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We have compiled a large sample of low-redshift active galactic nuclei (AGNs) identified via their emission-line characteristics from the spectroscopic data of the Sloan Digital Sky Survey. Since emission lines are often contaminated by stellar absorption lines, we developed an objective and efficient method of subtracting the stellar continuum from every galaxy spectrum before making emission-line measurements. The distribution of the measured Hα FWHM values of emission-line galaxies is strongly bimodal, with two populations separated at about 1200 km s^-1. This feature provides a natural separation between narrow-line and broad-line AGNs. The narrow-line AGNs are identified using standard emission-line ratio diagnostic diagrams. There are 1317 broad-line and 3074 narrow-line AGNs identified from about 100,000 galaxy spectra selected over 1151 deg². This sample is used in a companion paper to determine the emission-line luminosity function of AGNs.

The emission-line luminosity function of active galactic nuclei (AGNs) is measured from about 3000 AGNs included in the main galaxy sample of the Sloan Digital Sky Survey within a redshift range of 0 < z < 0.15. The Hα and [O III] λ5007 luminosity functions for Seyfert galaxies cover a luminosity range of 10⁵–10⁹L_⊙ in Hα, and the shapes are well fitted by broken power laws, without a turnover at fainter nuclear luminosities. Assuming a universal conversion from emission-line strength to continuum luminosity, the inferred B-band magnitude luminosity function is comparable to both the AGN luminosity function of previous studies and the low-redshift quasar luminosity function derived from the Two-Degree Field redshift survey. The inferred AGN number density is approximately one-fifth of all galaxies, and about 6 × 10^-3 of the total light of galaxies in the r band comes from nuclear activity. The numbers of Seyfert 1 and Seyfert 2 galaxies are comparable at low luminosity, while at high luminosity, Seyfert 1 galaxies outnumber Seyfert 2 galaxies by a factor of 2–4. In making the luminosity function measurements, we assume that the nuclear luminosity is independent of the host galaxy luminosity, an assumption we test a posteriori and show to be consistent with the data. Given the relationship between black hole mass and host galaxy bulge luminosity, the lack of correlation between nuclear and host luminosity suggests that the main variable that determines the AGN luminosity is the Eddington ratio, not the black hole mass. This appears to be different from luminous quasars, which are most likely to be shining near the Eddington limit.

We present sensitive phase-referenced VLBI observations of the radio continuum emission from the z = 4.7 double source BRI 1202-0725. The observations were carried out at 1425 MHz using the Very Long Baseline Array, the phased Very Large Array, and the Green Bank Telescope. Our sensitive VLBI images of BRI 1202-0725 at 025 × 014 resolution show a continuum structure in each of its two components. Fitting Gaussian models to these continuum structures yields total flux densities of 315 ± 38 and 250 ± 39 μJy for the northern and the southern components, respectively. The estimated intrinsic brightness temperatures of these continuum structures are ∼2 × 10⁴ K. Neither component is detected at the full VLBI resolution (29 × 7 mas²), with a 4 σ point-source upper limit of 40 μJy beam^-1, or an upper limit to the intrinsic brightness temperature of 6.7 × 10⁵ K. The highest angular resolution with at least a 4 σ detection is ∼85 mas. At this resolution, the images reveal a single continuum feature in the northern component of BRI 1202-0725 and two continuum features in the southern component, separated by 320 mas. This is similar to the structures seen in the high-resolution images of the CO emission. The extent of the observed continuum sources at 1.4 GHz and the derived brightness temperatures are consistent with nuclear starbursts. Moreover, the absence of any compact high brightness temperature source suggests that there is no radio-loud active galactic nucleus in BRI 1202-0725.

Optical monitoring of S5 0716+714 was performed with a 60/90 Schmidt telescope in 2003 November and December and 2004 January for studying the variability of the object on short timescales. Because of the high brightness of the source, we could carry out quasi-simultaneous measurements in three bands with a temporal resolution of about 20 minutes by using one single telescope. Intraday and intranight variations were observed, showing an overall change of ∼0.9 mag during the whole campaign. Two outbursts were recorded on Julian Dates 2,453,005 and 2,453,009. Minimum timescales of a few hours were derived from the light curves of individual nights, but they were different from night to night. A bluer-when-brighter chromatism was present when the object was showing a fast flare but was absent when it was in a relatively quiescent state. Our results are basically consistent with the shock-in-jet model and demonstrate that geometric effects can sometimes play an important role in the variability of blazars.

The Cl 1604 supercluster at z ∼ 0.9 is known to contain at least four distinct member clusters, separated in both projection and redshift. In this paper we present deep, multicolor, wide-field imaging of a region spanning ∼45' on a side, corresponding to 21 h Mpc (physical) at the supercluster redshift. We select galaxies whose colors correspond to those of spectroscopically confirmed cluster members in the i' versus r' - i' color-magnitude diagram. Using an adaptive kernel, we generate a map of the projected red galaxy density and identify numerous new candidate clusters that are likely supercluster members. Assuming that all of the density peaks are associated with the supercluster, its transverse size is ∼10 h Mpc, which is still significantly smaller than the nearly 93 h Mpc depth in redshift space.

This paper is part of a series that focuses on investigating galaxy formation and evolution in small-scale systems of galaxies in low-density environments. We present results from a study of the NGC 4756 group, which is dominated by the elliptical galaxy NGC 4756. The characteristics of the group are investigated through (1) the detailed investigation of the morphological, photometric, and spectroscopic properties of nine galaxies among the dominant members of the group; (2) the determination of the photometric parameters of the faint galaxy population in an area of 34' × 34' centered on NGC 4756; and (3) an analysis of the X-ray emission in the area based on archival data.

The nine member galaxies are located in the core part of the NGC 4756 group (a strip ≈300 kpc in diameter, H₀ = 70 km s^-1 Mpc^-1), which has a very loose configuration. The central part of the NGC 4756 group contains a significant fraction of early-type galaxies. Three new group members with previously unknown systemic velocities are identified, one of which is type dE. At about 75 southwest of NGC 4756 a substructure of the group is detected, including IC 829, MCG -2-33-35, MCG -2-33-36, and MCG -2-33-38, that meets the Hickson criteria for being a compact group. Most of the galaxies in this substructure show interaction signatures. We do not detect apparent fine structure and signatures of recent interaction events in the early-type galaxy population, with the exception of a strong dust lane in the elliptical galaxy MCG -2-33-38. However, this galaxy displays signatures of nuclear activity. Strong [O III], [N II], and [S II] line emission, combined with comparatively weak but broad Hα emission, suggests an intermediate Seyfert type classification. Although the area is heavily contaminated by the background cluster A1631, X-ray data suggest the presence of a hot intergalactic medium related to the detected X-ray emission of the group. The present results are discussed in the context of group evolution.

Using the IRAM 30 m telescope, we have obtained ¹²CO J = 1–0 and 2–1 spectral line observations toward the nuclear regions of 15 edge-on, low surface brightness (LSB) spiral galaxies. Our sample comprises extreme late-type LSB spirals with disk-dominated morphologies and rotational velocities V_rot ≲ 120 km s^-1. We report detections of four galaxies in at least one transition (≳5 σ); for the remainder of the sample we provide upper limits on the nuclear CO content. Adopting a standard Galactic I_CO-to-H₂ conversion factor implies molecular gas masses of (3.3–9.8) × 10⁶M_⊙ in the nuclear regions (inner 1.1–1.8 kpc) of the detected galaxies. Combining our new data with samples of late-type spirals from the literature, we find that CO-detected LSB spirals adhere to the same M–far-infrared correlation as more luminous and higher surface brightness galaxies. The amount of CO in the central regions of late-type spirals appears to depend more strongly on mass than on central optical surface brightness, and CO detectability declines significantly for moderate to low surface brightness spirals with V_rot ≲ 90 km s^-1; no LSB spirals have so far been detected in CO below this threshold. Metallicity effects alone are unlikely to account for this trend, and we speculate that we are seeing the effects of a decrease in the mean fraction of a galaxy disk able to support giant molecular cloud formation with decreasing galaxy mass.

Hubble Space Telescope imaging and slitless spectroscopy are used to examine where the strong Lyα emission escapes from the interstellar medium in the starburst galaxy Mrk 357. An Hα image shows that the ionized gas is mostly in a global wind, rather than associated with the individual star-forming regions seen in the optical and UV continuum. The Lyα emission comes predominantly from the northwest side of the wind structure spatially, and shows a significant redshift relative to the optical lines. Both of these properties are signatures of seeing the line photons backscattered from the far side of a prolate or bipolar starburst wind, fitting both with escape calculations and evidence for winds in high-redshift galaxies with net Lyα emission. Scattering is most important within this wind itself, rather than involving a surrounding neutral medium, as shown by the decreasing relative redshift of the line peak from 250 to ≈30 km s^-1 between the center and edge of the detected emission. The Lyα emission exhibits strong asymmetry in comparison with both the starlight and Hα structures. These results add to the evidence that kinematics, rather than gas metallicity or dust content, are the dominant effect in determining which galaxies have strong Lyα emission, and that powerful (and perhaps episodic) starbursts are common among Lyman break galaxies as well as those discovered from Lyα line emission.

We report the results of a preliminary nova survey of Local Group dwarf elliptical galaxies. We used the 15' field-of-view CCD camera on the 0.8 m telescope at the Tenagra Observatory to observe M32, NGC 205, NGC 147, and NGC 185 in their entirety every clear night over a 4.5 month interval and discovered one nova in M32 and a candidate nova in NGC 205. The nova in M32 was verified spectroscopically. The nova candidate in NGC 205 had an unusually low peak luminosity (M_V = -5.1), and we were unable to obtain spectroscopic verification. Archival Hubble Space Telescope images provide us with a limit on the outburst amplitude for this object of >4.6 V magnitudes. These facts prompt us to consider the possibility that this object is not a genuine nova. We report a high bulk nova rate for M32 of 2 yr^-1 and, assuming that the candidate nova is correctly identified, for NGC 205 of 2 yr^-1. If the NGC 205 variable is not a nova, we calculate an upper limit on the bulk nova rate for NGC 205 of 1.5 yr^-1. We report upper limits on the bulk nova rates in NGC 147 of 2 yr^-1 and NGC 185 of 1.8 yr^-1 and a combined bulk nova rate for the four galaxies of 4 yr^-1 (2 yr^-1 without the NGC 205 nova candidate). The bulk rates we report here are based on Monte Carlo simulations using nova maximum magnitudes and decline rates and individual epoch frame limits. From the Monte Carlo rates, integrated and extinction corrected V-band photometry, and (V - K)₀ colors we derive a luminosity specific nova rate for M32 of 12.0 yr^-1 (10¹⁰L_⊙,K)^-1 and for NGC 205 of 29.3 yr^-1 (10¹⁰L_⊙,K)^-1 and for the combined four galaxies of 14.1 yr^-1 (10¹⁰L_⊙,K)^-1 [7.0 yr^-1 (10¹⁰L_⊙,K)^-1 without the NGC 205 nova candidate]. The higher combined rate is 2.5 σ higher than expected from assuming a constant luminosity specific nova rate as a function of K-band luminosity as derived from more massive galaxies. If the higher rate is confirmed by surveys in subsequent seasons, it would imply either that dwarf elliptical galaxies have a higher interacting binary fraction than their higher mass counterparts, or that the completeness is higher for these less complex systems and the nova rates for larger, more distant systems are systematically underestimated.

We compare the frequency of field binary stars as a function of Galactic velocity vectors and find a deficiency of such stars on strongly retrograde orbits. Metal-poor stars moving on prograde Galactic orbits have a binary frequency of 28% ± 3%, whereas the retrograde stars' binary frequency is only 10% ± 2% for V ≤ -300 km s^-1. No such binary deficiencies are seen for the U or W velocities, nor for [Fe/H]. Some mechanism exists that either disrupts binary systems or preferentially adds single stars moving primarily on retrograde orbits. Theoretical analyses and critical evaluations of our observational data appear to rule out preferential disruption of preexisting binary stars due to such causes as tidal interactions with massive gravitational perturbers, including giant molecular clouds, black holes, or the Galactic center.

Dynamically evolved stellar ensembles, such as globular clusters, provide a possible source of single stars. Three lines of evidence rule out this explanation. First, there is no mechanism to significantly enhance dissolution of clusters moving on retrograde orbits. Second, a study of globular clusters moving on prograde and retrograde orbits and with perigalacticon distances such that they are unlikely to be affected strongly by central tidal effects shows that clusters moving on prograde Galactic orbits may be more evolved dynamically than clusters moving on retrograde orbits. Finally, we have undertaken a comprehensive search for star streams that might be discernible. Monte Carlo modeling suggests that our sample may include one moving group, but it contains only five stars. Although the Galactic orbit of this group passes near the Galactic center, it is not moving on a retrograde Galactic orbit and falls short by a factor of at least 20 in supplying the necessary number of single stars.

There is one intriguing possibility to explain our results. A dissolved dwarf galaxy may have too large a velocity spread to be easily detected in our sample using our technique. However, dwarf galaxies appear to often show element-to-iron versus [Fe/H] abundance patterns that are not similar to the bulk of the stellar field and cluster halo stars. We explore the s-process elements Y and Ba. Eight stars in our sample have such elemental abundances already measured and also lie in the critical domain with -1.6 ≤ [Fe/H] ≤ -1.0 and V ≤ -300 km s^-1. The admittedly small samples appears to show a bimodal distribution in [Y/Fe], [Ba/Fe], and [α/Fe], where "α" represents an average abundance of Mg, Si, Ca, and Ti. This behavior is reminiscent of the difference in the abundances found between the globular cluster ω Centauri and other globular clusters. It is also intriguing that the stars most similar to ω Cen in their chemical abundances show a relatively coherent set of kinematic properties, with a modest velocity dispersion. The stars less like ω Cen define a dynamically hot population. The binary frequency of the stars in ω Cen does not appear to be enhanced, but detailed modeling of the radial velocity data remains to be done.

We present some results of numerical simulations of a globular cluster orbiting in the central region of a triaxial galaxy on a set of "loop" orbits. Tails start forming after about a quarter of the globular cluster orbital period and develop, in most cases, along the cluster orbit, showing clumpy substructures as observed, for example, in Palomar 5. If completely detectable, clumps can contain about 7000 M_⊙ each, i.e., about 10% of the cluster mass at that epoch. The morphology of tails and clumps and the kinematical properties of stars in the tails are studied and compared with available observational data. Our finding is that the stellar velocity dispersion tends to level off at large radii, in agreement with that found for M15 and ω Cen.

We carried out wide-field BVI CCD photometric observations of the globular clusters M3 (NGC 5272) and M13 (NGC 6205) using the Bohyun Optical Astronomy Observatory 1.8 m telescope equipped with a SITe 2K CCD. We present color-magnitude diagrams (V vs. B - V, V vs. V - I, and V vs. B - I) of M3 and M13. We have found asymptotic giant branch (AGB) bumps at V = 14.85 ± 0.05 mag for M3 and at V = 14.25 ± 0.05 mag for M13. We also found that AGB stars in M3 are more concentrated near the bump, while those in M13 are scattered along the AGB sequence. We identified the red giant branch (RGB) bump of M3 at V = 15.50 ± 0.05 mag and that of M13 at V = 14.80 ± 0.05 mag through luminosity functions and slope changes of the integrated luminosity functions of M3 and M13. We have estimated the ratios R and R₂ for M3 and M13 and found that the value of R for M3 is larger than that for M13, while values of R₂ for M3 and M13 are similar and compatible with the value expected from evolutionary theory when only normal horizontal-branch (HB) stars are used for estimation of R and R₂ for M13. However, we found that values of R for M3 and M13 are similar, while the value of R₂ for M3 is larger than that for M13 when all the HB stars are included for estimation of R and R₂ for M13. We have compared the observed RGB luminosity functions of M3 and M13 with the theoretical RGB luminosity function of Bergbusch & VandenBerg at the same radial distances from the cluster centers as used in the estimation of the ratios R and R₂ for M3 and M13. We found "extra stars" belonging to M13 in the comparison of the observed RGB luminosity function of M13 and the theoretical RGB luminosity function of Bergbusch & VandenBerg and even in the comparison of the observed RGB luminosity functions of M3 and M13. In the original definition of the ratio R of Buzzoni et al., N_HB corresponds to the lifetime of HB stars in the RR Lyrae instability strip at log T_eff = 3.85. Thus, the smaller R value resulting for M13 compared with that for M3 in the case in which only normal HB stars are included in the estimation of R and R₂ for M13 may be partially caused by extra stars, and the similar R values for M3 and M13 in the case in which all the HB stars are included in the estimation of R and R₂ for M13 may be caused by extra stars in the upper RGB of M13. If extra stars in the upper RGB of M13 are caused by an effective "deep mixing," these facts support the contention that an effective deep mixing could lead to different HB morphologies between M3 and M13 and subsequent sequences.

We study the color-magnitude diagram (CMD) morphologies of M3 and M13 using high-precision Hubble Space Telescope photometry. Asymmetric broadening above and to the red of the main sequence is apparent. We use extensive artificial star experiments to synthetically reproduce chance superposition and photometric error and examine whether a main-sequence binary population is required to account for the observed asymmetric broadening. We find that the most probable binary fraction f_b in the center of M3 lies between 6% and 22%. For those stars of M3 with distances from the cluster center between 1 and 2 core radii, the most probable value of f_b lies between 1% and 3%. The similar radial distributions of binaries and blue stragglers (BSs) support the model that the BSs in the center of M3 are of collisional origin. A similar comparison between the color distributions of real stars and artificial stars in the CMD of M13 suggests that the real star distributions are consistently broader than the artificial ones. After corrections of real and artificial differences in color uncertainties, we find evidence for an intrinsic color dispersion among main-sequence stars of about 0.013–0.014 mag in both the center and outer regions of M13. This is larger than the expected value resulting from the spectroscopically observed [Fe/H] dispersion and might reflect differences in [C/Fe] and [N/Fe] that have been noted spectroscopically among upper main-sequence stars in M13.

We present the first set of definitive trigonometric parallaxes and proper motions from the Cerro Tololo Inter-American Observatory Parallax Investigation. Full astrometric reductions for the program are discussed, including methods of reference star selection, differential color refraction corrections, and conversion of relative to absolute parallax. Using data acquired at the 0.9 m telescope at CTIO, full astrometric solutions and VRIJHK_s photometry are presented for 36 red and white dwarf stellar systems with proper motions faster than 10 yr^-1. Of these, 33 systems have their first ever trigonometric parallaxes, which comprise 41% of MOTION systems (those reported to have proper motions greater than 10 yr^-1) south of δ = 0° that have no parallaxes. Four of the systems are new members of the RECONS 10 pc sample for which the first accurate trigonometric parallaxes are published here: DENIS J1048-3956 (4.04 ± 0.03 pc), GJ 1128 (LHS 271, 6.53 ± 0.10 pc), GJ 1068 (LHS 22, 6.97 ± 0.09 pc), and GJ 1123 (LHS 263, 9.02 ± 0.16 pc). In addition, two red subdwarf–white dwarf pairs, LHS 193AB and LHS 300AB, are identified. The white dwarf secondaries fall in a previously uncharted region of the H-R diagram.

The Spitzer Space Telescope (formerly SIRTF) extragalactic First Look Survey covered about 5 deg² centered on (J2000.0) α = 17^h18^m, δ = 59°30' in order to characterize the infrared sky with high sensitivity. We used the 100 m Green Bank Telescope to image the 21 cm Galactic H I emission over a 3° × 3° square, covering this position with an effective angular resolution of 98 and a velocity resolution of 0.62 km s^-1. In the central square degree of the image the average column density is N = 2.5 × 10²⁰ cm^-2 with an rms fluctuation of 0.3 × 10²⁰ cm^-2. The Galactic H I in this region has a very interesting structure. There is a high-velocity cloud, several intermediate-velocity clouds (one of which is probably part of the Draco Nebula), and narrow-line low-velocity filaments. The H I emission shows a strong and detailed correlation with dust. Except for the high-velocity cloud, all features in the N_{H I} map have counterparts in an E(B - V) map derived from infrared data. Relatively high E(B - V)/N_{H I} ratios in some directions suggest the presence of molecular gas. The best diagnostic of such regions is the peak H I line brightness temperature, not the total N_{H I}: directions where T_b > 12 K have E(B - V)/N_{H I} significantly above the average value. The data corrected for stray radiation have been released via the World Wide Web.

The unusual pre–main-sequence binary star KH 15D undergoes remarkably deep and long-lasting periodic eclipses. Some clues about the reason for these eclipses have come from the observed evolution of the system's light curve over the last century. Here we present UBVRI photometry of KH 15D from 1954 to 1997 based on photographic plates from various observatories. The system has been variable at the ≈1 mag level since at least 1965. There is no evidence of color variations, with a typical limit of Δ(B - V) < 0.2 mag. We confirm some previously published results that were based on a smaller sample of plates: from approximately 1965 to 1990, the total flux was modulated with the 48 day orbital period of the binary, but the maximum flux was larger, the fractional variations were smaller, and the phase of minimum flux was shifted by almost a half-cycle relative to the modern light curve. All these results are consistent with the recently proposed theory that KH 15D is being occulted by an inclined, precessing, circumbinary ring.

The intermediate polar, EX Hydrae, was the object of a large simultaneous multiwavelength observational campaign during 2000 May–June. Here we present the Rossi X-Ray Timing Explorer photometry and optical photometry and spectroscopy from ground-based observatories obtained as part of this campaign. Balmer line radial velocities and Doppler maps provide evidence for an extended bulge along the outer edge of the accretion disk and some form of extended/overflowing material originating from the hot spot. In addition, the optical binary eclipse possesses an extended egress shoulder, an indication that an additional source (other than the white dwarf) is coming out of eclipse. We also compare the X-ray and optical results with the results obtained from the EUV and UV observations from the multiwavelength data set.

We have compiled a new and complete catalog of the main properties of the 1509 pulsars for which published information currently exists. The catalog includes all spin-powered pulsars, as well as anomalous X-ray pulsars and soft gamma-ray repeaters showing coherent pulsed emission, but excludes accretion-powered systems. References are given for all data listed. We have also developed a new World Wide Web interface for accessing and displaying either tabular or plotted data with the option of selecting pulsars to be displayed via logical conditions on parameter expressions. The Web interface has an "expert" mode giving access to a wider range of parameters and allowing the use of custom databases. For users with locally installed software and database on Unix or Linux systems, the catalog may be accessed from a command-line interface. C-language functions to access specified parameters are also available. The catalog is updated from time to time to include new information.

We present 668 new photometric observations for 24 Cepheids with periods less than 3 days. Most of the stars are probable type II Cepheids, but we have included some type I Cepheids for comparison. A discussion of the Fourier parameters of the light curves leads to the conclusion that they can be used to distinguish among the several types of light curves found among the type II stars but are of limited usefulness for distinguishing between type I and type II Cepheids. The pulsational stability is investigated by searching for long-term changes in the light-curve shapes, period changes, and light-curve scatter. In terms of these parameters, the pulsation is more stable than those that were found for the long-period stars, but for each there are several stars that show unusually large effects. However, there does not seem to be any obvious difference in light-curve stability of type II Cepheids compared with type I Cepheids.

We present monitoring observations by the Rossi X-Ray Timing Explorer of the 2–10 keV X-ray emission from the supermassive star η Carinae from 1996 through late 2003. These data cover more than one of the stellar variability cycles in temporal detail and include especially detailed monitoring through two X-ray minima. We compare the current X-ray minimum, which began on 2003 June 29, with the previous X-ray minimum, which began on 1997 December 15, and refine the X-ray period to 2024 days. We examine the variations in the X-ray spectrum with phase and with time, and also refine our understanding of the X-ray "peaks," which have a quasi period of 84 days, with significant variation. Cycle-to-cycle differences are seen in the level of X-ray intensity and in the detailed variations of the X-ray flux on the rise to maximum just prior to the X-ray minimum. Despite these differences, the similarities between the decline to minimum, the duration of the minimum, and correlated variations of the X-ray flux and other measures throughout the electromagnetic spectrum leave little doubt that the X-ray variation is strictly periodic and produced by orbital motion as the wind from η Carinae collides with the wind of an otherwise unseen companion.

We have discovered the first example of a star pulsating intrinsically with both γ Doradus and δ Scuti frequencies. The star, HD 8801, is an Am metallic-line star that appears to be single. Since the vast majority of Am stars are members of binary systems with periods less than 1000 days and also do not pulsate, HD 8801 possesses a very unusual, if not unique, combination of physical properties. Our photometry, acquired with an automatic telescope at Fairborn Observatory, resolves six independent pulsation periods between 0.048 and 0.404 days. The two longest periods lie within the range of γ Dor variables, while the four shorter periods are within the range of δ Sct stars. Eleven radial velocities, obtained over an 11 month period, have a mean of 0.8 ± 0.3 km s^-1, providing no evidence for a spectroscopic companion. The star is on the main sequence and lies within both the γ Dor and δ Sct instability strips. Pulsation constants computed for the six periods agree with pulsation constants computed for other γ Dor and δ Sct variables. HD 8801 is also the first confirmed case of a metallic-line star pulsating with γ Dor frequencies. Its projected rotational velocity of 55 km s^-1 is typical for Am stars, which, as a group, rotate more slowly than normal A stars. HD 8801's slow rotation compared to normal A stars does not appear to arise from either a binary companion or evolutionary expansion and thus remains a puzzle. The coexistence of metallicism and pulsation in several main-sequence stars near the red edge of the δ Sct strip contradicts recent models that predict pulsations only in more evolved stars.

Interstellar scintillation has been conclusively demonstrated to be the principal cause of the intraday variability (IDV) observed in the centimeter-wavelength emission of many active galactic nuclei. A few sources show large amplitude modulation in their flux density on a timescale of hours. However, the majority of IDV sources exhibit variability on timescales of a day or more. Some sources have been found to show an annual cycle in the pattern of their variability. Such an annual cycle occurs because the relative speeds of the Earth and the interstellar medium change as the Earth orbits the Sun. To search for these annual variations, as well as to follow the source evolution, requires a dedicated instrument; the necessary amounts of observing time are beyond the capability of the National Facility instruments. Here we describe the scientific motivation for and present an outline of the COSMIC (Continuous Single-Dish Monitoring of Intraday Variability at Ceduna) project, which uses the University of Tasmania's 30 m diameter radio telescope at Ceduna, which has been monitoring the flux density of a number of the stronger southern scintillators at 6.65 GHz since 2003 March.