- ID:
- ivo://CDS.VizieR/J/AJ/117/1708
- Title:
- NGC 1741 HST photometry
- Short Name:
- J/AJ/117/1708
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Hubble Space Telescope (HST) Faint Object Camera (FOC) ultraviolet (UV) and WFPC2 optical images in conjunction with UV spectroscopic observations taken with the Goddard High Resolution Spectrograph to examine the star formation history and properties of the interacting galaxy system NGC 1741 in the Hickson Compact Group 31. The high spatial resolution afforded by HST has allowed us to identify a large number of starburst knots, or "superstar clusters" (SSCs), in the starburst regions of this system. Photometry of these SSCs in the UV and optical bands indicates that most of these objects have ages of a few Myr, with a few up to ~100Myr, and masses between 10^4^ and 10^6^M_{sun}_. The estimated age is confirmed by a spectral synthesis analysis of one knot for which we have obtained a UV spectrum. The V-band luminosity function of the SSCs is well represented by a power law {Phi}(L)~L^-{alpha}^ with an index of -1.85, with no evidence of a turnover brighter than the completeness limit. These properties are in good agreement with those found for SSCs in other starburst galaxies. Our results support the suggestion that some of these SSCs may be extremely young globular clusters formed in a relatively recent starburst episode that has been triggered by a merger event.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/423/2901
- Title:
- NGC 6752 multiwavelength survey
- Short Name:
- J/MNRAS/423/2901
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a multiwavelength (far-ultraviolet to I band) survey of the stellar populations of the globular cluster NGC 6752, using Space Telescope Imaging Spectrograph (STIS, FUV, 2001/03/01), Advanced Camera for Surveys (ACS, VI on 2006/06/24) and Wide Field Camera 3 (WFC3, NUV on 2010/07/31, 2010/08/07 and 2010/08/21, and UB on 2010/05/1-5) on board the Hubble Space Telescope. We have confirmed that two previously identified cataclysmic variable (CV) candidates are, in fact, dwarf novae which underwent outbursts during our observations. We have also identified previously unknown optical counterparts to two X-ray sources.
- ID:
- ivo://CDS.VizieR/J/AJ/140/1975
- Title:
- Normal spiral galaxies optical and UV photometry
- Short Name:
- J/AJ/140/1975
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We compare the UV-optical colors of a well-defined set of optically selected pre-merger interacting galaxy pairs with those of normal spirals. The shorter wavelength colors show a larger dispersion for the interacting galaxies than for the spirals. This result can best be explained by higher star formation rates on average in the interacting galaxies, combined with higher extinctions on average. This is consistent with earlier studies which found that the star formation in interacting galaxies tends to be more centrally concentrated than in normal spirals, perhaps due to gas being driven into the center by the interaction. As noted in earlier studies, there is a large variation from galaxy to galaxy in the implied star formation rates of the interacting galaxies, with some galaxies having enhanced rates but others being fairly quiescent.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/23
- Title:
- NUV and FUV measurements of planet host stars
- Short Name:
- J/ApJ/890/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We search for evidence of the cause of the exoplanet radius gap, i.e., the dearth of planets with radii near 1.8R_{Earth}_. If the cause were photoevaporation, the radius gap should trend with proxies for the early-life high-energy emission of the planet-hosting stars. If, alternatively, the cause were core-powered mass loss, no such trends should exist. Critically, spurious trends between the radius gap and stellar properties arise from an underlying correlation with instellation. After accounting for this underlying correlation, we find that no trends remain between the radius gap and stellar mass or present-day stellar activity as measured by near-UV emission. We dismiss the nondetection of a radius gap trend with near-UV emission because present-day near-UV emission is unlikely to trace early-life high-energy emission, but we provide a catalog of Galaxy Evolution Explorer near-UV and far-UV emission measurements for general use. We interpret the nondetection of a radius gap trend with stellar mass by simulating photoevaporation with mass-dependent evolution of stellar high-energy emission. The simulation produces an undetectable trend between the radius gap and stellar mass under realistic sources of error. We conclude that no evidence, from this analysis or others in the literature, currently exists that clearly favors either photoevaporation or core-powered mass loss as the primary cause of the exoplanet radius gap. However, repeating this analysis once the body of well-characterized <4R_{Earth}_ planets has roughly doubled could confirm or rule out photoevaporation.
- ID:
- ivo://CDS.VizieR/J/ApJ/873/L3
- Title:
- NUV to NIR photometry of type IIP ASASSN-16at
- Short Name:
- J/ApJ/873/L3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report distinctly double-peaked H{alpha} and H{beta} emission lines in the late-time, nebular-phase spectra (>~200 days) of the otherwise normal at early phases (<~100 days) type IIP supernova ASASSN-16at (SN2016X). Such distinctly double-peaked nebular Balmer lines have never been observed for a type II SN. The nebular-phase Balmer emission is driven by the radioactive ^56^Co decay, so the observed line profile bifurcation suggests a strong bipolarity in the ^56^Ni distribution or in the line-forming region of the inner ejecta. The strongly bifurcated blueshifted and redshifted peaks are separated by ~3x10^3^km/s and are roughly symmetrically positioned with respect to the host-galaxy rest frame, implying that the inner ejecta are composed of two almost-detached blobs. The red peak progressively weakens relative to the blue peak, and disappears in the 740 days spectrum. One possible reason for the line-ratio evolution is increasing differential extinction from continuous formation of dust within the envelope, which is also supported by the near-infrared flux excess that develops after ~100 days.
- ID:
- ivo://CDS.VizieR/II/83
- Title:
- OAO2 filter Photometry of 531 stars
- Short Name:
- II/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog contains the ultraviolet photometry of 531 stars observed with the Wisconsin Experiment Package aboard the Orbiting Astronomical Observatory (OAO-2). The data were obtained with medium-band interference filters and have been reduced to a uniform magnitude system. The ultraviolet magnitudes contained in the catalog have been published by Code et al. (1980). While the published tables contain 11 tabulated magnitudes, the machine version includes a twelfth filter (S2F2 at 2945 A). The catalog includes cross identifications to the numbering systems of the Bright Star Catalogue, The Henry Draper Catalogue, and the GC, star name, spectral type, V magnitude, B-V, U-B, references, remarks, and 12 ultraviolet magnitudes. The effective wavelengths (for a flat spectrum source) are 4250A, 3320A, 2980A, 2965A, 2460A, 2380A, 2035A, 1910A, 1680A, 1550A, 1430A, and 1330A. For most filters, the full width, half maximum is about 30% of the central wavelength.
- ID:
- ivo://CDS.VizieR/J/ApJS/98/595
- Title:
- OB associations in M31
- Short Name:
- J/ApJS/98/595
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Images of the central and southern parts of the local group Sb spiral galaxy M31 were obtained by the Ultraviolet Imaging Telescope during the Astro-1 Spacelab mission. Stellar photometry is obtained for 611 stars in 59 van den Bergh associations in the near-UV A1 band (central wavelength 2490A), and for 130 of these stars in the far-UV B1 band (central wavelength 1520A). In addition, B-band magnitudes for 456 of the stars in ~30 associations, together with U- and R-band photometry for ~290 stars in ~15 associations are determined from CCD images. B-magnitudes from the catalog of Magnier et al. (1992A&AS...96..379M) are given for 137 stars and R-magnitudes for 233 stars. Stellar positions are obtained from the ground-based CCD images and from UIT images. Total fluxes in the UV bands are measured for 63 associations. Finding charts are presented in the NUV and FUV bands, as well as one optical band. Tables give the images utilized in this investigation, the associations observed, with positions, total UV fluxes, extinctions estimated from color-magnitude diagrams, and stellar positions with photometry in up to five bands. UV color magnitude diagrams are presented with extinctions estimated by comparing the observed association color magnitude diagrams with colors and magnitudes of early-type stars computed from the IUE spectral atlas of Fanelli et al. (1992ApJS...82..197F). Comparison with evolutionary models suggests a maximum initial mass ~85M_{sun}_. Ultraviolet extinction within most M31 OB associations is found to follow an extinction curve similar to that of Hutchings et al. (1992ApJ...400L..35H). The variation in the fraction of near-UV stars also measured in the far-UV among the associations is probably caused by variations in age, extinction, and the degree of foreground contamination.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/L114
- Title:
- OGLE16aaa UVOT light curves
- Short Name:
- J/MNRAS/465/L114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery and first three months of follow-up observations of a currently on-going unusual transient detected by the Optical Gravitational Lensing Experiment (OGLE-IV) survey, located in the centre of a galaxy at redshift z=0.1655. The long rise to absolute magnitude of -20.5mag, slow decline, very broad He and H spectral features make OGLE16aaa similar to other optical/UV tidal disruption events (TDEs). Weak narrow emission lines in the spectrum and archival photometric observations suggest the host galaxy is a weak-line active galactic nucleus, which has been accreting at higher rate in the past. OGLE16aaa, along with SDSS J0748, seems to form a sub-class of TDEs by weakly or recently active supermassive black holes (SMBHs). This class might bridge the TDEs by quiescent SMBHs and flares observed as "changing-look quasars", if we interpret the latter as TDEs. If this picture is true, the previously applied requirement for identifying a flare as a TDE that it had to come from an inactive nucleus, could be leading to observational bias in TDE selection, thus affecting TDE-rate estimations.
- ID:
- ivo://CDS.VizieR/J/AJ/108/1350
- Title:
- Omega Cen FUV photometry
- Short Name:
- J/AJ/108/1350
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present far-ultraviolet images of the globular cluster {omega} Centauri obtained with the Ultraviolet Imaging Telescope (UIT) during the 1990 December Astro-1 mission. A total of 1957 sources are detected at 1620{AA} to a limiting UV magnitude of 16.4 in the central 24' diameter region of the field and a limit of 15.6 over the remainder of the 40' diameter field. Over 1400 of these sources are matched with stars on a Stroemgren u band CCD frame obtained with the CTIO 0.9m telescope to produce a (far-UV, u) color-magnitude diagram. Completeness of the sample and error estimates are determined by photometry of artificial stars added to the images. The horizontal branch (HB) of the CMD is heavily populated hotter than 9000K. A large number of "extreme HB" stars are found hotter than a conspicuous break in the HB at Te~16000K. There is also a significant population of stars above the HB, the brightest of which is 4mag brighter than the HB. Most of the hotter of these appear to be "AGB-manque" or "Post-Early Asymptotic Giant Branch" stars. We compare the observations to recent theoretical evolutionary tracks for the zero-age HB and subsequent phases. The tracks match the data well, with the exception of the hotter HB stars, many of which fall below the zero-age horizontal branch. It is unclear as yet whether these are a special population or an artifact of errors in the models or photometry. We identify 33 stars with Te>~50000K, which are hotter than zero-age HB stars with envelope masses of 0.003M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/AJ/148/1
- Title:
- Optical and ultraviolet photometry of SN 2012fr
- Short Name:
- J/AJ/148/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extensive optical and UltraViolet (UV) observations of the type Ia supernova (SN Ia) 2012fr are presented in this paper. It has a relatively high luminosity, with an absolute B-band peak magnitude of about -19.5mag and a smaller post-maximum decline rate than normal SNe Ia (e.g., {Delta}m_15_(B)=0.85+/-0.05mag). Based on the UV and optical light curves, we derived that a ^56^Ni mass of about 0.88M_{sun}_ was synthesized in the explosion. The earlier spectra are characterized by noticeable high-velocity features of Si II {lambda}6355 and Ca II with velocities in the range of ~22000-25000km/s. At around the maximum light, these spectral features are dominated by the photospheric components which are noticeably narrower than normal SNe Ia. The post-maximum velocity of the photosphere remains almost constant at ~12000km/s for about one month, reminiscent of the behavior of some luminous SNe Ia like SN 1991T. We propose that SN 2012fr may represent a subset of the SN 1991T-like SNe Ia viewed in a direction with a clumpy or shell-like structure of ejecta, in terms of a significant level of polarization reported in Maund et al. (2013MNRAS.433L..20M).