- ID:
- ivo://CDS.VizieR/J/ApJ/880/155
- Title:
- RI photometry of blazars S5 0716+714 and 3C 273
- Short Name:
- J/ApJ/880/155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric observations of blazars S5 0716+714 and 3C 273 with high temporal resolution (30-60s) in the I or R bands. The observations were performed with a 1.02m optical telescope from 2007 March 7 to 2012 May 16. The F-test, one-way analysis of variance (ANOVA) test, and z-transformed discrete correlation function (ZDCF) cross-correlation zero lag test are used to search for intra-day variability (IDV). Four and five reliable IDVs survive three tests for S5 0716+714 and 3C 273, respectively. IDVs are found for S5 0716+714 and 3C 273. A flare on 2008 May 8 has {Delta}I~0.06+/-0.01mag in a duration of 0.54hr for S5 0716+714. A flare on 2011 May 10 shows {Delta}R~0.05+/-0.01mag in a duration of 0.40hr for 3C 273. Sharp dips appear on 2011 May 9 for 3C 273 and show {Delta}R~0.05+/-0.01mag. Under the assumptions that the IDV is tightly connected to black hole mass, M*, and that the flare durations are representative of the minimum characteristic timescales, we can estimate upper bounds to M*. In the case of the Kerr black holes, M*<~10^8.91^M_{sun}_ and M*<~10^9.02^M_{sun}_ are given for S5 0716+714 and 3C 273, respectively. These mass measurements are consistent with those measurements reported in the literature. Also, we discuss the origins of optical variations found in this work.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/94/749
- Title:
- RI photometry of cool dwarfs
- Short Name:
- J/ApJS/94/749
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The luminosity function at the end of the main sequence is determined from V, R, and I data taken by the CCD/Transit Instrument (CTI), a dedicated telescope surveying an 8.25' wide strip of sky centered at {delta}=+28{deg}, thus sampling Galactic latitudes of +90{deg} down to -35{deg}. A selection of 133 objects chosen via R-I and V-I colors has been observed spectroscopically at the 4.5m Multiple Mirror Telescope to assess contributions by giants and subdwarfs and to verify that the reddest targets are objects of extremely late spectral class. Eighteen dwarfs of type M6 or later have been discovered, with the latest being of type M8.5. Data used for the determination of the luminosity function cover 27.3{deg}^2^ down to a completeness limit of R=19.0.
- ID:
- ivo://CDS.VizieR/J/A+A/418/33
- Title:
- RI photometry of C stars in NGC 147
- Short Name:
- J/A+A/418/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have imaged a 42'x28' field centered on the spheroidal galaxy NGC 147 to study its AGB population and determine the main structural properties of this M31 companion. This field was observed through two broadband (R and I) and two narrowband (CN and TiO) filters, following the standard approach of our systematic survey of C stars in nearby galaxies. We identified 288 C stars in NGC 147. The average I-magnitude of such sample of C stars is <I>=20.31 with {sigma}=0.40. If we adopt a distance modulus {mu}0=24.39, derived from the luminosity of both the tip of the red giant branch (TRGB) and the horizontal branch (HB) by Han et al. (1997, Cat. <J/AJ/113/1001>, we conclude that the average absolute I-magnitude of C stars is <M_I_>=-4.39, thus slightly under luminous with respect to what was found for other galaxies in our survey.
- ID:
- ivo://CDS.VizieR/J/A+A/369/932
- Title:
- RI photometry of LMC carbon stars
- Short Name:
- J/A+A/369/932
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue of 7760 carbon stars in the Large Magellenic Cloud is presented. The stars were identified during a systematic survey of objective-prism plates taken with the UK 1.2m Schmidt Telescope. The catalogue is compared with other lists of carbon stars and the distribution of the carbon stars is discussed.
- ID:
- ivo://CDS.VizieR/J/PASP/118/659
- Title:
- RI photometry of 2MASS late M and L dwarfs
- Short Name:
- J/PASP/118/659
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report R and I band observations for 201 late M and L dwarfs selected on the basis of Two Micron All Sky Survey (Cat. II/246) JHKs and photographic red colors, made with a telescope of modest aperture. It is shown that deep surveys covering these red bands can provide data sets that complement JHKs, permitting a fairly good photometric classification system for L dwarfs. Due primarily to the disappearance of strong TiO opacities, R-I reaches a maximum at late M type and turns blueward for subtypes M9 to about L3. Apart from a small plateau at L0-L2, the I-Ks color remains as a monotonic measure of spectral type or temperature over this range, and likewise for M dwarfs. For late L types, both colors probably get redder again, although the accuracy of our data and number of objects do not give us robust conclusions by L6-L8. It is also interesting to look at the dispersions of the IJKs bands at a given spectral type. It is widely believed that this dispersion is caused by object-to-object variations in the amount, location, or other properties of dust or clouds. We find a moderately larger spread for the J-Ks color than for I-J.
- ID:
- ivo://CDS.VizieR/J/A+A/417/479
- Title:
- RI photometry of NGC 185 carbon stars
- Short Name:
- J/A+A/417/479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the CFH12K wide field camera to survey the carbon star population of NGC 185 using the CN-TiO technique. 145 C stars are identified with a mean <I>=19.99+/-0.05, corresponding to <M_I_>=-4.41+/-0.05, a mean luminosity similar to what was recently found for the C star population of NGC 147. The stellar surface density profile of NGC 185 follows a power law with an exponential scale length of 2.53+/-0.07'. The surface density of C stars follows also a power law but with a smaller scale length, 1.56+/-0.06, demonstrating that the intermediate-age population of NGC 185 is more concentrated than its old population. A tidal radius, r_t_=22.5+/-2.2' is determined from red giant star counts. The C/M ratio of NGC 185 is 0.17+/-0.02 with no apparent sign of a radial gradient. We compare the carbon star populations of NGC 185 and NGC 147 to conclude that it is unlikely that they form a close pair.
- ID:
- ivo://CDS.VizieR/J/AJ/125/3037
- Title:
- RI photometry of NGC 205 carbon stars
- Short Name:
- J/AJ/125/3037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a CFH12K survey of the carbon stars in NGC 205 and its surrounding field. We find that the number of C stars in NGC 205 is low (~500) for its luminosity and that very few C stars are seen outside of the 10 isophote, suggesting tidal stripping by M31. Their <M_I_>=-4.54, a magnitude nearly identical to what has been found in other galaxies with numerous C stars. Stars with accurate (R-I) photometry, to I~22.5, are used to determine the outer profile of NGC 205.
- ID:
- ivo://CDS.VizieR/J/ApJS/202/19
- Title:
- riz photometry in Cyg OB2
- Short Name:
- J/ApJS/202/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to fully understand the gravitational collapse of molecular clouds, the star formation process, and the evolution of circumstellar disks, these phenomena must be studied in different Galactic environments with a range of stellar contents and positions in the Galaxy. The young massive association Cygnus OB2, in the Cygnus-X region, is a unique target to study how star formation and the evolution of circumstellar disks proceed in the presence of a large number of massive stars. We present a catalog obtained with recent optical observations in the r, i, z filters with OSIRIS, mounted on the 10.4m Gran Telescopio CANARIAS telescope, which is the deepest optical catalog of CygOB2 to date. The catalog consists of 64,157 sources down to M=0.15M_{sun}_ at the adopted distance and age of Cyg OB2. A total of 38,300 sources have good photometry in all three bands. We combined the optical catalog with existing X-ray data of this region, in order to define the cluster locus in the optical diagrams. The cluster locus in the r-i versus i-z diagram is compatible with an extinction of the optically selected cluster members in the 2.64m<A_V_<5.57m range. We derive an extinction map of the region, finding a median value of A_V_=4.33m in the center of the association, decreasing toward the northwest. In the color-magnitude diagrams, the shape of the distribution of main-sequence stars is compatible with the presence of an obscuring cloud in the foreground ~850+/-25pc from the Sun.
- ID:
- ivo://CDS.VizieR/J/A+A/419/249
- Title:
- RJHKs photometry of sigma Ori low-mass stars
- Short Name:
- J/A+A/419/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Coordinates and photometry of probable cluster members in the sigma Ori cluster. Time series observations of this cluster were carried out using the CCD cameras at the 2m Schmidt telescope of the Thuringer Landessternwarte Tautenburg (TLS) and the 1.23m telescope on Calar Alto (CA). From these images, we derived coordinates (columns 2 and 3) as well as photometry in the R- and I-band (columns 5 and 6). Additional near- infrared photometry in J, H, K comes from the 2MASS database (columns 7-9). The cluster member selection is based on (I,I-J) colour magnitude diagrams. The R-I and J-H colours were used to reject contaminating field stars. The column 4 indicates whether the object was identified with the CA photometry (c), the TLS photometry (t), or both. The masses given in column 10 were estimated by comparing the near-infrared photometry with the evolutionary tracks of Baraffe et al. (1998A&A...337..403B). These tracks cover the mass range from 0.02 to 1.4 solar masses, for some objects with lower or higher masses we give upper or lower mass limits. The last two columns contain information about the results of the time series analysis. Column 10 gives the RMS of the CA lightcurve for targets No 1-52 and the RMS of the TLS lightcurve for all others. The last column indicates whether the target is classified as variable (v) and/or periodically variable (p). For a few objects, time series analysis was not possible, because they are either too faint or too bright in most of the images.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A56
- Title:
- R136 JKs photometry from VLT/SPHERE EAO
- Short Name:
- J/A+A/602/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the sharpest near-IR images of the massive cluster R 136 to date, based on the extreme adaptive optics of the SPHERE focal instrument implemented on the ESO Very Large Telescope and operated in its IRDIS imaging mode. The crowded stellar population in the core of the R 136 starburst compact cluster remains still to be characterized in terms of individual luminosities, age, mass and multiplicity. SPHERE/VLT and its high contrast imaging possibilities open new windows to make progress on these questions. Stacking-up a few hundreds of short exposures in J and Ks spectral bands over a Field of View (FoV) of 10.9"x12.3" centered on the R136a1 stellar component, enabled us to carry a refined photometric analysis of the core of R136. We detected 1110 and 1059 sources in J and Ks images respectively with 818 common sources. Thanks to better angular resolution and dynamic range for 818 common sources being detected, we found that more than 62.6% (16.5%) of the stars, detected both in J and Ks data, have neighbours closer than 0.2" (0.1"). The closest stars are resolved down to the full width at half maximum (FWHM) of the point spread function (PSF) measured by Starfinder. Among newly resolved and/or detected sources R136a1 and R136c are found to have optical companions and R136a3 is resolved as two stars (PSF fitting) separated by 59+/-2mas. This new companion of R136a3 presents a correlation coefficient of 86% in J and 75% in Ks. The new set of detected sources were used to re-assess the age and extinction of R 136 based on 54 spectroscopically stars that have been recently studied with HST slit-spectroscopy (Crowther et al., 2016MNRAS.458..624C) of the core of this cluster. Over 90% of these 54 sources identified visual companions (closer than 0.2"). We found the most probable age and extinction for these sources are 1.8+1.2-0.8Myr, A_J_=(0.45+/-0.5)mag and A_K_=(0.2+/-0.5) mag within the photometric and spectroscopic error-bars. Additionally, using PARSEC evolutionary isochrones and tracks, we estimated the stellar mass range for each detected source (common in J and K data) and plotted the generalized histogram of mass (MF with error-bars). Using SPHERE data, we have gone one step further and partially resolved and studied the IMF covering mass range of (3-300)M_{sun}_ at the age of 1 and 1.5Myr. The density in the core of R 136 (0.1-1.4pc) is estimated and extrapolated in 3D and larger radii (up to 6pc). We show that the stars in the core are still unresolved due to crowding, and the results we obtained are upper limits. Higher angular resolution is mandatory to overcome these difficulties.