Jonathan E. Grindlay

Bio: Jonathan E. Grindlay is an academic researcher from Harvard University. The author has contributed to research in topics: Neutron star & Population. The author has an hindex of 30, co-authored 122 publications receiving 3595 citations. Previous affiliations of Jonathan E. Grindlay include CFA Institute.

Advection-Dominated Accretion Model of Sagittarius A ∗ : Evidence for a Black Hole at the Galactic Center

Abstract: Sagittarius A*, which is located at the Galactic center, is a puzzling source. It has a mass of M = (2.5 ± 0.4) × 106 M☉, which makes it an excellent black hole candidate. Observations of stellar winds and other gas flows in its vicinity suggest a mass accretion rate of few × 10−6 M☉ yr-1. However, such an accretion rate would imply a luminosity greater than 1040 ergs-1 if the radiative efficiency is the usual 10%, whereas observations indicate a bolometric luminosity less than 1037 ergs-1. The spectrum of Sgr A* is unusual, with emission extending over many decades of wavelength. We present a model of Sgr A* that is based on a two-temperature optically thin advection-dominated accretion flow. The model is consistent with the estimated M and and fits the observed fluxes in the centimeter/millimeter and X-ray bands, as well as upper limits in the submillimeter and infrared bands; the fit is less good in the radio spectrum below 86 GHz and in γ-rays above 100 MeV. The very low luminosity of Sgr A* is explained naturally in the model by means of advection. Most of the viscously dissipated energy is advected into the central mass by the accreting gas, and therefore the radiative efficiency is extremely low, ~5 × 10-6. A critical element of the model is the presence of an event horizon at the center that swallows the advected energy. The success of the model could thus be viewed as confirmation that Sgr A* is a black hole.

A Hydrogen Atmosphere Spectral Model Applied to the Neutron Star X7 in the Globular Cluster 47 Tucanae

Abstract: Current X-ray missions are providing high-quality X-ray spectra from neutron stars (NSs) in quiescent low-mass X-ray binaries (qLMXBs). This has motivated us to calculate new hydrogen atmosphere models, including opacity due to free-free absorption and Thomson scattering, thermal electron conduction, and self-irradiation by photons from the compact object. We have constructed a self-consistent grid of neutron star models covering a wide range of surface gravities, as well as effective temperatures, which we make available to the scientific community. We present multiepoch Chandra X-ray observations of the qLMXB X7 in the globular cluster 47 Tuc, which is remarkably nonvariable on timescales from minutes to years. Its high-quality X-ray spectrum is adequately fitted by our hydrogen atmosphere model without any hard power-law component or narrow spectral features. If a mass of 1.4 M☉ is assumed, our spectral fits require that its radius be in the range Rns = 14.5 km (90% confidence), which is larger than that expected from currently preferred models of NS interiors. If its radius is assumed to be 10 km, then a mass of Mns = 2.20 M☉ is required. Using models with the appropriate surface gravity for each value of the mass and radius becomes important for interpretation of the highest quality data.

Advection-Dominated Accretion Model of Sagittarius A*: Evidence for a Black Hole at the Galactic Center

Abstract: Sgr A* at the Galactic Center is a puzzling source. It has a mass M=(2.5+/-0.4) x 10^6 solar masses which makes it an excellent black hole candidate. Observations of stellar winds and other gas flows in its vicinity suggest a mass accretion rate approximately few x 10^{-6} solar masses per year. However, such an accretion rate would imply a luminosity > 10^{40} erg/s if the radiative efficiency is the usual 10 percent, whereas observations indicate a bolometric luminosity <10^{37} erg/s. The spectrum of Sgr A* is unusual, with emission extending over many decades of wavelength. We present a model of Sgr A* which is based on a two-temperature optically-thin advection-dominated accretion flow. The model is consistent with the estimated mass and accretion rate, and fits the observed fluxes in the cm/mm and X-ray bands as well as upper limits in the sub-mm and infrared bands; the fit is less good in the radio below 86 GHz and in gamma-rays above 100 MeV. The very low luminosity of Sgr A* is explained naturally in the model by means of advection. Most of the viscously dissipated energy is advected into the central mass by the accreting gas, and therefore the radiative efficiency is extremely low, approximately 5 x 10^{-6}. A critical element of the model is the presence of an event horizon at the center which swallows the advected energy. The success of the model could thus be viewed as confirmation that Sgr A* is a black hole.

Relativistic Iron Emission Lines in Neutron Star Low-Mass X-Ray Binaries as Probes of Neutron Star Radii

Abstract: Using Suzaku observations of three neutron star low-mass X-ray binaries ( Ser X-1, 4U 1820-30, and GX 349+2) we have found broad, asymmetric, relativistic Fe K emission lines in all three objects. These Fe K lines can be well fit by a model for lines from a relativistic accretion disk ("diskline''), allowing a measurement of the inner radius of the accretion disk and hence an upper limit on the neutron star radius. These upper limits correspond to 14.5-16.5 km for a 1.4 M-circle dot neutron star. The inner disk radii that we measure with Fe K lines are in good agreement with the inner disk radii implied by kHz QPOs observed in both 4U 1820-30 and GX 349+2, supporting the inner disk origin for kHz QPOs. In addition, the Fe K lines observed in these neutron stars are narrower than those in the black holes that are thought to be close to maximally spinning, as one would expect if inferences for spin are robust.

X-Ray Processing of ChaMPlane Fields: Methods and Initial Results for Selected Anti-Galactic Center Fields

Abstract: We describe the X-ray analysis procedure of the ongoing Chandra Multiwavelength Plane (ChaMPlane) Survey and report the initial results from the analysis of 15 selected anti-Galactic center observations (90° < l < 270°). We describe the X-ray analysis procedures for ChaMPlane using custom-developed analysis tools appropriate for Galactic sources but also of general use: optimum photometry in crowded fields using advanced techniques for overlapping sources, rigorous astrometry and 95% error circles for combining X-ray images or matching to optical/IR images, and application of quantile analysis for spectral analysis of faint sources. We apply these techniques to 15 anti-Galactic center observations (of 14 distinct fields), in which we have detected 921 X-ray point sources. We present log N-log S distributions and quantile analysis to show that in the hard band (2-8 keV) active galactic nuclei dominate the sources. Complete analysis of all ChaMPlane anti-Galactic center fields will be given in a subsequent paper, followed by papers on sources in the Galactic center and bulge regions.

The Observation of Gravitational Waves from a Binary Black Hole Merger

Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

Monthly Notices of the Royal Astronomical Society

Abstract: Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

Parameter estimation in astronomy through application of the likelihood ratio. [satellite data analysis techniques

Abstract: Many problems in the experimental estimation of parameters for models can be solved through use of the likelihood ratio test. Applications of the likelihood ratio, with particular attention to photon counting experiments, are discussed. The procedures presented solve a greater range of problems than those currently in use, yet are no more difficult to apply. The procedures are proved analytically, and examples from current problems in astronomy are discussed.

GLIMPSE. I. An SIRTF Legacy Project to Map the Inner Galaxy

Abstract: The Galactic Legacy Infrared Mid‐Plane Survey Extraordinaire (GLIMPSE), a Space Infrared Telescope Facility (SIRTF) Legacy Science Program, will be a fully sampled, confusion‐limited infrared survey of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} ewcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} ormalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\frac{2}{3}$ \end{document} of the inner Galactic disk with a pixel resolution of ∼1 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \u...