An Updated Ultraviolet Calibration for the Swift∕UVOT

Breeveld, A. A.; Landsman, W. B.; Holland, S. T.; Roming, P. W. A.; Kuin, N. P. M.; Page, M. J.

doi:10.1063/1.3621807

Cited by 308 publications

(296 citation statements)

References 5 publications

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“…Furthermore, the UVOT photometry was obtained from the Swift Optical/Ultraviolet Supernova Archive (SOUSA; Brown et al 2014). The reduction is based on that of Brown et al (2009), including subtraction of the host-galaxy count rates, and uses the revised UV zeropoints and time-dependent sensitivity from Breeveld et al (2011). All photometry is presented in Table 2 and the light curves are shown in Fig.…”

Section: Discovery and Observations Of Sn 2013gh And Iptf 13dgementioning

confidence: 99%

Time-varying sodium absorption in the Type Ia supernova 2013gh

Ferretti

Amanullah

Goobar

et al. 2016

A&A

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Context. Temporal variability of narrow absorption lines in high-resolution spectra of Type Ia supernovae (SNe Ia) is studied to search for circumstellar matter. Time series which resolve the profiles of absorption lines such as Na I D or Ca II H&K are expected to reveal variations due to photoionisation and subsequent recombination of the gases. The presence, composition, and geometry of circumstellar matter may hint at the elusive progenitor system of SNe Ia and could also affect the observed reddening law. Aims. To date, there are few known cases of time-varying Na I D absorption in SNe Ia, all of which occurred during relatively late phases of the supernova (SN) evolution. Photoionisation, however, is predicted to occur during the early phases of SNe Ia, when the supernovae peak in the ultraviolet. We attempt, therefore, to observe early-time absorption-line variations by obtaining high-resolution spectra of SNe before maximum light. Methods. We have obtained photometry and high-resolution spectroscopy of SNe Ia 2013gh and iPTF 13dge, to search for absorptionline variations. Furthermore, we study interstellar absorption features in relation to the observed photometric colours of the SNe. Results. Both SNe display deep Na I D and Ca II H&K absorption features. Furthermore, small but significant variations are detected in a feature of the Na I D profile of SN 2013gh. The variations are consistent with either geometric effects of rapidly moving or patchy gas clouds or photoionisation of Na I gas at R ≈ 10 19 cm from the explosion. Conclusions. Our analysis indicates that it is necessary to focus on early phases to detect photoionisation effects of gases in the circumstellar medium of SNe Ia. Different absorbers such as Na I and Ca II can be used to probe for matter at different distances from the SNe. The nondetection of variations during early phases makes it possible to put limits on the abundance of the species at those distances.

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Section: Discovery and Observations Of Sn 2013gh And Iptf 13dgementioning

confidence: 99%

Time-varying sodium absorption in the Type Ia supernova 2013gh

Ferretti

Amanullah

Goobar

et al. 2016

A&A

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“…We performed aperture photometry for all filters in all the observations using the standard UVOT software distributed within the HEAsoft package (version 6.10) and the calibration included in the latest release of the CALDB. Counts were extracted from an aperture of 5″ radius for all filters and converted to fluxes using the standard zero points from Breeveld et al (2011). The fluxes were then dereddened using the value of E B V 0.014 Schlegel et al 1998;Schlafly & Finkbeiner 2011) with A E B V ( ) -l ratios calculated using the mean Galactic interstellar extinction curve from Fitzpatrick (1999).…”

Section: Swift Uvot and Xrtmentioning

confidence: 99%

MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF Mrk 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

Baloković¹,

Paneque²,

Madejski³

et al. 2016

ApJ

113

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We present coordinated multiwavelength observations of the bright, nearby BL Lacertae object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very high energy(VHE) γ-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep 3 G » power law, with no evidence for an exponential cutoff or additional hard components up to ∼80keV. For the first time, we observed both the synchrotron and the inverse-Compton peaks of the spectral energy distribution (SED) simultaneously shifted to frequencies below the typical quiescent state by an order of magnitude. The fractional variability as a function of photon energy shows a double-bump structure that relates to the two bumps of the broadband SED. In each bump, the variability increases with energy, which, in the framework of the synchrotron self-Compton model, implies that the electrons with higher energies are more variable. The measured multi band variability, the significant X-ray-to-VHE correlation down to some of the lowest fluxes ever observed in both bands, the lack of correlation between optical/UV and X-ray flux, the low degree of polarization and its significant (random) variations, the short estimated electron cooling time, and the significantly longer variability timescale observed in the NuSTAR light curves point toward in situ electron acceleration and suggest that there are multiple compact regions contributing to the broadband emission of Mrk 421 during low-activity states.

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“…The tool uvotsource v.3.3 was used to extract the fluxes from each of the images using aperture photometry. The observed magnitudes were corrected for Galactic extinction (E B−V = 0.019 mag) using the dust maps of Schlegel et al (1998) and converted to flux units using the zero-point magnitudes and conversion factors of Breeveld et al (2011). The tool flx2xsp v.2.1 was used to convert the fluxes to pha files for use in XSPEC.…”

Section: Swift Observationsmentioning

confidence: 99%

Underlying particle spectrum of Mkn 421 during the huge X-ray flare in April 2013

Sinha

Shukla

Misra

et al. 2015

A&A

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Context. In April 2013, the nearby TeV blazar, Mkn 421, showed one of the largest flares in X-rays in the past decade. Aims. We study all multiwavelength data available during MJD 56 392 to 56 403, with special emphasis on X-ray data to understand the underlying particle energy distribution. Methods. We studied the correlations between the UV and gamma-ray bands with the X-ray band using the z-transformed discrete correlation function. We modelled the underlying particle energy spectrum with a single population of electrons emitting synchrotron radiation, and statistically fitted the simultaneous time-resolved data from Swift-XRT and NuSTAR. Results. The flux varied rapidly in the X-ray band, with a minimum doubling timescale of 1.69 ± 0.13 h. There were no corresponding flares in UV and gamma-ray bands. The variability in UV and gamma rays was relatively modest with ∼8% and ∼16%, respectively, and no significant correlation was found with the X-ray light curve. The observed X-ray spectrum shows a clear curvature that can be fit by a log parabolic spectral form. This is best explained as originating from a log parabolic electron spectrum. However, a broken power law or a power law with an exponentially falling electron distribution cannot be ruled out either. Moreover, the excellent broadband spectrum from 0.3-79 keV allows us to make predictions of the UV flux. We find that this prediction is compatible with the observed flux during the low state in X-rays. However, during the X-ray flares, depending on the adopted model, the predicted flux is a factor of 2-50 lower than the observed one. This suggests that the X-ray flares are probably caused by a separate population that does not contribute significantly to the radiation at lower energies. Alternatively, the underlying particle spectrum can be much more complex than those explored in this work.

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An Updated Ultraviolet Calibration for the Swift∕UVOT

Cited by 308 publications

References 5 publications

Time-varying sodium absorption in the Type Ia supernova 2013gh

Time-varying sodium absorption in the Type Ia supernova 2013gh

MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF Mrk 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

Underlying particle spectrum of Mkn 421 during the huge X-ray flare in April 2013

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