[vsnet-grb 154735] MOA Gravitational Lensing Event Notice added to GCN

Tue Aug 2 03:47:21 JST 2011

TO:  All GCN Notice recipients
RE:  MOA Gravitational Lensing Event Notice added to GCN
DT:  01 Aug 11

INTRODUCTION
The GCN system has been modified to incorporate the distribution
of the MOA notice type.  This notice type contains the gravitational
lensing events detected by the MOA instrument.  When a compact mass
passes in front a field star (in the Galactic Bulge), the lensing effect causes
the star to brighten.  The time dependence of the apparent brightening yields
information about the mass of the lensing object.

ACTION ITEM:
If, after reviewing the information below, you want to receive
this MOA notice type, please send me a request to have them enabled.
You can do this by forwarding this email with your request to  scott at milkyway.gsfc.nasa.gov
(since it already has your "site name").
Or you can go to  http://gcn.gsfc.nasa.gov/gcn/config_builder.html
and select "#2 Modify an existing config".
You can also take this opportunity to make other changes to your config.

CONTENT and PURPOSE:
These GCN/MOA Notices contain: the RA,Dec location of the lensed star,
the date/time when the maximum brightness will occur and a characteristic
width of the lightcurve cusp.
Of particular usefulness to the follow-up observer is that these notices
are often issued prior to the cusp in the light curve (2/3 of the notices).
Hence, follow-up observers can be on target filling in the lightcurve
during the most productive time of the event.
The max expected magnitude of the cusp and its characteristic width
are also given in the Notice.
The baseline (quiescent) magnitudes of the lensed stars ranges
from 14-22 mag (10-90 percentile) and 50% of the events have
a delta_mag decrease of 2 or more.
Plots of these lead/lag and amplitude distributions can be found on the webpage:
http://gcn.gsfc.nasa.gov/gcn/moa.html .

OCCURRENCE RATE:
These GCM/MOA notices occur at a rate of these notices is 60/month
for the ~9 months a year that the Galactic Bulge is observable.
Eg MOA detected 607 events in 2010, 563 in 2009, and 477 in 2008.

FALSE POSITIVES:
Less than 10% of these events will turn out to be nonlensing events
(ie cataclysmic variables (CVs), other variable stars; but even these
are astrophysical and are of some interest).

POSITION ERRORS:
The location error of the lensed star is about 1 arcsec.

ARCHIVE STORAGE:
The GCN/MOA Notices are archived within the GCN website in the Table of MOA Events:
http://gcn.gsfc.nasa.gov/gcn/moa_events.html

MORE INFORMATION:
Can be found at: http://gcn.gsfc.nasa.gov/gcn/moa.html

NOTICE EXAMPLE:
Here is an example of a full-format email MOA Event Notice:
    TITLE:           GCN/MOA NOTICE
    NOTICE_DATE:     Sun 31 Jul 11 12:40:20 UT
    NOTICE_TYPE:     MOA Lensing Event
    SRC_ID_NUM:      201100341
    SRC_RA:          267.8037d {+17h 51m 13s} (J2000),
                     267.9963d {+17h 51m 59s} (current),
                     266.9720d {+17h 47m 53s} (1950)
    SRC_DEC:         -34.5123d {-34d 30' 43"} (J2000),
                     -34.5147d {-34d 30' 52"} (current),
                     -34.4996d {-34d 29' 58"} (1950)
    DISCOVERY_DATE:  15773 TJD;   212 DOY;   11/07/31
    DISCOVERY_TIME:  45577 SOD {12:39:37.00} UT
    LEAD_TIME:       0.342 [days]
    MAX_DATE:        15773 TJD;   212 DOY;   11/07/31
    MAX_TIME:        75167 SOD {20:52:47.00} UT
    MAX_UNCERT:      0.080 [days]
    CUSP_WIDTH:      0.50 +/- 0.20 [days]
    u0:              0.24 +/- 0.34 [RingUnits]
    MAX_MAG:         15.3 mag (estimated)
    BASE_MAG:        18.86 +/- 0.23 [mag]
    AMPLIFICATION:   4.15 factor
    LC_URL:          https://it019909.massey.ac.nz/moa/alert/display.php?id=gb2-R-3-6138
    SUN_POSTN:       130.39d {+08h 41m 34s}  +18.27d {+18d 16' 19"}
    SUN_DIST:        139.07 [deg]
    MOON_POSTN:      139.11d {+09h 16m 27s}  +11.49d {+11d 29' 22"}
    MOON_DIST:       128.30 [deg]
    MOON_ILLUM:      1 [%]
    GAL_COORDS:      355.83, -3.89 [deg] galactic lon,lat of the burst (or transient)
    ECL_COORDS:      268.16,-11.09 [deg] ecliptic lon,lat of the burst (or transient)
    COMMENTS:        MOA Gravitational Lensing Event.  
    COMMENTS:        New transient event detected by MOA

The socket packets contents can be found at:
http://gcn.gsfc.nasa.gov/gcn/sock_pkt_def_doc.html

REMINDER OF RECENT ADDITIONS TO GCN:
In case you have missed them, here is a brief list of the most recent
additions to the GCN system.  You might consider signing up
for these Notice types as well.  The full anouncements/dscriptions
for each of these can be found at:  http://gcn.gsfc.nasa.gov/gcn/whats_new.html
DOW_TOD  (13 Jun 2011)            // Preprogrammed notices at specific days-of-week & time-of-day
FERMI_GBM FIN_POS  (07 Jun 2011)  // Human-in-the-loop ground-based analysis
MAXI_UNKNOWN/_KNOWN (Apr 2011)    // Unknown transients & Flares-ups from Known sources
INTEGRAL_WEAK  (Feb 2011)         // Subthreshold detections by INTEGRAL
SWIFT_BAT_MONITOR (Feb 2010)      // Flares-ups from known sources monitored by Swift-BAT

Sincerely,
Scott

Scott Barthelmy                      NASA-GSFC, Code 661, Greenbelt, MD   20771
PHONE:  301-286-3106                 (office)       CELL:   301-346-3733
FAX:    301-286-1684                 (1st choice,  -1682 2nd choice)
EMAIL:  scott at lheamail.gsfc.nasa.gov
PAGER:  3013463733 at cingularme.com
WEB:    http://gcn.gsfc.nasa.gov/gcn

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