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23381. UVOT imaging of M81 and Holmberg IX
ID:
ivo://CDS.VizieR/J/AJ/141/205
Title:
UVOT imaging of M81 and Holmberg IX
Short Name:
J/AJ/141/205
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Swift UV/Optical Telescope (UVOT) imaging of the galaxies M81 and Holmberg IX. We combine UVOT imaging in three near-ultraviolet (NUV) filters (uvw2: 1928{AA}; uvm2: 2246{AA}; uvw1: 2600{AA}) with ground-based optical imaging from the Sloan Digital Sky Survey to constrain the stellar populations of both galaxies. Our analysis consists of three different methods. First, we use the NUV imaging to identify UV star-forming knots and then perform spectral energy distribution (SED) modeling on the UV/optical photometry of these sources. Second, we measure surface brightness profiles of the disk of M81 in the NUV and optical. Lastly, we use SED fitting of individual pixels to map the properties of the two galaxies.
23382. UVOT light curves of supernovae
ID:
ivo://CDS.VizieR/J/AJ/137/4517
Title:
UVOT light curves of supernovae
Short Name:
J/AJ/137/4517
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present ultraviolet (UV) observations of supernovae (SNe) obtained with the UltraViolet/Optical Telescope (UVOT) on board the Swift spacecraft. This is the largest sample of UV light curves from any single instrument and covers all major SN types and most subtypes.
23383. UVOT photometry of Super-Chandrasekhar mass SNe Ia
ID:
ivo://CDS.VizieR/J/ApJ/787/29
Title:
UVOT photometry of Super-Chandrasekhar mass SNe Ia
Short Name:
J/ApJ/787/29
Date:
21 Oct 2021
Publisher:
CDS
Description:
Among Type Ia supernovae (SNe Ia), a class of overluminous objects exist whose ejecta mass is inferred to be larger than the canonical Chandrasekhar mass. We present and discuss the UV/optical photometric light curves, colors, absolute magnitudes, and spectra of three candidate Super-Chandrasekhar mass SNe - 2009dc, 2011aa, and 2012dn - observed with the Swift Ultraviolet/Optical Telescope. The light curves are at the broad end for SNe Ia, with the light curves of SN 2011aa being among the broadest ever observed. We find all three to have very blue colors which may provide a means of excluding these overluminous SNe from cosmological analysis, though there is some overlap with the bluest of "normal" SNe Ia. All three are overluminous in their UV absolute magnitudes compared to normal and broad SNe Ia, but SNe 2011aa and 2012dn are not optically overluminous compared to normal SNe Ia. The integrated luminosity curves of SNe 2011aa and 2012dn in the UVOT range (1600-6000 {AA}) are only half as bright as SN 2009dc, implying a smaller ^56^Ni yield. While it is not enough to strongly affect the bolometric flux, the early time mid-UV flux makes a significant contribution at early times. The strong spectral features in the mid-UV spectra of SNe 2009dc and 2012dn suggest a higher temperature and lower opacity to be the cause of the UV excess rather than a hot, smooth blackbody from shock interaction. Further work is needed to determine the ejecta and ^56^Ni masses of SNe 2011aa and 2012dn and to fully explain their high UV luminosities.
23384. UVOT, ZTF gri LCs and spectra of the SN Ia 2019yvq
ID:
ivo://CDS.VizieR/J/ApJ/898/56
Title:
UVOT, ZTF gri LCs and spectra of the SN Ia 2019yvq
Short Name:
J/ApJ/898/56
Date:
16 Mar 2022 00:53:53
Publisher:
CDS
Description:
Early observations of Type Ia supernovae (SNe Ia) provide essential clues for understanding the progenitor system that gave rise to the terminal thermonuclear explosion. We present exquisite observations of SN 2019yvq, the second observed SN Ia, after iPTF 14atg, to display an early flash of emission in the ultraviolet (UV) and optical. Our analysis finds that SN 2019yvq was unusual, even when ignoring the initial flash, in that it was moderately underluminous for an SN Ia (M_g_~-18.5mag at peak) yet featured very high absorption velocities (v~15000km/s for SiII{lambda}6355 at peak). We find that many of the observational features of SN 2019yvq, aside from the flash, can be explained if the explosive yield of radioactive 56Ni is relatively low (we measure M_56Ni_=0.31+/-0.05M_{sun}_) and it and other iron-group elements are concentrated in the innermost layers of the ejecta. To explain both the UV/optical flash and peak properties of SN 2019yvq we consider four different models: interaction between the SN ejecta and a nondegenerate companion, extended clumps of ^56^Ni in the outer ejecta, a double-detonation explosion, and the violent merger of two white dwarfs. Each of these models has shortcomings when compared to the observations; it is clear additional tuning is required to better match SN 2019yvq. In closing, we predict that the nebular spectra of SN 2019yvq will feature either H or He emission, if the ejecta collided with a companion, strong [CaII] emission, if it was a double detonation, or narrow [OI] emission, if it was due to a violent merger.
23385. UV photometry in M79
ID:
ivo://CDS.VizieR/J/AJ/112/601
Title:
UV photometry in M79
Short Name:
J/AJ/112/601
Date:
21 Oct 2021
Publisher:
CDS
Description:
Ultraviolet photometry is presented for the globular cluster M79 (NGC 1904) according to the final calibration of the images obtained on the Astro-1 Spacelab mission by the Ultraviolet Imaging Telescope. These results include both point-source and surface photometry at 152nm and 249nm. An ultraviolet color-magnitude (C-M) diagram in these bandpasses is presented. The detected stars are also cross-matched with the ground-based photometry of Ferraro et al. (1992MNRAS.256..391F) to produce C-M and two-color diagrams covering a 4000A span in wavelength. The observed horizontal branch (HB) is compared with stellar interior models of the zero-age HB (ZAHB). Many stars are found in post-HB evolutionary stages more luminous than the ZAHB. The distribution of stars along the ZAHB in m152-m249 color is investigated, and an indication of possible bimodality is found. The relative population of the blue HB tail may vary with radius for radii greater than 1'. Ultraviolet surface brightness and color-index profiles are presented. The previously reported central gradient in the m152-V color index is confirmed, and a faint diffuse component is detected outside a radius of 40" in the 152nm band. Two possible causes of the central color gradient are discussed: mass segregation, and the destruction of red giant envelopes by enhanced mass loss in the cluster core.
23386. U,V photometry in M2 (NGC 7089)
ID:
ivo://CDS.VizieR/J/A+A/548/A107
Title:
U,V photometry in M2 (NGC 7089)
Short Name:
J/A+A/548/A107
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present U, V photometry of the globular cluster M2. Stars within 1' and outside of 4' from the cluster center are excluded from the CMD to reduce blending effects and the field star contamination, respectively. We imposed on all stars the selection limits of CHI<2.0 and -1<SHARP<1 on DAOPHOT II photometric parameters. To select a sample of well-measured stars we have followed the procedure given in Lardo et al. (2012A&A...541A.141L), Sect. 5.1. M2 photometry displays an anomalous branch beyond the red edge of the main body of the RGB. The difference in color between stars belonging to this structure and normal RGB stars is quite large (of the order of 0.2-0.3mag, well above the typical measurement errors) and extends down to the SGB region. There may be a second group of stars that are 0.3mag redder with respect to this sequence and can possibly be more, anomalous RGB stars. The observations were carried out during the nights of 2010 July 15 at the Telescopio Nazionale Galileo (TNG) located in La Palma, Canary Islands (Spain), with he DOLORES camera. The DOLORES camera offers a field of view of 8.6'x8.6' with a 0.252"/pix scale. We obtained images of the cluster in the standard Johnson U and V filters for a total of 540s shifted in 3 single exposures in each filter. The seeing condition were average during (~1.2-1.3") during the observing night.
23387. UV photometry in NGC 2808
ID:
ivo://CDS.VizieR/J/ApJ/562/368
Title:
UV photometry in NGC 2808
Short Name:
J/ApJ/562/368
Date:
21 Oct 2021
Publisher:
CDS
Description:
We examine new observations of NGC 2808, taken with the far-UV and near-UV cameras on the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). Images were obtained in the far-UV crystal quartz (FUV/F25QTZ; pivot wavelength 1600{AA}), near-UV 2700{AA} continuum (NUV/F25CN270), and clear CCD (CCD/50CCD; pivot wavelength 5850{AA}) modes, employing a cross-shaped dither pattern.
23388. UV photometry of GALEX QSO candidates
ID:
ivo://CDS.VizieR/J/ApJ/664/53
Title:
UV photometry of GALEX QSO candidates
Short Name:
J/ApJ/664/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 36120 QSO candidates from the Galaxy Evolution Explorer (GALEX) Release Two (GR2) UV catalog and the USNO-A2.0 optical catalog. The selection criteria are established using known quasars from the Sloan Digital Sky Survey (SDSS). The SDSS sample is then used to assign individual probabilities to our GALEX USNO candidates. The mean probability is ~50% and would rise to ~65% if better morphological information than that from USNO were available to eliminate galaxies. The sample is ~40% complete for i<=19.1. Candidates are cross identified in 2MASS, FIRST, SDSS, and the XMM-Newton Slewing Survey (XMMSL1), whenever such counterparts exist. The present catalog covers the 8000deg^2^ of GR2 lying above |b|=25{deg}, but can be extended to all 24000deg^2^ that satisfy this criterion as new GALEX data become available.
23389. UV photometry of M15
ID:
ivo://CDS.VizieR/J/ApJ/670/379
Title:
UV photometry of M15
Short Name:
J/ApJ/670/379
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained deep FUV and NUV images of the inner region of the dense globular cluster M15 with the HST ACS. The FUV-NUV color-magnitude diagram shows a well-defined track of horizontal branch stars, as well as a trail of blue stragglers and white dwarfs. The main-sequence turnoff is clearly visible at FUV~22.5mag and FUV-NUV~3mag, and the main-sequence stars form a prominent track that extends at least 2mag below the main-sequence turnoff. As such, this is the deepest FUV-NUV color-magnitude diagram of a globular cluster presented so far. Cataclysmic variable and blue straggler candidates are the most centrally concentrated stellar populations, which might either be an effect of mass segregation or reflect the preferred birthplace in the dense cluster core of such dynamically formed objects. We find 41 FUV sources that exhibit significant variability. We classify the variables based on an analysis of their UV colors and variability properties. We find four previously known RR Lyrae and 13 further RR Lyrae candidates, one known Cepheid and six further candidates, six cataclysmic variable candidates, one known and one probable SX Phoenicis star, and the well-known low-mass X-ray binary AC 211. Our analysis represents the first detection of SX Phoenicis pulsations in the FUV. We find that Cepheids, RR Lyrae stars, and SX Phoenicis exhibit massive variability amplitudes in this wave band (several magnitudes).
23390. UV photometry of NGC 6397
ID:
ivo://CDS.VizieR/J/A+A/287/769
Title:
UV photometry of NGC 6397
Short Name:
J/A+A/287/769
Date:
21 Oct 2021
Publisher:
CDS
Description:
The core of the nearby and very concentrated globular cluster NGC 6397 has been imaged through the f/96-F140W, f/48-F140W, f/96-F210M and f/48-F220W ultraviolet filters of the Faint Object Camera on board the Hubble Space Telescope down to an ultraviolet limiting magnitude of ~19. The most interesting objects in the field of view are six very bright centrally concentrated, blue stragglers observed for the first time in the UV. Using these and other data from ground-based observations, we have been able to deduce from a comparison with Kurucz's atmosphere models, temperatures of ~10000K and masses of ~1.6M_{sun}_ for the four brightest ones, which is remarkably close to twice the turn-off mass of NGC 6397. This finding supports the idea that two-star mechanisms (collisions, mergers) are at the origin of the blue stragglers in the core of NGC 6397. Since the central density is very high, collisions between main sequence stars are frequent, therefore providing the best formation mechanism. We have computed the number of such collisions in the core of NGC 6397 and found it to be of the same order as the number of bright blue stragglers observed there. Thanks to the HST resolution, we have also been able to resolve one object, previously classified as a yellow straggler, into a blend of a blue straggler and three redder stars.

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