The Wendelstein Calar Alto Pixellensing Project (WeCAPP): the M 31 variable star catalogue

Fliri, J.; Riffeser, A.; Seitz, S.; Bender, Ralf

doi:10.1051/0004-6361:20042223

Cited by 36 publications

(49 citation statements)

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“…If any other references are found corresponding to the Cepheid identified in our study (see the discussion in Sect. 6.1), we give those identifications with prefixes D, J and W respectively for the DIRECT (Kaluzny et al 1999), Joshi et al (2003) and WeCAPP (Fliri et al 2006) the last column of the table. Their corresponding periods are also mentioned in brackets.…”

Section: The Cataloguementioning

confidence: 99%

“…Cepheids, Miras) and optical transient events. Several groups dedicated to searching for microlensing events in the direction of M 31 have already uncovered a large number of variable stars, most of which are previously unidentified (Joshi et al 2003;Ansari et al 2004;Fliri et al 2006), as well as nova outbursts (Joshi et al 2004, Darnley et al 2004) as a major by-product.These variable stars are of cosmological interest, particularly Cepheids, which are massive (M ∼ 3−20 M ) pulsating stars placed in the instability strip of the Hertzsprung-Russell diagram. They can be identified by their characteristic "saw-tooth" shaped light curves and high intrinsic brightness.…”

Section: Introductionmentioning

confidence: 99%

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Nainital Microlensing Survey – detection of short period Cepheids in the disk of M 31

Joshi

Narasimha

Pandey³

et al. 2010

A&A

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Context. Cepheids are the primary distance indicators for the external galaxies, so discovery of large number of Cepheid variables in far-off galaxies offers a unique opportunity to determine the accurate distance of the host galaxy through their period-luminosity relation. Aims. The main purpose of this study is to identify short-period and relatively faint Cepheids in the crowded field of M 31 disk, which was observed as part of the Nainital Microlensing Survey. Methods. The Cousins R and I band photometric observations were carried out in the direction of M 31 with the aim of detecting microlensing events. The data was obtained with a 1-m telescope on more than 150 nights over the period between November 1998 and January 2002. The data was analysed using the pixel technique and the mean magnitudes of the Cepheids were determined by correlating their pixel fluxes with the corresponding PSF-fitted photometric magnitudes. Results. In the present study we report identification of short-period Cepheid variables in the M 31 disk. We present a catalogue of 39 short-period (P < 15 days) Cepheids in a ∼13 × 13 region of the M 31 disk and give positions and pulsation periods along with their R and I bands photometric magnitudes wherever possible. Most of the Cepheids are found with R (mean) ∼ 20-21 mag, and the dense phase coverage of our observations enabled us to identify Cepheids with periods as short as 3.4 days. The period distribution of these Cepheids peaks at log P ∼ 0.9 and 1.1 days. Conclusions. We demonstrate that using the pixel method, faint and short-period Cepheids in M 31 can even be detected with smallsize telescopes and moderate observing conditions.

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Section: The Cataloguementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nainital Microlensing Survey – detection of short period Cepheids in the disk of M 31

Joshi

Narasimha

Pandey³

et al. 2010

A&A

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“…We note here that individual long period variables have been detected in nearby galaxies including the Magellanic Clouds 25 , M31 26 , and M32 27 . The most distant galaxy with secure detections of individual long period variable stars is NGC 5128 28 , and in this case the observations were confined to the outskirts where the stellar density was sufficiently low to permit the separation of the brightest evolved stars from the background sea of lower luminosity stars.…”

Section: Methodsmentioning

confidence: 61%

Ubiquitous time variability of integrated stellar populations

Conroy

Dokkum

Choi

2015

Nature

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Long period variable stars arise in the final stages of the asymptotic giant branch phase of stellar evolution. They have periods of up to ∼ 1000d and amplitudes that can exceed a factor of three in the I-band flux. These stars pulsate predominantly in their fundamental mode 1-3 , which is a function of mass and radius, and so the pulsation periods are sensitive to the age of the underlying stellar population 4 . The overall number of long period variables in a population is directly related to their lifetime, which is difficult to predict from first principles because of uncertainties associated with stellar mass-loss and convective mixing. The time variability of these stars has not been previously taken into account when modeling the spectral energy distributions of galaxies. Here we construct time-dependent stellar population models that include the effects of long period variable stars, and report the ubiquitous detection of this expected 'pixel shimmer' in the massive metal-rich galaxy M87. The pixel light curves display a variety of behaviors, including linearly rising and falling curves, semi-periodic curves, and sudden increases or decreases in the flux level. The observed variation of 0.1 − 1% is very well matched to the predictions of our models. The data provide a strong and novel constraint on the properties of variable stars in an old and metal-rich stellar population, and we infer that the lifetime of long period variables in M87 is shorter by approximately 30% compared to predictions from the latest stellar evolution models.In typical massive galaxies with ∼ 10 11 stars, the variation in the total light due to long period variables will be small as the summed light curves of many such stars effectively cancel each other out (with random phases the net effect scales as N −1/2 ). If the light is spread out over many (e.g., ∼ 10 4 −10 6 ) pixels, then the number of stars per pixel can range from 10 4 − 10 7 and in this regime the number of asymptotic giant branch stars per pixel is small and governed by Poisson statistics. This 'semi-resolved' regime is well known 5 and the expected surface brightness fluctuations due to Poisson statistics of rare luminous stars have been observed and studied in several hundred nearby galaxies 6-8 . We expect in this regime to be able to detect the presence of variable stars through the time dependence of the pixel flux (i.e., the pixel light curve): essentially every pixel is expected to 'shimmer' on timescales of several hundred days.In order to quantify the expected pixel shimmer, we created a stellar population model at solar metallicity that includes the time-dependent effect of long period variables. We started with a new library of stellar isochrones (Choi et al., in prep) that densely samples fast phases of stellar evolution, and assigned periods to evolved stars assuming that they pulsate in the fundamental mode 4 . We then used observations of variable stars in the Galactic bulge from the OGLE survey to estimate a period-amplitude relation in the I−band 9...

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“…(Note that the disk-bulge lensing does show the reversed asymmetry). It has been pointed out in the past ) that dust lanes in the M31 disk are an additional source of asymmetry; this is obvious if one considers the spatial distributions of variables found in pixel-lensing experiments (see An et al (2004a), Ansari et al (2004) and Fliri et al (2006)). These can, however, be taken to quantitatively account for extinction, in addition to extinction maps.…”

Section: Chapter 2 Theory Of Microlensing Toward Crowded Fieldsmentioning

confidence: 99%