- ID:
- ivo://CDS.VizieR/J/ApJ/872/198
- Title:
- UV-Opt LC of tidal disruption flare AT2018zr
- Short Name:
- J/ApJ/872/198
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Zwicky Transient Facility (ZTF) observations of the tidal disruption flare AT2018zr/PS18kh reported by Holoien+ (2019ApJ...880..120H) and detected during ZTF commissioning. The ZTF light curve of the tidal disruption event (TDE) samples the rise-to-peak exceptionally well, with 50 days of g- and r-band detections before the time of maximum light. We also present our multi-wavelength follow-up observations, including the detection of a thermal (kT~100eV) X-ray source that is two orders of magnitude fainter than the contemporaneous optical/UV blackbody luminosity, and a stringent upper limit to the radio emission. We use observations of 128 known active galactic nuclei (AGNs) to assess the quality of the ZTF astrometry, finding a median host-flare distance of 0.2" for genuine nuclear flares. Using ZTF observations of variability from known AGNs and supernovae we show how these sources can be separated from TDEs. A combination of light-curve shape, color, and location in the host galaxy can be used to select a clean TDE sample from multi-band optical surveys such as ZTF or the Large Synoptic Survey Telescope.
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- ID:
- ivo://CDS.VizieR/J/ApJ/883/111
- Title:
- UV-Opt LCs of ASASSN-19bt detected by TESS
- Short Name:
- J/ApJ/883/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery and early evolution of ASASSN-19bt, a tidal disruption event (TDE) discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d~115Mpc and the first TDE to be detected by TESS. As the TDE is located in the TESS Continuous Viewing Zone, our data set includes 30 minute cadence observations starting on 2018 July 25, and we precisely measure that the TDE begins to brighten ~8.3 days before its discovery. Our data set also includes 18 epochs of Swift UVOT and XRT observations, 2 epochs of XMM-Newton observations, 13 spectroscopic observations, and ground data from the Las Cumbres Observatory telescope network, spanning from 32 days before peak through 37 days after peak. ASASSN-19bt thus has the most detailed pre-peak data set for any TDE. The TESS light curve indicates that the transient began to brighten on 2019 January 21.6 and that for the first 15 days, its rise was consistent with a flux {propto}t^2^ power-law model. The optical/UV emission is well fit by a blackbody spectral energy distribution, and ASASSN-19bt exhibits an early spike in its luminosity and temperature roughly 32 rest-frame days before peak and spanning up to 14 days, which has not been seen in other TDEs, possibly because UV observations were not triggered early enough to detect it. It peaked on 2019 March 4.9 at a luminosity of L~1.3x10^44^erg/s and radiated E~3.2x10^50^erg during the 41 day rise to peak. X-ray observations after peak indicate a softening of the hard X-ray emission prior to peak, reminiscent of the hard/soft states in X-ray binaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/169
- Title:
- UV-Opt light curves of the type Ic SN 2018gep
- Short Name:
- J/ApJ/887/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4+/-0.1mag/hr) and luminous (M_g,peak_=-20mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (L_bol>~3x10^44^erg/s), the short rise time (t_rise_=3days in g band), and the blue colors at peak (g-r~-0.4) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (T_eff_>~40000K) spectra of a stripped-envelope SN. A retrospective search revealed luminous (M_g_~M_r_~-14mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release E_{gamma,iso}_<4.9x10^48^erg, a limit on X-ray emission L_X_<10^40^erg/s, and a limit on radio emission {nu}L_{nu}_<~10^37^erg/s. Taken together, we find that the early (<10days) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02M_{sun}_) at large radii (3x10^14^cm) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time (>10days) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.
- 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.
- 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.
4386. 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).
- ID:
- ivo://CDS.VizieR/J/A+A/545/A141
- Title:
- UV selected sources in the GOODS-S field
- Short Name:
- J/A+A/545/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dust attenuation in galaxies is poorly known, especially at high redshift. And yet the amount of dust attenuation is a key parameter to deduce accurate star formation rates from ultraviolet (UV) rest-frame measurements. The wavelength dependence of the dust attenuation is also of fundamental importance to interpret the observed spectral energy distributions (SEDs) and to derive photometric redshifts or physical properties of galaxies. We want to study dust attenuation at UV wavelengths at high redshift, where the UV is redshifted to the observed visible light wavelength range. In particular, we search for a UV bump and related implications for dust attenuation determinations.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A97
- Title:
- UV structure of 11 galaxies with Swift-UVOT
- Short Name:
- J/A+A/602/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- GALEX detected a significant fraction of early-type galaxies, in particular S0s, showing Far-UV bright structures, sometimes involving an entire galaxy out to its outskirts. These features suggest the presence of either recent, ongoing and/or prolonged star formation episodes, shedding new light on the evolution of these systems. We aim at understanding the evolutionary path[s] of these early-type galaxies and the mechanisms at the origin of their UV-bright structures. We investigate with a multi{lambda} approach the link between the inner and the outer galaxy regions of a set of eleven early-type galaxies selected because of their nearly passive stage of evolution in the nuclear region. This paper, second of a series, focuses on the information coming from the comparison between UV features detected by Swift-UVOT, tracing recent star formation, and the galaxy optical structure mapping older stellar populations. We performed a surface photometric study of these early-type galaxies, observed with Swift-UVOT UV filters, W2 2030{AA} {lambda_0}, M2 2231{AA} {lambda_0}, W1 2634{AA} {lambda_0}, and UBV bands. BVRI photometry from other sources in the literature is also used. Our integrated magnitude measurements have been analyzed and compared with corresponding values in the literature. We characterize the overall galaxy structure best fitting the UV and optical luminosity profiles using a single Sersic law. NGC 1366, NGC 1426, NGC 3818, NGC 3962 and NGC 7192 show featureless luminosity profiles. Excluding NGC~1366 which has a clear edge-on disk (n~1-2), and NGC 3818, the remaining three have Sersic's indices n~3-4 in optical and a lower index in the UV. Bright ring/arm-like structures are revealed by UV images and luminosity profiles of NGC 1415, NGC 1533, NGC 1543, NGC 2685, NGC 2974 and IC 2006. The ring/arm-like structures are different from galaxy to galaxy. Sersic indices of UV profiles for those galaxies are in the range n=1.5-3 both in S0s and in galaxies classified as "bona fide" ellipticals, such as NGC 2974 and IC 2006. We notice that in our sample optical Sersic indices are usually larger than in the UV ones. (M2-V) color profiles are bluer in ring/arm-like structures with respect to the galaxy body. The lower values of Sersic's indices in the UV bands with respect to optical ones, suggesting the presence of a disk, point out that the role of the dissipation cannot be neglected in recent evolutionary phases of these early-type galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/199/22
- Title:
- UV to far-IR photometry of galaxies
- Short Name:
- J/ApJS/199/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present a sample of cluster galaxies devoted to study the environmental influence on the star formation activity. This sample of galaxies inhabits in clusters showing a rich variety in their characteristics and have been observed by the SDSS-DR6 down to M_B_~-18, and by the Galaxy Evolution Explorer AIS throughout sky regions corresponding to several megaparsecs. We assign the broadband and emission-line fluxes from ultraviolet to far-infrared to each galaxy performing an accurate spectral energy distribution for spectral fitting analysis. The clusters follow the general X-ray luminosity versus velocity dispersion trend of L_X_{propto}{sigma}^4.4^_c_.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A142
- Title:
- UV-to-IR fluxes of Hickson compact groups
- Short Name:
- J/A+A/533/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive study on the impact of the environment of compact galaxy groups on the evolution of their members using a multi-wavelength analysis, from the UV to the infrared, for a sample of 32 Hickson compact groups (HCGs) containing 135 galaxies. Fitting the SEDs of all galaxies with the state-of-the-art model of da Cunha (2008MNRAS.388.1595D) we can accurately calculate their mass, SFR, and extinction, as well as estimate their infrared luminosity and dust content. We compare our findings with samples of field galaxies, early-stage interacting pairs, and cluster galaxies with similar data. We find that classifying the groups as dynamically "old" or "young", depending on whether or not at least one quarter of their members are early-type systems, is physical and consistent with past classifications of HCGs based on their atomic gas content. Dynamically "old" groups are more compact and display higher velocity dispersions than "young" groups. Late-type galaxies in dynamically "young" groups have specific star formation rates (sSFRs), NUV-r, and mid-infrared colors which are similar to those of field and early stage interacting pair spirals. Late-type galaxies in dynamically "old" groups have redder NUV-r colors, as they have likely experienced several tidal encounters in the past building up their stellar mass, and display lower sSFRs. We identify several late-type galaxies which have sSFRs and colors similar to those of elliptical galaxies, since they lost part of their gas due to numerous interactions with other group members. Also, 25% of the elliptical galaxies in these groups have bluer UV/optical colors than normal ellipticals in the field, probably due to star formation as they accreted gas from other galaxies of the group, or via merging of dwarf companions. Finally, our SED modeling suggests that in 13 groups, 10 of which are dynamically "old", there is diffuse cold dust in the intragroup medium. All this evidence point to an evolutionary scenario in which the effects of the group environment and the properties of the galaxy members are not instantaneous. Early on, the influence of close companions to group galaxies is similar to the one of galaxy pairs in the field. However, as the time progresses, the effects of tidal torques and minor merging, shape the morphology and star formation history of the group galaxies, leading to an increase of the fraction of early-type members and a rapid built up of the stellar mass in the remaining late-type galaxies.
