arXiv subjects

S. S. Eikenberry

Publications and source records attributed to S. S. Eikenberry.

26 records · Page 2Linked to original sources

arXiv2002

The Infrared Counterpart of the Microquasar GRS 1758-258

We present revised infrared (2.2 micron) astrometry of the field containing the Galactic microquasar GRS 1758-258, using observations at the Keck I 10-m telescope. We find three candidates for the microquasar within a 3 sigma error circle, but none within 2 sigma. We show that if the 18.4 day X-ray period of GRS 1758-258 is due to a binary orbit, then only one of the three candidates, an early K-type giant, is large enough to power the microquasar via Roche lobe overflow. We therefore identify this star as the infrared counterpart of GRS 1758-258, which we classify as a low mass X-ray binary. Long term infrared monitoring of this source should provide further information about the microquasar system, including a confirmation of the X-ray period and an estimate of the compact object's mass.

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arXiv2001

Possible Infrared Counterparts to the Soft Gamma-Ray Repeater SGR 1806-20

We report the discovery of possible infrared counterparts to SGR 1806-20. We use archival {\it Chandra} observations to determine the location of SGR 1806-20 to $<1 \arcsec$ accuracy. We then locate 2 infrared objects within this error circle in K-band ($2.2 μ$m) images of this field. Based on the X-ray absorption towards SGR 1806-20 and the extinction towards the nearby star cluster, we discuss the likelihood of association for the possible counterparts, and the implications for SGR 1806-20's physical properties and origins.

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arXiv2001

Twenty Years of Timing SS433

We present observations of the optical ``moving lines'' in spectra of the Galactic relativistic jet source SS433 spread over a twenty year baseline from 1979 to 1999. The red/blue-shifts of the lines reveal the apparent precession of the jet axis in SS433, and we present a new determination of the precession parameters based on these data. We investigate the amplitude and nature of time- and phase-dependent deviations from the kinematic model for the jet precession, including an upper limit on any precessional period derivative of $\dot P < 5 \times 10^{-5}$. We also dicuss the implications of these results for the origins of the relativistic jets in SS433.

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arXiv2001

Deep Infrared Imaging of the Microquasars 1E1740-2942 and GRS 1758-258

We present deep infrared ($2.2 μ$m) imaging of the Galactic microquasars 1E1740-2942 and GRS 1758-258 using the Keck-I 10-meter telescope in June 1998. The observations were taken under excellent seeing conditions ($\sim 0.45 \arcsec$ full-width half-maximum), making them exceptionally deep for these crowded fields. We used the USNO-A2.0 catalog to astrometrically calibrate the infrared images (along with an optical CCD image in the case of GRS 1758-258), providing independent frame ties to the known radio positions of the objects. For 1E1740-2942, we confirm potential candidates for the microquasar previously identified by Marti et al., and show that none of the objects near the microquasar have varied significantly from 1998 to 1999. For GRS 1758-258, our astrometry indicates a position shifted from previous reports of candidates for the microquasar. We find no candidates inside our 90% confidence radius to a $2 σ$ limiting magnitude of $K_s = 20.3$ mag. We discuss the implications of these results for the nature of the microquasar binary systems.

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arXiv1997

Evidence for a Disk-Jet Interaction in the Microquasar GRS 1915+105

We report simultaneous X-ray and infrared (IR) observations of the Galactic microquasar GRS1915+105 using XTE and the Palomar 200-inch telescope on August 13-15, 1997 UTC. During the last two nights, the microquasar GRS 1915+105 exhibited quasi-regular X-ray/infrared (IR) flares with a spacing of $\sim 30$ minutes. While the physical mechanism triggering the flares is currently unknown, the one-to-one correspondence and consistent time offset between the X-ray and IR flares establish a close link between the two. At late times in the flares the X-ray and IR bands appear to ``decouple'', with the X-ray band showing large-amplitude fast oscillations while the IR shows a much smoother, more symmetrical decline. In at least three cases, the IR flare has returned to near its minimum while the X-rays continue in the elevated oscillatory state, ruling out thermal reprocessing of the X-ray flux as the source of IR flare. Furthermore, observations of similar IR and radio flares by Fender et al. (1997) imply that the source of the IR flux in such flares is synchrotron emission. The common rise and subsequent decoupling of the X-ray and IR flux and probable synchrotron origin of the IR emission is consistent with a scenario wherein the IR flux originates in a relativistic plasma which has been ejected from the inner accretion disk. In that case, these simultaneous X-ray/IR flares from a black-hole/relativistic-jet system are the first clear observational evidence linking of the time-dependent interaction of the jet and the inner disk in decades of quasar and microquasar studies.

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arXiv1997

ROSAT Timing of the LMC Pulsar 0540-69

We present a timing study of the young rotation-powered pulsar 0540-69 in the Large Magellanic Cloud, based on 130 kiloseconds of archival ROSAT data spanning a $\sim 3$-year period. We use ``$f- \dot f$'' techniques to measure the pulsar frequency as a function of frequency derivative at 17 independent epochs. From these measurements we derive a timing solution with a braking index $n = 2.5^{+0.6}_{-0.7}$, and we compare this solution to previous timing studies of 0540-69. Using this frequency-based solution, we create 27 pulse profiles and perform a time-of-arrival (TOA) analysis to investigate further the pulsar's timing behavior. While we can successfully fit smooth spin-down models to subsets of the TOAs spanning up to 2 years, we are unable to obtain acceptable phase-coherent fits to the entire 3-year set of TOAs. This behavior provides the first clear evidence for timing noise in 0540-69. We discuss the implications of these results for understanding previous studies of the timing behavior of 0540-69.

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arXiv1996

An SSPM-Based High-Speed Near-Infrared Photometer for Astronomy

We describe the design, operation, and performance of a new high-speed infrared photometer using the Solid-State Photomultiplier (SSPM) detector. The SSPM was developed by Rockwell International Science Center and has single-photon counting capability over the 0.4-28 micron wavelength range, intrinsic time response of order 1 ns, and low detector noise (Petroff, 1987). We have operated a 200x200-micron back-illuminated SSPM in a liquid-helium cooled dewar with a room-temperature transimpedance amplifier output. Single photon pulses can be easily distinguished above the amplifier noise. The individual photon pulses are binned at a selectable time resolution ranging from $5 μ$s to 64 ms, and then written to Exabyte tape. In the first astronomical application of such a device, we have made observations of the Crab Nebula pulsar and Her X-1 at near-infrared wavelengths (J-, H-, and K-bands), and we present the instrument sensitivities established by these observations. We discuss other astronomical observations which are either planned or currently underway. Finally, we present design specifications and predicted performances for a second-generation SSPM high-speed infrared photometer.

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arXiv1996

Infrared to Ultraviolet Wavelength-Dependent Variations Within the Pulse Profile Peaks of the Crab Nebula Pulsar

We present evidence of wavelength-dependent variations within the infrared, optical, and ultraviolet pulse profile peaks of the Crab Nebula pulsar. The leading and trailing edge half-width half-maxima of the peaks display clear differences in their wavelength dependences. In addition, phase-resolved infrared-to-ultraviolet color spectra show significant variations from the leading to trailing edges of the peaks. The color variations between the leading and trailing edges remain significant over phase differences smaller than 0.0054, corresponding to timescales of $<180 μ$s. These results are not predicted by any current models of the pulsar emission mechanism and offer new challenges for the development of such models.

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