Stellar or Non-Stellar Light? Determining Near-Infrared Contamination in Low Mass X-ray Binaries

Low-mass X-ray binary (LMXB) systems are comprised of a low-mass, K or M dwarflike star orbiting a compact object. Stellar black hole masses and their distributions are important inputs for binary evolution and supernova models. Currently, the main limiting factor in determining accurate black hole masses in LMXBs is the uncertainty of the orbital inclination angle due to an unknown amount of contaminating light in the near infrared. If present, this light dilutes the ellipsoidal variations of the low-mass secondary star, and thus gives the appearance of a lower orbital inclination system. It has been generally thought that the near infrared ellipsoidal light curves of these systems were relatively uncontaminated and represented primarily the light from the low-mass secondary star; however, recent disk and jet models have thrust this thinking into question. We combine our data from the Spitzer Space Telescope with our ground-based optical and near infrared data for several LMXBs to characterize and derive the amount of light contaminating the near-infrared ellipsoidal variations of the low-mass secondary star

INTEGRAL and New Classes of High-Mass X-ray Binaries

The gamma-ray observatory INTEGRAL, launched in October 2002, produces a wealth of discoveries and new results on compact high energy Galactic objects, nuclear gamma-ray line emission, diffuse line and continuum emission, cosmic background radiation, AGN and high energy transients. Two important serendipitous discoveries made by the INTEGRAL mission are new classes of X-ray binaries, namely the highly-obscured high-mass X-ray binaries, and the super-giant fast transients. In this paper I will review the current status of these discoveries.Comment: 3 pages, 1 figure, submitted; Proceedings "The nature and evolution of X-ray binaries in diverse environments", St Petersburg/FL, USA, 28 Oct - 02 Nov 200

X-Ray Binaries and the Dynamical States of Globular Clusters

We summarize and discuss recent work (Fregeau 2007) that presents the confluence of three results suggesting that most Galactic globular clusters are still in the process of core contraction, and have not yet reached the thermal equilibrium phase driven by binary scattering interactions: that 1) the three clusters that appear to be overabundant in X-ray binaries per unit encounter frequency are observationally classified as "core-collapsed," 2) recent numerical simulations of cluster evolution with primordial binaries show that structural parameters of clusters in the binary-burning phase agree only with "core-collapsed" clusters, and 3) a cluster in the binary-burning phase for the last few Gyr should have about 5 times more dynamically formed X-ray sources than if it were in the core contraction phase for the same time.Comment: Conference proceedings from "A Population Explosion: The Nature and Evolution of X-ray Binaries in Diverse Environments," 28 Oct - 2 Nov, St. Petersburg Beach, FL. 4 page

Spitzer Space Telescope Observations of Low Mass X-ray Binaries

We present preliminary results from our archival Spitzer Space Telescope program aimed at characterizing the mid-IR properties of compact objects, both isolated and in binary systems, i.e. white dwarfs, X-ray binaries, cataclysmic variables, and magnetars. Most of these sources are too faint at mid-IR wavelengths to be observable from the ground, so this study provides the very first comprehensive look at the mid-IR emission of these objects. Here we present our results for the low mass X-ray binaries. We considered all of the systems listed in the most recent catalog of Liu et al. (2007) that have known optical counterparts. The particular goals of our projects encompass: to establish the mid-IR spectral energy distribution, to search for the signatures of jets, circumbinary disks, low mass or planetary companions and debris disks, and to study the local environment of these sources.Comment: 6 pages, updated and expanded version of article to appear in Proceedings of "A Population Explosion: The Nature and Evolution of X-ray Binaries in Diverse Environments", 28 Oct - 2 Nov, St. Pete Beach, FL; eds. R.M. Bandyopadhyay, S. Wachter, D. Gelino, C.R. Gelino; AIP Conference Proceedings Serie

Multiwavelength Studies of X-ray Binaries

Simultaneous multiwavelength studies of X-ray binaries have been remarkably successful and resulted in improved physical constraints, a new understanding of the dependence of mass accretion rate on X-ray state, as well as insights on the time-dependent relationship between disk structure and mass-transfer rate. I will give some examples of the tremendous gains we have obtained in our understanding of XRBs by using multiwavelength observations. I will end with an appeal that while Spitzer cryogens are still available a special effort be put forth to obtaining coordinated observations including the mid-infrared: Whereas the optical and near-IR originate as superpositions of the secondary star and of accretion processes, the mid-IR crucially detects jet synchrotron emission from NSs that is virtually immeasurable at other wavelengths. A further benefit of Spitzer observations is that mid-infrared wavelengths can easily penetrate regions that are heavily obscured. Many X-ray binaries lie in the Galactic plane and as such are often heavily obscured in the optical by interstellar extinction. The infrared component of the SED, vital to the study of jets and dust, can be provided {\it only} by Spitzer; in the X-rays we currently have an unprecedented six satellites available and in the optical and radio dozens of ground-based facilities to complement the Spitzer observations.Comment: 5 pages including figures, in conference proceedings A Population Explosion: The Nature and Evolution of X-ray Binaries in Diverse Environments, eds. Bandyopadhyay, Wachter, Gelino, & Gelin

The Galactic population of HMXBs as seen with INTEGRAL during its four first years of activity

We collected the parameters (position, absorption, spin, orbital period, etc..), when known, of all Galactic sources detected by INTEGRAL during its four first years of activity. We use these parameters to test theoretical predictions. For example, it is clear that HMXBs tend to be found mostly in the tangential direction of the Galactic arms, while LMXBs tend to be clustered in the Galactic bulge. We then focus on HMXBs and present two possible new tools, in addition to the well-known ``Corbet-diagram'', to distinguish between Be-HMXBs and Sg-HMXBsComment: 5 pages, 3 figures proceedings of "A population explosion: the nature and evolution of X-ray binaries in diverse environments", conference held in St.Petersburg Beach, Florida; R.M.Bandyopadhyay, S.Wachter, D.Gelino, C.R.Gelino, ed

Phase Curves of the Kepler-11 Multi-Planet System

The Kepler mission has allowed the detection of numerous multi-planet exosystems where the planetary orbits are relatively compact. The first such system detected was Kepler-11 which has six known planets at the present time. These kinds of systems offer unique opportunities to study constraints on planetary albedos by taking advantage of both the precision timing and photometry provided by Kepler data to monitor possible phase variations. Here we present a case study of the Kepler-11 system in which we investigate the phase modulation of the system as the planets orbit the host star. We provide predictions of maximum phase modulation where the planets are simultaneously close to superior conjunction. We use corrected Kepler data for Q1-Q17 to determine the significance of these phase peaks. We find that data quarters where maximum phase peaks occur are better fit by a phase model than a "null hypothesis" model.Comment: 9 pages, 4 figures, 2 tables, accepted for publication in Ap

Spitzer Observations of Black Hole Low-mass X-ray Binaries: Assessing the Non-stellar Infrared Component

We have combined ground-based optical and near-infrared data with Spitzer Space Telescope mid-infrared data for five black hole (BH) soft X-ray transients (SXTs) in order to determine the levels of near- and mid-infrared emission from sources other than the secondary star. Mid-infrared emission from an accretion disk, circumbinary dust, and/or a jet could act as sources of near-infrared contamination, thereby diluting ellipsoidal variations of the secondary star and affecting determined BH mass estimates. Based on optical to mid-infrared spectral energy distribution modeling of the five SXTs along with the prototype, V616 Mon, we detected mid-infrared excesses in half of the systems, and suggest that the excesses detected from these systems arise from non-thermal synchrotron jets rather than circumbinary dust disks

On the Inclination and Habitability of the HD 10180 System

There are numerous multi-planet systems that have now been detected via a variety of techniques. These systems exhibit a range of both planetary properties and orbital configurations. For those systems without detected planetary transits, a significant unknown factor is the orbital inclination. This produces an uncertainty in the mass of the planets and their related properties, such as atmospheric scale height. Here we investigate the HD~10180 system which was discovered using the radial velocity technique. We provide a new orbital solution for the system which allows for eccentric orbits for all planets. We show how the inclination of the system affects the mass/radius properties of the planets and how the detection of phase signatures may resolve the inclination ambiguity. We finally evaluate the Habitable Zone properties of the system and show that the g planet spends 100\% of an eccentric orbit within the Habitable Zone.Comment: 7 pages, 6 figures, 2 tables, accepted for publication in the Astrophysical Journa

Spitzer Observations of GX17+2: Confirmation of a Periodic Synchrotron Source

GX17+2 is a low-mass X-ray binary (LMXB) that is also a member of a small family of LMXBs known as "Z-sources" that are believed to have persistent X-ray luminosities that are very close to the Eddington limit. GX17+2 is highly variable at both radio and X-ray frequencies, a feature common to Z-sources. What sets GX17+2 apart is its dramatic variability in the near-infrared, where it changes by ΔK ~ 3 mag. Previous investigations have shown that these brightenings are periodic, recurring every 3.01 days. Given its high extinction (A_V≥9 mag), it has not been possible to ascertain the nature of these events with ground-based observations. We report mid-infrared Spitzer observations of GX17+2 which indicate a synchrotron spectrum for the infrared brightenings. In addition, GX17+2 is highly variable in the mid-infrared during these events. The combination of the large-scale outbursts, the presence of a synchrotron spectrum, and the dramatic variability in the mid-infrared suggest that the infrared brightening events are due to the periodic transit of a synchrotron jet across our line of sight. An analysis of both new, and archival, infrared observations has led us to revise the period for these events to 3.0367 days. We also present new Rossi X-Ray Timing Explorer (RXTE) data for GX17+2 obtained during two predicted infrared brightening events. Analysis of these new data, and data from the RXTE archive, indicates that there is no correlation between the X-ray behavior of this source and the observed infrared brightenings. We examine various scenarios that might produce periodic jet emission