Kilonovae represent an important electromagnetic counterpart for compact binary mergers, which could become the most commonly detected gravitational wave (GW) source. Follow-up observations, triggered by GW events, of kilonovae are nevertheless diffi
cult due to poor localization by GW detectors and due to their faint near-infrared peak emission that has limited observational capability. We show that the Near-Infrared Camera (NIRCam) on the James Webb Space Telescope (JWST) will be able to detect kilonovae within the relevant GW-detection range of $sim$ 200 Mpc in short ($lesssim$ 12-second) exposure times for a week following the merger. Despite this sensitivity, a kilonova search fully covering a fiducial localized area of $10$ $mbox{deg}^2$ will not be viable with NIRCam due to its limited field of view. However, targeted surveys may be developed to optimize the likelihood of discovering kilonovae efficiently within limited observing time. We estimate that a survey of $10$ $mbox{deg}^2$ focused on galaxies within 200 Mpc would require about 13 hours, dominated by overhead times; a survey further focused on galaxies exhibiting high star-formation rates would require $sim$ 5 hours. The characteristic time may be reduced to as little as $sim$4 hours, without compromising the likelihood of detecting kilonovae, by surveying sky areas associated with 50%, rather than 90%, confidence regions of 3 GW events, rather than a single event. On detection and identification of a kilonova, a limited number of NIRCam follow-up observations could constrain the properties of matter ejected by the binary and the equation of state of dense nuclear matter.
Infrared extinction maps and submillimeter dust continuum maps are powerful probes of the density structure in the envelope of star-forming cores. We make a direct comparison between infrared and submillimeter dust continuum observations of the low-m
ass Class 0 core, B335, to constrain the ratio of submillimeter to infrared opacity (kaprat) and the submillimeter opacity power-law index ($kappa propto lambda^{-beta}$). Using the average value of theoretical dust opacity models at 2.2 micron, we constrain the dust opacity at 850 and 450 micron . Using new dust continuum models based upon the broken power-law density structure derived from interferometric observations of B335 and the infall model derived from molecular line observations of B335, we find that the opacity ratios are $frac{kappa_{850}}{kappa_{2.2}} = (3.21 - 4.80)^{+0.44}_{-0.30} times 10^{-4}$ and $frac{kappa_{450}}{kappa_{2.2}} = (12.8 - 24.8)^{+2.4}_{-1.3} times 10^{-4}$ with a submillimeter opacity power-law index of $beta_{smm} = (2.18 - 2.58)^{+0.30}_{-0.30}$. The range of quoted values are determined from the uncertainty in the physical model for B335. For an average 2.2 micron opacity of $3800 pm 700$ cm$^2$g$^{-1}$, we find a dust opacity at 850 and 450 micron of $kappa_{850} = (1.18 - 1.77)^{+0.36}_{-0.24}$ and $kappa_{450} = (4.72 - 9.13)^{+1.9}_{-0.98}$ cm$^2$g$^{-1}$ of dust. These opacities are from $(0.65 - 0.97) kappa^{rm{OH}5}_{850}$ of the widely used theoretical opacities of Ossenkopf and Henning for coagulated ice grains with thin mantles at 850micron.
We discuss the results from the combined IRAC and MIPS c2d Spitzer Legacy observations of the Serpens star-forming region. In particular we present a set of criteria for isolating bona fide young stellar objects, YSOs, from the extensive background c
ontamination by extra-galactic objects. We then discuss the properties of the resulting high confidence set of YSOs. We find 235 such objects in the 0.85 deg^2 field that was covered with both IRAC and MIPS. An additional set of 51 lower confidence YSOs outside this area is identified from the MIPS data combined with 2MASS photometry. We describe two sets of results, color-color diagrams to compare our observed source properties with those of theoretical models for star/disk/envelope systems and our own modeling of the subset of our objects that appear to be star+disks. These objects exhibit a very wide range of disk properties, from many that can be fit with actively accreting disks to some with both passive disks and even possibly debris disks. We find that the luminosity function of YSOs in Serpens extends down to at least a few x .001 Lsun or lower for an assumed distance of 260 pc. The lower limit may be set by our inability to distinguish YSOs from extra-galactic sources more than by the lack of YSOs at very low luminosities. A spatial clustering analysis shows that the nominally less-evolved YSOs are more highly clustered than the later stages and that the background extra-galactic population can be fit by the same two-point correlation function as seen in other extra-galactic studies. We also present a table of matches between several previous infrared and X-ray studies of the Serpens YSO population and our Spitzer data set.
