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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: GOTO candidate optical counterpart
  2. EP240908a: Optical afterglow confirmation
  3. GRB 240710A: SVOM/GRM observation
  4. GRB 240910A: Swift ToO observations
  5. IPN triangulation of GRB 240905B (short)
  6. GRB 240825A: 7DT Optical Upper Limit
  7. GRB 240905E: SVOM/VT optical observations
  8. GRB 240905E: SVOM/VT optical observations (duplicate submission of GCN 37453)
  9. LIGO/Virgo/KAGRA S240910ci: NED Galaxies in the Localization Volume
  10. GRB 240910A: GRBAlpha detection
  11. GRB 240910B: Fermi GBM Final Real-time Localization
  12. LIGO/Virgo/KAGRA S240910ci: Coverage and upper limits from MAXI/GSC observations
  13. LIGO/Virgo/KAGRA S240910ci: Updated Sky localization and EM Bright Classification
  14. LIGO/Virgo/KAGRA S240910ci: Identification of a GW compact binary merger candidate
  15. GRB 240910A: SVOM/GRM observation
  16. EP240908a: Mondy and AbAO follow-up observations
  17. EP240908a: Updates on the WXT detection result around the trigger time
  18. Fermi GRB 240910A: Global MASTER-Net observations report
  19. GRB 240910A: Fermi GBM Final Real-time Localization
  20. LIGO/Virgo/KAGRA S240908bs: Upper limits from Swift/BAT-GUANO
  21. LIGO/Virgo/KAGRA S240907cg: Upper limits from Swift/BAT-GUANO
  22. EP240908a: optical afterglow candidate
  23. EP EP240908a: Global MASTER-Net observations report
  24. GRB 240905B: Fermi GBM Observation
  25. Fermi trigger No 747553301: Global MASTER-Net observations report
  26. EP240908a: TRT optical upper limit
  27. GRB 240905B: GOTO optical upper limits
  28. EP240908a: EP detection of a fast X-ray transient
  29. Fermi GRB 240908A: Global MASTER-Net observations report
  30. LIGO/Virgo/KAGRA S240908dg: Updated Sky localization
  31. LIGO/Virgo/KAGRA S240908bs: Updated Sky localization
  32. GRB 240908A: Fermi GBM Final Real-time Localization
  33. LIGO/Virgo/KAGRA S240908dg: Identification of a GW compact binary merger candidate
  34. LIGO/Virgo/KAGRA S240908bs: Identification of a GW compact binary merger candidate
  35. LIGO/Virgo/KAGRA S240907cg: Updated Sky localization
  36. GRB 240801A: SVOM/GRM observation
  37. LIGO/Virgo/KAGRA S240907cg: Identification of a GW compact binary merger candidate
  38. GRB 240905E: GIT optical upper limit
  39. GRB 240905B: Swift-XRT observations
  40. GRB 240905E: Gaoyazi/GOT optical upper limits
  41. GRB 240905E: NUTTelA-TAO / BSTI Optical Limits
  42. GRB 240905B: Fermi-LAT detection
  43. GRB 240905B: Swift ToO observations
  44. GRB 240905E: J-band observations with WINTER
  45. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  46. GRB 240905E: AKO Optical Upper Limit
  47. GRB 240905E: SVOM/C-GFT optical upper limit
  48. GRB 240905E: OHP/MISTRAL T193 optical upper limit
  49. Fermi GRB 240905D: Global MASTER-Net observations report
  50. Fermi GRB 240905A: Global MASTER-Net observations report
  51. GRB 240905E: NOT optical upper limits
  52. GRB 240905E: REM optical/NIR upper limits
  53. GRB 240902B: AstroSat CZTI detection of a long burst
  54. GRB 240905E: Swift-XRT refined Analysis
  55. GRB 240902A: AstroSat CZTI detection of a long burst
  56. GRB 240905E: SVOM/GRM observation
  57. GRB 240905E: LCOGT Optical Upper Limit
  58. GRB 240905E: Swift/UVOT Upper Limits
  59. GRB 240905E: SAO RAS optical upper limit
  60. GRB 240825A: Montarrenti Observatory optical follow-up observations
  61. GRB 240905E: Nanshan/HMT optical upper limit
  62. Swift GRB 240905E: Global MASTER-Net observations report
  63. GRB 240905E: Swift detection of a burst
  64. GRB 240819A: Optical upper limits from TESS
  65. GRB 240905D: AstroSat CZTI detection
  66. GRB 240905A: SVOM/GRM observation
  67. Fermi GRB 240905B: Global MASTER-Net observations report
  68. GRB 240905D: Fermi GBM Final Real-time Localization
  69. GRB 240905B: AstroSat CZTI detection and localization
  70. GRB 240905C: Fermi GBM Final Real-time Localization
  71. GRB 240905B: Fermi GBM Final Real-time Localization
  72. GRB 240825A: ATCA Detection of Radio Counterpart
  73. Swift GRB 240904A: Global MASTER-Net observations report
  74. GRB 240905A: Fermi GBM Final Real-time Localization
  75. Fermi Gamma-ray Burst Monitor trigger 747163821/240904729 is not a GRB
  76. Fermi trigger No 747163821: Global MASTER-Net observations report
  77. GRB 240904A: Swift detection of a burst
  78. GRB 240828A: SVOM/GRM observation
  79. LIGO/Virgo/KAGRA S240825ar: Upper limits from Swift/BAT-GUANO
  80. LIGO/Virgo/KAGRA S240807h: Upper limits from Swift/BAT-GUANO
  81. Fermi Gamma-ray Burst Monitor trigger 240831A is not a GRB
  82. LIGO/Virgo/KAGRA S240902bq: Updated Sky localization
  83. GRB 240828A: GECAM detection
  84. GRB 240831B: Fermi GBM Final Localization
  85. Fermi Gamma-ray Burst Monitor trigger 746882332/240901471 is not a GRB
  86. LIGO/Virgo/KAGRA S240902bq: Identification of a GW compact binary merger candidate
  87. GRB 240825A: Magnitude Correction in SVOM/C-GFT Optical Observations
  88. GRB 240825A: MeerLICHT afterglow detection
  89. Fermi trigger No 746923430: Global MASTER-Net observations report
  90. GRB 240828A: SAO RAS AS-500(2) optical observations
  91. GRB 240821A: VLT spectroscopic observations
  92. Fermi trigger No 746882332: Global MASTER-Net observations report
  93. GRB 240825A: TSHAO Optical Upper Limit
  94. GRB 240829B: GRBAlpha detection
  95. GRB240828B: REM optical/NIR upper limits
  96. Fermi trigger No 746816563: Global MASTER-Net observations report
  97. GRB 240828B: AbAO optical upper limit
  98. GRB 240831A: Fermi GBM Final Real-time Localization
  99. GRB 240825A: SOAR observations
  100. GRB 240828B: Mephisto optical upper limit

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