Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/462/1081
- Title:
- BVRIJHK light curves of 4U 0115+63/V635 Cas
- Short Name:
- J/A+A/462/1081
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 4U 0115+63 is one of the most active and best studied Be/X-ray transients. Previous studies of 4U 0115+63 have led to the suggestion that 4U 0115+63 undergoes relatively fast quasi-cyclic activity. However, due to the lack of good coverage of the observations, the variability time scales are uncertain. Our objective is to investigate the long-term behaviour of 4U 0115+63/V635 Cas to confirm its quasi-cyclic nature and to explain its correlated optical/IR and X-ray variability. We have performed optical/IR photometric observations and optical spectroscopic observations of 4U 0115+63/V635 Cas over the last decade with unprecedented coverage. We have focused on the H{alpha} line variability and the long-term changes of the photometric magnitudes and colours and investigated these changes in correlation with the X-ray activity of the source.
- ID:
- ivo://CDS.VizieR/J/ApJS/133/413
- Title:
- BVRIJHK photometry of cool white dwarfs
- Short Name:
- J/ApJS/133/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A detailed photometric and spectroscopic analysis of cool (T_eff_<~12000K) white dwarf stars is presented. The sample has been drawn from the Yale Parallax Catalog and from a proper motion survey in the southern hemisphere. Optical BVRI and infrared JHK photometry, as well as spectroscopy at H{alpha}, have been secured for a sample of 152 white dwarfs. The discovery of seven new DA white dwarfs, two new DQ white dwarfs, one new magnetic white dwarf, and three weak magnetic white dwarf candidates, is reported. Our sample also identifies 19 known or suspected double degenerates.
- ID:
- ivo://CDS.VizieR/J/A+A/385/884
- Title:
- BVRIJHK photometry of 27 post-AGB candidates
- Short Name:
- J/A+A/385/884
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BVRIJHK photometric observations are presented for 27 post-AGB candidates. Almost all objects show a double peaked spatial energy distribution (SED) curve in the optical to far-infrared wavelengths. Seventeen objects were classified as post-AGB stars on the basis of their spectral type, location in the IRAS color-color diagram and SED. The physical parameters of the observed post-AGB stars, the inner radius of the detached shell, the mass of the shell and the distance were derived using the simple dust shell model. We compared our observational sequence of post-AGB objects to the theoretical evolutionary sequence (Schoenberner, 1983ApJ...272..708S; Bloecker, 1995, Cat. <J/A+A/299/755>) in the stellar temperatures versus age diagram. We found that two post-AGB stars, IRAS 05040+4820 and 08187-1905, have low stellar temperature with a large dynamical age of the dust shell. They appear to provide the first observational evidence that some low-mass stars bypass the planetary nebulae stage because of their slow increase in stellar temperature.
- ID:
- ivo://CDS.VizieR/J/MNRAS/289/729
- Title:
- BVRIJHK photometry of red LMC supergiants
- Short Name:
- J/MNRAS/289/729
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (BV)_J_(RI)_C_ observations for 185 and additional JHK observations for 53 red supergiant candidates in the Large Magellanic Cloud (LMC) are presented. The data have been reduced discussing carefully the dependence of effective wavelengths on the spectral energy distribution of the star, which is very strong especially for the Cousins R band. Non-linear colour dependences of transformation coefficients vor the V magnitude and the R-I colour have been taken into account. The mean error of the BVRI data is 0.03 to 0.04 mag, while that of the JHK observations is 0.02mag. The MK types are not given to the stars, as the classifications given in the literature are mostly very uncertain. The spectra we have obtained for 88 of the stars will be discussed in a forthcoming paper where we will give directly physical properties like Mbol and Teff instead of MK types. Most of the stars are supergiants of type late K to early M.
- ID:
- ivo://CDS.VizieR/J/ApJ/743/118
- Title:
- BVRIJHK photometry of the 2008 OT in NGC 300
- Short Name:
- J/ApJ/743/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 2008 optical transient in NGC 300 is one of a growing class of intermediate-luminosity transients that brighten several orders of magnitude from a previously optically obscured state. The origin of their eruptions is not understood. Our multi-wavelength photometry and spectroscopy from maximum light to more than a year later provide a record of its post-eruption behavior. We describe its changing spectral energy distribution, the evolution of its absorption- and emission-line spectrum, the development of a bipolar outflow, and the rapid transition from a dense wind to an optically thin ionized wind. In addition to strong, narrow hydrogen lines, the F-type absorption-line spectrum of the transient is characterized by strong CAII and [CAII] emission. The very broad wings of the CAII triplet and the asymmetric [CAII] emission lines are due to strong Thomson scattering in the expanding ejecta. Post-maximum, the hydrogen and CaII lines developed double-peaked emission profiles that we attribute to a bipolar outflow. Between approximately 60 and 100 days after maximum, the F-type absorption spectrum, formed in its dense wind, weakened and the wind became transparent to ionizing radiation. We discuss the probable evolutionary state of the transient and similar objects such as SN 2008S and conclude that they were most likely post-red supergiants or post-asymptotic giant branch stars on a blue loop to warmer temperatures when the eruption occurred. These objects are not luminous blue variables.
- ID:
- ivo://CDS.VizieR/J/AJ/128/2316
- Title:
- BVRIJHKs photometry in sigma Ori cluster
- Short Name:
- J/AJ/128/2316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report an optical photometric survey of 0.89deg^2^ of the Orion OB1b association centered on sigma Ori. This region includes most of the sigma Ori cluster, the highest-density region within Orion OB1b. We have developed a statistical procedure to identify the young, low-mass, pre-main-sequence population of the association. We estimate that the cluster has 160 members in the mass range (0.2M_{sun}_<=M<=1.0M_{sun}_). The cluster has a radius of 35pc and an estimated age of 2.5+/-0.3Myr. We estimate that the total mass of the cluster is 225+/-30M_{sun}_. This mass is similar to the estimated mass of the ~5x10^5^yr old cluster NGC 2024. NGC 2024 and sigma Ori appear to be a well-matched pair of clusters, except for the ~2Myr difference in their ages.
- ID:
- ivo://CDS.VizieR/J/A+A/415/521
- Title:
- BVRIJK and velocities for MC Cepheids
- Short Name:
- J/A+A/415/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high precision and well sampled BVRIJK light curves and radial velocity curves for a sample of five (+1) Cepheids in the SMC. In addition we present radial velocity curves for five (+1) Cepheids in the LMC. The low metallicity ([Fe/H]~-0.7) SMC stars have been selected for use in a Baade-Wesselink type analysis to constrain the metallicity effect on the Cepheid Period-Luminosity relation. The stars have periods of around 15 days so they are similar to the Cepheids observed by the Extragalactic Distance Scale Key Project on the Hubble Space Telescope. We show that the stars are representative of the SMC Cepheid population at that period and thus will provide a good sample for the proposed analysis. The actual Baade-Wesselink analysis are presented in Strom et al., 2004, Cat. <J/A+A/415/531>.
- ID:
- ivo://CDS.VizieR/J/A+A/416/1037
- Title:
- BVRIK Photometry for the field of 4U 0142+61
- Short Name:
- J/A+A/416/1037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new optical and infrared observations of the counterpart to the Anomalous X-ray Pulsar (AXP) 4U 0142+61 taken with the Keck I telescope. The counterpart is found to be variable in the infrared. This contrasts with our optical observations, which do not show any evidence for variability. Apart from the variability the AXP shows a remarkable spectral energy distribution. In particular, we find a sudden drop in flux going from V to B, presumably due to a spectral feature. We compare our results to those obtained for the two other securely identified AXP counterparts, to 1E 2259+586 and 1E 1048.1-5937. 4U 0142+61 is very similar to the former source in its X-ray timing and spectral properties, and we find that this similarity extends to the quiescent infrared to X-ray flux ratio. For 1E 1048.1-5937, which has different X-ray properties, the situation is less clear: in one observation, the infrared to X-ray flux ratio was much larger, but another observation gave an upper limit which is consistent with that observed for 4U 0142+61. Assuming the quiescent ratios are all similar, we estimate the optical and infrared brightnesses for the three AXPs that remain to be identified as well as for the four Soft Gamma-ray Repeaters. We also discuss briefly how the observed optical and infrared emission might arise, in particular in the context of the magnetar model.
- ID:
- ivo://CDS.VizieR/J/A+A/425/797
- Title:
- BVRIK photometry of A2163B galaxies
- Short Name:
- J/A+A/425/797
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed analysis of the photometric properties of galaxies in the cluster A2163B at redshift z~0.2 . R-, I- and K-band structural parameters, (half light radius Re, mean surface brightness <{mu}>e within Re and Sersic index n) are derived for N~60 galaxies, and are used to study their internal colour gradients.
