| 1. |
- Smartt, S. J., et al.
(författare)
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PESSTO : survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 579
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Tidskriftsartikel (refereegranskat)abstract
- Context. The Public European Southern Observatory Spectroscopic Survey of Transient Objects (PESSTO) began as a public spectroscopic survey in April 2012. PESSTO classifies transients from publicly available sources and wide-field surveys, and selects science targets for detailed spectroscopic and photometric follow-up. PESSTO runs for nine months of the year, January - April and August - December inclusive, and typically has allocations of 10 nights per month. Aims. We describe the data reduction strategy and data products that are publicly available through the ESO archive as the Spectroscopic Survey data release 1 (SSDR1). Methods. PESSTO uses the New Technology Telescope with the instruments EFOSC2 and SOFI to provide optical and NIR spectroscopy and imaging. We target supernovae and optical transients brighter than 20.5(m) for classification. Science targets are selected for follow-up based on the PESSTO science goal of extending knowledge of the extremes of the supernova population. We use standard EFOSC2 set-ups providing spectra with resolutions of 13-18 angstrom between 3345-9995 angstrom. A subset of the brighter science targets are selected for SOFI spectroscopy with the blue and red grisms (0.935-2.53 mu m and resolutions 23-33 angstrom) and imaging with broadband JHK(s) filters. Results. This first data release (SSDR1) contains flux calibrated spectra from the first year (April 2012-2013). A total of 221 confirmed supernovae were classified, and we released calibrated optical spectra and classifications publicly within 24 h of the data being taken (via WISeREP). The data in SSDR1 replace those released spectra. They have more reliable and quantifiable flux calibrations, correction for telluric absorption, and are made available in standard ESO Phase 3 formats. We estimate the absolute accuracy of the flux calibrations for EFOSC2 across the whole survey in SSDR1 to be typically similar to 15%, although a number of spectra will have less reliable absolute flux calibration because of weather and slit losses. Acquisition images for each spectrum are available which, in principle, can allow the user to refine the absolute flux calibration. The standard NIR reduction process does not produce high accuracy absolute spectrophotometry but synthetic photometry with accompanying JHK(s) imaging can improve this. Whenever possible, reduced SOFI images are provided to allow this. Conclusions. Future data releases will focus on improving the automated flux calibration of the data products. The rapid turnaround between discovery and classification and access to reliable pipeline processed data products has allowed early science papers in the first few months of the survey.
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| 2. |
- Valenti, S., et al.
(författare)
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PESSTO spectroscopic classification of La Silla-Quest Transients
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- PESSTO is the "Public ESO Spectroscopic Survey of Transient Objects" (http://www.pessto.org) using the ESO New Technology Telescope (NTT) at La Silla and the EFOSC2 (optical) and SOFI (near-IR) spectrographs. It is one of two currently running public spectroscopic surveys at ESO. The survey details are as follows: - PESSTO has 90 nights per year on the NTT: 9 lunations (August to April), 10 nights per lunation (we are not observing May-July).
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| 3. |
- Barbarino, C., et al.
(författare)
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SN 2012ec : mass of the progenitor from PESSTO follow-up of the photospheric phase
- 2015
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 448:3, s. 2312-2331
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of a photometric and spectroscopic monitoring campaign of SN 2012ec, which exploded in the spiral galaxy NGC 1084, during the photospheric phase. The photometric light curve exhibits a plateau with luminosity L = 0.9 x 10(42) erg s(-1) and duration similar to 90 d, which is somewhat shorter than standard Type II-P supernovae (SNe). We estimate the nickel mass M(Ni-56) = 0.040 +/- 0.015 M-circle dot from the luminosity at the beginning of the radioactive tail of the light curve. The explosion parameters of SN 2012ec were estimated from the comparison of the bolometric light curve and the observed temperature and velocity evolution of the ejecta with predictions from hydrodynamical models. We derived an envelope mass of 12.6 M-circle dot, an initial progenitor radius of 1.6 x 10(13) cm and an explosion energy of 1.2 foe. These estimates agree with an independent study of the progenitor star identified in pre-explosion images, for which an initial mass of M = 14-22 M-circle dot was determined. We have applied the same analysis to two other Type II-P SNe (SNe 2012aw and 2012A), and carried out a comparison with the properties of SN 2012ec derived in this paper. We find a reasonable agreement between the masses of the progenitors obtained from pre-explosion images and masses derived from hydrodynamical models. We estimate the distance to SN 2012ec with the standardized candle method (SCM) and compare it with other estimates based on other primary and secondary indicators. SNe 2012A, 2012aw and 2012ec all follow the standard relations for the SCM for the use of Type II-P SNe as distance indicators.
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| 4. |
- Dall'Ora, M., et al.
(författare)
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THE TYPE IIP SUPERNOVA 2012aw IN M95 : HYDRODYNAMICAL MODELING OF THE PHOTOSPHERIC PHASE FROM ACCURATE SPECTROPHOTOMETRIC MONITORING
- 2014
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 787:2, s. 139-
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Tidskriftsartikel (refereegranskat)abstract
- We present an extensive optical and near-infrared photometric and spectroscopic campaign of the Type IIP supernova SN 2012aw. The data set densely covers the evolution of SN 2012aw shortly after the explosion through the end of the photospheric phase, with two additional photometric observations collected during the nebular phase, to fit the radioactive tail and estimate the Ni-56 mass. Also included in our analysis is the previously published Swift UV data, therefore providing a complete view of the ultraviolet-optical-infrared evolution of the photospheric phase. On the basis of our data set, we estimate all the relevant physical parameters of SN 2012aw with our radiation-hydrodynamics code: envelope mass M-env similar to 20 M-circle dot, progenitor radius R similar to 3 x 10(13) cm (similar to 430 R-circle dot), explosion energy E similar to 1.5 foe, and initial Ni-56 mass similar to 0.06 M-circle dot. These mass and radius values are reasonably well supported by independent evolutionary models of the progenitor, and may suggest a progenitor mass higher than the observational limit of 16.5 +/- 1.5 M-circle dot of the Type IIP events.
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| 5. |
- da Silva, R., et al.
(författare)
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Oxygen, sulfur, and iron radial abundance gradients of classical Cepheids across the Galactic thin disk
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 678, s. A195-A195
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Tidskriftsartikel (refereegranskat)abstract
- Context. Classical Cepheids (CCs) are solid distance indicators and tracers of young stellar populations. Dating back to the beginning of the 20th century, they have been safely adopted to trace the rotation, kinematics, and chemical enrichment history of the Galactic thin disk.Aims. The main aim of this investigation is to provide iron, oxygen, and sulfur abundances for the largest and most homogeneous sample of Galactic CCs analyzed so far (1118 spectra of 356 objects). The current sample, containing 70 CCs for which spectroscopic metal abundances are provided for the first time, covers a wide range in galactocentric distances, pulsation modes, and pulsation periods.Methods. Optical high-resolution spectra with a high signal-to-noise ratio that were collected with different spectrographs were adopted to provide homogeneous estimates of the atmospheric parameters (effective temperature, surface gravity, and microturbulent velocity) that are required to determine the abundance. Individual distances were based either on trigonometric parallaxes by the Gaia Data Release 3 (Gaia DR3) or on distances based on near-infrared period-luminosity relations.Results. We found that iron and α-element radial gradients based on CCs display a well-defined change in the slope for galactocentric distances larger than ~12 kpc. We also found that logarithmic regressions account for the variation in [X/H] abundances from the inner to the outer disk. Radial gradients for the same elements, but based on open clusters covering a wide range in cluster ages, display similar trends. This means that the flattening in the outer disk is an intrinsic feature of the radial gradients because it is independent of age. Empirical evidence indicates that the S radial gradient is steeper than the Fe radial gradient. The difference in the slope is a factor of two in the linear fit (−0.081 vs. −0.041 dex kpc−1) and changes from −1.62 to −0.91 in the logarithmic distance. Moreover, we found that S (explosive nucleosynthesis) is underabundant on average when compared with O (hydrostatic nucleosynthesis). The difference becomes clearer in the metal-poor regime and for the [O/Fe] and [S/Fe] abundance ratios. We performed a detailed comparison with Galactic chemical evolution models and found that a constant star formation efficiency for galactocentric distances larger than 12 kpc accounts for the flattening observed in both iron and α-elements. To further constrain the impact of the predicted S yields for massive stars on radial gradients, we adopted a toy model and found that the flattening in the outermost regions requires a decrease of a factor of four in the current S predictions.Conclusions. CCs are solid beacons for tracing the recent chemical enrichment of young stellar populations. Sulfur photospheric abundances, when compared with other α-elements, have the key advantage of being a volatile element. Therefore, stellar S abundances can be directly compared with nebular sulfur abundances in external galaxies.
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| 9. |
- Jerkstrand, A., et al.
(författare)
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Supersolar Ni/Fe production in the Type IIP SN 2012ec
- 2015
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 448:3, s. 2482-2494
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Tidskriftsartikel (refereegranskat)abstract
- SN 2012ec is a Type IIP supernova (SN) with a progenitor detection and comprehensive photospheric phase observational coverage. Here, we present Very Large Telescope and Public ESO Spectroscopic Survey of Transient Objects observations of this SN in the nebular phase. We model the nebular [O I] lambda lambda 6300, 6364 lines and find their strength to suggest a progenitor main-sequence mass of 13-15 M-circle dot. SN2012ec is unique among hydrogen-rich SNe in showing a distinct line of stable nickel [Ni II] lambda 7378. This line is produced by Ni-58, a nuclear burning ash whose abundance is a sensitive tracer of explosive burning conditions. Using spectral synthesis modelling, we use the relative strengths of [Ni II] lambda 7378 and [Fe II] lambda 7155 (the progenitor of which is Ni-56) to derive a Ni/Fe production ratio of 0.20 +/- 0.07 (by mass), which is a factor 3.4 +/- 1.2 times the solar value. High production of stable nickel is confirmed by a strong [Ni II] 1.939 mu m line. This is the third reported case of a core-collapse SN producing a Ni/Fe ratio far above the solar value, which has implications for core-collapse explosion theory and galactic chemical evolution models.
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| 10. |
- Fraser, M., et al.
(författare)
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RED AND DEAD : THE PROGENITOR OF SN 2012aw IN M95
- 2012
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Ingår i: The Astrophysical Journal Letters. - 2041-8205. ; 759:1, s. L13-
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Tidskriftsartikel (refereegranskat)abstract
- Core-collapse supernovae (SNe) are the spectacular finale to massive stellar evolution. In this Letter, we identify a progenitor for the nearby core-collapse SN 2012aw in both ground-based near-infrared and space-based optical pre-explosion imaging. The SN itself appears to be a normal Type II Plateau event, reaching a bolometric luminosity of 10(42) erg s(-1) and photospheric velocities of similar to 11,000 km s(-1) from the position of the H beta P-Cygni minimum in the early SN spectra. We use an adaptive optics image to show that the SN is coincident to within 27 mas with a faint, red source in pre-explosion HST+WFPC2, VLT+ISAAC, and NTT+SOFI images. The source has magnitudes F555W = 26.70 +/- 0.06, F814W = 23.39 +/- 0.02, J = 21.1 +/- 0.2, K = 19.1 +/- 0.4, which, when compared to a grid of stellar models, best matches a red supergiant. Interestingly, the spectral energy distribution of the progenitor also implies an extinction of A(V) > 1.2 mag, whereas the SN itself does not appear to be significantly extinguished. We interpret this as evidence for the destruction of dust in the SN explosion. The progenitor candidate has a luminosity between 5.0 and 5.6 log L/L-circle dot, corresponding to a zero-age main-sequence mass between 14 and 26 M-circle dot (depending on A(V)), which would make this one of the most massive progenitors found for a core-collapse SN to date.
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