Observing Gravitational Waves with a Single Detector

A major challenge of any search for gravitational waves is to distinguish true astrophysical signals from those of terrestrial origin. Gravitational-wave experiments therefore make use of multiple detectors, considering only those signals which appear in coincidence in two or more instruments. It is unclear, however, how to interpret loud gravitational-wave candidates observed when only one detector is operational. In this paper, we demonstrate that the observed rate of binary black hole mergers can be leveraged in order to make confident detections of gravitational-wave signals with one detector alone. We quantify detection confidences in terms of the probability $P(S)$ that a signal candidate is of astrophysical origin. We find that, at current levels of instrumental sensitivity, loud signal candidates observed with a single Advanced LIGO detector can be assigned $P(S)\gtrsim0.4$. In the future, Advanced LIGO may be able to observe single-detector events with confidences exceeding $P(S)\sim90\%$.Comment: 8 pages, 4 figures; published in CQG; minor updates to match published versio

Detection of electronic excited states in conjugated polymers by picosecond transient strain spectroscopy

Journal ArticleWe describe a new type of spectroscopy based on picosecond transient strain in absorption photomodulation that can be used to detect and identify both allowed and forbidden optical transitions in solid thin films. We have applied the new spectroscopy to a variety of conducting polymer films such as polythiophene, trans and cis polyacetylene, and poly(diethynyl-silane), in which we measured energy levels of various excitonic states with odd and even symmetry that are, respectively, allowed and forbidden in the optical absorption

Kennedy Space Center: Apollo to Multi-User Spaceport

NASA Kennedy Space Center (KSC) was established as the gateway to exploring beyond earth. Since the establishment of KSC in December 1963, the Center has been critical in the execution of the United States of Americas bold mission to send astronauts beyond the grasp of the terra firma. On May 25, 1961, a few weeks after a Soviet cosmonaut became the first person to fly in space, President John F. Kennedy laid out the ambitious goal of landing a man on the moon and returning him safely to the Earth by the end of the decade. The resultant Apollo program was massive endeavor, driven by the Cold War Space Race, and supported with a robust budget. The Apollo program consisted of 18 launches from newly developed infrastructure, including 12 manned missions and six lunar landings, ending with Apollo 17 that launched on December 7, 1972. Continuing to use this infrastructure, the Skylab program launched four missions. During the Skylab program, KSC infrastructure was redesigned to meet the needs of the Space Shuttle program, which launched its first vehicle (STS-1) on April 12, 1981. The Space Shuttle required significant modifications to the Apollo launch pads and assembly facilities, as well as new infrastructure, such as Orbiter and Payload Processing Facilities, as well as the Shuttle Landing Facility. The Space Shuttle was a workhorse that supported many satellite deployments, but was key for the construction and maintenance of the International Space Station, which required additional facilities at KSC to support processing of the flight hardware. After reaching the new Millennium, United States policymakers searched for new ways to reduce the cost of space exploration. The Constellation Program was initiated in 2005 with a goal of providing a crewed lunar landing with a much smaller budget. The very successful Space Shuttle made its last launch on July 8, 2011, after 135 missions. In the subsequent years, KSC continues to evolve, and this paper will address past and future efforts of the transformation of the KSC Apollo and Space Shuttle heritage infrastructure into a more versatile, multi-user spaceport. The paper will also discuss the US Congressional and NASA initiatives for developing and supporting multiple commercial partners, while simultaneously supporting NASAs human exploration initiative, consisting of Space Launch System (SLS), Orion spacecraft and associated ground launch systems. In addition, the paper explains the approach with examples for NASA KSC to leverage new technologies and innovative capabilities developed to reduce the cost to individual users

Enhancing gravitational wave astronomy with galaxy catalogues

Joint gravitational wave (GW) and electromagnetic (EM) observations, as a key research direction in multi-messenger astronomy, will provide deep insight into the astrophysics of a vast range of astronomical phenomena. Uncertainties in the source sky location estimate from gravitational wave observations mean follow-up observatories must scan large portions of the sky for a potential companion signal. A general frame of joint GW-EM observations is presented by a multi-messenger observational triangle. Using a Bayesian approach to multi-messenger astronomy, we investigate the use of galaxy catalogue and host galaxy information to reduce the sky region over which follow-up observatories must scan, as well as study its use for improving the inclination angle estimates for coalescing binary compact objects. We demonstrate our method using a simulated neutron stars inspiral signal injected into simulated Advanced detectors noise and estimate the injected signal sky location and inclination angle using the Gravitational Wave Galaxy Catalogue. In this case study, the top three candidates in rank have $72\%$, $15\%$ and $8\%$ posterior probability of being the host galaxy, receptively. The standard deviation of cosine inclination angle (0.001) of the neutron stars binary using gravitational wave-galaxy information is much smaller than that (0.02) using only gravitational wave posterior samples.Comment: Proceedings of the Sant Cugat Forum on Astrophysics. 2014 Session on 'Gravitational Wave Astrophysics

Solid Rocket Booster (SRB) - Evolution and Lessons Learned During the Shuttle Program

The Solid Rocket Booster (SRB) element integrates all the subsystems needed for ascent flight, entry, and recovery of the combined Booster and Motor system. These include the structures, avionics, thrust vector control, pyrotechnic, range safety, deceleration, thermal protection, and retrieval systems. This represents the only human-rated, recoverable and refurbishable solid rocket ever developed and flown. Challenges included subsystem integration, thermal environments and severe loads (including water impact), sometimes resulting in hardware attrition. Several of the subsystems evolved during the program through design changes. These included the thermal protection system, range safety system, parachute/recovery system, and others. Obsolescence issues occasionally required component recertification. Because the system was recovered, the SRB was ideal for data and imagery acquisition, which proved essential for understanding loads and system response. The three main parachutes that lower the SRBs to the ocean are the largest parachutes ever designed, and the SRBs are the largest structures ever to be lowered by parachutes. SRB recovery from the ocean was a unique process and represented a significant operational challenge; requiring personnel, facilities, transportation, and ground support equipment. The SRB element achieved reliability via extensive system testing and checkout, redundancy management, and a thorough postflight assessment process. Assembly and integration of the booster subsystems was a unique process and acceptance testing of reused hardware components was required for each build. Extensive testing was done to assure hardware functionality at each level of stage integration. Because the booster element is recoverable, subsystems were available for inspection and testing postflight, unique to the Shuttle launch vehicle. Problems were noted and corrective actions were implemented as needed. The postflight assessment process was quite detailed and a significant portion of flight operations. The SRBs provided fully redundant critical systems including thrust vector control, mission critical pyrotechnics, avionics, and parachute recovery system. The design intent was to lift off with full redundancy. On occasion, the redundancy management scheme was needed during flight operations. This paper describes some of the design challenges, how the design evolved with time, and key areas where hardware reusability contributed to improved system level understanding

Electromagnetic follow-up of gravitational wave transient signal candidates

Pioneering efforts aiming at the development of multi-messenger gravitational wave and electromagnetic astronomy have been made. An electromagnetic observation follow-up program of candidate gravitational wave events has been performed (Dec 17 2009 to Jan 8 2010 and Sep 4 to Oct 20 2010) during the recent runs of the LIGO and Virgo gravitational wave detectors. It involved ground-based and space electromagnetic facilities observing the sky at optical, X-ray and radio wavelengths. The joint gravitational wave and electromagnetic observation study requires the development of specific image analysis procedures able to discriminate the possible electromagnetic counterpart of gravitational wave triggers from contaminant/background events. The paper presents an overview of the electromagnetic follow-up program and the image analysis procedures.Comment: Proceedings of the 12th International Conference on "Topics in Astroparticle and Underground Physics" (TAUP 2011), Munich, September 2011 (to appear in IoP Journal of Physics: Conference Series

Parameter Estimation for Gravitational-wave Bursts with the BayesWave Pipeline

We provide a comprehensive multi-aspect study of the performance of a pipeline used by the LIGO-Virgo Collaboration for estimating parameters of gravitational-wave bursts. We add simulated signals with four different morphologies (sine-Gaussians (SGs), Gaussians, white-noise bursts, and binary black hole signals) to simulated noise samples representing noise of the two Advanced LIGO detectors during their first observing run. We recover them with the BayesWave (BW) pipeline to study its accuracy in sky localization, waveform reconstruction, and estimation of model-independent waveform parameters. BW localizes sources with a level of accuracy comparable for all four morphologies, with the median separation of actual and estimated sky locations ranging from 25 degrees. 1 to 30 degrees. 3. This is a reasonable accuracy in the two-detector case, and is comparable to accuracies of other localization methods studied previously. As BW reconstructs generic transient signals with SG wavelets, it is unsurprising that BW performs best in reconstructing SG and Gaussian waveforms. The BW accuracy in waveform reconstruction increases steeply with the network signal-to-noise ratio (S/N-net), reaching a 85% and 95% match between the reconstructed and actual waveform below S/N-net approximate to 20 and S/N-net approximate to 50, respectively, for all morphologies. The BW accuracy in estimating central moments of waveforms is only limited by statistical errors in the frequency domain, and is also affected by systematic errors in the time domain as BW cannot reconstruct low-amplitude parts of signals that are overwhelmed by noise. The figures of merit we introduce can be used in future characterizations of parameter estimation pipelines

LOOC UP: Locating and observing optical counterparts to gravitational wave bursts

Gravitational wave (GW) bursts (short duration signals) are expected to be associated with highly energetic astrophysical processes. With such high energies present, it is likely these astrophysical events will have signatures in the EM spectrum as well as in gravitational radiation. We have initiated a program, "Locating and Observing Optical Counterparts to Unmodeled Pulses in Gravitational Waves" (LOOC UP) to promptly search for counterparts to GW burst candidates. The proposed method analyzes near real-time data from the LIGO-Virgo network, and then uses a telescope network to seek optical-transient counterparts to candidate GW signals. We carried out a pilot study using S5/VSR1 data from the LIGO-Virgo network to develop methods and software tools for such a search. We will present the method, with an emphasis on the potential for such a search to be carried out during the next science run of LIGO and Virgo, expected to begin in 2009.Comment: 11 pages, 2 figures; v2) added acknowledgments, additional references, and minor text changes v3) added 1 figure, additional references, and minor text changes. v4) Updated references and acknowledgments. To be published in the GWDAW 12 Conf. Proc. by Classical and Quantum Gravit

A List of Galaxies for Gravitational Wave Searches

We present a list of galaxies within 100 Mpc, which we call the Gravitational Wave Galaxy Catalogue (GWGC), that is currently being used in follow-up searches of electromagnetic counterparts from gravitational wave searches. Due to the time constraints of rapid follow-up, a locally available catalogue of reduced, homogenized data is required. To achieve this we used four existing catalogues: an updated version of the Tully Nearby Galaxy Catalog, the Catalog of Neighboring Galaxies, the V8k catalogue and HyperLEDA. The GWGC contains information on sky position, distance, blue magnitude, major and minor diameters, position angle, and galaxy type for 53,255 galaxies. Errors on these quantities are either taken directly from the literature or estimated based on our understanding of the uncertainties associated with the measurement method. By using the PGC numbering system developed for HyperLEDA, the catalogue has a reduced level of degeneracies compared to catalogues with a similar purpose and is easily updated. We also include 150 Milky Way globular clusters. Finally, we compare the GWGC to previously used catalogues, and find the GWGC to be more complete within 100 Mpc due to our use of more up-to-date input catalogues and the fact that we have not made a blue luminosity cut.Comment: Accepted for publication in Classical and Quantum Gravity, 13 pages, 7 figure

Deaf children's understanding of emotions: desires take precedence

Deaf children frequently have trouble understanding other people's emotions. It has been suggested that an impaired theory of mind can account for this. This research focused on the spontaneous use of mental states in explaining other people's emotions by 6- and 10-year-old deaf children as compared to their hearing peers. Within both age-groups deaf children referred to others' beliefs as often as their hearing peers and their references to desires even exceeded those of hearing children. This relative priority for the expression of desires is discussed in terms of possible communicative patterns of deaf children. The specific problems that deaf children meet in their daily communication might explain their abundance of desire-references: plausibly, they give a high priority to stress their own desires and needs unambiguously