- ID:
- ivo://CDS.VizieR/J/ApJ/446/622
- Title:
- UV and optical imagery of LH 52 and LH 53
- Short Name:
- J/ApJ/446/622
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A 40' field including the stellar associations LH 52 and LH 53 and the supernova remnant N49 in the Large Magellanic Cloud was observed by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Space Shuttle mission in 1990 December. The image in the 162 nm bandpass is discussed together with ground-based BV data on subfields containing LH 52 and LH 53. Point-spread function photometry in the 162nm, B, and V bands is presented in the form of color-magnitude diagrams and two-color diagrams, which are compared with stellar models. The far-ultraviolet extinction curve of the dust in LH 52 is unusually steep for the LMC. The most probable age of both associations is ~10 Myr, which constrains the scenario for the evolution of the supergiant Halpha shell LMC 4 by stochastic self-propagated star formation. The initial mass function (IMF) slope for LH 52 is Gamma~-1, in agreement with previous work, and the slope for LH 53, which is less densely populated, is Gamma~-2. A similar relationship between surface density of stars and IMF slope is reported for a UIT field near 30 Dor. The ultraviolet morphology of N49, which is contained in LH 53, is dominated by two bright features that straddle an X-ray bright spot, consistent with an encounter between the blast wave and a cloud. The estimated age of ~10Myr for LH 53 implies an initial mass of ~20M_{sun}_ for the N49 progenitor star.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/402/509
- Title:
- uvby photometry of four MC eclipsing binaries
- Short Name:
- J/A+A/402/509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new accurate CCD uvby light curves for the LMC eclipsing binaries HV 982 and HV 12578, and for the SMC systems HV 1433 and HV 11284 obtained at the Danish 1.5m telescope at ESO, La Silla, equipped with a direct camera and CCD #28 (a thinned 1024x1024 Tek device), during several periods between November 1992 and November 1995. The light curves were derived from DoPHOT photometry, and typical accuracies are between 0.007 and 0.012mag per point. Standard uvby indices have also been established for each binary, primarily for determination of interstellar reddening and absorption. For HV 982 and HV 12578, accurate photometric elements have been established. Both systems consist of two detached components of comparable sizes in an eccentric orbit.
- ID:
- ivo://CDS.VizieR/J/MNRAS/349/833
- Title:
- uVI photometry of 3 LMC eclipsing binaries
- Short Name:
- J/MNRAS/349/833
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD differential photometry in the Stromgren u, Johnson V and Cousins I bands is presented of three hot, luminous eclipsing binary stars in the Magellanic Clouds. Observations were made between 1999 April and 2002 July using the McLellan Cassegrain 1-m telescope at MJUO in its f/7.7 configuration in conjunction with the CCD photometer head. The photometry has been extracted using the ISIS difference imaging method and is presented as normalized light.
- ID:
- ivo://CDS.VizieR/J/ApJ/771/13
- Title:
- UV-IR photometry of SMC stars
- Short Name:
- J/ApJ/771/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nature of the progenitors of Type Ia supernovae (SNe Ia) is still a mystery. While plausible candidates are known for both the single-degenerate and double-degenerate models, the observed numbers fall significantly short of what is required to reproduce the SNe Ia rate. Some of the most promising single-degenerate Type Ia progenitors are recurrent novae and super-soft sources (SSS). White dwarfs (WDs) with higher mass transfer rates can also be SN Ia progenitors. For these rapidly accreting white dwarfs (RAWDs), more material than is needed for steady burning accretes on the WD, and extends the WD's photosphere. Unlike SSS, such objects will likely not be detectable at soft X-ray energies, but will be bright at longer wavelengths, such as the far-ultraviolet (UV). Possible examples include LMC N66 and the V Sagittae stars. We present a survey using multi-object spectrographs looking for RAWDs in the central core of the Small Magellanic Cloud (SMC), from objects selected to be bright in the far-UV and with blue far UV-V colors. While we find some unusual objects, and recover known planetary nebula and Wolf-Rayet (WR) stars, we detect no candidate RAWD. The upper limits from this non-detection depend on our expectations of what an RAWD should look like, as well assumptions about the internal extinction of the SMC. Assuming they resemble LMC N66 or fainter versions of WR stars we set an upper limit of 10-14 RAWDs in the SMC. However, our survey is unlikely to detect objects like V Sge, and hence we cannot set meaningful upper limits if RAWDs generally resemble V Sge.
- ID:
- ivo://CDS.VizieR/J/AJ/113/1011
- Title:
- UV Observations of the SMC
- Short Name:
- J/AJ/113/1011
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A mosaic of four UIT (Ultraviolet Imaging Telescope) far-UV (FUV) ({lambda}_(eff)_=1620{AA}) images, with derived stellar and H II region photometry, is presented for most of the Bar of the SMC. The UV morphology of the SMC's Bar shows that recent star formation there has left striking features including: (a) four concentrations of UV-bright stars spread from northeast to southwest at nearly equal (~30arcmin=0.5kpc) spacings; (b) one of the concentrations, near DEM 55, comprises a well-defined 8-arcmin diameter ring surrounded by a larger H{alpha} ring, suggestive of sequential star formation. FUV PSF photometry is obtained for 11,306 stars in the FUV images, resulting in magnitudes m(162). We present a FUV luminosity function for the SMC Bar, complete to m(162)~14.5. Detected objects are well correlated with other SMC Population I material; of 711 H{alpha} emission-line stars and small nebulae within the UIT fields of view, 520 are identified with FUV sources. The FUV photometry is compared with available ground-based catalogs of supergiants, yielding 191 detections of 195 supergiants with spectral type earlier than F0 in the UIT fields. The (m(162)-V) color for supergiants is a sensitive measure of spectral type. The bluest observed colors for each type agree well with colors computed from unreddened Galactic spectral atlas stars for types earlier than about A0; for later spectral types the observed SMC stars range significantly bluer, as predicted by comparison of low-metallicity and Galactic-composition models. Redder colors for some stars of all spectral types are attributed to the strong FUV extinction arising from even small amounts of SMC dust. Internal SMC reddenings are determined for all catalog stars. All stars with E(B-V)>0.15 are within regions of visible H{alpha} emission. FUV photometry for 42 H{alpha} -selected H II regions in the SMC Bar is obtained for stars and for total emission (as measured in H II-region-sized apertures). The flux-weighted average ratio of total to stellar FUV flux is 2.15; consideration of the stellar FUV luminosity function indicates that most of the excess total flux is due to scattered FUV radiation, rather than stars fainter than m(162)=14.5. Both stellar and total emission are well correlated with H{alpha} fluxes measured by Kennicutt and Hodge (1986ApJ...306..130K), yielding FUV/H{alpha} flux ratios that are consistent with models of SMC metallicity, ages from 1-5Myr, and moderate (E(B-V)=0.0-0.1mag) internal SMC extinction. (Copyright) 1997 American Astronomical Society.
- ID:
- ivo://CDS.VizieR/J/A+A/377/945
- Title:
- Variability and spectra of LMC giants
- Short Name:
- J/A+A/377/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first cross-identifications of sources in the near-infrared DENIS survey and in the micro-lensing EROS survey in a field of about 0.5 square degrees around the optical center (OC) of the Large Magellanic Cloud. We analyze the photometric history of these stars in the EROS data base and obtain light-curves for about 800 variables. Most of the stars are long period variables (Miras and Semi-Regulars); a few Cepheids are also present. We also present new spectroscopic data on 126 asymptotic giant branch stars in the OC field, 30 previously known and 96 newly discovered by the DENIS survey. The visible spectra are used to assign a carbon- (C-) or oxygen-rich (O-rich) nature to the observed stars on the basis of the presence of molecular bands of TiO, VO, CN, C_2_. For the remaining of the stars we used the (J-K_S_) color to determine whether they are O-rich or C-rich. Plotting Log(period) versus K_S_ we find three very distinct period-luminosity relations, mainly populated by Semi-Regular stars of type a (SRa), b (SRb) and Mira variables. Carbon-rich stars occupy mostly the upper part of these relations. We find that 65% of the asymptotic giant branch population are long period variables (LPVs).
- ID:
- ivo://CDS.VizieR/J/ApJ/660/1486
- Title:
- Variability of LMC semiregular variables
- Short Name:
- J/ApJ/660/1486
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observational arguments supporting the binary explanation of the long secondary period (LSP) phenomenon in red giants are presented. Photometry of about 1200 semiregular variables with LSPs in the Large Magellanic Cloud is analyzed using the MACHO and OGLE photometry. For about 5% of these objects, additional ellipsoidal-like or eclipsing-like modulation with the same periods as the LSP is detectable. These double-humped variations are usually shifted in phase compared to LSP light curves. I discuss the model of a binary system with a red giant as the primary component and a low-mass object as the secondary. The mass lost by the red giant through the wind follows a spiral pattern in the orbit around the primary star and obscures it, causing LSP variations.
- ID:
- ivo://CDS.VizieR/J/AJ/140/14
- Title:
- Variability of luminous stars in LMC
- Short Name:
- J/AJ/140/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Motivated by the detection of a recent outburst of the massive luminous blue variable LMC-R71, which reached an absolute magnitude M_V_=-9.3mag, we undertook a systematic study of the optical variability of 1268 massive stars in the Large Magellanic Cloud, using a recent catalog by Bonanos et al. (2009, Cat. J/AJ/138/1003) as the input. The ASAS All Star Catalog provided well-sampled light curves of these bright stars spanning 10 years. Combining the two catalogs resulted in 599 matches, on which we performed a variability search. We identified 117 variable stars, 38 of which were not known before, despite their brightness and large amplitude of variation. We found 13 periodic stars that we classify as eclipsing binary (EB) stars, 8 of which are newly discovered bright massive EBs composed of OB-type stars. The remaining 104 variables are either semi- or non-periodic, the majority (85) being red supergiants (RSGs). Most (26) of the newly discovered variables in this category are also RSGs with only three B and four O stars.
- ID:
- ivo://CDS.VizieR/J/AJ/145/160
- Title:
- Variables in LMC globular clusters. III. Reticulum
- Short Name:
- J/AJ/145/160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the third in a series of papers studying the variable stars in old globular clusters in the Large Magellanic Cloud. The primary goal of this series is to look at how the characteristics and behavior of RR Lyrae stars in Oosterhoff-intermediate systems compare to those of their counterparts in Oosterhoff-I/II systems. In this paper we present the results of our new time-series BVI photometric study of the globular cluster Reticulum. We found a total of 32 variables stars (22 RRab, 4 RRc, and 6 RRd stars) in our field of view. We present photometric parameters and light curves for these stars. We also present physical properties, derived from Fourier analysis of light curves, for some of the RR Lyrae stars. We discuss the Oosterhoff classification of Reticulum and use our results to re-derive the distance modulus and age of the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/144/186
- Title:
- Variables in LMC globular clusters. II. NGC 1786
- Short Name:
- J/AJ/144/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B-V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters.
