An Optical-UV Survey of the North Celestial Cap

We present preliminary results of an optical-UV survey of the North Celestial Cap (NCCS) based on ~5% areal coverage. The NCCS will provide good photometric and astrometric data for the North Celestial Cap region (80 < DEC < 90). This region, at galactic latitudes 17 < b < 37, is poorly covered by modern CCD-based surveys. The expected number of detected objects in NCCS is ~1,500,000. We discuss issues of galactic structure, extinction, and the galaxy clustering in the colour-colour diagrams.Comment: 5 pages, 3 figures Accepted for publication in Astrophysics & Space Scienc

A Two-Colour CCD Survey of the North Celestial Cap: I. The Method

We describe technical aspects of an astrometric and photometric survey of the North Celestial Cap (NCC), from the Pole (DEC=90 deg) to DEC=80 deg, in support of the TAUVEX mission. This region, at galactic latitudes from ~ 17 deg to ~ 37 deg, has poor coverage in modern CCD-based surveys. The observations are performed with the Wise Observatory one-meter reflector and with a new mosaic CCD camera (LAIWO) that images in the Johnson-Cousins R and I bands a one-square-degree field with subarcsec pixels. The images are treated using IRAF and SExtractor to produce a final catalogue of sources. The astrometry, based on the USNO-A2.0 catalogue, is good to ~ 1 arcsec and the photometry is good to ~ 0.1 mag for point sources brighter than R=20.0 or I=19.1 mag. The limiting magnitudes of the survey, defined at photometric errors smaller than 0.15 mag, are 20.6 mag (R) and 19.6 (I). We separate stars from non-stellar objects based on the object shapes in the R and I bands, attempting to reproduce the SDSS star/galaxy dichotomy. The completeness test indicates that the catalogue is complete to the limiting magnitudes.Comment: 31 pages, 15 figures, Accepted for publication in Astrophysics & Space Scienc

iPTF13beo: The Double-Peaked Light Curve of a Type Ibn Supernova Discovered Shortly after Explosion

We present optical photometric and spectroscopic observations of the Type Ibn (SN 2006jc-like) supernova iPTF13beo. Detected by the intermediate Palomar Transient Factory ~3 hours after the estimated first light, iPTF13beo is the youngest and the most distant (~430 Mpc) Type Ibn event ever observed. The iPTF13beo light curve is consistent with light curves of other Type Ibn SNe and with light curves of fast Type Ic events, but with a slightly faster rise-time of two days. In addition, the iPTF13beo R-band light curve exhibits a double-peak structure separated by ~9 days, not observed before in any Type Ibn SN. A low-resolution spectrum taken during the iPTF13beo rising stage is featureless, while a late-time spectrum obtained during the declining stage exhibits narrow and intermediate-width He I and Si II features with FWHM ~ 2000-5000 km/s and is remarkably similar to the prototypical SN Ibn 2006jc spectrum. We suggest that our observations support a model of a massive star exploding in a dense He-rich circumstellar medium (CSM). A shock breakout in a CSM model requires an eruption releasing a total mass of ~0.1 Msun over a time scale of couple of weeks prior to the SN explosion.Comment: 8 pages, 5 figures, submitted to MNRA

An Early and Comprehensive Millimetre and Centimetre Wave and X-ray Study of SN 2011dh: a Non-Equipartition Blast Wave Expanding into a Massive Stellar Wind

Only a handful of supernovae (SNe) have been studied in multiwavelengths from the radio to X-rays, starting a few days after the explosion. The early detection and classification of the nearby Type IIb SN 2011dh/PTF 11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at one of the youngest phase ever of a core-collapse SN (days 3–12 after the explosion) in the radio, millimetre and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding SN shock wave does not exhibit equipartition (ϵe/ϵB ∼ 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R−2. Within modelling uncertainties we find an average velocity of the fast parts of the ejecta of 15 000 ± 1800 km s−1, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast wave regime between the previously defined compact and extended SN Type IIb subtypes. Our results highlight the importance of early (∼1 d) high-frequency observations of future events. Moreover, we show the importance of combined radio/X-ray observations for determining the microphysics ratio ϵe/ϵB

An Early & Comprehensive Millimeter and Centimeter Wave and X-ray Study of Supernova 2011dh: A Non-Equipartition Blastwave Expanding into A Massive Stellar Wind

Only a handful of supernovae (SNe) have been studied in multi-wavelength from radio to X-rays, starting a few days after explosion. The early detection and classification of the nearby type IIb SN2011dh/PTF11eon in M51 provides a unique opportunity to conduct such observations. We present detailed data obtained at the youngest phase ever of a core-collapse supernova (days 3 to 12 after explosion) in the radio, millimeter and X-rays; when combined with optical data, this allows us to explore the early evolution of the SN blast wave and its surroundings. Our analysis shows that the expanding supernova shockwave does not exhibit equipartition (e_e/e_B ~ 1000), and is expanding into circumstellar material that is consistent with a density profile falling like R^-2. Within modeling uncertainties we find an average velocity of the fast parts of the ejecta of 15,000 +/- 1800 km/s, contrary to previous analysis. This velocity places SN 2011dh in an intermediate blast-wave regime between the previously defined compact and extended SN IIb subtypes. Our results highlight the importance of early (~ 1 day) high-frequency observations of future events. Moreover, we show the importance of combined radio/X-ray observations for determining the microphysics ratio e_e/e_B.Comment: 9 pages, 5 figures, submitted to Ap

PTF11eon/SN2011dh: Discovery of a Type IIb Supernova From a Compact Progenitor in the Nearby Galaxy M51

On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We discovered this event using small telescopes equipped with CCD cameras, as well as by the Palomar Transient Factory (PTF) survey, and rapidly confirmed it to be a Type II supernova. Our early light curve and spectroscopy indicates that PTF11eon resulted from the explosion of a relatively compact progenitor star as evidenced by the rapid shock-breakout cooling seen in the light curve, the relatively low temperature in early-time spectra and the prompt appearance of low-ionization spectral features. The spectra of PTF11eon are dominated by H lines out to day 10 after explosion, but initial signs of He appear to be present. Assuming that He lines continue to develop in the near future, this SN is likely a member of the cIIb (compact IIb; Chevalier and Soderberg 2010) class, with progenitor radius larger than that of SN 2008ax and smaller than the eIIb (extended IIb) SN 1993J progenitor. Our data imply that the object identified in pre-explosion Hubble Space Telescope images at the SN location is possibly a companion to the progenitor or a blended source, and not the progenitor star itself, as its radius (~10^13 cm) would be highly inconsistent with constraints from our post-explosion photometric and spectroscopic data