Galactic Cepheids with Spitzer: I. Leavitt Law and Colors (2009)
Marengo, M., Evans, N. R., Barmby, P., Bono, G., Welch, D. L., Romaniello, M.
Classical Cepheid variable stars have been important indicators of extragalactic distance and Galactic evolution for over a century. The Spitzer Space Telescope has opened the possibility of...
Rest, A., Foley, R. J., Gezari, S., Narayan, G., Draine, B., Olsen, K., ...
We report the discovery of a supernova (SN) with the highest apparent energy output to date and conclude that it represents an extreme example of the Type IIn subclass. The SN, which was discovered...
The destruction and survival of dust in the shell around SN 2008S (2009)
Wesson, R., Barlow, M. J., Ercolano, B., Andrews, J. E., Clayton, Geoffrey C., Fabbri, J., ...
SN 2008S erupted in early 2008 in the grand design spiral galaxy NGC 6946. The progenitor was detected by Prieto et al. in Spitzer Space Telescope images taken over the four years prior to the...
V532 Oph is a New R Coronae Borealis Star (2009)
Clayton, Geoffrey C., Kilkenny, D., Wils, P., Welch, D. L.
V532 Oph has been found to be a member of the rare, hydrogen-deficient R Coronae Borealis (RCB) stars from new photometric and spectroscopic data reported in this paper. The lightcurve of V532 Oph...
Application of the Trend Filtering Algorithm on the MACHO Database (2009)
Szulagyi, J., Kovacs, G., Welch, D. L.
Due to the strong effect of systematics/trends in variable star observations, we employ the Trend Filtering Algorithm (TFA) on a subset of the MACHO database and search for variable stars. TFA has...
Rest, A., Welch, D. L., Suntzeff, N. B., Oaster, L., Lanning, H., Olsen, K., ...
We report the discovery of an extensive system of scattered light echo arclets associated with the recent supernovae in the local neighbourhood of the Milky Way: Tycho (SN 1572) and Cassiopeia A....
Spectral Identification of an Ancient Supernova using Light Echoes in the LMC (2008)
Rest, A., Matheson, T., Blondin, S., Bergmann, M., Welch, D. L., Suntzeff, N. B., ...
We report the successful identification of the type of the supernova responsible for the supernova remnant SNR 0509-675 in the Large Magellanic Cloud (LMC) using Gemini spectra of surrounding light...
A Search for sub-km KBOs with the Method of Serendipitous Stellar Occultations (2008)
Bickerton, S. J., Kavelaars, J. J., Welch, D. L.
The results of a search for sub-km Kuiper Belt Objects (KBOs) with the method of serendipitous stellar occultations are reported. Photometric time series were obtained on the 1.8m telescope at the...
D. L. Welch, A. Rorabeck, C. Alcock, D. P. Bennett, D. Minniti, K. C. Freeman
3 B.A. PETERSON 3, A.W. RODGERS 3, K. GRIEST
Cepheids in the Magellanic Clouds (2007)
D. L. Welch, C. Alcock, D.P. Bennett, K.H. Cook, A. W. Rodgers, K. Griest, ...
. In the past few years, the Magellanic Clouds have been the targets for several major variable star surveys. The results of these surveys are now becoming available and it is clear that a...
An Extremely Bright Echo Associated With SN 2002hh (2007)
Welch, D. L., Clayton, Geoffrey C., Campbell, Amy, Barlow, M. J., Sugerman, Ben E. K., Meixner, Margaret, ...
We present new, very late-time optical photometry and spectroscopy of the interesting Type II-P supernova, SN 2002hh, in NGC 6946. Gemini/GMOS-N has been used to acquire visible spectra at six epochs...
Light echoes of supernovae in the large magellanic cloud (2006)
R. C. Smith, N. B. Suntzeff, K. Olsen, P. Challis, A. C. Becker, A. Miceli, ...
Light echoes of supernovae in the large magellanic cloud
Massive-star supernovae as major dust factories (2006)
Sugerman, B.E.K., Ercolano, B., Barlow, M.J., Tielens, A.G.G., Clayton, G.C., Zijlstra, A.A., ...
We present late-time optical and mid-infrared observations of the Type II supernova 2003gd in the galaxy NGC 628. Mid-infrared excesses consistent with cooling dust in the ejecta are observed 499 to...
Removing the Microlensing Blending-Parallax Degeneracy Using Source Variability (2006)
Assef, R.J., Gould, A., Afonso, C., Albert, J.N., Andersen, J., Ansari, R., ...
Microlensing event MACHO 97-SMC-1 is one of the rare microlensing events for which the source is a variable star, simply because most variable stars are systematically eliminated from microlensing...
Removing the Microlensing Blending-Parallax Degeneracy Using Source Variability (2006)
Assef, R.J., Gould, A., Afonso, C., Albert, J.N., Andersen, J., Ansari, R., ...
Microlensing event MACHO 97-SMC-1 is one of the rare microlensing events for which the source is a variable star, simply because most variable stars are systematically eliminated from microlensing...
Removing the microlensing blending-parallax degeneracy using source variability (2006)
Assef, R. J., Gould, A., Afonso, C., Albert, J. N., Andersen, J., Ansari, R., ...
Microlensing event MACHO 97-SMC-1 is one of the rare microlensing events for which the source is a variable star, simply because most variable stars are systematically eliminated from microlensing...
Light echoes of supernovae in the large magellanic cloud (2006)
Becker, A. C., Challis, P., Clocchiatti, A., Garg, A., Miceli, A., Miknaitis, G. A., ...
Echoes from Ancient Supernovae in the Large Magellanic Cloud (2005)
Rest, A., Suntzeff, N. B., Olsen, K., Prieto, J. L., Smith, R. C., Welch, D. L., ...
In principle, the light from historical supernovae could still be visible as scattered-light echoes even centuries later. However, while echoes have been discovered around some nearby extragalactic...
Stellar Variability in the Sub-Horizontal Branch Region of the LMC (2005)
We present the initial results from an in-depth re-examination of the MACHO project Large Magellanic Cloud database to identify and characterize stellar variability near the intersection of the...
Rest, A., Stubbs, C., Becker, A. C., Miknaitis, G. A., Miceli, A., Covarrubias, R., ...
Characterizing the nature and spatial distribution of the lensing objects that produce the previously measured microlensing optical depth toward the Large Magellanic Cloud (LMC) remains an open...
Discovery of Five New R Coronae Borealis Stars in the MACHO Galactic Bulge Database (2005)
Zaniewski, A., Clayton, Geoffrey C., Welch, D. L., Gordon, Karl D., Minniti, D., Cook, K. H.
We have identified five new R Coronae Borealis (RCB) stars in the Galactic bulge using the MACHO Project photometry database, raising the total number of known Galactic RCB stars to about 40. We have...
Galactic bulge microlensing events from the MACHO Collaboration (2005)
Thomas, C. L., Griest, K., Popowski, P., Cook, K. H., Drake, A. J., Minniti, D., ...
Galactic Bulge Microlensing Events from the MACHO Collaboration (2004)
Thomas, C. L., Griest, K., Popowski, P., Cook, K. H., Drake, A. J., Minniti, D., ...
We present a catalog of 450 high signal-to-noise microlensing events observed by the MACHO collaboration between 1993 and 1999. The events are distributed throughout our fields and, as expected, they...
The SuperMACHO Microlensing Survey (2004)
Becker, A. C., Rest, A., Stubbs, C., Miknaitis, G. A., Miceli, A., Covarrubias, R., ...
We present the first results from our next-generation microlensing survey, the SuperMACHO project. We are using the CTIO 4m Blanco telescope and the MOSAIC imager to carry out a search for...
The Nature of the Companion to the Eclipsing Overtone Cepheid MACHO 81.8997.87 (2004)
The lightcurve of the Large Magellanic Cloud (LMC) variable star MACHO 81.8997.87 shows evidence for photometric variations due to both stellar pulsation, with a 2.035 day period, and eclipsing...
Alcock, C., Alves, D. R., Axelrod, T. S., Becker, A. C., Bennett, D. P., Clement, C. M., ...
Fourier coefficents have been derived for the $V$ and $R$ light curves of 785 overtone RR Lyrae variables in 16 MACHO fields near the bar of the LMC. The $\phi_{31}$ and $R_{21}$ coefficients have...
Alcock, C., Alves, D. R., Becker, A., Bennett, D., Cook, K. H., Drake, A., ...
We have frequency analyzed 6391 variables classified earlier as fundamental mode RR Lyrae (RR0) stars in the MACHO database on the Large Magellanic Cloud (LMC). The overwhelming majority of these...
Variable Stars in Metal-Rich Globular Clusters. II. NGC 6316 (2003)
Layden, A. C., Bowes, B. T., Welch, D. L., Webb, T. M. A.
We present time-series VI photometry of the metal-rich globular cluster NGC 6316. Our color-magnitude diagrams show a predominantly red-clump horizontal branch morphology with no evidence of the blue...
Variability-selected quasars in MACHO project Magellanic Cloud fields (2003)
Geha, M., Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., ...
We present 47 spectroscopically confirmed quasars discovered behind the Magellanic Clouds identified via photometric variability in the MACHO database. Thirty-eight quasars lie behind the Large...
Variability-Selected Quasars in MACHO Project Magellanic Cloud Fields (2002)
Geha, M., Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., ...
We present 47 spectroscopically-confirmed quasars discovered behind the Magellanic Clouds identified via photometric variability in the MACHO database. Thirty-eight quasars lie behind the Large...
Alcock, C., Allsman, R. A., Alves, D. R., Becker, A. C., Bennett, D. P., Cook, K. H., ...
We present a method for solving the lightcurve of an eclipsing binary system which contains a Cepheid variable as one of its components as well as the solutions for three eclipsing Cepheids in the...
Alcock, C., Allsman, R. A., Alves, D. R., Becker, A. C., Bennett, D. P., Cook, K. H., ...
We present a method for solving the light curve of an eclipsing binary system that contains a Cepheid variable as one of its components as well as the solutions for three eclipsing Cepheids in the...
The MACHO Project LMC Variable Star Inventory: X. The R Coronae Borealis Stars (2001)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A., Bennett, D. P., ...
We report the discovery of eight new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The discovery of these new stars increases the...
MACHO Project Limits on Black Hole Dark Matter in the 1-30 Solar Mass Range (2000)
Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
We report on a search for long duration microlensing events towards the Large Magellanic Cloud. We find none, and therefore put limits on the contribution of high mass objects to the Galactic dark...
A 421 d Activity Cycle in the BeX Recurrent Transient A0538-66 from MACHO monitoring (2000)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
We present a ~ 5-yr optical light curve of the recurrent Be/X-ray transient A0538-66 obtained as a by-product of the MACHO Project. These data reveal both a long-term modulation at P = 420.8 +/- 0.8...
Alcock, C., Allsman, R., Alves, D. R., Axelrod, T., Becker, A., Bennett, D., ...
More than 1300 variables classified provisionally as first overtone RR Lyrae pulsators in the MACHO variable star database of the Large Magellanic Cloud (LMC) have been subjected to standard...
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
We present the microlensing optical depth towards the Galactic bulge based on the detection of 99 events found in our Difference Image Analysis (DIA) survey. This analysis encompasses three years of...
The MACHO Project 9 Million Star Color-Magnitude Diagram of the Large Magellanic Cloud (2000)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Basu, A., Becker, A. C., ...
We present a 9 million star color-magnitude diagram (9M CMD) of the LMC bar. The 9M CMD reveals a complex superposition of different age and metallicity stellar populations, with important stellar...
Calibration of the MACHO Photometry Database (1999)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
The MACHO Project is a microlensing survey that monitors the brightnesses of 60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. Our database presently...
Difference Image Analysis of Galactic Microlensing II. Microlensing Events (1999)
Alcock, C., Allsman, R. A., Alves, D., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
The MACHO collaboration has been carrying out Difference Image Analysis (DIA) since 1996 with the aim of increasing the sensitivity to the detection of gravitational microlensing. This is a...
Difference Image Analysis of Galactic Microlensing I. Data Analysis (1999)
Alcock, C., Allsman, R. A., Alves, D., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
This is a preliminary report on the application of Difference Image Analysis (DIA) to galactic bulge images. The aim of this analysis is to increase the sensitivity to the detection of gravitational...
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
We present an analysis of the period distribution of $\sim 1800$ Cepheids in the Large Magellanic Cloud, based on data obtained by the MACHO microlensing experiment and on a previous catalogue by...
Alves, D. R., Basu, A., Cook, K. H., Welch, D. L., Alcock, C., Marshall, S., ...
This paper has been withdrawn
The Variable Stars and Blue Horizontal Branch of the Metal-Rich Globular Cluster NGC 6441 (1998)
Layden, A. C., Ritter, L. A., Welch, D. L., Webb, T. M. A.
We present time-series VI photometry of the metal-rich ([Fe/H] = -0.53) globular cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space...
Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A., Bennett, D. P., ...
MACHO Project photometry of 45 LMC FO/SO beat Cepheids which pulsate in the first and second overtone (FO and SOo, respectively) has been analysed to determine the lightcurve characteristics for the...
Alves, D. R., Becker, A., Bennett, D. P., Cook, K. H., Freeman, K. C., ...
Using the novel data set of the MACHO project, we show that three ``Blazhko Effect'' RR Lyrae stars show nearly-pure amplitude modulation of a single pulsation mode. This is strong observational...
Pulsating Variable Stars in the MACHO Bulge database: The Semiregular Variables (1997)
Minniti, D., Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A., ...
We review the pulsating stars contained in the top 24 fields of the MACHO bulge database, with special emphasis on the red semiregular stars. Based on period, amplitude and color cuts, we have...
New Observing Techniques (1997)
The influence of new techniques on the discovery and characterization of pulsating variables has been enormous. In this paper, I will review the methods and results of a number of research programmes...
First detection of a gravitational microlensing candidate towards the Small Magellanic Cloud (1997)
Allsman, R. A., Alves, D., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
We report the first discovery of a gravitational microlensing candidate towards a new population of source stars, the Small Magellanic Cloud (SMC). The candidate event's light curve shows no...
The MACHO Project: Microlensing and Variable Stars (1997)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A., ...
The MACHO Project monitors millions of stars in the Large Magellanic Cloud, the Small Magellanic Cloud and the bulge of the Milky Way searching for the gravitational microlensing signature of...
Bulge delta Scuti Stars in the MACHO Database (1997)
Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A., Bennett, D. P., ...
We describe the search for delta Scuti stars in the MACHO database of bulge fields. Concentrating on a sample of high amplitude delta Scutis, we examine the light curves and pulsation modes. We also...
Is the LMC Microlensing Due to an Intervening Dwarf Galaxy? (1997)
Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A., Bennett, D. P., ...
The recent suggestion that the microlensing events observed towards the Large Magellanic Cloud are due to an intervening Sgr-like dwarf galaxy is examined. A search for foreground RR Lyrae in the...
The RR Lyrae Population of the Galactic Bulge from the MACHO Database (1997)
Allsman, R. A., Alves, D. R., Axelrod, T. S., Basu, A., Baskett, L., ...
Mean colors and magnitudes of RR Lyrae stars in 24 fields towards the Galactic bulge from the MACHO database are presented. Accurate mean reddenings are computed for these fields on the basis of the...
The Zero Point of Extinction Toward Baade's Window From RR Lyrae Stars (1997)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
We measure the zero point of the Stanek (1996) extinction map by comparing the observed (V-K) colors of 20 RR Lyrae stars (type ab) found in the MACHO survey with their intrinsic (V-K)_0 colors as a...
Alcock, C., Allen, W. H., Allsman, R. A., Alves, D., Axelrod, T. S., Banks, T. S., ...
We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event towards the Galactic bulge whose peak magnification departs significantly from the standard point-source...
Gravitational Microlensing Results from MACHO (1996)
Alcock, C., Allsman, R. A., Alves, D., Axelrod, T. S., Becker, A. C., ...
The MACHO project is searching for dark matter in the form of massive compact halo objects (Machos), by monitoring the brightness of millions of stars in the Magellanic Clouds to search for...
RR Lyrae Stars in the MACHO Database (1996)
Alcock, C., Alves, D. R., Allsman, R. A., Axelrod, T. S., Becker, A., ...
The MACHO Project has catalogued $\sim 8000$ RR Lyrae stars in the Large Magellanic Cloud, $\sim 1800$ in the Galactic bulge, and $\sim$ 50 in the Sgr dwarf galaxy. These variables are excellent...
Alcock, C., Allsman, R. A., Alves, D., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
We report the discovery of 73 double-mode RR Lyrae (RRd) stars in fields near the bar of the LMC. The stars are detected among the MACHO database of short-period variables that currently contains...
Beat Cepheid Period Ratios from OPAL Opacities (1996)
The discovery of a large number of beat Cepheids in the Large Magellanic Cloud in the MACHO survey, provides an opportunity to compare the characteristics of such Cepheids over a range of...
Alcock, C., Allsman, R. A., Alves, D., Axelrod, T. S., Becker, A. C., Bennett, D. P., ...
The MACHO Project is a search for dark matter in the form of massive compact halo objects (Machos). Photometric monitoring of millions of stars in the Large Magellanic Cloud (LMC), Small Magellanic...
The MACHO Project 2nd Year LMC Microlensing Results and Dark Matter Implications (1996)
Pratt, M. R., Alcock, C., Allsman, R. A., Alves, D., Axelrod, T. S., Becker, A. C., ...
The MACHO Project is searching for galactic dark matter in the form of massive compact halo objects (Machos). Millions of stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and...
MACHO Project Photometry of RR Lyrae Stars in the Sgr Dwarf Galaxy (1996)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A., Bennett, D. P., ...
We report the discovery of 30 type a,b RR Lyrae (RRab) which are likely members of the Sagittarius (Sgr) dwarf galaxy. Accurate positions, periods, amplitudes and magnitudes are presented. Their...
The MACHO Project LMC Variable Star Inventory: III. New R Coronae Borealis Stars (1996)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A., Bennett, D. P., ...
We report the discovery of two new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The identification of both stars has been confirmed...
The Distance to IC 10 from Near-Infrared Observations of Cepheids (1995)
Wilson, C. D., Welch, D. L., Reid, I. N., Saha, A., Hoessel, J.
We have measured the distance to the Local Group dwarf irregular galaxy IC 10 from near-infrared $JHK$ observations of Cepheids. The reddening-corrected distance modulus is $24.57\pm0.21$ mag or...
Cepheids in the Magellanic Clouds (1995)
Welch, D. L., Alcock, C., Bennett, D. P., Cook, K. H., Allsman, R. A., Axelrod, T. S., ...
In the past few years, the Magellanic Clouds have been the targets for several major variable star surveys. The results of these surveys are now becoming available and it is clear that a Renaissance...
Alcock, C., Allsman, R. A., Axelrod, T. S., Bennett, D. P., Cook, K. H., Freeman, K. C., ...
We report the discovery of 45 beat Cepheids in the Large Magellanic Cloud (LMC) using the MACHO Project photometry database. The variables which are pulsating simultaneously in two radial modes are...
The advantages of a near-infrared variant of the Barnes-Evans method for estimating distances to Cepheid variables are described and quantified. A surface brightness-color relation for $K$ photometry...
Dynamics of the Globular Cluster NGC 362 (1993)
Fischer, P., Welch, D. L., Mateo, M., Côté, P.
In this paper we have examined the internal dynamics of the globular cluster NGC 362. A V band surface brightness profile (SBP) was constructed from CCD images, and, after it was determined that the...
Dynamics of the Young Binary LMC Cluster NGC 1850 (1992)
Fischer, P., Welch, D. L., Mateo, M.
In this paper we have examined the age and internal dynamics of the young binary LMC cluster NGC 1850 using BV CCD images and echelle spectra of 52 supergiants. Isochrone fits to a BV color-magnitude...