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

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