The Wendelstein Calar Alto Pixellensing Project (WeCAPP): First MACHO Candidates

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

doi:10.1086/381019

Cited by 59 publications

(88 citation statements)

References 28 publications

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“…The rms of the solution is 0.10 in declination and 0.12 in right ascension. The coordinates derived here agree perfectly with the ones derived in Riffeser et al (2001) and Riffeser et al (2003). The reduction package includes full error propagation for each pixel through all reduction steps.…”

Section: Astrometrysupporting

confidence: 69%

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

Fliri¹,

Riffeser

Seitz³

et al. 2005

A&A

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In this paper we present the WeCAPP catalogue of variable stars found in the bulge of M 31. Observations in the WeCAPP microlensing survey (optical R and I bands) for a period of three years (2000)(2001)(2002)(2003) resulted in a database with unprecedented time coverage for an extragalactic variable star study. We detected 23781 variable sources in a 16.1 × 16.6 field centered on the nucleus of M 31. The catalogue of variable stars contains the positions, the periods, and the variation amplitudes in the R and I bands. We classified the variables according to their position in the R-band period-amplitude plane. Three groups can be distinguished; while the first two groups can be mainly associated with Cepheid-like variables (population I Cepheids in group I; type II Cepheids and RV Tauri stars in group II), the third one consists of Long Period Variables (LPVs). We detected 37 RV Tauri stars and 11 RV Tauri candidates, which makes this catalogue one of the largest collections of this class of stars to date. The classification scheme is supported by Fourier decomposition of the light curves. Our data shows a correlation of the low-order Fourier coefficients Φ 21 with Φ 31 for classical Cepheids, as well as for type II Cepheids and RV Tauri stars. Correlating our sample of variable stars with X-ray based catalogues of Kaaret (2002, ApJ, 578, 114) and Kong et al. (2002, ApJ, 577, 738) results in 23 and 31 coincidences, 8 and 12 of which are M 31 globular clusters. The number density of detected variables is clearly not symmetric, which has to be included in the calculations of the expected microlensing event rate towards M 31. This asymmetry is due to the enhanced extinction in the spiral arms superimposed on the bulge of M 31, which reduces the number of sources to about 60%, if compared to areas of equivalent bulge brightness without enhanced extinction present.

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Section: Astrometrysupporting

confidence: 69%

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

Fliri¹,

Riffeser

Seitz³

et al. 2005

A&A

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“…This analysis shows that the observed signal is much larger than expect from self-lensing alone and that some fraction of the halo mass must be in form of MACHOs. Other collaborations have also reported preliminary results for pixel lensing towards M 31 (Calchi Novati et al 2002Uglesich et al 2004;Riffeser et al 2003;Joshi et al 2004).…”

Section: Introductionmentioning

confidence: 89%

Monte Carlo analysis of MEGA microlensing events towards M 31

Ingrosso

Novati

Paolis

et al. 2005

A&A

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We perform an analytical study and a Monte Carlo (MC) analysis of the main features for microlensing events in pixel lensing observations towards M 31. Our main aim is to investigate the lens nature and location of the 14 candidate events found by the MEGA collaboration. Assuming a reference model for the mass distribution in M 31 and the standard model for our galaxy, we estimate the MACHO-to-self lensing probability and the event time duration towards M 31. Reproducing the MEGA observing conditions, as a result we get the MC event number density distribution as a function of the event full-width half-maximum duration t 1/2 and the magnitude at maximum R max . For a MACHO mass of 0.5 M we find typical values of t 1/2 20 day and R max 22, for both MACHO-lensing and self-lensing events occurring beyond about 10 arcmin from the M 31 center. A comparison of the observed features (t 1/2 and R max ) with our MC results shows that for a MACHO mass > 0.1 M the four innermost MEGA events are most likely self-lensing events, whereas the six outermost events must be genuine MACHO-lensing events.

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“…The observations are carried out in R and I filters close to the Kron-Cousins system. Data were reduced using the WeCAPP reduction pipeline mupipe, which implements an image subtraction technique (Alard & Lupton 1998) to overcome the crowding effects and allow proper photometry of variable sources in the central bulge of M 31 (Riffeser et al 2003).…”

Section: Optical Nova Cataloguementioning

confidence: 99%

X-ray monitoring of optical novae in M 31 from July 2004 to February 2005

Pietsch¹,

Haberl²,

Sala³

et al. 2007

A&A

116

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Context. Optical novae have recently been identified as the major class of supersoft X-ray sources in M 31 based on ROSAT and early XMM-Newton and Chandra observations. Aims. This paper reports on a search for X-ray counterparts of optical novae in M 31 based on archival Chandra HRC-I and ACIS-I as well as XMM-Newton observations of the galaxy center region obtained from July 2004 to February 2005. Methods. We systematically determine X-ray brightness or upper limit for counterparts of all known optical novae with outbursts between November 2003 to the end of the X-ray coverage. In addition, we determine the X-ray brightnesses for counterparts of four novae with earlier outbursts. Results. For comparison with the X-ray data we created a catalogue of optical novae in M 31 based on our own nova search programs and on all novae reported in the literature. We collected all known properties and named the novae consistently following the CBAT scheme. We detect eleven out of 34 novae within a year after the optical outburst in X-rays. While for eleven novae we detect the end of the supersoft source phase, seven novae are still bright more than 1200, 1600, 1950, 2650, 3100, 3370 and 3380 d after outburst. One nova is detected to turn on 50 d, another 200 d after outburst. Three novae unexpectedly showed short X-ray outbursts starting within 50 d after the optical outburst and lasting only two to three months. The X-ray emission of several of the novae can be characterized as supersoft from hardness ratios and/or X-ray spectra or by comparing HRC-I count rates with ACIS-I count rates or upper limits. Conclusions. The number of detected optical novae at supersoft X-rays is much higher than previously estimated (>30%). We use the X-ray light curves to estimate the burned masses of the White Dwarf and of the ejecta.

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The Wendelstein Calar Alto Pixellensing Project (WeCAPP): First MACHO Candidates

Cited by 59 publications

References 28 publications

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

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

Monte Carlo analysis of MEGA microlensing events towards M 31

X-ray monitoring of optical novae in M 31 from July 2004 to February 2005

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