J/ApJ/828/3 Swift obs. of the superluminous SNI ASASSN-15lh (Brown+, 2016)
ASASSN-15lh: a superluminous ultraviolet rebrightening observed by Swift and
Hubble.
Brown P.J., Yang Y., Cooke J., Olaes M., Quimby R.M., Baade D., Gehrels N.,
Hoeflich P., Maund J., Mould J., Wang L., Wheeler J.C.
<Astrophys. J., 828, 3-3 (2016)>
=2016ApJ...828....3B 2016ApJ...828....3B (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Photometry, ultraviolet ; X-ray sources ;
Photometry, UBV
Keywords: polarization; supernovae: individual (ASASSN-15lh, SN2015L);
ultraviolet: general; X-rays: general
Abstract:
We present and discuss ultraviolet and optical photometry from the
Ultraviolet/Optical Telescope, X-ray limits from the X-Ray Telescope
on Swift, and imaging polarimetry and ultraviolet/optical spectroscopy
with the Hubble Space Telescope, all from observations of ASASSN-15lh.
It has been classified as a hydrogen-poor superluminous supernova
(SLSN I), making it more luminous than any other supernova observed.
ASASSN-15lh is not detected in the X-rays in individual or co-added
observations. From the polarimetry we determine that the explosion was
only mildly asymmetric. We find the flux of ASASSN-15lh to increase
strongly into the ultraviolet, with an ultraviolet luminosity 100
times greater than the hydrogen-rich, ultraviolet-bright SLSN II SN
2008es. We find that objects as bright as ASASSN-15lh are easily
detectable beyond redshifts of ∼4 with the single-visit depths planned
for the Large Synoptic Survey Telescope. Deep near-infrared surveys
could detect such objects past a redshift of ∼20, enabling a probe of
the earliest star formation. A late rebrightening-most prominent at
shorter wavelengths-is seen about two months after the peak
brightness, which is itself as bright as an SLSN. The ultraviolet
spectra during the rebrightening are dominated by the continuum
without the broad absorption or emission lines seen in SLSNe or tidal
disruption events (TDEs) and the early optical spectra of ASASSN-15lh.
Our spectra show no strong hydrogen emission, showing only Lyα
absorption near the redshift previously found by optical absorption
lines of the presumed host. The properties of ASASSN-15lh are extreme
when compared to either SLSNe or TDEs.
Description:
ASASSN-15lh, was discovered by the ASAS-SN on UT 2015 June 14.25
(MJD 57187.25).
Observations with Swift began 2015 June 24 00:37:49 (MJD 57197). The
early UVOT data were reported by Dong+ (2016Sci...351..257D 2016Sci...351..257D).
We triggered our Swift Guest Investigator programs "Ultraviolet
Properties of Superluminous Supernovae over Ten Billion Years"
(PI: Brown) to obtain UV/optical photometry with Swift/UVOT and
"Late-time X-Rays from Superluminous Supernovae: How Hard Could it
Be?" (PI: Quimby). We have reduced all of the data obtained through
2016 April 1.
Objects:
----------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------
22 02 15.45 -61 39 34.6 ASASSN-15lh = SN 2015L
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 67 476 Swift/UVOT photometry of ASASSN-15lh
table2.dat 38 97 0.3-10keV X-ray 3σ upper limits
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See also:
B/eso : ESO Science Archive Catalog (ESO, 1991-2016)
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
J/other/Nat/491.228 : Light curves of 2 superluminous supernovae (Cooke+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- --- [ASASSN-15lh]
13- 16 A4 --- Filt Filter used in the observation (U B V UVW1 UVM2
or UVW2)
18- 27 F10.4 d MJD Modified Julian Date
29- 34 F6.3 mag mag [15.24/19.04]? Observed Swift/UVOT magnitude
in Filter (Vega system) (1)
36- 40 F5.3 mag e_mag [0.05/0.4]? Error in mag
42- 47 F6.3 mag UpLim [17.8/21.7] 3σ upper limit magnitude
in Filter (2)
49- 54 F6.3 mag LoLim [10.5/13] Lower (saturation) limit magnitude
in Filter (2)
56- 61 F6.3 ct/s Rate [0.2/15.3] Count rate in Filter
63- 67 F5.3 ct/s e_Rate [0.02/0.8] Error in Rate
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Note (1): Magnitudes are given in the UVOT/Vega system for easier comparison
with other SNe published in that system
(see Brown+ 2014Ap&SS.354...89B 2014Ap&SS.354...89B for a review).
Note (2): Both limits come from the exposure and background parameters. Most of
the photometry of ASASSN-15lh is not close to either of these limits,
but they are given for completeness and easy comparison with other
SN photometry tables from the Swift Optical/Ultraviolet Supernova
Archive (SOUSA; Brown+ 2014Ap&SS.354...89B 2014Ap&SS.354...89B).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 d MJD Modified Julian Date of the observation (1)
13- 18 I6 s Exp [172/227634] Exposure time
20- 28 E9.3 mW/m2 FluxLim 0.3-10keV X-ray flux limit; erg/s/cm2
30- 38 E9.3 10-7W LumLim 0.3-10keV X-ray luminosity limit; erg/s
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Note (1): The MJD column gives the start:stop range of dates for the coadded
limits and the midpoint for the single observations.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Dec-2016