Engineering topics

Neill, James D.

Publications and source records attributed to Neill, James D..

5 records

NASA NTRS2019

The First Tidal Disruption Flare in ZTF: From Photometric Selection to Multi-Wavelength Characterization

We present Zwicky Transient Facility (ZTF) observations of the tidal disruption flare AT2018zr/PS18kh reported by Holoien et al. and detected during ZTF commissioning. The ZTF light curve of the tidal disruption event (TDE) samples the rise-to-peak exceptionally well, with 50 days of g- and r-band detections before the time of maximum light. We also present our multi-wavelength follow-up observations, including the detection of a thermal (kT ≈ 100 eV) X-ray source that is two orders of magnitude fainter than the contemporaneous optical/UV blackbody luminosity, and a stringent upper limit to the radio emission. We use observations of 128 known active galactic nuclei (AGNs) to assess the quality of the ZTF astrometry, finding a median host-flare distance of 0farcs2 for genuine nuclear flares. Using ZTF observations of variability from known AGNs and supernovae we show how these sources can be separated from TDEs. A combination of light-curve shape, color, and location in the host galaxy can be used to select a clean TDE sample from multi-band optical surveys such as ZTF or the Large Synoptic Survey Telescope.

van Velzen, Sjoert↗

NASA NTRS2019

2900 Square Degree Search for the Optical Counterpart of Short Gamma-Ray Burst GRB 180523B with the Zwicky Transient Facility

There is significant interest in the models for production of short gamma-ray bursts (GRBs). Until now, the number of known short GRBs with multi-wavelength afterglows has been small. While the Fermi GRB Monitor detects many GRBs relative to the Neil Gehrels Swift Observatory, the large localization regions makes the search for counterparts difficult. With the Zwicky Transient Facility (ZTF - part of Palomar Observatory) recently achieving first light, it is now fruitful to use its combination of depth (m (sub AB) approximating 20.6), field of view (approximately 47 square degrees), and survey cadence (every approximately 3 days) to perform Target of Opportunity observations. We demonstrate this capability on GRB 180523B, which was recently announced by the Fermi GRB Monitor as a short GRB. ZTF imaged 2900 square degrees of the localization region, resulting in the coverage of 61.6 percent of the enclosed probability over two nights to a depth of m (sub AB) approximating 20.5. We characterized 14 previously unidentified transients, and none were found to be consistent with a short GRB counterpart. This search with the ZTF shows it is an efficient camera for searching for coarsely localized short GRB and gravitational-wave counterparts, allowing for a sensitive search with minimal interruption to its nominal cadence.

Coughlin, Michael W.↗

NASA NTRS2012

Constructing a WISE High Resolution Galaxy Atlas

After eight months of continuous observations, the Wide-field Infrared Survey Explorer (WISE) mapped the entire sky at 3.4 micron, 4.6 micron, 12 micron, and 22 micron. We have begun a dedicated WISE High Resolution Galaxy Atlas project to fully characterize large, nearby galaxies and produce a legacy image atlas and source catalog. Here we summarize the deconvolution techniques used to significantly improve the spatial resolution of WISE imaging, specifically designed to study the internal anatomy of nearby galaxies. As a case study, we present results for the galaxy NGC 1566, comparing the WISE enhanced-resolution image processing to that of Spitzer, Galaxy Evolution Explorer, and ground-based imaging. This is the first paper in a two-part series; results for a larger sample of nearby galaxies are presented in the second paper.

Jarrett, T. H.↗

NASA NTRS1990

The H-alpha light curves of novae in M31

H-alpha and B light curves are presented for 11 M31 novae, four of which were well observed near maximum. These data, along with the H-alpha light curves of two Galactic novae, demonstrate that a nova's maximum H-alpha flux occurs days or weeks after its continuum maximum at a monochromatic intensity 1-2 magnitudes above its peak flux in B. Moreover, after this maximum is achieved, a typical nova will radiate a third as many photons in H-alpha as in the entire B bandpass. The most interesting part of a nova's H-alpha light curve, however, is its decline. It is found that, regardless of a nova's speed, its H-alpha decay rate after maximum is almost identical to its decay rate in B. This behavior suggests that most of a nova's optical luminosity during early decline is continuum emission from the nebula, rather than direct radiation from the central source.

Ciardullo, Robin↗

NASA NTRS1987

The spatial distribution and population of novae in M31

Results from an H-alpha survey for novae in the bulge of M31 are reported, and the spatial distribution of the nova population is analyzed. It is shown that in M31's central bulge the distribution of novae follows that of the light to within about 10 arcsec of the nucleus, refuting the notion that there is a nova 'hole' near the center of the galaxy. The Hubble-Arp nova sample is reanalyzed, concluding that the novae observed in the central 30 arcmin x 15 arcmin region belong almost exclusively to the bulge population. This result is compared to the observed cataclysmic variable distribution in the Galaxy, concluding that M31's spheroidal nova population is still compatible with the thin disk distribution of cataclysmic variables measured in the solar neighborhood. Possible explanations for the high specific nova rate of the bulge are discussed.

Ciardullo, Robin↗