<i>UBVRI</i>PHOTOMETRIC STANDARD STARS AROUND THE CELESTIAL EQUATOR: UPDATES AND ADDITIONS

Landolt, A. U.

doi:10.1088/0004-6256/137/5/4186

Cited by 321 publications

(265 citation statements)

References 28 publications

Supporting

Mentioning

259

Contrasting

Order By: Relevance

“…10.1 and (d) the MegaCam passband model detailed in Appendix B. The filter model at the exact focal plane location of the science target may be obtained by interpolating between the filter scans detailed in Tables 14 to 18. Very recently, Landolt (2009) published an extension of the catalog used in this paper. Bluer as well as fainter stars were added to the Landolt (1992b) catalog.…”

Section: Discussionmentioning

confidence: 99%

Photometric calibration of the Supernova Legacy Survey fields

Regnault¹,

Conley

Guy³

et al. 2009

A&A

122

159

View full text Add to dashboard Cite

Aims. We present the photometric calibration of the Supernova Legacy Survey (SNLS) fields. The SNLS aims at measuring the distances to SNe Ia at (0.3 < z < 1) using MegaCam, the 1 deg 2 imager on the Canada-France-Hawaii Telescope (CFHT). The uncertainty affecting the photometric calibration of the survey dominates the systematic uncertainty of the key measurement of the survey, namely the dark energy equation of state. The photometric calibration of the SNLS requires obtaining a uniform response across the imager, calibrating the science field stars in each survey band (SDSS-like ugriz bands) with respect to standards with known flux in the same bands, and binding the calibration to the UBVRI Landolt standards used to calibrate the nearby SNe from the literature necessary to produce cosmological constraints. Methods. The spatial non-uniformities of the imager photometric response are mapped using dithered observations of dense stellar fields. Photometric zero-points against Landolt standards are obtained. The linearity of the instrument is studied. Results. We show that the imager filters and photometric response are not uniform and publish correction maps. We present models of the effective passbands of the instrument as a function of the position on the focal plane. We define a natural magnitude system for MegaCam. We show that the systematics affecting the magnitude-to-flux relations can be reduced if we use the spectrophotometric standard star BD +17 4708 instead of Vega as a fundamental flux standard. We publish ugriz catalogs of tertiary standards for all the SNLS fields.

show abstract

Section: Discussionmentioning

confidence: 99%

Photometric calibration of the Supernova Legacy Survey fields

Regnault¹,

Conley

Guy³

et al. 2009

A&A

122

159

View full text Add to dashboard Cite

show abstract

“…The bias and the flat-field corrections were applied to each of the eight CCD images independently, while the combination of the different exposures, the astrometry, the reconstruction of the final image and the construction of the weight images were done with the modules MissFITS, SCAMP, and SWarp of TERAPIX (Bertin et al 2002). The photometric calibration was performed using the observation of the Landolt calibration stars S107a, S107b, S104, and S98 (Landolt 2009), giving an extinction coefficient of 0.095 ± 0.043 mag and a zero point of 25.57 ± 0.02 mag. The extraction of the stellar positions and magnitudes was done using SExtractor with the weight images produced by the SWarp module.…”

Section: R Band Ctio Imagesmentioning

confidence: 99%

Statistical study of OB stars in NGC 6334 and NGC 6357

Russeil

Zavagno

Adami

et al. 2012

A&A

View full text Add to dashboard Cite

Context. Star-forming complexes are large structures exhibiting massive star-formation at different stages of evolution, from dense cores to well-developed H ii regions. They are very interesting for the study of the formation and evolution of stars. NGC 6334 and NGC 6357 are two active and relatively nearby star-forming complexes. From the extinction map and the sub-mm cold dust emission, and because they have similar velocities, these regions are most likely connected. However, located in the direction of the Galactic center their radial velocity is not representative of their distance. An alternative is then to determine the distance of NGC 6334 and NGC 6357 from their stellar content. Aims. Our aim is to perform a census of O-B3 ionising stars in NGC 6334 and NGC 6357, to determine the extinction coefficient, and the distance of both regions. A census of O-B3 stars is an essential basis for estimating the statistical lifetime of the earliest massive star-forming phases. Methods. We performed a U, B, V, and R photometric survey of a large area covering NGC 6334 and NGC 6357 with the VIMOS (ESO-VLT) and the MOSAIC (CTIO) instruments. This allows us to have a complete census of O to B3 stars up to V = 22.6 mag. The OB stars are selected based on their U − B and B − V colors. The most robust extinction coefficient is determined from color−color plots before computing the distance of the OB stars. Results. We find a higher value than typical of the diffuse interstellar medium for R V of 3.53 ± 0.08 and 3.56 ± 0.15 for NGC 6357 and NGC 6334, respectively. Adopting these R V values, the distances of NGC 6357 and NGC 6334 are 1.9 ± 0.4 kpc and 1.7 ± 0.3 kpc. We conclude that, within the error bars, both regions are thus at the same distance of 1.75 kpc (weighted mean). We confirm that the value of R V is linked to the large dust grain content. In particular, we found that there are more very small grains in NGC 6357 than in NGC 6334, suggesting that NGC 6357 could be more evolved than NGC 6334. Placed in the Galactic context, the NGC 6334-NGC 6357 complex appears to be located at the inner edge of the Sagittarius-Carina arm. Our census of O to B3 stars leads to a count of ∼230, which allows us to determine the statistical lifetime of the earliest phases of the massive stars. The starless and the protostellar phases have a mean statistical lifetime of ∼1.5 × 10 4 yr and ∼2.2 × 10 5 yr, respectively.

show abstract

“…A proper sky subtraction was performed measuring the sky statistics in regions of blank sky near, but not adjacent, to the object to avoid the contaminating effects of the coma background. To perform the absolute flux calibration of our science frames, we took images of photometric standard stars in Landolt fields (Landolt 2009) at airmasses similar to the comet observations, and we applied the methodology described in Palmer & Davenhall (2001). The comet images were therefore calibrated using the JohnsonKron-Cousins photometric system used by Landolt (2009).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…To perform the absolute flux calibration of our science frames, we took images of photometric standard stars in Landolt fields (Landolt 2009) at airmasses similar to the comet observations, and we applied the methodology described in Palmer & Davenhall (2001). The comet images were therefore calibrated using the JohnsonKron-Cousins photometric system used by Landolt (2009). The extinction correction was performed assuming the standard atmospheric conditions for La Palma 4 and Tenerife 5 .…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Photometric observations of comet 81P/Wild 2 during the 2010 perihelion passage

Bertini

Barbieri

et al. 2012

A&A

View full text Add to dashboard Cite

Context. The Jupiter-family comet 81P/Wild 2, target of the NASA Stardust mission, is very important in the context of the studies of pristine objects in the solar system. First, it was only recently deflected into the present orbit, having spent at least 300 yr at higher heliocentric distance prior to the orbital change in 1974. It is therefore likely that the comet experienced a recent activation with consequent low alteration of its original material. Second, it is the only comet whose coma material was brought back to Earth for laboratory analysis. We observed the object between 2010 February 9 and September 9 for a total of 11 nights during the 2010 perihelion passage. Aims. The goals of the campaign were the characterization of the comet's dust activity and the comparison with previous apparitions to derive hints on the secular behavior of the object. Methods. Broadband R-and I-images were acquired using three instruments: ALFOSC, CAMELOT, and TCP. The first one is mounted at the Nordic Optical Telescope on La Palma, while the second and the third are mounted at the Instituto de Astrofisica de Canarias 0.82-m telescope on Tenerife. We analyzed the presence and variability of dust structures in the coma with image-enhancing techniques, the radial profile of the dust brightness, and we measured the dust production rate and the dust reddening. Results. We found evidence of a long-lasting sunward fan and anti-solar tail activity throughout all our observations up to a heliocentric distance of 2.42 AU. A f ρ measurements suggest a pre-perihelion peak of the activity, caused by a seasonal effect, plus two post-perihelion outbursts. Both spatial and A f ρ radial profiles indicate a steady-state coma at nucleocentric distances greater than ∼1000-2000 km. The color analysis reveals a moderately reddened dust with a 6-9%/1000 Å reddening, consistent with the current picture of cometary dust. The second outburst emitted dust with lower reddening. Conclusions. The comparison with previous perihelion passages points toward a recurrent main activity always driven by the same areas on the nucleus, producing dust with similar characteristics and in similar coma structures in different years. Our A f ρ measurement at the longest heliocentric distance suggests the comet was less dust-productive in 2010, pointing toward a possible secular aging of the object and its activity. The change of dust colors during the unusual second outburst suggests that an internal part of the nucleus has different physical properties compared with those that produce the recurrent main activity, pointing toward a heterogeneous comet.

show abstract

UBVRIPHOTOMETRIC STANDARD STARS AROUND THE CELESTIAL EQUATOR: UPDATES AND ADDITIONS

Cited by 321 publications

References 28 publications

Photometric calibration of the Supernova Legacy Survey fields

Photometric calibration of the Supernova Legacy Survey fields

Statistical study of OB stars in NGC 6334 and NGC 6357

Photometric observations of comet 81P/Wild 2 during the 2010 perihelion passage

Contact Info

Product

Resources

About