- ID:
- ivo://CDS.VizieR/J/ApJ/853/62
- Title:
- Optical and NIR spectra and LCs of SN2016ija
- Short Name:
- J/ApJ/853/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our analysis of the Type II supernova DLT16am (SN2016ija). The object was discovered during the ongoing D<40Mpc (DLT40) one-day cadence supernova search at r~20.1mag in the "edge-on" nearby (D=20.0+/-4.0Mpc) galaxy NGC1532. The subsequent prompt and high-cadenced spectroscopic and photometric follow-up revealed a highly extinguished transient, with E(B-V)=1.95+/-0.15mag, consistent with a standard extinction law with R_V_=3.1 and a bright (M_V_=-18.48+/-0.77mag) absolute peak magnitude. A comparison of the photometric features with those of large samples of SNe II reveals a fast rise for the derived luminosity and a relatively short plateau phase, with a slope of S_50V_=0.84+/-0.04mag/50days, consistent with the photometric properties typical of those of fast-declining SNeII. Despite the large uncertainties on the distance and the extinction in the direction of DLT16am, the measured photospheric expansion velocity and the derived absolute V-band magnitude at ~50days after the explosion match the existing luminosity-velocity relation for SNeII.
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- ID:
- ivo://CDS.VizieR/J/A+A/578/A9
- Title:
- Optical and NIR spectra of SN iPTF13ebh
- Short Name:
- J/A+A/578/A9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared (NIR) time-series spectroscopy, as well as complementary ultraviolet (UV), optical, and NIR data, of the Type Ia supernova (SN Ia) iPTF13ebh, which was discovered within two days from the estimated time of explosion. The first NIR spectrum was taken merely 2.3 days after explosion and may be the earliest NIR spectrum yet obtained of a SN Ia. The most striking features in the spectrum are several NIR CI lines, and the CI {lambda}1.0693um line is the strongest ever observed in a SN Ia. Interestingly, no strong optical CII counterparts were found, even though the optical spectroscopic time series began early and is densely-cadenced. Except at the very early epochs, within a few days from the time of explosion, we show that the strong NIR CI compared to the weaker optical CII appears to be general in SNe Ia. iPTF13ebh is a fast decliner with {Delta}m15(B)=1.79+/-0.01, and its absolute magnitude obeys the linear part of the width-luminosity relation. It is therefore categorized as a "transitional" event, on the fast-declining end of normal SNe Ia as opposed to subluminous/91bg-like objects. iPTF13ebh shows NIR spectroscopic properties that are distinct from both the normal and subluminous/91bg-like classes, bridging the observed characteristics of the two classes. These NIR observations suggest composition and density of the inner core similar to that of 91bg-like events, and a deep reaching carbon burning layer not observed in slower declining SNe Ia. There is also a substantial difference between the explosion times inferred from the early-time light curve and the velocity evolution of the SiII {lambda}0.6355um line, implying a long dark phase of ~4 days.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/94
- Title:
- Optical and UV follow-up of 1ES 1927+654
- Short Name:
- J/ApJ/883/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the sudden optical and ultraviolet (UV) brightening of 1ES1927+654, which until now was known as a narrow-line active galactic nucleus (AGN). 1ES 1927+654 was part of the small and peculiar class of "true Type-2" AGNs that lack broad emission lines and line-of-sight obscuration. Our high-cadence spectroscopic monitoring captures the appearance of a blue, featureless continuum, followed several weeks later by the appearance of broad Balmer emission lines. This timescale is generally consistent with the expected light travel time between the central engine and the broadline emission region in (persistent) broadline AGN. Hubble Space Telescope spectroscopy reveals no evidence for broad UV emission lines (e.g., CIV{lambda}1549, CIII]{lambda}1909, MgII{lambda}2798), probably owing to dust in the broadline emission region. To the best of our knowledge, this is the first case where the lag between the change in continuum and in broadline emission of a "changing look" AGN has been temporally resolved. The nature and timescales of the photometric and spectral evolution disfavor both a change in line-of-sight obscuration and a change of the overall rate of gas inflow as driving the drastic spectral transformations seen in this AGN. Although the peak luminosity and timescales are consistent with those of tidal disruption events seen in inactive galaxies, the spectral properties are not. The X-ray emission displays a markedly different behavior, with frequent flares on timescales of hours to days, and will be presented in a companion publication.
- ID:
- ivo://CDS.VizieR/J/A+AS/92/685
- Title:
- Optical and UV Spectrum of KQ Pup
- Short Name:
- J/A+AS/92/685
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/1380
- Title:
- Optical chromospheric activity of V711 Tau
- Short Name:
- J/MNRAS/449/1380
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present long-term high-resolution spectroscopic observations of the very active RS Canum Venaticorum-type star V711 Tau, obtained during several observing runs from 1998 to 2004, and study its chromospheric activity. Using the spectral subtraction technique, several optical chromospheric activity indicators [including the He I D_3_, Na I D_1_, D_2_, H{alpha} and Ca II infrared triplet (IRT) lines] formed at different atmospheric heights are analysed. Strong chromospheric emission supports earlier results that indicate that V711 Tau is a very active system. Two large optical flares were detected during our observations. The results suggest that the main part of chromospheric emission is attributed to the primary star of the system. The secondary also presents weak emission but is less active. The ratios of EW_8542_/EW_8498_ indicate that CaII IRT emission arises predominantly from plage-like regions. We have found rotational modulation of chromospheric activity in the H{alpha} and CaII IRT lines, which suggests the presence of the chromospheric active longitudes over the surface of V711 Tau. Two active longitudes separated by about 180{deg} were observed to dominate the activity, and the so-called flip-flop phenomenon was seen during our observations. Moreover, the chromospheric activity level shows a long-term variation that gradually increases from a deep minimum near the year 2002. A close spatial connection of photospheric spots and chromospheric active regions in both short and long timescales was found for V711 Tau.
- ID:
- ivo://CDS.VizieR/J/MNRAS/414/702
- Title:
- Optical classification of southern ULIRGs
- Short Name:
- J/MNRAS/414/702
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the optical spectral properties of 115 ultraluminous infrared galaxies (ULIRGs) in the southern sky. Using the optical spectra obtained at the Cerro Tololo Inter-American Observatory (CTIO) 4m telescope and provided by the Two-degree Field (2dF) Galaxy Redshift Survey and the Six-degree Field (6dF) Galaxy Survey, we measure emission linewidths and fluxes for spectral classification.
- ID:
- ivo://CDS.VizieR/J/ApJ/701/1347
- Title:
- Optical constants of H_2_O-ice
- Short Name:
- J/ApJ/701/1347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using new laboratory spectra, we have calculated the real and imaginary parts of the index of refraction of amorphous and crystalline H_2_O-ice from 20-150K in the wavelength range 2.5-22um (4000-455cm^-1^) and joined these results with previous measurement from 1.25 to 2.5um. These optical constants improve on previous measurements by having better temperature and spectral resolution and can be used to create model spectra for comparison to spectra of solar system objects and interstellar materials. In this wavelength range, the infrared band shapes and positions of amorphous H_2_O-ice are strongly dependent on deposition temperature. Amorphous and crystalline H_2_O-ice have distinctive spectral bands at all wavelengths in this region with bands weakening and shifting to shorter wavelength in amorphous H_2_O-ice compared to crystalline H_2_O-ice. Some notable exceptions are the band near 6um, which is stronger in amorphous H2O-ice, and the bands near 4.5um and 12.5um, which shift to longer wavelength in amorphous H_2_O-ice.
- ID:
- ivo://CDS.VizieR/J/ApJ/596/768
- Title:
- Optical depths in 19 QSOs
- Short Name:
- J/ApJ/596/768
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measure the distribution of carbon in the intergalactic medium as a function of redshift z and overdensity {delta}. Using a hydrodynamical simulation to link the H I absorption to the density and temperature of the absorbing gas, and a model for the UV background radiation, we convert ratios of C IV to H I pixel optical depths into carbon abundances. For the median metallicity this technique was described and tested in Paper I (Aguirre et al., 2002ApJ...576....1A) of this series. Here we generalize it to reconstruct the full probability distribution of the carbon abundance and apply it to 19 high-quality quasar absorption spectra.
- ID:
- ivo://CDS.VizieR/J/ApJ/876/115
- Title:
- Optical follow-up of ASAS-SN M dwarf flares
- Short Name:
- J/ApJ/876/115
- Date:
- 18 Jan 2022 15:06:46
- Publisher:
- CDS
- Description:
- The All-sky Automated Survey for Supernovae (ASAS-SN) is the only project in existence to scan the entire sky in optical light approximately every day, reaching a depth of g~18mag. Over the course of its first 4yr of transient alerts (2013-2016), ASAS-SN observed 53 events classified as likely M dwarf flares. We present follow-up photometry and spectroscopy of all 53 candidates, confirming flare events on 47 M dwarfs, one K dwarf, and one L dwarf. The remaining four objects include a previously identified T Tauri star, a young star with outbursts, and two objects too faint to confirm. A detailed examination of the 49 flare star light curves revealed an additional six flares on five stars, resulting in a total of 55 flares on 49 objects ranging in V-band contrast from {Delta}V=-1 to -10.2mag. Using an empirical flare model to estimate the unobserved portions of the flare light curve, we obtain lower limits on the V-band energy emitted during each flare, spanning log(E_V_/erg)=32-35, which are among the most energetic flares detected on M dwarfs. The ASAS-SN M dwarf flare stars show a higher fraction of H{alpha} emission, as well as stronger H{alpha} emission, compared to M dwarfs selected without reference to activity, consistent with belonging to a population of more magnetically active stars. We also examined the distribution of tangential velocities, finding that the ASAS-SN flaring M dwarfs are likely to be members of the thin disk and are neither particularly young nor old.
- ID:
- ivo://CDS.VizieR/J/ApJS/174/379
- Title:
- Optical imaging and spectra of 3C 58
- Short Name:
- J/ApJS/174/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive imaging and spectroscopic survey of optical emission knots associated with the young Galactic supernova remnant 3C 58. H{alpha} images show hundreds of clumpy filaments and knots arranged in a complex structure covering a nearly circular area roughly 400" in diameter. A quite different emission structure is seen in [OIII], where the brightest features are less clumpy and largely confined to the remnant's northwest quadrant. Measured radial velocities of over 450 knots reveal two distinct kinematic populations; one with average and peak expansion velocities of 770 and 1100km/s, respectively, forming a thick shell, and the other showing |v|<=250km/s. High-velocity knots (|v|>=500km/s) exhibit a strong bipolar expansion pattern with redshifted and blueshifted knots located in northeastern and southwestern regions, respectively. These knots also show strong [NII]/H{alpha} line emission ratios, suggesting enhanced N/H. In contrast, the slower expanding knot population shows much lower [NII]/H{alpha} line ratios and likely represents circumstellar mass loss material from the 3C 58 progenitor. Proper-motion estimates using images spanning a 28yr time interval suggest positional shifts of between 0.5" and 2.0", implying proper motions of 0.02-0.07"/yr. These values agree with previous estimates but are much less than the ~0.2"/yr expected if 3C 58 were associated with historic guest star of 1181 CE.
