J/ApJ/836/232 Swift-UVOT obs. analysis of 29 SNe Ia (Brown+, 2017)
Reddened, redshifted, or intrinsically red?
Understanding near-ultraviolet colors of Type Ia supernovae.
Brown P.J., Landez N.J., Milne P.A., Stritzinger M.D.
<Astrophys. J., 836, 232-232 (2017)>
=2017ApJ...836..232B 2017ApJ...836..232B (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Photometry, ultraviolet ; Photometry, UBV
Keywords: dust, extinction; supernovae: general;
supernovae: individual: (SN2011fe, SN2011ia); ultraviolet: general
Abstract:
The intrinsic colors of Type Ia supernovae (SNe Ia) are important to
understanding their use as cosmological standard candles.
Understanding the effects of reddening and redshift on the observed
colors are complicated and dependent on the intrinsic spectrum, the
filter curves, and the wavelength dependence of reddening. We present
ultraviolet and optical data of a growing sample of SNe Ia observed
with the Ultraviolet/Optical Telescope on the Swift spacecraft and use
this sample to re-examine the near-UV (NUV) colors of SNe Ia. We find
that a small amount of reddening (E(B-V)=0.2mag) could account for the
difference between groups designated as NUV-blue and NUV-red, and a
moderate amount of reddening (E(B-V)=0.5mag) could account for the
whole NUV-optical differences. The reddening scenario, however, is
inconsistent with the mid-UV colors and color evolution. The effect of
redshift alone only accounts for part of the variation. Using a
spectral template of SN2011fe, we can forward model the effects of
redshift and reddening and directly compare those with the observed
colors. We find that some SNe are consistent with reddened versions of
SN2011fe, but most SNe Ia are much redder in the uvw1-v color than
SN2011fe reddened to the same b-v color. The absolute magnitudes show
that two out of five NUV-blue SNe Ia are blue because their near-UV
luminosity is high, and the other three are optically fainter. We also
show that SN 2011fe is not a "normal" SN Ia in the UV, but has colors
placing it at the blue extreme of our sample.
Description:
Swift/UVOT has observed over 500 SNe of all types in its 12 years of
operation (see Brown+ 2015JHEAp...7..111B 2015JHEAp...7..111B for a review of the first
10yrs). Most of the observations use six UV and optical filters. All
photometry comes from the Swift Optical/Ultraviolet Supernova Archive
(SOUSA; Brown+ 2014Ap&SS.354...89B 2014Ap&SS.354...89B) and is available at the Swift SN
website and the Open Supernova Archive (Guillochon+ 2017ApJ...835...64G 2017ApJ...835...64G).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 124 29 Supernovae Ia information
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See also:
J/AJ/131/527 : UBVRI light curves of 44 type Ia supernovae (Jha+, 2006)
J/ApJ/659/122 : Improved distances to type Ia supernovae (Jha+, 2007)
J/ApJ/689/377 : PAIRITEL SNe Ia as NIR standard candles (Wood-Vasey+, 2008)
J/AJ/137/4517 : UVOT light curves of supernovae (Brown+, 2009)
J/ApJS/185/32 : First-year SDSS-II SN results (Kessler+, 2009)
J/ApJ/721/1608 : Absolute UV magnitudes of type Ia SNe (Brown+, 2010)
J/AJ/139/120 : Low-redshift Type-Ia supernovae (Folatelli+, 2010)
J/ApJ/731/120 : Intrinsic SN Ia light curves (Mandel+, 2011)
J/ApJ/753/22 : Swift/UVOT observations of SN 2011fe (Brown+, 2012)
J/A+A/554/A27 : 2011fe spectrophotometric time series (Pereira+, 2013)
J/A+A/568/A22 : Joint analysis of the SDSS-II and SNLS SNe Ia (Betoule+, 2014)
J/ApJS/212/18 : An atlas of UV-to-MIR galaxy SEDs (Brown+, 2014)
J/ApJ/796/L18 : Type Ia supernova 2011de UVOT photometry (Brown, 2014)
J/MNRAS/438/1391 : Host galaxies of Type Ia SN from PTF (Pan+, 2014)
J/AJ/152/102 : Flux conversion factors for Swift/UVOT filters (Brown+, 2016)
J/ApJ/826/56 : HST/WFC3 obs. of Cepheids in SN Ia host gal. (Riess+, 2016)
http://people.physics.tamu.edu/pbrown/SwiftSN/swift_sn.html : Swift SNe webpage
http://sne.space/ : The online Open Supernova Catalog
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Supernova identifier
11- 14 F4.2 mag Dm15B [1/1.4] The B band decline rate parameter (1)
16- 19 F4.2 mag e_Dm15B [0.01/0.2] Uncertainty in Dm15B
21- 26 F6.3 mag w1mag [11/18.8] Swift/UVOT w1 band magnitude
at B band peak
28- 32 F5.3 mag e_w1mag [0.001/0.2] Uncertainty in w1mag
34- 39 F6.3 mag Vmag [10/17] The Johnson V band magnitude
at B band peak
41- 45 F5.3 mag e_Vmag [0.001/0.03] Uncertainty in Vmag
47- 52 F6.3 mag B-V The (B-V) color index at B band peak
54- 58 F5.3 mag e_B-V Uncertainty in (B-V)
60- 65 F6.3 mag DM [29.1/35.6] Distance modulus
67- 71 F5.3 mag e_DM [0.04/0.4] Uncertainty in DM
73- 80 A8 --- n_DM Method used to derive DB (2)
82-124 A43 --- r_DM Reference for DM
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Note (1): Decline in the B band from 15 days after maximum.
Note (2):
z = redshift distance is derived using the referenced recessional velocity
corrected for the galaxy-flow model of Mould+ (2000ApJ...529..786M 2000ApJ...529..786M)
implemented by the NASA Extragalactic Database (NED) and converted to a
distance modulus assuming H0=72km/s/Mpc
Freedman+ (2001ApJ...553...47F 2001ApJ...553...47F).
SBF = surface brightness fluctuation (1 occurrence)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 06-Oct-2017