[en] We present a search for eclipses of ∼1700 white dwarfs (WDs) in the Pan-STARRS1 medium-deep fields. Candidate eclipse events are selected by identifying low outliers in over 4.3 million light curve measurements. We find no short-duration eclipses consistent with being caused by a planetary size companion. This large data set enables us to place strong constraints on the close-in planet occurrence rates around WDs for planets as small as 2 R _⊕. Our results indicate that gas giant planets orbiting just outside the Roche limit are rare, occurring around less than 0.5% of WDs. Habitable-zone super-Earths and hot super-Earths are less abundant than similar classes of planets around main-sequence stars. These constraints provide important insight into the ultimate fate of the large population of exoplanets orbiting main-sequence stars.

[en] We present a preliminary survey of 58 radio sources within the isoplanatic patches (r < 25'') of bright (11 < R < 12) stars suitable for use as natural guide stars with high-order adaptive optics (AO). An optical and near-infrared imaging survey was conducted utilizing tip-tilt corrections in the optical and AO in the near-infrared. Spectral energy distributions were fit to the multi-band data for the purpose of obtaining photometric redshifts using the Hyperz code. Several of these photometric redshifts were confirmed with spectroscopy, a result that gives more confidence to the redshift distribution for the whole sample. Additional long-wavelength data from Spitzer, SCUBA, SHARC2, and VLA supplement the optical and near-infrared data. We find the sample generally follows and extends the magnitude-redshift relation found for more powerful local radio galaxies. The survey has identified several reasonably bright (H = 19 - 20) objects at significant redshifts (z > 1) that are now within the capabilities of the current generation of AO-fed integral-field spectrographs. These objects constitute a unique sample that can be used for detailed ground-based AO studies of galactic structure, evolution, and active galactic nucleus formation at high redshift.

[en] We present a sample of M31 beat Cepheids from the Pan-STARRS 1 PAndromeda campaign. By analyzing 3 years of PAndromeda data, we identify 17 beat Cepheids, spreading over a galactocentric distance of 10-16 kpc. Since the relation between the fundamental mode period and the ratio of the fundamental to the first overtone period places a tight constraint on metallicity, we are able to derive the metallicity at the position of the beat Cepheids using the relations from the model of Buchler. Our metallicity estimates show sub-solar values within 15 kpc, similar to the metallicities from H II regions. We then use the metallicity estimates to calculate the metallicity gradient of the M31 disk, which we find to be closer to the metallicity gradient derived from planetary nebula than the metallicity gradient from H II regions

[en] As of 2012 January 21, the Pan-STARRS 1 3π Survey has observed the 3/4 of the sky visible from Hawaii with a minimum of 2 and mean of 7.6 observations in five filters, g _P1, r _P1, i _P1, z _P1, y _P1. Now at the end of the second year of the mission, we are in a position to make an initial public release of a portion of this unprecedented data set. This article describes the PS1 Photometric Ladder, Release 12.01. This is the first of a series of data releases to be generated as the survey coverage increases and the data analysis improves. The Photometric Ladder has rungs every hour in right ascension and at four intervals in declination. We will release updates with increased area coverage (more rungs) from the latest data set until the PS1 survey and the final re-reduction are completed. The currently released catalog presents photometry of ∼1000 objects per square degree in the rungs of the ladder. Saturation occurs at g _P1, r _P1, i _P1 ∼ 13.5; z _P1 ∼ 13.0; and y _P1 ∼ 12.0. Photometry is provided for stars down to g _P1, r _P1, i _P1 ∼ 19.1 in the AB system. This data release depends on the rigid 'Ubercal' photometric calibration using only the photometric nights, with systematic uncertainties of (8.0, 7.0, 9.0, 10.7, 12.4) mmag in (g _P1, r _P1, i _P1, z _P1, y _P1). Areas covered only with lower quality nights are also included, and have been tied to the Ubercal solution via relative photometry; photometric accuracy of the non-photometric regions is lower and should be used with caution.

[en] We present a sample of Cepheid variable stars toward M31 based on the first year of regular M31 observations of the PS1 survey in the r_P1 and i_P1 filters. We describe the selection procedure for Cepheid variable stars from the overall variable source sample and develop an automatic classification scheme using Fourier decomposition and the location of the instability strip. We find 1440 fundamental mode (classical δ) Cep stars, 126 Cepheids in the first overtone mode, and 147 belonging to the Population II types. Two hundred ninety-six Cepheids could not be assigned to one of these classes and three hundred fifty-four Cepheids were found in other surveys. These 2009 Cepheids constitute the largest Cepheid sample in M31 known so far and the full catalog is presented in this paper. We briefly describe the properties of our sample in its spatial distribution throughout the M31 galaxy, in its age properties, and we derive an apparent period-luminosity relation (PLR) in our two bands. The Population I Cepheids nicely follow the dust pattern of the M31 disk, whereas the 147 Type II Cepheids are distributed throughout the halo of M31. We outline the time evolution of the star formation in the major ring found previously and find an age gradient. A comparison of our PLR to previous results indicates a curvature term in the PLR.

[en] The Pan-STARRS1 survey has obtained multi-epoch imaging in five bands (Pan-STARRS1 g_P1, r_P1, i_P1, z_P1, and y_P1) on 12 'Medium-Deep fields', each of which spans a 3.⁰3 circle. For the period between 2009 April and 2011 April these fields were observed 50-200 times. Using a reduced proper motion diagram, we have extracted a list of 47 white dwarf (WD) candidates whose Pan-STARRS1 astrometry indicates a non-zero proper motion at the 6σ level, with a typical 1σ proper motion uncertainty of 10 mas yr^–1. We also used astrometry from the Sloan Digital Sky Survey (when available) and USNO-B to assess our proper motion fits. None of the WD candidates exhibits evidence of statistically significant parallaxes, with a typical 1σ uncertainty of 8 mas. Twelve of these candidates are known WDs, including the high proper motion (1.''7 yr^–1) WD LHS 291. We confirm seven more objects as WDs through optical spectroscopy. Based on the Pan-STARRS1 colors, ten of the stars are likely to be cool WDs with 4170 K < T_eff < 5000 K and cooling ages ≈ 8 Gyr. Based on their kinematics, these objects are likely thick disk WDs, but a subset may belong to the halo. Our current sample represents only a small fraction of the Pan-STARRS1 data. With continued coverage from the Medium-Deep Field Survey and the 3π survey, Pan-STARRS1 should find many more high proper motion WDs that are part of the old thick disk and halo.

[en] We have searched ∼8200 deg² for high proper motion (∼0.''5-2.''7 year^-1) T dwarfs by combining first-epoch data from the Pan-STARRS1 (PS1) 3π Survey, the Two Micron All Sky Survey (2MASS) All-Sky Point Source Catalog, and the WISE Preliminary Data Release. We identified two high proper motion objects with the very red (W1 - W2) colors characteristic of T dwarfs, one being the known T7.5 dwarf GJ 570D. Near-IR spectroscopy of the other object (PSO J043.5395+02.3995 ≡ WISEP J025409.45+022359.1) reveals a spectral type of T8, leading to a photometric distance of 7.2 ± 0.7 pc. The 2.''56 year^-1 proper motion of PSO J043.5+02 is the second highest among field T dwarfs, corresponding to a tangential velocity of 87 ± 8 km s^-1. According to the Besancon galaxy model, this velocity indicates that its galactic membership is probably in the thin disk, with the thick disk an unlikely possibility. Such membership is in accord with the near-IR spectrum, which points to a surface gravity (age) and metallicity typical of the field population. We combine 2MASS, Sloan Digital Sky Survey, WISE, and PS1 astrometry to derive a preliminary parallax of 171 ± 45 mas (5.8^+2.0_-1.2 pc), the first such measurement using PS1 data. The proximity and brightness of PSO J043.5+02 will facilitate future characterization of its atmosphere, variability, multiplicity, distance, and kinematics. The modest number of candidates from our search suggests that the immediate (∼10 pc) solar neighborhood does not contain a large reservoir of undiscovered T dwarfs earlier than about T8.

[en] A complete well-defined sample of ultracool dwarfs is one of the key science programs of the Pan-STARRS 1 optical survey telescope (PS1). Here we combine PS1 commissioning data with the Two Micron All Sky Survey (2MASS) to conduct a proper motion search (0.''1-2.''0 yr^-1) for nearby T dwarfs, using optical+near-IR colors to select objects for spectroscopic follow-up. The addition of sensitive far-red optical imaging from PS1 enables discovery of nearby ultracool dwarfs that cannot be identified from 2MASS data alone. We have searched 3700 deg² of PS1 y-band (0.95-1.03 μm) data to y ∼ 19.5 mag (AB) and J ∼ 16.5 mag (Vega) and discovered four previously unknown bright T dwarfs. Three of the objects (with spectral types T1.5, T2, and T3.5) have photometric distances within 25 pc and were missed by previous 2MASS searches due to more restrictive color selection criteria. The fourth object (spectral type T4.5) is more distant than 25 pc and is only a single-band detection in 2MASS. We also examine the potential for completing the census of nearby ultracool objects with the PS1 3π survey.

[en] We report the discovery of a wide brown dwarf companion to the mildly metal-poor ([Fe/H] = –0.24), low Galactic latitude (b = 1.⁰88) K4V star HIP 38939. The companion was discovered by its common proper motion with the primary and its red optical (Pan-STARRS1) and blue infrared (Two Micron All Sky Survey) colors. It has a projected separation of 1630 AU and a near-infrared spectral type of T4.5. As such it is one of only three known companions to a main-sequence star which have early/mid T spectral types of (the others being HN Peg B and ε Indi B). Using chromospheric activity we estimate an age for the primary of 900±¹⁹⁰⁰₆₀₀ Myr. This value is also in agreement with the age derived from the star's weak ROSAT detection. Comparison with evolutionary models for this age range indicates that HIP 38939B falls in the mass range 38 ± 20 M_Jup with an effective temperature range of 1090 ± 60 K. Fitting our spectrum with atmospheric models gives a best-fitting temperature of 1100 K. We include our object in an analysis of the population of benchmark T dwarfs and find that while older atmospheric models appeared to overpredict the temperature of the coolest objects compared to evolutionary models, more recent atmospheric models provide better agreement.

[en] We measure quasar variability using the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS1 or PS1) and the Sloan Digital Sky Survey (SDSS) and establish a method of selecting quasars via their variability in 10⁴ deg² surveys. We use 10⁵ spectroscopically confirmed quasars that have been well measured in both PS1 and SDSS and take advantage of the decadal timescales that separate SDSS measurements and PS1 measurements. A power law model fits the data well over the entire time range tested, 0.01-10 yr. Variability in the current PS1-SDSS data set can efficiently distinguish between quasars and nonvarying objects. It improves the purity of a griz quasar color cut from 4.1% to 48% while maintaining 67% completeness. Variability will be very effective at finding quasars in data sets with no u band and in redshift ranges where exclusively photometric selection is not efficient. We show that quasars' rest-frame ensemble variability, measured as a root mean squared in Δ magnitudes, is consistent with V(z, L, t) = A ₀(1 + z)^0.37(L/L ₀)^–0.16(t/1 yr)^0.246, where L ₀ = 10⁴⁶ erg s^–1 and A ₀ = 0.190, 0.162, 0.147, or 0.141 in the g _P1, r _P1, i _P1, or z _P1filter, respectively. We also fit across all four filters and obtain median variability as a function of z, L, and λ as V(z, L, λ, t) = 0.079(1 + z)^0.15(L/L ₀)^–0.2(λ/1000 nm)^–0.44(t/1 yr)^0.246.