halpern et al. 2005

11. XTE J1810-197 is a Radio Pulsar! Camilo et al. 2006a Subsequent observations of the Halpern et al. 2005 radio source with Parkes revealed radio pulsations at the spin-frequency of the AXP (Camilo et al. 2006a). First time a magnetar has been seen as a radio pulsar. No evidence the radio pulsar was there before the X-ray turn-on. Implies cause & effect. Flux (few mJy) var. from day to day, unlike normal rad. pulsars. Cannot rule out non-pulsed component. Obs Frequency

12. Very flat spectral index, unlike most radio pulsars. Brightest pulsar above 20 GHz! New link between magnetars and normal pulsars. Diff. conditions in the magnetosphere? Rule out alternative accretion models for AXPs. Narrow profile. Individual pulsations from almost every rotation (made of <10-ms-wide subpulses). XTE J1810-197 is a Radio Pulsar! Camilo et al. 2006a

13. Camilo et al. 2006b Further Radio Monitoring of XTE J1810-197 Radical changes in pulse profile morphology, sometimes during observations. Also large changes in flux. General trend towards decreasing flux and widening of profile. Coincides with 10% decrease in torque. Radio emission cease soon? Overall, 30% decrease in the torque on the neutron star. 2006 May - October

14. Further Radio Monitoring of XTE J1810-197 Camilo et al. 2006b

15. Timing Profile changes make timing much more difficult. Also, lots of timing noise. But not unprecedented for a magnetar. Pdot varies with time. 7 derivatives are required to whiten the residuals. No glitches found. Include Pddot

16. Camilo et al. 2006b Pdot measured as a function of time by making piece-wise fits (<= 30 days). Large torque change within 15 days in 2006 Jul. Change in torque larger than that powering 3/4 of all known pulsars! Marked change in flux around the same time. Profiles getting wider. large torque variation peak flux, large change avg flux, smaller change

17. Camilo et al. 2006b Contemporaneous radio and X-ray profiles are aligned. Same emission area? Large changes in radio profile and flux during Chandra obs. Profiles changes can occur suddenly (< 10s). Transitions occur on avg every 15 hours. No X-ray bursts, flux/profile changes seen with Chandra.

18. “With observations of XTE J1810-197, we now find ourselves in the curious position of relying upon energetically insignificant radio pulsations exhibiting a remarkably diverse phenomenology to illustrate rather more energetic events on the magnetar. Attempting to understand key aspects of the radio observations may perhaps lead to a deeper understanding of both magnetars and radio pulsar emission.” Camilo et al. 2006b

19. Where are the other New Kids on the Block? 4U 0142+61 1E 1048.1-5937 AX J1845-0258 1E 1841-045 1RXS J170849.0-400910 Sensitive searches for radio emission from other AXPs have been unsuccessful (e.g. Crawford, Hessels, & Kaspi 2007 and Burgay et al. 2006). Recent WSRT & GBT obs of 4U 0142+61 after burst. No radio source (yet).

20. Where are the other New Kids on the Block? 4U 0142+61 1E 1048.1-5937 AX J1845-0258 1E 1841-045 1RXS J170849.0-400910 AX J1845-0256 (Gotthelf & Vasisht 1998) is a transient AXP candidate. P ~ 6.97s, no Pdot measured. Long periods of magnetars imply small active polar caps and narrow beams. Is geometry the culprit?

21. Simultaneous Radio Obs Kramer, Stappers et al 2007