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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 200324A: LCO Optical Upper Limit
  2. GRB 200324A: Swift-XRT refined Analysis
  3. GRB 200325A: Fermi GBM Final Real-time Localization
  4. GRB 200324A: Konkoly Obs. optical upper limit
  5. GRB 200324A: NOT optical upper limit
  6. GRB 200324A: Tautenburg observations
  7. GRB 200324A: Enhanced Swift-XRT position
  8. GRB 200324A:MITSuME Akeno optical upper limits
  9. GRB 200324A: Swift detection of a burst
  10. Swift GRB200324.69: Global MASTER-Net observations report
  11. GRB 200318A : AstroSat CZTI detection
  12. GRB 200317A: AstroSat CZTI detection
  13. Fermi trigger No 606681997: Global MASTER-Net observations report
  14. GRB 200323A: Fermi GBM detection
  15. GRB 200323A: Fermi GBM Final Real-time Localization
  16. LIGO/Virgo S200316bj: no counterpart candidate in SVOM/GWAC-F30 observations
  17. Fermi trigger No 606614927: Global MASTER-Net observations report
  18. LIGO/Virgo S200316bj: Updated Sky Localization and EM Bright Classification
  19. GRB 200320B: MAXI/GSC detection
  20. GRB 200320A: Fermi GBM Final Localization
  21. GRB 200319A: BALROG localization (Fermi Trigger 606296685 / GRB 200319323)
  22. GRB 200319A: Fermi GBM Final Real-time Localization
  23. Chandra observations of GW170817 at 2.5 years since merger (All epochs 4 of 4)
  24. Fermi trigger No 606263732: Global MASTER-Net observations report
  25. GRB 200318A: Fermi GBM Final Real-time Localization
  26. GW170817: Continued X-ray emission detected with Chandra at 940 days post-merger
  27. LIGO/Virgo S200316bj : No significant candidates in TAROT - FRAM - GRANDMA observations.
  28. LIGO/Virgo S200316bj: Upper limits from Insight-HXMT/HE observations
  29. Konus-Wind observation of GRB 200313B
  30. LIGO/Virgo S200316bj: no counterpart candidate in SVOM/GWAC observations
  31. LIGO/Virgo S200316bj: Upper limits from CALET observations
  32. LIGO/Virgo S200316bj: No neutrino candidates at Pierre Auger Observatory
  33. LIGO/Virgo S200316bj: No counterpart candidates in Fermi-LAT observations
  34. LIGO/Virgo S200316bj: No Counterparts in DDOTI/OAN Optical Observations
  35. LIGO/Virgo S200316bj: no counterpart candidates in the Swift/BAT observations
  36. LIGO/Virgo S200213t: Continued Swift UVOT and XRT observations of ZTF20aamvmzj (AT2020cja)
  37. Konus-Wind observation of GRB 200313A
  38. Konus-Wind observation of GRB 200311A
  39. LIGO/Virgo S200316bj: No counterpart candidates in INTEGRAL SPI-ACS, and IBIS prompt observation
  40. LIGO/Virgo S200316bj: upper limits from AGILE/GRID observations
  41. LIGO/Virgo S200316bj: upper limits from AGILE/MCAL observations
  42. LIGO/Virgo S200316bj: Upper limits from Fermi-GBM Observations
  43. Fermi trigger No 606098435: Global MASTER-Net observations report
  44. GRB 200317A: Fermi GBM Final Real-time Localization
  45. LIGO/Virgo S200316bj: Coverage and upper limits from MAXI/GSC observations
  46. LIGO/Virgo S200316bj : no neutrino counterpart candidate in ANTARES search
  47. LIGO/Virgo S200316bj: Upper limits from IceCube neutrino searches
  48. LIGO/Virgo S200316bj: Identification of a GW compact binary merger candidate
  49. LIGO/Virgo S200316bj: Global MASTER-Net observations report
  50. IPN triangulation of GRB 200313B (short)
  51. IPN triangulation of GRB 200313A
  52. SGR Swift J1818.0-1607: Swift-BAT refined analysis
  53. GRB 200313A: Fermi GBM detection
  54. LIGO/Virgo S200311bg: Updated Sky Localization and EM Bright Classification
  55. IPN triangulation of GRB 200311A
  56. Fermi trigger No 605789837: Global MASTER-Net observations report
  57. GRB 200313B: Fermi GBM Final Real-time Localization
  58. SGR Swift J1818.0-1607: BOOTES-4/MET optical limit
  59. GRB 200313A: BALROG localization (Fermi Trigger 605756501 / GRB 200313071)
  60. Fermi trigger No 605756501: Global MASTER-Net observations report
  61. Swift GRB200312.89: Global MASTER-Net observations report
  62. GRB 200313A: Fermi GBM Final Real-time Localization
  63. Swift-BAT trigger 960986: Swift detection of a new SGR Swift J1818.0-1607
  64. LIGO/Virgo S200311bg: Not observable by CALET
  65. GRB 200311A: AstroSat CZTI detection
  66. Fermi trigger No 605632577: Global MASTER-Net observations report
  67. LIGO/Virgo S200311bg: Swift/BAT in the South Atlantic Anomaly
  68. LIGO/Virgo S200311bg: No significant counterpart candidates in Fermi-LAT observations
  69. IPN triangulation of GRB 200307A (short)
  70. LIGO/Virgo S200224ca: DESGW Summary of DECam Observations
  71. GRB 200311A: AGILE/MCAL and scientific ratemeters observations
  72. LIGO/Virgo S200311bg: not observable by Fermi GBM
  73. GRB 200311A: Fermi GBM Final Real-time Localization
  74. LIGO/Virgo S200311bg: Coverage and upper limits from MAXI/GSC observations
  75. LIGO/Virgo S200311bg: not observable by AGILE at the event time
  76. LIGO/Virgo S200311bg: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation
  77. LIGO/Virgo S200311bg: Upper limits from IceCube neutrino searches
  78. LIGO/Virgo S200311bg: Identification of a GW compact binary merger candidate
  79. Chandra observations of GW170817 ~ 2.5 years since merger (epoch 1 of 4)
  80. GRB 200307A: Updated localization from Fermi/GBM and Swift/BAT-GUANO
  81. GRB 200310A: MAXI/GSC detection
  82. GRB 200306C: ALMA 3mm upper limit
  83. GRB 200306C: Swift-BAT refined analysis
  84. GRB 200306C: Swift/UVOT Detection
  85. GRB 200306A: Swift/UVOT Upper Limits
  86. GRB 200308A: Fermi GBM Final Real-time Localization
  87. Fermi trigger No 605309224: Global MASTER-Net observations report
  88. GRB 200306C: Calar Alto 2.2m upper limit
  89. LIGO/Virgo S200308e: Retraction of GW compact binary merger candidate
  90. GRB 200306A: Swift-BAT refined analysis
  91. GRB 200306C: Swift-XRT refined Analysis
  92. GRB 200307A: Fermi GBM Final Real-time Localization
  93. GRB 200306A: RATIR Optical Observations
  94. GRB 200306C: Enhanced Swift-XRT position
  95. GRB 200306C: VIRT optical upper limits
  96. GRB 200306A: AstroSat CZTI detection
  97. GRB 200306C: KCT upper limit of the optical afterglow
  98. GRB200306C: First Hour Liverpool Telescope Observations
  99. GRB 200306C: LCO Optical Upper Limits
  100. GRB 200306B: Fermi GBM Final Localization Correction

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