TABLE OF CONTENTS:
The GCN system has been modified to incorporate the distribution of a neutrino burst detection
from a supernova (SN) explosion by the Super-Kamiokande (SK) detector and its position on the sky.
The SK detector is the world’s largest water Cherenkov detector consisting of 50,000 tons of ultra pure water
and 13,000 photomultiplier tubes, and it is located 1,000 m underground in a mountain in Kamioka, Gifu, Japan.
SK can detect lots of neutrinos from a SN explosion within a short period of time, typically 10 seconds, and
can estimate the location on the sky from the detected neutrino event topology.
The neutrino burst detection system issues an internal alert if SK detects more than 60 neutrinos within 20 seconds.
After detailed checks by SK analysis experts, a SK_SN Notice is published (typically in 1 hour
from the neutrino burst detection). With these criteria, SK can detect any SN explosions occurring in our galaxy,
the Large and Small Magellan Nebulie. Thanks to very low background rate, the expected false rate is extremely small.
For details of the SN detection system and algorithm, please refer [K. Abe et al. Astroparticle Physics].
The dominant interactions of SN neutrinos in SK are inverse beta decay of anti-electron neutrinos and
elastic scattering of electron neutrinos. The SN direction can be determined from the distribution of electrons
in these events, especially scattered electrons in the elastic scattering events.
The expected error depends on the number of neutrinos involved and if the SN is in our galaxy; it ranges from 1-4 deg.
The SK has started a new phase of operations in July 2020 with the loading of Gadolinium into the SK water
to improve the neutron tagging efficiency. This results in an improvement of the SN direction determination power.
The new algorithm for the SK-Gd phase will be introduced into the SN automatic detection system in Decemeber 2020.
Notice Types, Content, and Purpose
There are 2 variation in the GCN/SK_SN Notice type. They are:
1) SK_SN Real: That notice contains the number of detected neutrino events, timing information (the date, time and duration),
the SN direction, its errors and the estimated distance from the Earth. The neutrino events
with more than 7 MeV visible energies are counted. The provided event time corresponds
to the date and time of the first neutrino detection, and the duration is the difference of time
between the first and last neutrino events. The first (last) event is defined as the first (last) event
in the observed bunch of events (no other event at least 30 seconds before (after) the event is required.)
The distance is estimated with an assumption as the SN1987A like neutrino flux at the source.
2) SK_SN Test: That Notice contains dummy event information with the same format as SK_SN Real Notice.
It publishes once per month for testing the systems of both SK and follow-up observers.
The SK detector has mostly a uniform sensitivity for any SN location in the sky.
SK is operating 24 hours a day and its live-time fraction is approximately 98%.
The remaining 2% corresponds to test and calibration runs. Any neutrino burst alerts
issued during these test/calib runs are vetoed to avoid false alerts. Even in these cases,
SN neutrino events can be identified by a dedicated analysis, however it takes time.
The time delay from a SN neutrino burst detection to GCN/SK_SN notice publication
is expected to be less than 1 hour, and which includes the time for the automated analysis process and the human checking.
The optical-light increase in an SN explosion is delayed from the neutrino burst (ranges from 10's sec to 10's of K sec; and depends on SN type).
Samples of the E-mail, Cell/Pager, Short-form Cell/Pager, and Subject-only distribution methods
of the 2 GCN/SK_SN Notice types are included below. The format is very similar to the spacecraft-instrument sources
of GRB and Transient locations -- the GCN-standard "TOKEN: value" format.
(Also available in XML format via email and sockets (both binary and xml).)
The socket packet contents and format are similar to the other mission-specific packet types and
are described in detail in the socket packet definition document. This document also has explanations
of the various fields in the packet (their content, values, and implications for use).
(Therefore, it is useful for email-based recipients to read the socket packet definition document
to understand the contents of the email/cell/pager notifications.)
The SK_SN Notice is type=175; for both the "real event" and the "test event" occurances.
For the 160-byte binary format, if the 2^1 bit in the "trig_id" slot has a value of "1" then it is a "test" event notice, and
and if the 2^1 has a 0 then it is a "real" event notice.
NUM TYPE VOEVENT SOCKET FullFmt_EMAIL PAGER/CELL XML
w/Txt (all 4 variants)
=== ========= ======= ====== ============= ================ ====
175 SK_SN Y P B B B&A
where:
Y = Also available in XML VOEvent format for XML_Sockets and VOEvent server sockets.
P = Packet (the GCN-standard 40 longword socket packet format)
B = Body of email (the GCN-standard "TOKEN: value" format)
A = As an attachment to a full-format email.
--------
Sites can select to receive each of the 2 SK_SN Notice sub-types (the "Real" event and the "Test" event).
You can elect to disable the "Test" subtype by having the SK_SN_no_test" flag set to 1 to block all incoming "Test" notices.
See filtering to see the full list of filtering criteria for this Type.
This filtering applies to all the existing distribution methods/media.
The uncertainty in the location will depend on the number of detected neutrinos in Super-Kamiokande,
which strongly depends on the distance to the SN and the type. The expected number
of neutrino detections, and the error size of the location is 7000-8000 and 3-4 deg for a SN in our galaxy.
The statistical error sizes for 68%, 90% and 95% containment are provided for each event.
The distance estimation band (with the SN1987A-like flux assumption)
is calculated for 68% containment considering only statistical uncertainty
of both the burst event and the SN1987A events (11 events in SK).
The expected rate of the "real" SK_SN events is 0.03 per year.
The "Test" Notices are once per month on the first of the month.
Sites are encouraged to acknowledge SK in their publications
based on follow-up observations using these GCN/SK_SN locations.
The GCN/SK_SN Notices are archived within the GCN website
in the Table of SK_SN Notices.
Given that SuperNovas are so rare in our galaxy, the table will also contain
the "Test" sub-notice type.
The Test notices will also show that the SK is functioning (on a monthly update cycle).
For further information on this:
see the SK website
or please contact Scott Barthelmy (for GCN issues),
Scott Barthelmy (for GCN/TAN issues).
Examples of the 1 Notice type of the various e-mail formats are shown below.
The "/////" divider bars are NOT part of the messages.
Do not take the actual values shown in these examples as real SK_SN event.
.
///////////// REAL ////////////////////////////////////////////////////////////
TITLE: GCN/SK_SN NOTICE
NOTICE_DATE: Wed 10 Feb 21 21:32:06 UT
NOTICE_TYPE: SK_SN REAL
TRIGGER_NUMBER: SK_SN 1
SRC_RA: 318.3000d {+21h 13m 12s} (J2000),
318.5203d {+21h 14m 05s} (current),
317.7725d {+21h 11m 05s} (1950)
SRC_DEC: +31.3700d {+31d 22' 12"} (J2000),
+31.4569d {+31d 27' 25"} (current),
+31.1630d {+31d 09' 47"} (1950)
SRC_ERROR68: 0.64 [deg radius, stat-only, 68% containment]
SRC_ERROR90: 0.91 [deg radius, stat-only, 90% containment]
SRC_ERROR95: 1.04 [deg radius, stat-only, 95% containment]
DISCOVERY_DATE: 19166 TJD; 318 DOY; 20/11/13 (yy/mm/dd)
DISCOVERY_TIME: 30601 SOD {08:30:01.22} UT
N_EVENTS: 54029 (Number of detected neutrino events)
ENERGY_LIMIT: 7.00 [MeV] (Minimum energy of the neutrinos)
DURATION: 10.0 [sec] (Collection duration of the neutrinos)
DISTANCE: 2.35 - 3.22 [kpc] (low - high as SN1987A like SNe)
COMMENTS: The position error is statistical only, there is no systematic added.
COMMENTS: All numbers are preliminary.
COMMENTS:
COMMENTS: NOTE: This is a REAL EVENT! It is NOT a TEST event.
COMMENTS:
///////////// TEST ////////////////////////////////////////////////////////////
TITLE: GCN/SK_SN NOTICE
NOTICE_DATE: Wed 10 Feb 21 20:37:44 UT
NOTICE_TYPE: SK_SN TEST
TRIGGER_NUMBER: SK_SN 10001
SRC_RA: 318.3000d {+21h 13m 12s} (J2000),
318.5203d {+21h 14m 05s} (current),
317.7725d {+21h 11m 05s} (1950)
SRC_DEC: +31.3700d {+31d 22' 12"} (J2000),
+31.4569d {+31d 27' 25"} (current),
+31.1630d {+31d 09' 47"} (1950)
SRC_ERROR68: 0.64 [deg radius, stat-only, 68% containment]
SRC_ERROR90: 0.91 [deg radius, stat-only, 90% containment]
SRC_ERROR95: 1.04 [deg radius, stat-only, 95% containment]
DISCOVERY_DATE: 19166 TJD; 318 DOY; 20/11/13 (yy/mm/dd)
DISCOVERY_TIME: 30601 SOD {08:30:01.22} UT
N_EVENTS: 54029 (Number of detected neutrino events)
ENERGY_LIMIT: 7.00 [MeV] (Minimum energy of the neutrinos)
DURATION: 10.0 [sec] (Collection duration of the neutrinos)
DISTANCE: 2.35 - 3.22 [kpc] (low - high as SN1987A like SNe)
COMMENTS: The position error is statistical only, there is no systematic added.
COMMENTS: All numbers are preliminary.
COMMENTS:
COMMENTS: NOTE: This is a TEST Notice.
COMMENTS:
//////////////////////////////////////////////////////////////////////////////
Cell/Pager Examples:
Examples of the (regular) cell/pager formats are shown below.
There are no "Subject" lines for these e-mails sent to the cell/pager companies
because the Subject line would use up valuable character counts
from the maximum displayable for the body of the message.
The RA,Dec is Current epoch.
/////////////////////////REAL Cell/Pager format////////////////////////////////
GCN/SK_SN
Position REAL
RA=318.520d DEC=+31.457d
Err=0.6 (68%)
T=08:30:01.22 UT
/////////////////////////TEST Cell/Pager format////////////////////////////////
GCN/SK_SN
Position TEST
RA=318.520d DEC=+31.457d
Err=0.6 (68%)
TrigNum=10001
T=08:30:01.22 UT
///////////////////////////////////////////////////////////////////////////////
Short-form Cell/Pager Examples:
Examples of the short-form cell/pager format are shown below.
There are no "Subject" lines for these e-mails sent to the cell/pager companies,
because the Subject-line would use up valuable character counts from the maximum
displayable for the body of the message. And it was the very limited
display character count of some companies that motivated the short-form cell/pager
method in the first place.
The RA,Dec is 1950 epoch.
/////////////////////////REAL Short-Cell/Pager format//////////////////////////
SK_SN
Position REAL
RA=317.773 DEC=+31.163d
DATE: 20/11/13
T=08:30:01.22
TRIG_NUM=1
/////////////////////////TEST Short-Cell/Pager format//////////////////////////
SK_SN
Position TEST
RA=317.773 DEC=+31.163d
DATE: 20/11/13
T=08:30:01.22
TRIG_NUM=10001
///////////////////////////////////////////////////////////////////////////////
Subject-only Examples
There are two variations of the Subject-only format: decimal degrees (Current epoch)
and RA=hh:mm:ss Dec=DDdMMmSSs format (J2000 epoch). The two variations are shown below:
/////////////////////////REAL Subject-only format (Current epoch)//////////////
SK_SN REAL RA=318.5203 DEC=+31.4569d T=08:30:01.22 UT TrigNum=1
/////////////////////////TEST Subject-only format (Current epoch)//////////////
SK_SN TEST RA=318.5203 DEC=+31.4569d T=08:30:01.22 UT TrigNum=10001
///////////////////////////////////////////////////////////////////////////////
///////////////REAL Subject-only format HH:MM:SS format (J2000 epoch)//////////
SK_SN REAL RA=+21:13:12 DEC=+31:22:12 Num_events=54029
///////////////TEST Subject-only format HH:MM:SS format (J2000 epoch)//////////
SK_SN TEST RA=+21:13:12 DEC=+31:22:12 Num_events=54029
///////////////////////////////////////////////////////////////////////////////
VOEvent by Email or Socket Examples
/////////////////////////REAL VOEvent format///////////////////////////////////
<?xml version = '1.0' encoding = 'UTF-8'?>
<voe:VOEvent
ivorn="ivo://nasa.gsfc.gcn/SK_SN#Event_2021-03-11T19:42:06.07_000001-069"
role="observation" version="2.0"
xmlns:voe="http://www.ivoa.net/xml/VOEvent/v2.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.ivoa.net/xml/VOEvent/v2.0 http://www.ivoa.net/xml/VOEvent/VOEvent-v2.0.xsd" >
<Who>
<AuthorIVORN>ivo://nasa.gsfc.tan/gcn</AuthorIVORN>
<Author>
<shortName>SK_SN (via VO-GCN/TAN)</shortName>
<contactName>Menjo Hiroaki</contactName>
<contactEmail>menjo@isee.nagoya-u.ac.jp</contactEmail>
</Author>
<Date>2021-03-17T19:31:36</Date>
<Description>This VOEvent message was created with GCN/TAN VOE version: 15.06 10feb21</Description>
</Who>
<What>
<Param name="Packet_Type" dataType="int" value="175" />
<Param name="Pkt_Ser_Num" dataType="int" value="1" />
<Param name="Trigger_Number" dataType="int" value="1" ucd="meta.id" />
<Param name="Pkt_TJD" dataType="int" value="19284" unit="days" ucd="time" />
<Param name="Pkt_SOD" dataType="float" value="70926.07" unit="sec" ucd="time" />
<Param name="Energy_Limit" dataType="float" value="7.0" >
<Description>The lower energy limit of the neutrinos.</Description>
</Param>
<Param name="Duration" dataType="float" value="6.8" >
<Description>The duration of the window for the collected neutrinos.</Description>
</Param>
<Param name="Src_Error68" dataType="float" value="70.7" >
<Description>The location uncertainty with 68% containment.</Description>
</Param>
<Param name="Src_Error90" dataType="float" value="118.0" >
<Description>The location uncertainty with 90% containment.</Description>
</Param>
<Param name="Src_Error95" dataType="float" value="134.7" >
<Description>The location uncertainty with 95% containment.</Description>
</Param>
<Param name="N_Events" dataType="int" value="11" >
<Description>The number of neutrinos in the event.</Description>
</Param>
<Param name="Min_Distance" dataType="float" value="152.80" unit="kpc" >
<Description>The minimum distance to this SN.</Description>
</Param>
<Param name="Max_Distance" dataType="float" value="237.62" unit="kpc" >
<Description>The maximum distance to this SN.</Description>
</Param>
<Param name="Discovery_date" dataType="int" value="19284" />
<Param name="Discovery_time" dataType="int" value="70926.07" unit="sec" />
</What>
<WhereWhen>
<ObsDataLocation>
<ObservatoryLocation id="GEOLUN" />
<ObservationLocation>
<AstroCoordSystem id="UTC-FK5-GEO" />
<AstroCoords coord_system_id="UTC-FK5-GEO">
<Time unit="s">
<TimeInstant>
<ISOTime>2021-03-11T19:42:06.07</ISOTime>
</TimeInstant>
</Time>
<Position2D unit="deg">
<Name1>RA</Name1>
<Name2>Dec</Name2>
<Value2>
<C1>213.2599</C1>
<C2>15.2400</C2>
</Value2>
<Error2Radius>0.0000</Error2Radius>
</Position2D>
</AstroCoords>
</ObservationLocation>
</ObsDataLocation>
<Description>The RA,Dec coordinates are of the type: pointing_direction.</Description>
</WhereWhen>
<How>
<Description>SK_SN SuperKamiokande SuperNova search</Description>
<Reference uri="http://gcn.gsfc.nasa.gov/gcn/sk_sn.html" type="url" />
</How>
<Why importance="1.0">
<Inference probability="1.0">
<Concept>process.variation.burst;em</Concept>
</Inference>
</Why>
<Description>
</Description>
</voe:VOEvent>
/////////////////////////TEST VOEvent format///////////////////////////////////
<voe:VOEvent
ivorn="ivo://nasa.gsfc.gcn/SK_SN#Event_2021-03-12T00:15:19.10_000002-025"
role="test" version="2.0"
xmlns:voe="http://www.ivoa.net/xml/VOEvent/v2.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.ivoa.net/xml/VOEvent/v2.0 http://www.ivoa.net/xml/VOEvent/VOEvent-v2.0.xsd" >
<Who>
<AuthorIVORN>ivo://nasa.gsfc.tan/gcn</AuthorIVORN>
<Author>
<shortName>SK_SN (via VO-GCN/TAN)</shortName>
<contactName>Menjo Hiroaki</contactName>
<contactEmail>menjo@isee.nagoya-u.ac.jp</contactEmail>
</Author>
<Date>2021-03-17T20:02:55</Date>
<Description>This VOEvent message was created with GCN/TAN VOE version: 15.06 10feb21</Description>
</Who>
<What>
<Param name="Packet_Type" dataType="int" value="175" />
<Param name="Pkt_Ser_Num" dataType="int" value="2" />
<Param name="Trigger_Number" dataType="int" value="10018" ucd="meta.id" />
<Param name="Pkt_TJD" dataType="int" value="19285" unit="days" ucd="time" />
<Param name="Pkt_SOD" dataType="float" value="919.10" unit="sec" ucd="time" />
<Param name="Energy_Limit" dataType="float" value="7.0" >
<Description>The lower energy limit of the neutrinos.</Description>
</Param>
<Param name="Duration" dataType="float" value="6.8" >
<Description>The duration of the window for the collected neutrinos.</Description>
</Param>
<Param name="Src_Error68" dataType="float" value="70.7" >
<Description>The location uncertainty with 68% containment.</Description>
</Param>
<Param name="Src_Error90" dataType="float" value="118.0" >
<Description>The location uncertainty with 90% containment.</Description>
</Param>
<Param name="Src_Error95" dataType="float" value="134.7" >
<Description>The location uncertainty with 95% containment.</Description>
</Param>
<Param name="N_Events" dataType="int" value="11" >
<Description>The number of neutrinos in the event.</Description>
</Param>
<Param name="Min_Distance" dataType="float" value="152.80" unit="kpc" >
<Description>The minimum distance to this SN.</Description>
</Param>
<Param name="Max_Distance" dataType="float" value="237.62" unit="kpc" >
<Description>The maximum distance to this SN.</Description>
</Param>
<Param name="Discovery_date" dataType="int" value="19285" />
<Param name="Discovery_time" dataType="int" value="919.10" unit="sec" />
</What>
<WhereWhen>
<ObsDataLocation>
<ObservatoryLocation id="GEOLUN" />
<ObservationLocation>
<AstroCoordSystem id="UTC-FK5-GEO" />
<AstroCoords coord_system_id="UTC-FK5-GEO">
<Time unit="s">
<TimeInstant>
<ISOTime>2021-03-12T00:15:19.10</ISOTime>
</TimeInstant>
</Time>
<Position2D unit="deg">
<Name1>RA</Name1>
<Name2>Dec</Name2>
<Value2>
<C1>213.2599</C1>
<C2>15.2400</C2>
</Value2>
<Error2Radius>0.0000</Error2Radius>
</Position2D>
</AstroCoords>
</ObservationLocation>
</ObsDataLocation>
<Description>The RA,Dec coordinates are of the type: pointing_direction.</Description>
</WhereWhen>
<How>
<Description>SK_SN SuperKamiokande SuperNova search</Description>
<Reference uri="http://gcn.gsfc.nasa.gov/gcn/sk_sn.html" type="url" />
</How>
<Why importance="1.0">
<Inference probability="1.0">
<Concept>process.variation.burst;em</Concept>
</Inference>
</Why>
<Description>
</Description>
</voe:VOEvent>
///////////////////////////////////////////////////////////////////////////////