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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 240905E: SVOM/VT optical observations (duplicate submission of GCN 37453)
  2. LIGO/Virgo/KAGRA S240910ci: NED Galaxies in the Localization Volume
  3. GRB 240910A: GRBAlpha detection
  4. GRB 240910B: Fermi GBM Final Real-time Localization
  5. LIGO/Virgo/KAGRA S240910ci: Coverage and upper limits from MAXI/GSC observations
  6. LIGO/Virgo/KAGRA S240910ci: Updated Sky localization and EM Bright Classification
  7. LIGO/Virgo/KAGRA S240910ci: Identification of a GW compact binary merger candidate
  8. GRB 240910A: SVOM/GRM observation
  9. EP240908a: Mondy and AbAO follow-up observations
  10. EP240908a: Updates on the WXT detection result around the trigger time
  11. Fermi GRB 240910A: Global MASTER-Net observations report
  12. GRB 240910A: Fermi GBM Final Real-time Localization
  13. LIGO/Virgo/KAGRA S240908bs: Upper limits from Swift/BAT-GUANO
  14. LIGO/Virgo/KAGRA S240907cg: Upper limits from Swift/BAT-GUANO
  15. EP240908a: optical afterglow candidate
  16. EP EP240908a: Global MASTER-Net observations report
  17. GRB 240905B: Fermi GBM Observation
  18. Fermi trigger No 747553301: Global MASTER-Net observations report
  19. EP240908a: TRT optical upper limit
  20. GRB 240905B: GOTO optical upper limits
  21. EP240908a: EP detection of a fast X-ray transient
  22. Fermi GRB 240908A: Global MASTER-Net observations report
  23. LIGO/Virgo/KAGRA S240908dg: Updated Sky localization
  24. LIGO/Virgo/KAGRA S240908bs: Updated Sky localization
  25. GRB 240908A: Fermi GBM Final Real-time Localization
  26. LIGO/Virgo/KAGRA S240908dg: Identification of a GW compact binary merger candidate
  27. LIGO/Virgo/KAGRA S240908bs: Identification of a GW compact binary merger candidate
  28. LIGO/Virgo/KAGRA S240907cg: Updated Sky localization
  29. GRB 240801A: SVOM/GRM observation
  30. LIGO/Virgo/KAGRA S240907cg: Identification of a GW compact binary merger candidate
  31. GRB 240905E: GIT optical upper limit
  32. GRB 240905B: Swift-XRT observations
  33. GRB 240905E: Gaoyazi/GOT optical upper limits
  34. GRB 240905E: NUTTelA-TAO / BSTI Optical Limits
  35. GRB 240905B: Fermi-LAT detection
  36. GRB 240905B: Swift ToO observations
  37. GRB 240905E: J-band observations with WINTER
  38. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  39. GRB 240905E: AKO Optical Upper Limit
  40. GRB 240905E: SVOM/C-GFT optical upper limit
  41. GRB 240905E: OHP/MISTRAL T193 optical upper limit
  42. Fermi GRB 240905D: Global MASTER-Net observations report
  43. Fermi GRB 240905A: Global MASTER-Net observations report
  44. GRB 240905E: NOT optical upper limits
  45. GRB 240905E: REM optical/NIR upper limits
  46. GRB 240902B: AstroSat CZTI detection of a long burst
  47. GRB 240905E: Swift-XRT refined Analysis
  48. GRB 240902A: AstroSat CZTI detection of a long burst
  49. GRB 240905E: SVOM/GRM observation
  50. GRB 240905E: LCOGT Optical Upper Limit
  51. GRB 240905E: Swift/UVOT Upper Limits
  52. GRB 240905E: SAO RAS optical upper limit
  53. GRB 240825A: Montarrenti Observatory optical follow-up observations
  54. GRB 240905E: Nanshan/HMT optical upper limit
  55. Swift GRB 240905E: Global MASTER-Net observations report
  56. GRB 240905E: Swift detection of a burst
  57. GRB 240819A: Optical upper limits from TESS
  58. GRB 240905D: AstroSat CZTI detection
  59. GRB 240905A: SVOM/GRM observation
  60. Fermi GRB 240905B: Global MASTER-Net observations report
  61. GRB 240905D: Fermi GBM Final Real-time Localization
  62. GRB 240905B: AstroSat CZTI detection and localization
  63. GRB 240905C: Fermi GBM Final Real-time Localization
  64. GRB 240905B: Fermi GBM Final Real-time Localization
  65. GRB 240825A: ATCA Detection of Radio Counterpart
  66. Swift GRB 240904A: Global MASTER-Net observations report
  67. GRB 240905A: Fermi GBM Final Real-time Localization
  68. Fermi Gamma-ray Burst Monitor trigger 747163821/240904729 is not a GRB
  69. Fermi trigger No 747163821: Global MASTER-Net observations report
  70. GRB 240904A: Swift detection of a burst
  71. GRB 240828A: SVOM/GRM observation
  72. LIGO/Virgo/KAGRA S240825ar: Upper limits from Swift/BAT-GUANO
  73. LIGO/Virgo/KAGRA S240807h: Upper limits from Swift/BAT-GUANO
  74. Fermi Gamma-ray Burst Monitor trigger 240831A is not a GRB
  75. LIGO/Virgo/KAGRA S240902bq: Updated Sky localization
  76. GRB 240828A: GECAM detection
  77. GRB 240831B: Fermi GBM Final Localization
  78. Fermi Gamma-ray Burst Monitor trigger 746882332/240901471 is not a GRB
  79. LIGO/Virgo/KAGRA S240902bq: Identification of a GW compact binary merger candidate
  80. GRB 240825A: Magnitude Correction in SVOM/C-GFT Optical Observations
  81. GRB 240825A: MeerLICHT afterglow detection
  82. Fermi trigger No 746923430: Global MASTER-Net observations report
  83. GRB 240828A: SAO RAS AS-500(2) optical observations
  84. GRB 240821A: VLT spectroscopic observations
  85. Fermi trigger No 746882332: Global MASTER-Net observations report
  86. GRB 240825A: TSHAO Optical Upper Limit
  87. GRB 240829B: GRBAlpha detection
  88. GRB240828B: REM optical/NIR upper limits
  89. Fermi trigger No 746816563: Global MASTER-Net observations report
  90. GRB 240828B: AbAO optical upper limit
  91. GRB 240831A: Fermi GBM Final Real-time Localization
  92. GRB 240825A: SOAR observations
  93. GRB 240828B: Mephisto optical upper limit
  94. GRB 240828B: GRANDMA Optical Upper Limit
  95. LIGO/Virgo/KAGRA S240830gn: Coverage and upper limits from MAXI/GSC observations
  96. LIGO/Virgo/KAGRA S240830gn: Updated Sky localization and EM Bright Classification
  97. GRB 240829A: Swift-BAT refined analysis
  98. GRB 240825A: Swift-BAT refined analysis
  99. LIGO/Virgo/KAGRA S240830gn: Identification of a GW compact binary merger candidate
  100. GRB 240825A: MeerKAT detection

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