We present 1210 Johnson/Cousins B, V , R, and I photometric observations of 22 recent Type Ia supernovae (SNe Ia) : SNe 1993ac, 1993ae, 1994M, 1994S, 1994T, 1994Q, 1994ae, 1995D, 1995E, 1995al, 1995ac, 1995ak, 1995bd, 1996C, 1996X, 1996Z, 1996ab, 1996ai, 1996bk, 1996bl, 1996bo, and 1996bv. Most of the photometry was obtained at the Fred Lawrence Whipple Observatory of the HarvardSmithsonian Center for Astrophysics in a cooperative observing plan aimed at improving the database for SNe Ia. The redshifts of the sample range from cz \ 1200 to 37,000 km s~1 with a mean of cz \ 7000 km s~1.

We describe new planetesimal accretion calculations in the Kuiper Belt that include fragmentation and velocity evolution. All models produce two power law cumulative size distributions, N C ∝ r −2.5 for radii ∼ < 0.3-3 km and N C ∝ r −3 for radii ∼ > 1-3 km. The power law indices are nearly independent of the initial mass in the annulus, M 0 ; the initial eccentricity of the planetesimal swarm, e 0 ; and the initial size distribution of the planetesimal swarm. The transition between the two power laws moves to larger radii as e 0 increases. The maximum size of objects depends on their intrinsic tensile strength, S 0 ; Pluto formation requires S 0 ∼ > 300 erg g −1 . The timescale to produce Pluto-sized objects, τ P , is roughly proportional to M −1 0 and e 0 , and is less sensitive to other input parameters. Our models yield τ P ≈ 30-40 Myr for planetesimals with e 0 = 10 −3 in a Minimum Mass Solar Nebula. The production of several 'Plutos' and ∼ 10 5 50 km radius Kuiper Belt objects leaves most of the initial mass in 0.1-10 km radius objects that can be collisionally depleted over the age of the solar system. These results resolve the puzzle of large Kuiper Belt objects in a small mass Kuiper Belt.

We present observations of the interstellar interloper 1I/2017 U1 ('Oumuamua) taken during its 2017 October flyby of Earth. The optical colors B -V=0.70±0.06, V -R=0.45±0.05, overlap those of the D-type Jovian Trojan asteroids and are incompatible with the ultrared objects that are abundant in the Kuiper Belt. With a mean absolute magnitude H V =22.95 and assuming a geometric albedo p V =0.1, we find an average radius of 55 m. No coma is apparent; we deduce a limit to the dust mass production rate of only ∼2×10 −4 kg s, ruling out the existence of exposed ice covering more than a few m 2 of the surface. Volatiles in this body, if they exist, must lie beneath an involatile surface mantle 0.5 m thick, perhaps a product of prolonged cosmic-ray processing in the interstellar medium. The light curve range is unusually large at ∼2.0±0.2 mag. Interpreted as a rotational light curve the body has axis ratio ³ -+ 6.3 1.1 1.3 :1 and semi-axes ∼230 m×35 m. A 6:1 axis ratio is extreme relative to most small solar system asteroids and suggests that albedo variations may additionally contribute to the variability. The light curve is consistent with a two-peaked period ∼8.26 hr, but the period is non-unique as a result of aliasing in the data. Except for its unusually elongated shape, 1I/2017 U1 is a physically unremarkable, sub-kilometer, slightly red, rotating object from another planetary system. The steady-state population of similar, ∼100 m scale interstellar objects inside the orbit of Neptune is ∼10 4 , each with a residence time of ∼10 years.

No abstract

We present a study of Jovian Trojan objects detected serendipitously during the course of a sky survey conducted at the University of Hawaii 2.2-meter telescope. We used a 8192 x 8192 pixel charge-coupled device (CCD) mosaic to observe 20 deg^2 at locations spread over the L4 Lagrangian swarm and reached a limiting magnitude V = 22.5 mag (50% of maximum detection efficiency). Ninety-three Jovian Trojans were detected with radii 2 - 20 km (assumed albedo 0.04). Their differential magnitude distribution has a slope of 0.40 +/- 0.05 corresponding to a power law size distribution index 3.0 +/- 0.3 (1-sigma). The total number of L4 Trojans with radii > 1 km is of order 1.6 x 10^5 and their combined mass (dominated by the largest objects) is ~ 10^{-4} M_{Earth}. The bias-corrected mean inclination is 13.7 +/- 0.5 deg. We also discuss the size and spatial distribution of the L4 swarm.Comment: 21 pages, 11 figures. AJ, in pres

We present UBVRI photometry of 44 type-Ia supernovae (SN Ia) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SN Ia to date, nearly doubling the number of well-observed, nearby SN Ia with published multicolor CCD light curves. The large sample of U-band photometry is a unique addition, with important connections to SN Ia observed at high redshift. The decline rate of SN Ia U-band light curves correlates well with the decline rate in other bands, as does the U −B color at maximum light. However, the U-band peak magnitudes show an increased dispersion relative to other bands even after accounting for extinction and decline rate, amounting to an additional ∼40% intrinsic scatter compared to B-band.Subject headings: supernovae: general -techniques: photometric Data and Reduction DiscoveryOur program of supernova photometry consists solely of follow-up; we search only our email, not the sky, to find new supernovae. A number of observers, both amateur and professional, are engaged in searching for supernovae. We rely on these searches, as well as prompt notification of candidates, coordinated by Dan Green and Brian Marsden of the IAU's Central Bureau for Astronomical Telegrams (CBAT), with confirmed SN reported in the IAU Circulars. In some cases the SN discoverers provide spectroscopic classification of the new objects, but generally spectroscopy is obtained by others, and reported separately in the IAU Circulars. With our spectroscopic SN follow-up program at the F. L. Whipple Observatory 1.5m telescope and FAST spectrograph (Fabricant et al. 1998), we have classified a large fraction of the new, nearby supernovae reported over the last several years and compiled a large spectroscopic database (Matheson et al. 2005, in preparation).Given a newly discovered and classified supernova, several factors help determine whether or not we include it in our monitoring program. Because of their importance, SN Ia are often given higher priority over other types, but factors such as ease of observability (southern targets and those discovered far to the west are less appealing), supernova phase (objects whose spectra indicate they are after maximum light are given lower priority), redshift (more nearby objects are favored), as well as the number of objects we are already monitoring are significant. Our final sample of well-observed SN Ia is not obtained from a single well-defined set of criteria, and selection effects in both the searches and follow-up may make this sample unsuitable for some applications (such as determining the intrinsic luminosity function of SN Ia, for example). A thorough discussion of the selection biases in the Calán/Tololo supernova search and follow-up campaign can be found in Hamuy & Pinto (1999).The discovery data for the sample of SN Ia presented here are given in Table 1. All of the ...

We describe planetesimal accretion calculations in the Kuiper Belt. Our evolution code simulates planetesimal growth in a single annulus and includes velocity evolution but not fragmentation. Test results match analytic solutions and duplicate previous simulations at 1 AU.In the Kuiper Belt, simulations without velocity evolution produce a single runaway body with a radius r i ∼ > 1000 km on a time scale τ r ∝ M −1 0 e x 0 , where M 0 is the initial mass in the annulus, e 0 is the initial eccentricity of the planetesimals, and x ≈ 1-2. Runaway growth occurs in 100 Myr for M 0 ≈ 10 M ⊕ and e 0 ≈ 10 −3 in a 6 AU annulus centered at 35 AU. This mass is close to the amount of dusty material expected in a minimum mass solar nebula extrapolated into the Kuiper Belt.Simulations with velocity evolution produce runaway growth on a wide range of time scales. Dynamical friction and viscous stirring increase particle velocities in models with large (8 km radius) initial bodies. This velocity increase delays runaway growth by a factor of two compared to models without velocity evolution. In contrast, collisional damping dominates over dynamical friction and viscous stirring in models with small (80-800 m radius) initial bodies. Collisional damping decreases the time scale to runaway growth by factors of 4-10 relative to constant velocity calculations. Simulations with minimum mass solar nebulae, M 0 ∼ 10 M ⊕ , and small eccentricities, e ≈ 10 −3 , reach runaway growth on time scales of 20-40 Myr with 80 m initial bodies, 50-100 Myr with 800 m bodies, and 75-250 Myr for 8 km initial bodies. These growth times vary linearly with the mass of the annulus, τ r ∝ M −1 0 , but are less sensitive to the initial eccentricity than constant velocity models.In both sets of models, the time scales to produce 1000+ km objects are comparable to estimated formation time scales for Neptune. Thus, Pluto-sized objects can form in the outer solar system in parallel with the condensation of the outermost large planets.

We present the results of a wide-Ðeld survey designed to measure the size, inclination, and radial distributions of Kuiper Belt objects (KBOs). The survey found 86 KBOs in 73 deg2 observed to limiting red magnitude of 23.7 using the Canada-France-Hawaii Telescope and the 12K ] 8K CCD mosaic camera. For the Ðrst time, both ecliptic and o †-ecliptic Ðelds were examined to more accurately constrain the inclination distribution of the KBOs. The survey data were processed using an automatic moving-object detection algorithm, allowing a careful characterization of the biases involved. In this work, we quantify fundamental parameters of the classical KBOs (CKBOs), the most numerous objects found in our sample, using the new data and a maximum likelihood simulation. Deriving results from our best-Ðt model, we Ðnd that the size distribution follows a di †erential power law with exponent(1 p, q \ 4.0~0 .5 0.6 or 68.27% conÐdence). In addition, the CKBOs inhabit a very thick disk consistent with a Gaussian distribution of inclinations with a half-width of deg (1 p). We estimate that there are i 1@2 \ 20~4 6 (1 p) CKBOs larger than 100 km in diameter. We also Ðnd com-N CKBO (D [ 100 km) \ 3.8~1 .5 2.0 ] 104 pelling evidence for an outer edge to the CKBOs at heliocentric distances R \ 50 AU.