The Fourth Us Naval Observatory CCD Astrograph Catalog (Ucac4)

Zacharias, N.; Finch, Charlie T.; Girard, T. M.; Henden, A.; Bartlett, Jennifer Lynn; Monet, D.; Zacharias, M. I.

doi:10.1088/0004-6256/145/2/44

Cited by 1,302 publications

(1,187 citation statements)

References 35 publications

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“…Starting from an initial list of all stars in the UCAC4 catalog (Zacharias et al 2013) in the same field of view as the target, we eliminated all known binary stars. We then made magnitude cuts, including only stars less than 0.5 mag brighter and 1 magnitude fainter than the target in the V-band.…”

Section: Observational Designmentioning

confidence: 99%

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Rackham

Espinoza

Apai

et al. 2017

ApJ

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GJ1214b is the most studied sub-Neptune exoplanet to date. Recent measurements have shown its near-infrared transmission spectrum to be flat, pointing to a high-altitude opacity source in the exoplanetʼs atmosphere, either equilibrium condensate clouds or photochemical hazes. Many photometric observations have been reported in the optical by different groups, though simultaneous measurements spanning the entire optical regime are lacking. We present an optical transmission spectrum (4500-9260Å) of GJ1214b in 14 bins, measured with Magellan/IMACS repeatedly over three transits. We measure a mean planet-to-star radius ratio of ( ) in the spectral bins. The optical transit depths are shallower on average than observed in the near-infrared. We present a model for jointly incorporating the effects of a composite photosphere and atmospheric transmission through the exoplanetʼs limb (the CPAT model), and use it to examine the cases of absorber and temperature heterogeneities in the stellar photosphere. We find the optical and near-infrared measurements are best explained by the combination of (1) photochemical haze in the exoplanetary atmosphere with a mode particle size r=0.1μm and haze-forming efficiency = f 10% haze and (2) faculae in the unocculted stellar disk with a temperature contrast D = -+ T 354 46 46 K, assuming 3.2% surface coverage. The CPAT model can be used to assess potential contributions of heterogeneous stellar photospheres to observations of exoplanet transmission spectra, which will be important for searches for spectral features in the optical.

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Section: Observational Designmentioning

confidence: 99%

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

Rackham

Espinoza

Apai

et al. 2017

ApJ

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“…0.2 − 0.3 arcsec root-mean-square (rms) accuracy per object was obtained by comparing source positions with 2MASS astrometry (Skrutskie et al 2006). The exposures were normalised to the same zero-point (ZP) by referencing to the closest photometric band measured in the fourth United States Naval Observatory (USNO) CCD Astrograph Catalog (UCAC4; Zacharias et al 2013). The fully-processed science exposures for each filter and each instrument were mediancombined to obtain final stacked images using SWARP (Bertin et al 2002).…”

Section: Photometric Reduction and Source Extractionmentioning

confidence: 99%

The rise and fall of star formation in z ∼ 0.2 merging galaxy clusters

Stroe¹,

Sobral²,

Dawson³

et al. 2015

Monthly Notices of the Royal Astronomical Society

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CIZA J2242.8+5301 ('Sausage') and 1RXS J0603.3+4213 ('Toothbrush') are two lowredshift (z ∼ 0.2), massive (∼ 2 × 10 15 M ), post-core passage merging clusters, which host shock waves traced by diffuse radio emission. To study their star-formation properties, we uniformly survey the 'Sausage' and 'Toothbrush' clusters in broad and narrow band filters and select a sample of 201 and 463 line emitters, down to a rest-frame equivalent width (13Å). We robustly separate between Hα and higher redshift emitters using a combination of optical multi-band (B, g, V, r, i, z) and spectroscopic data. We build Hα luminosity functions for the entire cluster region, near the shock fronts, and away from the shock fronts and find striking differences between the two clusters. In the dynamically younger, 1 Gyr old 'Sausage' cluster we find numerous (59) Hα emitters above a star-formation rate (SFR) of 0.17 M yr −1 surprisingly located in close proximity to the shock fronts, embedded in very hot intra-cluster medium plasma. The SFR density for the cluster population is at least at the level of typical galaxies at z ∼ 2. Down to the same star-formation rate, the possibly dynamically more evolved 'Toothbrush' cluster has only 9 Hα galaxies. The cluster Hα galaxies fall on the SFRstellar mass relation z ∼ 0.2 for the field. However, the 'Sausage' cluster has an Hα emitter density > 20 times that of blank fields. If the shock passes through gas-rich cluster galaxies, the compressed gas could collapse into dense clouds and excite star-formation for a few 100 Myr. This process ultimately leads to a rapid consumption of the molecular gas, accelerating the transformation of gas-rich field spirals into cluster S0s or ellipticals.

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“…SDSS (DR9), GSC2.3, USNO-B1, UCAC4, CMC15, DENIS, VVV (DR3), 2MASS, WISE (Ahn et al 2012;Lasker et al 2008;Monet et al 2003;Zacharias et al 2013;Epchtein et al 1997;Hempel et al 2014;Skrutskie et al 2006;Wright et al 2010). * Magnitudes from UCAC4 transformed to SDSS r and i filters, we assume a fixed error of 0.3 mag.…”

Section: Massmentioning

confidence: 99%

Spectrophotometric characterization of high proper motion sources fromWISE

Beamín

Ivanov

Minniti

et al. 2015

Mon. Not. R. Astron. Soc.

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The census of the solar neighborhood is almost complete for stars and becoming more complete in the brown dwarf regime. Spectroscopic, photometric and kinematic characterization of nearby objects helps us to understand the local mass function, the binary fraction, and provides new targets for sensitive planet searches. We aim to derive spectral types and spectro-photometric distances of a sample of new high proper motion sources found with the WISE satellite, and obtain parallaxes for those objects that fall within the area observed by the Vista Variables in the Vía Láctea survey (VVV). We used low resolution spectroscopy and template fitting to derive spectral types, multiwavelength photometry to characterize the companion candidates and obtain photometric distances. Multi-epoch imaging from the VVV survey was used to measure the parallaxes and proper motions for three sources. We confirm a new T2 brown dwarf within ∼15 pc. We derived optical spectral types for twenty four sources, mostly M dwarfs within 50 pc. We addressed the wide binary nature of sixteen objects found by the WISE mission and previously known high proper motion sources. Six of these are probably members of wide binaries, two of those are new, and present evidence against the physical binary nature of two candidate binary stars found in the literature, and eight that we selected as possible binary systems. We discuss a likely microlensing event produced by a nearby low mass star and a galaxy, that is to occur in the following five years.

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The Fourth Us Naval Observatory CCD Astrograph Catalog (Ucac4)

Cited by 1,302 publications

References 35 publications

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

ACCESS I. AN OPTICAL TRANSMISSION SPECTRUM OF GJ 1214b REVEALS A HETEROGENEOUS STELLAR PHOTOSPHERE

The rise and fall of star formation in z ∼ 0.2 merging galaxy clusters

Spectrophotometric characterization of high proper motion sources fromWISE

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