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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 240910A: GRBAlpha detection
  2. GRB 240910B: Fermi GBM Final Real-time Localization
  3. LIGO/Virgo/KAGRA S240910ci: Coverage and upper limits from MAXI/GSC observations
  4. LIGO/Virgo/KAGRA S240910ci: Updated Sky localization and EM Bright Classification
  5. LIGO/Virgo/KAGRA S240910ci: Identification of a GW compact binary merger candidate
  6. GRB 240910A: SVOM/GRM observation
  7. EP240908a: Mondy and AbAO follow-up observations
  8. EP240908a: Updates on the WXT detection result around the trigger time
  9. Fermi GRB 240910A: Global MASTER-Net observations report
  10. GRB 240910A: Fermi GBM Final Real-time Localization
  11. LIGO/Virgo/KAGRA S240908bs: Upper limits from Swift/BAT-GUANO
  12. LIGO/Virgo/KAGRA S240907cg: Upper limits from Swift/BAT-GUANO
  13. EP240908a: optical afterglow candidate
  14. EP EP240908a: Global MASTER-Net observations report
  15. GRB 240905B: Fermi GBM Observation
  16. Fermi trigger No 747553301: Global MASTER-Net observations report
  17. EP240908a: TRT optical upper limit
  18. GRB 240905B: GOTO optical upper limits
  19. EP240908a: EP detection of a fast X-ray transient
  20. Fermi GRB 240908A: Global MASTER-Net observations report
  21. LIGO/Virgo/KAGRA S240908dg: Updated Sky localization
  22. LIGO/Virgo/KAGRA S240908bs: Updated Sky localization
  23. GRB 240908A: Fermi GBM Final Real-time Localization
  24. LIGO/Virgo/KAGRA S240908dg: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/KAGRA S240908bs: Identification of a GW compact binary merger candidate
  26. LIGO/Virgo/KAGRA S240907cg: Updated Sky localization
  27. GRB 240801A: SVOM/GRM observation
  28. LIGO/Virgo/KAGRA S240907cg: Identification of a GW compact binary merger candidate
  29. GRB 240905E: GIT optical upper limit
  30. GRB 240905B: Swift-XRT observations
  31. GRB 240905E: Gaoyazi/GOT optical upper limits
  32. GRB 240905E: NUTTelA-TAO / BSTI Optical Limits
  33. GRB 240905B: Fermi-LAT detection
  34. GRB 240905B: Swift ToO observations
  35. GRB 240905E: J-band observations with WINTER
  36. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  37. GRB 240905E: AKO Optical Upper Limit
  38. GRB 240905E: SVOM/C-GFT optical upper limit
  39. GRB 240905E: OHP/MISTRAL T193 optical upper limit
  40. Fermi GRB 240905D: Global MASTER-Net observations report
  41. Fermi GRB 240905A: Global MASTER-Net observations report
  42. GRB 240905E: NOT optical upper limits
  43. GRB 240905E: REM optical/NIR upper limits
  44. GRB 240902B: AstroSat CZTI detection of a long burst
  45. GRB 240905E: Swift-XRT refined Analysis
  46. GRB 240902A: AstroSat CZTI detection of a long burst
  47. GRB 240905E: SVOM/GRM observation
  48. GRB 240905E: LCOGT Optical Upper Limit
  49. GRB 240905E: Swift/UVOT Upper Limits
  50. GRB 240905E: SAO RAS optical upper limit
  51. GRB 240825A: Montarrenti Observatory optical follow-up observations
  52. GRB 240905E: Nanshan/HMT optical upper limit
  53. Swift GRB 240905E: Global MASTER-Net observations report
  54. GRB 240905E: Swift detection of a burst
  55. GRB 240819A: Optical upper limits from TESS
  56. GRB 240905D: AstroSat CZTI detection
  57. GRB 240905A: SVOM/GRM observation
  58. Fermi GRB 240905B: Global MASTER-Net observations report
  59. GRB 240905D: Fermi GBM Final Real-time Localization
  60. GRB 240905B: AstroSat CZTI detection and localization
  61. GRB 240905C: Fermi GBM Final Real-time Localization
  62. GRB 240905B: Fermi GBM Final Real-time Localization
  63. GRB 240825A: ATCA Detection of Radio Counterpart
  64. Swift GRB 240904A: Global MASTER-Net observations report
  65. GRB 240905A: Fermi GBM Final Real-time Localization
  66. Fermi Gamma-ray Burst Monitor trigger 747163821/240904729 is not a GRB
  67. Fermi trigger No 747163821: Global MASTER-Net observations report
  68. GRB 240904A: Swift detection of a burst
  69. GRB 240828A: SVOM/GRM observation
  70. LIGO/Virgo/KAGRA S240825ar: Upper limits from Swift/BAT-GUANO
  71. LIGO/Virgo/KAGRA S240807h: Upper limits from Swift/BAT-GUANO
  72. Fermi Gamma-ray Burst Monitor trigger 240831A is not a GRB
  73. LIGO/Virgo/KAGRA S240902bq: Updated Sky localization
  74. GRB 240828A: GECAM detection
  75. GRB 240831B: Fermi GBM Final Localization
  76. Fermi Gamma-ray Burst Monitor trigger 746882332/240901471 is not a GRB
  77. LIGO/Virgo/KAGRA S240902bq: Identification of a GW compact binary merger candidate
  78. GRB 240825A: Magnitude Correction in SVOM/C-GFT Optical Observations
  79. GRB 240825A: MeerLICHT afterglow detection
  80. Fermi trigger No 746923430: Global MASTER-Net observations report
  81. GRB 240828A: SAO RAS AS-500(2) optical observations
  82. GRB 240821A: VLT spectroscopic observations
  83. Fermi trigger No 746882332: Global MASTER-Net observations report
  84. GRB 240825A: TSHAO Optical Upper Limit
  85. GRB 240829B: GRBAlpha detection
  86. GRB240828B: REM optical/NIR upper limits
  87. Fermi trigger No 746816563: Global MASTER-Net observations report
  88. GRB 240828B: AbAO optical upper limit
  89. GRB 240831A: Fermi GBM Final Real-time Localization
  90. GRB 240825A: SOAR observations
  91. GRB 240828B: Mephisto optical upper limit
  92. GRB 240828B: GRANDMA Optical Upper Limit
  93. LIGO/Virgo/KAGRA S240830gn: Coverage and upper limits from MAXI/GSC observations
  94. LIGO/Virgo/KAGRA S240830gn: Updated Sky localization and EM Bright Classification
  95. GRB 240829A: Swift-BAT refined analysis
  96. GRB 240825A: Swift-BAT refined analysis
  97. LIGO/Virgo/KAGRA S240830gn: Identification of a GW compact binary merger candidate
  98. GRB 240825A: MeerKAT detection
  99. GRB 240828B: J-band upper limit from WINTER
  100. Fermi trigger No 746684112: Global MASTER-Net observations report

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