We present the detection of 6371 RR Lyrae (RRL) stars distributed across ∼14 000 deg2 of the sky from the combined data of the Sloan Digital Sky Survey (SDSS), the Panoramic Survey Telescope and ...Rapid Response System 1 (Pan-STARRS1 or PS1), and the second photometric catalogue from the Catalina Survey (CSDR2), out of these, ∼2021 RRL stars (∼572 RRab and 1449 RRc) are new discoveries. The RRL stars have heliocentric distances in the 4–28 kpc distance range. RRL-like colour cuts from the SDSS and variability cuts from the PS1 are used to cull our candidate list. We then use the CSDR2 multi-epoch data to refine our sample. Periods were measured using the analysis of variance technique while the classification process is performed with the template fitting method in addition to the visual inspection of the light curves. A cross-match of our RRL star discoveries with previous published catalogues of RRL stars yields completeness levels of ∼50 per cent for both RRab and RRc stars, and an efficiency of ∼99 and ∼87 per cent for RRab and RRc stars, respectively. We show that our method for selecting RRL stars allows us to recover halo structures. The full lists of all the RRL stars are made publicly available.
Recent searches by unbiased, wide-field surveys have uncovered a group of extremely luminous optical transients. The initial discoveries of SN 2005ap by the Texas Supernova Search and SCP-06F6 in a ...deep Hubble pencil beam survey were followed by the Palomar Transient Factory confirmation of host redshifts for other similar transients. The transients share the common properties of high optical luminosities (peak magnitudes ~--21 to --23), blue colors, and a lack of H or He spectral features. The physical mechanism that produces the luminosity is uncertain, with suggestions ranging from jet-driven explosion to pulsational pair instability. Here, we report the most detailed photometric and spectral coverage of an ultra-bright transient (SN 2010gx) detected in the Pan-STARRS 1 sky survey. In common with other transients in this family, early-time spectra show a blue continuum and prominent broad absorption lines of O II. However, about 25 days after discovery, the spectra developed type Ic supernova features, showing the characteristic broad Fe II and Si II absorption lines. Detailed, post-maximum follow-up may show that all SN 2005ap and SCP-06F6 type transients are linked to supernovae Ic. This poses problems in understanding the physics of the explosions: there is no indication from late-time photometry that the luminosity is powered by 56Ni, the broad light curves suggest very large ejected masses, and the slow spectral evolution is quite different from typical Ic timescales. The nature of the progenitor stars and the origin of the luminosity are intriguing and open questions.
We present the discovery of eight young M7-L2 dwarfs in the Taurus star-forming region and the Scorpius-Centaurus OB Association, serendipitously found during a wide-field search for L/T transition ...dwarfs using Pan-STARRS1 (optical) and WISE (mid-infrared) photometry. We identify PSO J060.3200+25.9644 (near-infrared spectral type L1) and PSO J077.1033+24.3809 (L2) as new members of Taurus based on their vl-g gravity classifications, the consistency of their photometry and proper motions with previously known Taurus objects, and the low probability of contamination by field objects. PSO J077.1033+24.3809 is the coolest substellar member of Taurus found to date. Both Taurus objects are among the lowest-mass free-floating objects ever discovered, with estimated masses 6 , and provide further evidence that isolated planetary-mass objects can form as part of normal star formation processes. PSO J060.3200+25.9644 (a.k.a. DANCe J040116.80+255752.2) was previously identified as a likely member of the Pleiades (age ) based on photometry and astrometry, but its vl-g gravity classification and near-infrared photometry imply a much younger age and thus point to Taurus membership. We have also discovered six M7-L1 dwarfs in outlying regions of Scorpius-Centaurus with photometry, proper motions, and low-gravity spectral signatures consistent with membership. These objects have estimated masses 15-36 . The M7 dwarf, PSO J237.1470−23.1489, shows excess mid-infrared flux implying the presence of a circumstellar disk. Finally, we present catalogs of Pan-STARRS1 proper motions for low-mass members of Taurus and Upper Scorpius with median precisions of 3 mas yr−1, including 67 objects with no previous proper motion and 359 measurements that improve on literature values.
We present the discovery of two ultraluminous supernovae (SNe) at z 0.9 with the Pan-STARRS1 Medium Deep Survey. These SNe, PS1-10ky and PS1-10awh, are among the most luminous SNe ever discovered, ...comparable to the unusual transients SN 2005ap and SCP 06F6. Like SN 2005ap and SCP 06F6, they show characteristic high luminosities (M bol --22.5 mag), blue spectra with a few broad absorption lines, and no evidence for H or He. We have constructed a full multi-color light curve sensitive to the peak of the spectral energy distribution in the rest-frame ultraviolet, and we have obtained time series spectroscopy for these SNe. Given the similarities between the SNe, we combine their light curves to estimate a total radiated energy over the course of explosion of (0.9-1.4) X 1051 erg. We find photospheric velocities of 12,000-19,000 km s--1 with no evidence for deceleration measured across ~3 rest-frame weeks around light curve peak, consistent with the expansion of an optically thick massive shell of material. We show that, consistent with findings for other ultraluminous SNe in this class, radioactive decay is not sufficient to power PS1-10ky, and we discuss two plausible origins for these events: the initial spin-down of a newborn magnetar in a core-collapse SN, or SN shock breakout from the dense circumstellar wind surrounding a Wolf-Rayet star.
The Pan-STARRS Moving Object Processing System Denneau, Larry; Jedicke, Robert; Grav, Tommy ...
Publications of the Astronomical Society of the Pacific,
04/2013, Volume:
125, Issue:
926
Journal Article
Peer reviewed
Open access
ABSTRACT We describe the Pan-STARRS Moving Object Processing System (MOPS), a modern software package that produces automatic asteroid discoveries and identifications from catalogs of transient ...detections from next-generation astronomical survey telescopes. MOPS achieves >99.5% efficiency in producing orbits from a synthetic but realistic population of asteroids whose measurements were simulated for a Pan-STARRS4-class telescope. Additionally, using a nonphysical grid population, we demonstrate that MOPS can detect populations of currently unknown objects such as interstellar asteroids. MOPS has been adapted successfully to the prototype Pan-STARRS1 telescope despite differences in expected false detection rates, fill-factor loss, and relatively sparse observing cadence compared to a hypothetical Pan-STARRS4 telescope and survey. MOPS remains highly efficient at detecting objects but drops to 80% efficiency at producing orbits. This loss is primarily due to configurable MOPS processing limits that are not yet tuned for the Pan-STARRS1 mission. The core MOPS software package is the product of more than 15 person-years of software development and incorporates countless additional years of effort in third-party software to perform lower-level functions such as spatial searching or orbit determination. We describe the high-level design of MOPS and essential subcomponents, the suitability of MOPS for other survey programs, and suggest a road map for future MOPS development.
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The globular cluster system of NGC 6822 Veljanoski, J; Ferguson, A. M. N; Mackey, A. D ...
Monthly notices of the Royal Astronomical Society,
09/2015, Volume:
452, Issue:
1
Journal Article
Peer reviewed
Open access
We present a comprehensive analysis of the globular cluster (GC) system of the Local Group dwarf irregular galaxy NGC 6822. Our study is based on homogeneous optical and near-IR photometry, as well ...as long-slit spectroscopic observations which are used to determine new radial velocities for six GCs, two of which had no previous spectroscopic information. We construct optical-near-IR colour–colour diagrams and through comparison to simple stellar population models infer that the GCs have old ages consistent with being 9 Gyr or older, while their metallicities are in the range between −1.6 ≲ Fe/H ≲ −0.4. We conduct a kinematic analysis of the GC population and find tentative evidence for weak net rotation of the GC system, in the same sense as that exhibited by the underlying spheroid. The most likely amplitude of rotation is ≈10 km s−1, approximately half the magnitude of the observed velocity dispersion. Finally, we use the GCs to estimate the dynamical mass of NGC 6822 within ∼11 kpc and we formally find it to be in the range between (3 and 4) × 109 M⊙. This implies an overall mass-to-light ratio in the range of ∼30–40 and indicates that NGC 6822 is highly dark-matter-dominated. The mass and the corresponding mass-to-light ratio estimates are affected by various additional systematic effects due to limitations of the data and the model that are not necessary reflected in the formal uncertainties.
Using imaging from the Pan-STARRS1 survey, we identify a precursor outburst at 287 and 170 days prior to the reported explosion of the purported Type IIn supernova (SN) 2011ht. In the Pan-STARRS ...data, a source coincident with SN 2011ht is detected exclusively in the z sub(P1) and y sub(P1)-bands. An absolute magnitude of M sub(z) Asymptotically = to -11.8 suggests that this was an outburst of the progenitor star. Unfiltered, archival Catalina Real Time Transient Survey images also reveal a coincident source from at least 258 to 138 days before the main event. We suggest that the outburst is likely to be an intrinsically red eruption, although we cannot conclusively exclude a series of erratic outbursts which were observed only in the redder bands by chance. This is only the fourth detection of an outburst prior to a claimed SN, and lends credence to the possibility that many more interacting transients have pre-explosion outbursts, which have been missed by current surveys.
The Pan-STARRS1 Small Area Survey 2 Metcalfe, N; Farrow, D. J; Cole, S ...
Monthly Notices of the Royal Astronomical Society,
11/2013, Volume:
435, Issue:
3
Journal Article
Peer reviewed
Open access
The Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1) survey is acquiring multi-epoch imaging in five bands (g
P1, r
P1, i
P1, z
P1, y
P1) over the entire sky north of declination ...−30° (the 3π survey). In 2011 July a test area of about 70 deg2 was observed to the expected final depth of the main survey. In this, the first of a series of papers targeting the galaxy count and clustering properties of the combined multi-epoch test area data, we present a detailed investigation into the depth of the survey and the reliability of the Pan-STARRS1 analysis software. We show that the Pan-STARRS1 reduction software can recover the properties of fake sources, and show good agreement between the magnitudes measured by Pan-STARRS1 and those from Sloan Digital Sky Survey. We also examine the number of false detections apparent in the Pan-STARRS1 data. Our comparisons show that the test area survey is somewhat deeper than the Sloan Digital Sky Survey in all bands, and, in particular, the z band approaches the depth of the stacked Sloan Stripe 82 data.
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 10 super(4) deg super(2) surveys. We use 10 super(5) spectroscopically confirmed quasars that have been well measured in both PSI 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 Delta magnitudes, is consistent with V(z, L, t) = A sub(0)(1 + z) super(0.37)(L/L sub(0)) super(-0.16)(t/1 yr) super(0.246), where L sub(0) = 10 super(46) erg s super(-1) and A sub(0) = 0.190, 0.162, 0.147, or 0.141 in the g sub(P1), r sub(P1), i sub(P1), or z sub(P1) filter, respectively. We also fit across all four filters and obtain median variability as a function of z, L, and lambda as V(z, L, lambda, t) = 0.079(1 + z) super(0.15)(L/L sub(0)) super(-0.2)(lambda/1000nm) super(-0.44)(t /1 yr) super(0.246).
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