Difference image analysis: extension to a spatially varying photometric scale factor and other considerations

Bramich, D. M.; Horne, K.; Albrow, M. D.; Tsapras, Y.; Snodgrass, C.; Street, R. A.; Hundertmark, M.; Kains, N.; Ferro, A. Arellano; Jaimes, R. Figuera; Giridhar, Sunetra

doi:10.1093/mnras/sts184

Cited by 101 publications

(92 citation statements)

References 18 publications

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“…We used the Difference Image Analysis (DIA) technique with its pipeline DanDIA (Bramich 2008;Bramich et al 2013) to obtain high-precision photometry for all the point sources in the FoV of our images of M92. The strategy consists on creating a reference image by stacking the best quality images in each filter and then sequences of differential images in each filter were built by subtracting the respective reference image from the rest of the collection.…”

Section: Difference Image Analysismentioning

confidence: 99%

CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

Yepez

Ferro

Deras

2020

Monthly Notices of the Royal Astronomical Society

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We present an analysis of VI CCD time-series photometry of the Oo II type globular cluster M92. The variable star population of the cluster is studied with the aim of revising their classifications, identifications, frequency spectra and to select indicators of the parental cluster metallicity and distance. The Fourier decomposition of RR Lyrae light curves lead to the estimation of mean [Fe/H] spec = −2.20 ± 0.18, and distance of 8.3 ± 0.2 kpc. Four new variables are reported; one RRd (V40), a multimode SX Phe (V41), a SR (V42) and one RRc (F1) that is most likely not a cluster member. The AC nature of V7 is confirmed. The double mode nature of the RRc star V11 is not confirmed and its amplitude modulations are most likely due to the Blazhko effect. Two modes are found in the known RRc variable V13. It is argued that the variable V30, previously classified as RRab is, in fact, an BL Her-type star not belonging to the cluster. Making use of the Gaia-DR2 proper motions, we identified 5012 stars in the field of the cluster, that are very likely cluster members, and for which we possess photometry, enabling the production of a refined Colour-Magnitude Diagram. This also allowed us to identify a few variable stars that do not belong to the cluster. The RR Lyrae pulsation modes on the HB are cleanly separated by the first overtone red edge, a common feature in all Oo II type clusters.

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Section: Difference Image Analysismentioning

confidence: 99%

CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

Yepez

Ferro

Deras

2020

Monthly Notices of the Royal Astronomical Society

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“…We reduced our observations using the DanDIA 1 pipeline (Bramich 2008(Bramich , 2012b) to obtain high-precision photometry of sources in the images of NGC 1904, as was done in previous globular cluster studies (e.g. Bramich et al 2012b, see that paper for a detailed description of the software).…”

Section: Difference Image Analysismentioning

confidence: 99%

“…Bramich et al 2012b, see that paper for a detailed description of the software). We produce a stacked reference image in each band by selecting the best-seeing images (within 10% of the best-seeing value) and taking care to minimise the number of saturated stars.…”

Section: Difference Image Analysismentioning

confidence: 99%

Constraining the parameters of globular cluster NGC 1904 from its variable star population

Kains

Bramich

Jaimes

et al. 2012

A&A

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Aims. We present the analysis of 11 nights of V and I time-series observations of the globular cluster NGC 1904 (M 79). Using this we searched for variable stars in this cluster and attempted to refine the periods of known variables, making use of a time baseline spanning almost 8 years. We use our data to derive the metallicity and distance of NGC 1904. Methods. We used difference imaging to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate was possible.Results. Out of 13 stars previously classified as variables, we confirm that 10 are bona fide variables. We cannot detect variability in one other within the precision of our data, while there are two which are saturated in our data frames, but we do not find sufficient evidence in the literature to confirm their variability. We also detect a new RR Lyrae variable, giving a total number of confirmed variable stars in NGC 1904 of 11. Using the Fourier parameters, we find a cluster metallicity [Fe/H] ZW = −1.63 ± 0.14, or [Fe/H] UVES = −1.57 ± 0.18, and a distance of 13.3 ± 0.4 kpc (using RR0 variables) or 12.9 kpc (using the one RR1 variable in our sample for which Fourier decomposition was possible).

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“…We employed the technique of difference image analysis (DIA) to extract high-precision photometry for all of the point sources in the images of M5 and we used the DanDIA pipeline for the data reduction process (Bramich 2008;Bramich et al 2013). We constructed one reference image for the V filter and another for the I filter by stacking the best-quality images in our collection; then we created sequences of difference images in each filter by subtracting the respective convolved reference image from the rest of the collection.…”

Section: Difference Image Analysismentioning

confidence: 99%

“…As in most of our recent papers we have employed the DanDIA 1 implementation of difference image analysis (DIA) (Bramich 2008;Bramich et al 2013) to extract high-precision photometry for all of the point sources in the field of M5. We collected 6890 light cuves in the V and I bandpasses with the aim of building up a colour-magnitude diagram (CMD) and discussing the horizontal branch (HB) structure as compared to other Oosterhoff type I (OoI) and Oosterhoff type II (OoII) clusters.…”

Section: Introductionmentioning

confidence: 99%

RR Lyrae stars and the horizontal branch of NGC 5904 (M5)

Ferro

Luna

Bramich

et al. 2016

Astrophys Space Sci

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We report the distance and [Fe/H] value for the globular cluster NGC 5904 (M5) derived from the Fourier decomposition of the light curves of selected RRab and RRc stars. The aim in doing this was to bring these parameters into the homogeneous scales established by our previous work on numerous other globular clusters, allowing a direct comparison of the horizontal branch luminosity in clusters with a wide range of metallicities. Our CCD photometry of the large variable star population of this cluster is used to discuss light curve peculiarities, like Blazhko modulations, on an individual basis. New Blazhko variables are reported.From the RRab stars we found [Fe/H] UVES = −1.335 ± 0.003(statistical) ± 0.110(systematic), and a distance of 7.6 ± 0.2 kpc, and from the RRc stars we found [Fe/H] UVES = −1.39 ± 0.03(statistical) ± 0.12(systematic) and a distance of 7.5 ± 0.3 kpc. The results for RRab and RRc stars should be considered independent since they come from different calibrations and zero points. Absolute magnitudes, radii and masses are also reported for individual RR Lyrae stars. The distance to the cluster was also calculated by alternative methods like the Period-Luminosity relation of SX Phe and the luminosity of the stars at the tip of the red giant branch, and we obtained the results 7.7 ± 0.4 and 7.2 − 7.5 kpc respectively.The distribution of RR Lyrae stars in the instability strip is discussed and compared with other clusters in connection with the Oosterhoff and horizontal branch type. The Oosterhoff type II clusters systematically show a RRab-RRc segregation about the instability strip first-overtone red edge, while the Oosterhoff type I clusters may or may not display this feature. A group of RR Lyrae stars is identified in an advanced evolutionary stage, and two of them are likely binaries with unseen companions.

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Difference image analysis: extension to a spatially varying photometric scale factor and other considerations

Cited by 101 publications

References 18 publications

CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

Constraining the parameters of globular cluster NGC 1904 from its variable star population

RR Lyrae stars and the horizontal branch of NGC 5904 (M5)

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