IceCube-160427A
GCN Circular 19363
Subject
ICECUBE-160427A neutrino candidate event: updated direction information
Date
2016-04-29T16:29:47Z (9 years ago)
From
Erik Blaufuss at U. Maryland/IceCube <blaufuss@icecube.umd.edu>
IceCube detected a candidate cosmic neutrino IceCube-160427A, "AMON ICECUBE HESE 127853 67093193" at 05:52:32.00 UT
on 16/04/27 (http://gcn.gsfc.nasa.gov/notices_amon/67093193_127853.amon) The event was a high energy starting event (HESE)
with track-like characteristics and it arrived when the IceCube detector was in a normal operating state.
���
More sophisticated reconstruction algorithms have been applied offline, with the direction refined to RA=240.57d and DEC=+9.34d (J2000),
and the position uncertainty reduced to an estimated 0.6 degrees or 36 arcminuntes radius (stat+sys, 90% containment). We encourage followup
by ground and space-based instruments to help identify a possible astrophysical source for the neutrino.
���
The IceCube neutrino observatory is a cubic-kilometer neutrino detector operating at the geographic south Pole, Antarctica.
The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu
GCN Circular 19364
Subject
IceCube-160427A: Fermi GBM Observations
Date
2016-04-29T21:08:30Z (9 years ago)
From
Eric Burns at U of Alabama <eb0016@uah.edu>
Lindy Blackburn (CfA), Michael S. Briggs (UAH), Eric Burns (UAH), Jordan
Camp
(NASA/GSFC), Tito Dal Canton (NASA/GSFC), Nelson Christensen (Carleton
College),
Valerie Connaughton (USRA), Adam Goldstein (NASA/MSFC), C. M. Hui
(NASA/MSFC),
Peter Jenke (UAH), Tyson Littenberg (UAH), Judith Racusin (NASA/GSFC),
Peter
Shawhan (UMD), Leo Singer (NASA/GSFC), John Veitch (Birmingham), Colleen
Wilson-Hodge (NASA/MSFC), and Binbin Zhang (IAA-CSIC)
We have searched the Fermi Gamma-ray Burst Monitor data for a
gamma-ray counterpart for the IceCube High Energy Starting Event (HESE)
67093193, detected in run 127853 on 2016-04-27 05:52:32.00 UT (AMON GCN
notice rev. 2, http://gcn.gsfc.nasa.gov/notices_amon/67093193_127853.amon.
See http://gcn.gsfc.nasa.gov/doc/Public_Doc_AMON_IceCube_GCN_Alerts_v2.pdf
for a description of HESE events and related GCN notices).
The location of the neutrino was close to the Earth, but visible at event
time.
There were no on-board triggers in GBM near the time of the neutrino
detection.
We searched for associated gamma-ray emission with 3 different search
techniques.
A seeded search for impulsive emission with durations between 0.256 s and
8.192 s
around the time and sky location of the detected neutrino yielded no
candidates
above the GBM background. The search method was developed to look for
electromagnetic counterparts in the GBM data of sub-threshold gravitational
wave signals found in the LIGO data (Blackburn et al. 2015, ApJS, 217, 8),
and implemented here searching from 30 s before to 90 s after and seeded
with the position of the detected neutrino.
A blind search for untriggered impulsive emission in the GBM data
centered on the neutrino detection yielded no candidates consistent with the
position of the neutrino. This search technique was developed for the
detection
of untriggered short GRBs in the GBM data (Briggs et al., in prep.).
Measurements using the Earth Occultation technique (Wilson-Hodge et al.
2012,
ApJS, 201, 33) using the IceCube position in 17.5 hours around the neutrino
detection place a three sigma flux limit of 224 mCrab between 12 and 300
keV.
GCN Circular 19381
Subject
ICECUBE-160427A : Pan-STARRS imaging and optical transients in the field
Date
2016-05-04T18:43:58Z (9 years ago)
From
Stephen Smartt at Queen's U/Belfast <s.smartt@qub.ac.uk>
S. Smartt (Queen���s University Belfast), K. C. Chambers (IfA, Univ. of Hawaii),
K. Smith (QUB), M. E. Huber (IfA), D. Wright (QUB),
H. Flewelling, E. A. Magnier, N. Primak, A. S. B. Schultz (IfA), J. Tonry,
C. Waters, M. Willman (IfA), D. Young (QUB)
Further to the detection of a candidate cosmic neutrino, as event IceCube-160427A
(Blaufuss et al. GCN 19363) we report Pan-STARRS1 imaging of the field and a
search for optical transients.
We observed the field, entered on RA=240.57d and DEC=+9.34d (J2000)
beginning MJD 57508.5 UT (2016 April 30.5), which was 3.3
days after the IceCube detection (2016 April 27.2) with the Pan-STARRS1
telescope in the i-band filter. Difference imaging with respect to the
Pan-STARRS1 3Pi stacked reference sky reached 5-sigma limiting magnitudes of
around i~22.5. We repeated the observations on the 4 subsequent nights.
Similar to Lipunov et al. (GCN19362), we find no bright transient source
within the 90% containment area of 36 arc minutes radius of the above position
(RA=16:02:16.8, DEC=+09:20:24). We find the following 24 fainter sources
Eight QSOs (with SDSS spectra) are found to be significantly variable
(the variable flux was 18.8 < i < 21.4) and are in the
redshift range 0.345 to 2.384.
Seven supernova candidates (discovery mags 20.5 < i < 22.1) were found. These
are transient sources which have a detected candidate host galaxy, and either
offset from the host or are coincident but not known QSO/AGN. No
catalogued spectroscopic redshifts of the hosts are available.
A further 9 transients were found associated with faint point sources that
are either faint Galactic variable stars or QSO variability.
In summary, there is no obvious counterpart candidate in the optical
brighter than i ~ 21. Within the 90% containment field diameter of 1.2 degrees,
we have hit the confusion limit of the faint variable sky. While there are many
variable/transient candidates, there is no one object that is statistically
rare enough it could be considered further.
The SN candidates are as follows. Six of the candidates show flat
lightcurves across our 5 days of monitoring, consistent with being
SN at or after peak. One object is worth considering further :
Object | RA (J2000) | DEC (J2000) | Disc Date | i -mag
PS16cgv | 15 59 53.84 | +09 11 08.4 | 20160430 | 22.01
PS16cgw | 16 00 39.69 | +09 39 21.2 | 20160430 | 21.80
PS16cfu | 16 01 15.66 | +09 25 04.7 | 20160430 | 21.14
PS16cgx | 16 01 18.60 | +09 51 53.1 | 20160430 | 21.84 *
PS16cfz | 16 02 11.96 | +09 54 07.9 | 20160430 | 21.27
PS16cgb | 16 02 19.12 | +09 34 50.1 | 20160430 | 22.03
PS16cgi | 16 03 27.72 | +08 54 05.2 | 20160430 | 22.09
* PS16cgx rose at by 0.4 mag over 2 days. The rise time would
be consistent with a type Ic supernova at z ~ 0.1 to 0.2 that
exploded on or around 2016 April 27.2 (and possibly an off-axis GRB).
However the 4th data point shows it has peaked at i=21.5 +/- 0.1,
and is therefore more consistent with a type Ia SN from the normal
field population. Spectroscopic follow-up is needed to confirm.
GCN Circular 19392
Subject
IceCube-160427A: iPTF Observations
Date
2016-05-06T03:05:02Z (9 years ago)
From
Leo Singer at GSFC/iPTF <leo.p.singer@nasa.gov>
L. P. Singer (NASA/GSFC), M. M. Kasliwal (Caltech), S. B. Cenko (NASA/GSFC),
E. O. Ofek (Weizmann), N. Strotjohann (DESY), A. Franckowiak (DESY),
M. Kowalski (DESY), and G. Tesic (PSU) report on behalf of the
Intermediate Palomar Transient Factory (iPTF) collaboration:
Following the detection and updated localization of the cosmic neutrino
candidate IceCube-160427A (GCN 19363), we began searching for optical
counterparts using the Palomar 48-inch Oschin telescope (P48) on
2016-05-04 at 05:56 UT, 7.0 days after the trigger. The delay was due to
prolonged adverse weather conditions at Palomar.
We imaged 2 fields covering an area of 16 deg^2 to a limiting magnitude of
R=20.6--21, enclosing the entire final IceCube error circle. We estimate a
nearly 100% prior probability that these fields contain the true location
of the source. Sifting through candidate variable sources using image
subtraction and standard iPTF vetting procedures, we detected the
following optical transient candidates:
name RA Dec sep mag t
-----------------------------------------------
iPTF16apj 240.638236 +7.247857 2.1 20.07 7.00
iPTF16apk 240.284222 +7.124179 2.2 20.58 7.00
iPTF16apl 241.437244 +9.961542 1.1 20.27 7.00
All three transients are positionally consistent with the nuclei of their
respective host galaxies. All three have a prior history of variability in
iPTF dating to March 2016.
We checked for excess emission at the positions of the SN candidates
reported by Pan-STARRS (GCN 19381). PS16cgv is at the edge of an iPTF
chip, so reliable image subtraction is not possible. None of the other
candidates had significant detectable excesses in our difference images,
not surprising given the shallower depth of our observations relative to
Pan-STARRS.
Positions are in J2000. Separations are in degrees and relative to the
best-estimate IceCube position (240.57 +9.34). Magnitudes are in the Mould
R filter and in the AB system, calibrated with respect to point sources in
SDSS as described in Ofek et al. (2012, http://dx.doi.org/10.1086/664065).
Times are in days since the IceCube trigger.
GCN Circular 19426
Subject
Interplanetary Network Search for IceCube 160427A
Date
2016-05-12T18:05:09Z (9 years ago)
From
Kevin Hurley at UCBerkeley/SSL <khurley@ssl.berkeley.edu>
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, and T. Cline,
on behalf of the Konus-Wind team,
K. Hurley, on behalf of the Interplanetary Network,
I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,
W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on
behalf of the GRS-Odyssey GRB team,
S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of
the Swift-BAT team, and
V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein,
on behalf of the Fermi GBM team, report:
We have searched for an electromagnetic counterpart to the IceCube
neutrino event 160427A (GCN 19363) in the data of the six-spacecraft
Interplanetary Network. INTEGRAL SPI-ACS and RHESSI were not taking
data at the time of the event. Konus-Wind, Swift BAT, Odyssey HEND, and
Fermi GBM (GCN 19364) were taking data and the source direction was
unocculted to them. No events were found which could reasonably be
associated with 160427A. Specifically, the following limits can be
derived from the Konus Wind data. These apply to a 1000 s interval
centered at 05:52:32 UT (an interval duration consistent with the
expected delay of neutrino signals from GRBs, Baret et al., 2011,
arXiv:1101.4669), using standard KW GRB search procedures at a 5 sigma
threshold.
The 90% fluence upper limits for a typical short GRB spectrum (CPL with
alpha=-0.5, Ep=500 keV) over a 2.944 s time scale is ~1.0x10^-7
erg/cm2. This limit was calculated using count rates in the bins from
T0-1.524 s to T0+1.420 s (corrected for Konus to Earth time of
flight).
For a typical long GRB spectrum (Band function with alpha=-1,
beta=-2.5, Ep=300 keV) and a search interval duration of 24 s (a
typical KW long GRB duration) the upper limit is ~1.5x10^-6 erg/cm2.
Both limits are in the 10 keV - 10 MeV band.
The two Konus-Wind triggers closest in time to 160427A were at 2016-04-27 37785.294 s UT
(10:29:45.294) in the S1 detector (4.5 hours after the IceCube event)
and 2016-04-25 69940.132 s UT (19:25:40.132) in the S2 detector (about
two days before the event). The localization of GRB 20160427_37785 is
inconsistent with the neutrino event, while the ecliptic latitude
response for GRB 20160425_T69940 is consistent with it, but the
probability of a random coincidence is high. GRB 20160425_T69940 was
not detected by any other instrument, so no further analysis is possible.