K. Ackley

Method for detection and reconstruction of gravitational wave transients with networks of advanced detectors

We present a method for detection and reconstruction of the gravitational-wave (GW) transients with the networks of advanced detectors. Originally designed to search for transients with the initial GW detectors, it uses signicantly improved algorithms, which enhances both the low-latency searches with rapid localization of GW events for the electro-magnetic followup and high condence detection of a broad range of the transient GW sources. In the paper we present the analytic framework of the method. Following a short description of the core analysis algorithms, we introduce a novel approach to the reconstruction of the GW polarization from a pattern of detector responses to a GW signal. This polarization pattern is a unique signature of an arbitrary GW signal that can be measured independent from the other source parameters. The polarization measurements enable rapid reconstruction of the GW waveforms, sky localization and helps identication of the source origin.

All-sky search for long-duration gravitational wave transients with LIGO

We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10 - 500 seconds in a frequency band of 40 - 1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. We also report upper limits on the source rate density per year per Mpc^3 for specific signal models. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves.

First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data

We report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the first Advanced LIGO observing run. This search investigates the low frequency range of Advanced LIGO data, between 20 and 100 Hz, much of which was not explored in initial LIGO. The search was made possible by the computing power provided by the volunteers of the Einstein@Home project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population, corresponding to a sensitivity depth of 48.7  [1/√Hz]. At the frequency of best strain sensitivity, near 100 Hz, we set 90% confidence upper limits of 1.8×10^(−25). At the low end of our frequency range, 20 Hz, we achieve upper limits of 3.9×10^(−24). At 55 Hz we can exclude sources with ellipticities greater than 10^(−5) within 100 pc of Earth with fiducial value of the principal moment of inertia of 10^(38)  kg m^2.

Full Band All-sky Search for Periodic Gravitational Waves in the O1 LIGO Data

We report on a new all-sky search for periodic gravitational waves in the frequency band 475-2000 Hz and with a frequency time derivative in the range of [-1.0,+0.1]×10-8 Hz/s. Potential signals could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the data from Advanced LIGOs first observational run O1. No gravitational-wave signals were observed, and upper limits were placed on their strengths. For completeness, results from the separately published low-frequency search 20-475 Hz are included as well. Our lowest upper limit on worst-case (linearly polarized) strain amplitude h0 is ∼4×10-25 near 170 Hz, while at the high end of our frequency range, we achieve a worst-case upper limit of 1.3×10-24. For a circularly polarized source (most favorable orientation), the smallest upper limit obtained is ∼1.5×10-25.

CIRCE: The Canarias InfraRed Camera Experiment for the Gran Telescopio Canarias

The Canarias InfraRed Camera Experiment (CIRCE) is a near-infrared (1-2.5 micron) imager, polarimeter and low-resolution spectrograph operating as a visitor instrument for the Gran Telescopio Canarias 10.4-meter telescope. It was designed and built largely by graduate students and postdocs, with help from the UF astronomy engineering group, and is funded by the University of Florida and the U.S. National Science Foundation. CIRCE is intended to help fill the gap in near-infrared capabilities prior to the arrival of EMIR to the GTC, and will also provide the following scientific capabilities to compliment EMIR after its arrival: high-resolution imaging, narrowband imaging, high-time-resolution photometry, imaging polarimetry, low resolution spectroscopy. In this paper, we review the design, fabrication, integration, lab testing, and on-sky performance results for CIRCE. These include a novel approach to the opto-mechanical design, fabrication, and alignment.

A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni

Conditions in a black hole outburst The binary system V404 Cygni consists of a red giant star orbiting a black hole. In 2015, a surge of accretion by the black hole caused the surrounding plasma to brighten suddenly for the first time since 1989, briefly becoming the brightest x-ray source in the sky. Dallilar et al. combined observations from radio, infrared, optical, and x-ray telescopes taken during the outburst. They compared how fast the flux decayed at each wavelength, which allowed them to constrain the size of the emitting region, determine that the plasma within it cooled through synchrotron radiation, and measure the magnetic field around the black hole. Science, this issue p. 1299 A black hole binary system contains plasma cooling by synchrotron radiation in a weaker-than-expected magnetic field. Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kilo–electron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 33.1 ± 0.9 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems.

First results and future plans for the Canarias Infrared Camera Experiment (CIRCE) for the Gran Telescopio Canarias

CIRCE is a near-infrared (1-2.5 micron) imager (including low-resolution spectroscopy and polarimetery) in operation as a visitor instrument on the Gran Telescopio Canarias 10.-4m tele scope. It was built largely by graduate students and postdocs, with help from the UF Astronomy engineering group, and is funded by the University of Florida and the U.S. National Science Foundation. CIRCE is helping to fill the gap in time between GTC first light and the arrival of EMIR, and will also provide the following scientific capabilities to compliment EMIR after its arrival: high-resolution imaging, narrowband imaging, high-time-resolution photometry, polarimetry, and low-resolution spectroscopy. There are already scientific results from CIRCE, some of which we will review. Additionally, we will go over the observing modes of CIRCE, including the two additional modes that were added during a service and upgrading run in March 2016.

Demonstration of high-performance cryogenic probe arms for deployable IFUs

We describe the design, development, and laboratory test results of cryogenic probe arms feeding deployable integral field units (IFUs) for the Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS) - a near-infrared multi-object echelle spectrograph for the 10.4-meter Gran Telescopio Canarias. MIRADAS selects targets using 20 positionable pickoff mirror optics on cryogenic probe arms, each feeding a 3.7x1.2-arcsec field of view to the spectrograph integral field units, while maintaining excellent diffraction-limited image quality. The probe arms are based on a concept developed for the ACES instrument for Gemini and IRMOS for TMT. We report on the detailed design and opto-mechanical testing of MIRADAS prototype probe arms, including positioning accuracy, repeatability, and reliability under fully cryogenic operation, and their performance for MIRADAS. We also discuss potential applications of this technology to future instruments.

Status and first results of the Canarias infrared camera experiment (CIRCE) for the Gran Telescopio Canarias

CIRCE is a near-infrared (1-2.5 micron) imager, polarimeter and low-resolution spectrograph intended as a visitor instrument for the Gran Telescopio Canarias 10.-4m telescope. It was built largely by graduate students and postdocs, with help from the UF astronomy engineering group, and is funded by the University of Florida and the U.S. National Science Foundation. CIRCE is intended to help fill the gap in time between GTC first light and the arrival of EMIR, and will also provide the following scientific capabilities to compliment EMIR after its arrival: high- resolution imaging, narrowband imaging, high-time-resolution photometry, imaging- and spectro- polarimetry, low-resolution spectroscopy. In this poster, we review the lab testing results for CIRCE from 2013 and describe the instrument status (currently in shipment to GTC).