- 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.
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Search Results
- 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/ApJS/238/19
- Title:
- VANDAM IV. Free-free emission from protostars
- Short Name:
- J/ApJS/238/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Emission from protostars at centimeter radio wavelengths has been shown to trace the free-free emission arising from ionizing shocks as a result of jets and outflows driven by protostars. Therefore, measuring properties of protostars at radio frequencies can provide valuable insights into the nature of their outflows and jets. We present a C-band (4.1 and 6.4cm) survey of all known protostars (Class0 and ClassI) in Perseus as part of the VLA Nascent Disk and Multiplicity (VANDAM) Survey. We examine the known correlations between radio flux density and protostellar parameters, such as bolometric luminosity and outflow force, for our sample. We also investigate the relationship between radio flux density and far-infrared line luminosities from Herschel. We show that free-free emission most likely originates from J-type shocks; however, the large scatter indicates that those two types of emission probe different time and spatial scales. Using C-band fluxes, we removed an estimation of free-free contamination from the corresponding Ka- band (9mm) flux densities that primarily probe dust emission from embedded disks. We find that the compact (<1") dust emission is lower for Class I sources (median dust mass 96M_{Earth}_) relative to Class 0 (248M_{Earth}_), but several times higher than in Class II (5-15M_{Earth}_). If this compact dust emission is tracing primarily the embedded disk, as is likely for many sources, this result provides evidence of decreasing disk masses with protostellar evolution, with sufficient mass for forming giant planet cores primarily at early times.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/130
- Title:
- VANDAM survey of Orion protostars. II.
- Short Name:
- J/ApJ/890/130
- Date:
- 07 Mar 2022 13:26:15
- Publisher:
- CDS
- Description:
- We have conducted a survey of 328 protostars in the Orion molecular clouds with the Atacama Large Millimeter/submillimeter Array at 0.87mm at a resolution of ~0.1" (40au), including observations with the Very Large Array at 9mm toward 148 protostars at a resolution of ~0.08" (32au). This is the largest multiwavelength survey of protostars at this resolution by an order of magnitude. We use the dust continuum emission at 0.87 and 9mm to measure the dust disk radii and masses toward the Class 0, Class I, and flat-spectrum protostars, characterizing the evolution of these disk properties in the protostellar phase. The mean dust disk radii for the Class 0, Class I, and flat-spectrum protostars are 44.9_-3.4_^+5.8^, 37.0_-3.0_^+4.9^, and 28.5_-2.3_^+3.7^au, respectively, and the mean protostellar dust disk masses are 25.9_-4.0_^+7.7^, 14.9_-2.2_^+3.8^, 11.6_-1.9_^+3.5^M_{Earth}_, respectively. The decrease in dust disk masses is expected from disk evolution and accretion, but the decrease in disk radii may point to the initial conditions of star formation not leading to the systematic growth of disk radii or that radial drift is keeping the dust disk sizes small. At least 146 protostellar disks (35% of 379 detected 0.87mm continuum sources plus 42 nondetections) have disk radii greater than 50au in our sample. These properties are not found to vary significantly between different regions within Orion. The protostellar dust disk mass distributions are systematically larger than those of Class II disks by a factor of >4, providing evidence that the cores of giant planets may need to at least begin their formation during the protostellar phase.
- ID:
- ivo://CDS.VizieR/V/151
- Title:
- VANDELS High-Redshift Galaxy Evolution
- Short Name:
- V/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- VANDELS is a new ESO spectroscopic Public Survey targeting the high-redshift Universe. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the survey is obtaining ultra-deep optical spectroscopy of around 2100 galaxies in the redshift interval 1.0<z<7.0, with 85% of its targets selected to be at z>=3. The fundamental aim of the survey is to provide the high signal-to-noise spectra necessary to measure key physical properties such as stellar population ages, metallicities and outflow velocities from detailed absorption-line studies. By targeting two extragalactic survey fields with superb multi-wavelength imaging data, VANDELS will produce a unique legacy dataset for exploring the physics underpinning high-redshift galaxy evolution.
- ID:
- ivo://CDS.VizieR/J/AJ/159/8
- Title:
- Vanishing and appearing sources using USNO data
- Short Name:
- J/AJ/159/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we report the current status of a new research program. The primary goal of the "Vanishing and Appearing Sources during a Century of Observations" project is to search for vanishing and appearing sources using existing survey data to find examples of exceptional astrophysical transients. The implications of finding such objects extend from traditional astrophysics fields to the more exotic searches for evidence of technologically advanced civilizations. In this first paper we present new, deeper observations of the tentative candidate discovered by Villarroel et al. (2016AJ....152...76V). We then perform the first searches for vanishing objects throughout the sky by comparing 600 million objects from the US Naval Observatory Catalogue (USNO) B1.0 (Cat. I/284) down to a limiting magnitude of ~20-21 with the recent Pan-STARRS Data Release-1 (DR1, Cat. II/349) with a limiting magnitude of ~23.4. We find about 150000 preliminary candidates that do not have any Pan-STARRS counterpart within a 30" radius. We show that these objects are redder and have larger proper motions than typical USNO objects. We visually examine the images for a subset of about 24000 candidates, superseding the 2016 study with a sample 10 times larger. We find about 100 point sources visible in only one epoch in the red band of the USNO, which may be of interest in searches for strong M-dwarf flares, high-redshift supernovae, or other categories of unidentified red transients.
- ID:
- ivo://CDS.VizieR/J/AJ/134/2099
- Title:
- Variability of point sources in infrared
- Short Name:
- J/AJ/134/2099
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a list of 552 sources with suspected variability, based on a comparison of mid-infrared photometry from the GLIMPSE I and Midcourse Space Experiment (MSX) surveys, which were carried out nearly a decade apart. We were careful to address issues such as the difference in resolution and sensitivity between the two surveys, as well as the differences in the spectral responses of the instruments. We selected only sources where the IRAC 8.0um and MSX 8.28um fluxes differ by more than a factor of 2, in order to minimize contamination from sources where the difference in fluxes at 8um is due to a strong 10um silicate feature. We present a subset of 40 sources for which additional evidence suggests variability, using 2MASS and MIPSGAL data. Based on a comparison with the variability flags in the IRAS and MSX point-source catalogs we estimate that at least a quarter of the 552 sources and at least half of the 40 sources in the subset are truly variable. In addition, we tentatively confirm the variability of one source using multiepoch IRAS LRS spectra. We suggest that most of the sources in our list are likely to be asymptotic giant branch stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/73
- Title:
- Variability of RSGs in M31 from the iPTF survey
- Short Name:
- J/ApJ/859/73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most massive stars end their lives as red supergiants (RSGs), a short-lived evolutionary phase when they are known to pulsate with varying amplitudes. The RSG period-luminosity (PL) relation has been measured in the Milky Way, the Magellanic Clouds and M33 for about 120 stars in total. Using over 1500 epochs of R-band monitoring from the Palomar Transient Factory survey over a five-year period, we study the variability of 255 spectroscopically cataloged RSGs in M31. We find that all RGSs brighter than M_K_~-10mag (log(L/L_{sun}_)>4.8) are variable at {Delta}m_R_>0.05mag. Our period analysis finds 63 with significant pulsation periods. Using the periods found and the known values of M_K_ for these stars, we derive the RSG PL relation in M31 and show that it is consistent with those derived earlier in other galaxies of different metallicities. We also detect, for the first time, a sequence of likely first-overtone pulsations. Comparison to stellar evolution models from MESA confirms the first-overtone hypothesis and indicates that the variable stars in this sample have 12M_{sun}_<M<24M_{sun}_. As these RSGs are the immediate progenitors to Type II-P core-collapse supernovae (SNe), we also explore the implication of their variability in the initial-mass estimates for SN progenitors based on archival images of the progenitors. We find that this effect is small compared to the present measurement errors.
- ID:
- ivo://CDS.VizieR/J/AJ/155/39
- Title:
- Variability properties of TIC sources with KELT
- Short Name:
- J/AJ/155/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kilodegree Extremely Little Telescope (KELT) has been surveying more than 70% of the celestial sphere for nearly a decade. While the primary science goal of the survey is the discovery of transiting, large-radii planets around bright host stars, the survey has collected more than 10^6^ images, with a typical cadence between 10-30 minutes, for more than four million sources with apparent visual magnitudes in the approximate range 7<V<13. Here, we provide a catalog of 52741 objects showing significant large-amplitude fluctuations likely caused by stellar variability, as well as 62229 objects identified with likely stellar rotation periods. The detected variability ranges in rms-amplitude from ~3 mmag to ~2.3 mag, and the detected periods range from ~0.1 to >~2000 days. We provide variability upper limits for all other ~4000000 sources. These upper limits are principally a function of stellar brightness, but we achieve typical 1{sigma} sensitivity on 30 min timescales down to ~5 mmag at V~8, and down to ~43 mmag at V~13. We have matched our catalog to the TESS Input catalog and the AAVSO Variable Star Index to precipitate the follow-up and classification of each source. The catalog is maintained as a living database on the Filtergraph visualization portal at the URL https://filtergraph.com/kelt_vars.
- ID:
- ivo://CDS.VizieR/J/A+A/497/81
- Title:
- Variability-selected AGN in CDFS
- Short Name:
- J/A+A/497/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Supermassive black holes with masses of 10^5^-10^9^M_{sun}_ are believed to inhabit most, if not all, nuclear regions of galaxies, and both observational evidence and theoretical models suggest a scenario where galaxy and black hole evolution are tightly related. Luminous AGNs are usually selected by their non-stellar colours or their X-ray emission. Colour selection cannot be used to select low-luminosity AGNs, since their emission is dominated by the host galaxy. Objects with low X-ray to optical ratio escape even the deepest X-ray surveys performed so far. In a previous study we presented a sample of candidates selected through optical variability in the Chandra Deep Field South, where repeated optical observations were performed in the framework of the STRESS supernova survey. The analysis is devoted to breaking down the sample in AGNs, starburst galaxies, and low-ionisation narrow-emission line objects, to providing new information about the possible dependence of the emission mechanisms on nuclear luminosity and black-hole mass, and eventually studying the evolution in cosmic time of the different populations.
