Engineering topics

Butler, Nathaniel R.

Publications and source records attributed to Butler, Nathaniel R..

5 records

DOE OSTI2020

A search for optical and near-infrared counterparts of the compact binary merger GW190814

Here, we report on our observing campaign of the compact binary merger GW190814, detected by the Advanced LIGO and Advanced Virgo detectors on 2019 August 14. This signal has the best localization of any observed gravitational wave (GW) source, with a 90 per cent probability area of 18.5 deg 2 , and an estimated distance of ≈240 Mpc. We obtained wide-field observations with the Deca-Degree Optical Transient Imager (DDOTI) covering 88 per cent of the probability area down to a limiting magnitude of w = 19.9 AB. Nearby galaxies within the high probability region were targeted with the Lowell Discovery Telescope (LDT), whereas promising candidate counterparts were characterized through multicolour photometry with the Reionization and Transients InfraRed (RATIR) and spectroscopy with the Gran Telescopio de Canarias (GTC). We use our optical and near-infrared limits in conjunction with the upper limits obtained by the community to constrain the possible electromagnetic counterparts associated with the merger. A gamma-ray burst seen along its jet’s axis is disfavoured by the multiwavelength data set, whereas the presence of a burst seen at larger viewing angles is not well constrained. Although our observations are not sensitive to a kilonova similar to AT2017gfo, we can rule out high-mass (>0.1 M ⊙ ) fast-moving (mean velocity ≥0.3c) wind ejecta for a possible kilonova associated with this merger.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2016

DDOTI: the Deca-Degree Optical Transient Imager

DDOTI (Deca-Degree Optical Transient Imager) will be a wide-field robotic imager consisting of six 28-centimeter telescopes with prime focus CCDs (Charge-Coupled Devices) mounted on a common equatorial mount. Each telescope will have a field of view of 12 degrees squared, will have 2 arcsec pixels, and will reach a 10 sigma limiting magnitude in 60 seconds of r (redshift) equal to 18.7 in dark time and r (redshift) equal to 18.0 in bright time. The set of six will provide aninstantaneous field of view of about 72 degrees squared. DDOTI uses commercial components almost entirely. The first DDOTI willbe installed at the Observatorio Astronmico Nacional in Sierra San Pedro Martir, Baja California, Mexico in early 2017. The main science goals of DDOTI are the localization of the optical transients associated with GRBs (Gamma Ray Bursts) detected by the GBM (Gamma Ray Burst Monitor) instrument on the Fermi satellite and with gravitational-wave transients. DDOTI will also be used for studies of AGN (Active Galactic Nuclei) and YSO (Young Stellar Object) variability and to determine the occurrence of hot Jupiters. The principal advantage of DDOTI compared to other similar projects is cost: a single DDOTI installation costs only about US $500,000. This makes it possible to contemplate a global network of DDOTI installations. Such geographic diversity would give earlier access and a higher localization rate.We are actively exploring this option.

optical transients↗

NASA NTRS2016

An Ultraviolet Spectrum of the Tidal Disruption Flare ASASSN-14li

We present a Hubble Space Telescope Space Telescope Imaging Spectrograph spectrum of ASASSN-14li, the first rest-frame ultraviolet (UV) spectrum of a tidal disruption flare (TDF). The underlying continuum is well fit by a blackbody with T(sub UV) = 3.5 x 10(exp. 4) K, an order of magnitude smaller than the temperature inferred from X-ray spectra (and significantly more precise than previous efforts based on optical and near-UV photometry).Superimposed on this blue continuum, we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad {approx. 2000-8000 km s(exp. -1)} emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by Delta(sub v) = -(250-400) km s(exp. -1). Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and N-rich quasars.

accretion disks â€“ stars: flare â€“ ultraviolet: ↗

NASA NTRS2012

Performance and Calibration of H2RG Detectors and SIDECAR ASICs for the RATIR Camera

The Reionization And Transient Infra-Red (RATIR) camera has been built for rapid Gamma-Ray Burst (GRE) followup and will provide simultaneous optical and infrared photometric capabilities. The infrared portion of this camera incorporates two Teledyne HgCdTe HAWAII-2RG detectors, controlled by Teledyne's SIDECAR ASICs. While other ground-based systems have used the SIDECAR before, this system also utilizes Teledyne's JADE2 interface card and IDE development environment. Together, this setup comprises Teledyne's Development Kit, which is a bundled solution that can be efficiently integrated into future ground-based systems. In this presentation, we characterize the system's read noise, dark current, and conversion gain.

Fox, Ori D.↗

NASA NTRS2011

Swift J2058.4+0516: Discovery of a Possible Second Relativistic Tidal Disruption Flare

We report the discovery by the Swift hard X-ray monitor of the transient source Swift J2058.4+0516 (Sw J2058+05). Our multi-wavelength follow-up campaign uncovered a long-lived (duration approximately greater than months), luminous X-ray (L(sub x.iso) approximates 3 X 10(exp47) erg/s) and radio (vL(sub v.iso) approximates 10(exp 42) erg/s) counterpart. The associated optical emission, however, from which we measure a redshift of 1.1853, is relatively faint, and this is not due to a large amount of dust extinction in the host galaxy. Based on numerous similarities with the recently discovered GRB 110328A / Swift 1164449.3+573451 (Sw 11644+57), we suggest that Sw J2058+05 may be the second member of a new class of relativistic outbursts resulting from the tidal disruption of a star by a supermassive black hole. If so, the relative rarity of these sources implies that either these outflows are extremely narrowly collimated (theta < 1 deg), or only a small fraction of tidal disruptions generate relativistic ejecta. Analogous to the case of long duration gamma-ray bursts and core-collapse supernovae, we speculate that the spin of the black hole may be a necessary condition to generate the relativistic component. Alternatively, if powered by gas accretion (i.e., an active galactic nucleus), this would imply that some galaxies can transition from apparent quiescence to a radiatively efficient state of accretion on quite short time scales.

Cenko, S. Bradely↗