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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 241209A: GRANDMA/TAROT upper limit
  2. GRB 241209B: BOOTES-5 optical upper limit
  3. Swift GRB 241209D: Global MASTER-Net observations report
  4. Fermi GRB 241209C: Global MASTER-Net observations report
  5. Fermi GRB 241209E: Global MASTER-Net observations report
  6. GRB 241209E: Fermi GBM Final Real-time Localization
  7. GRB 241209B: Swift ToO observations
  8. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  9. GRB 241209A: REM optical/NIR observations
  10. GRB 241209D: Enhanced Swift-XRT position
  11. GRB 241209C: AstroSat CZTI detection
  12. GRB 241209D: Swift detection of a burst
  13. GRB 241209D: Fermi GBM Final Real-time Localization
  14. GRB 241209A: VLT/X-shooter spectroscopy
  15. GRB 241209A: Enhanced Swift-XRT position
  16. GRB 241114B: cubesat Avion detection
  17. GRB 241209A: VLT optical observations
  18. Fermi GRB 241209A: Global MASTER-Net observations report
  19. GRB 241209C: Fermi GBM Final Real-time Localization
  20. GRB 241209A: GOTO optical upper limits
  21. EP241206a: 1.5m OSN optical limit
  22. GRB 241209A: Prompt enhanced Swift-XRT position
  23. GRB 241209B: SVOM/ECLAIRs and GRM detection of a long burst
  24. EP241208a: EP detection of a fast X-ray transient
  25. GRB 241209A: Swift detection of a short burst
  26. Swift GRB241209.23: Global MASTER-Net observations report
  27. GRB 241209A: Fermi GBM Final Real-time Localization
  28. Fermi GRB 241207B: Global MASTER-Net observations report
  29. GRB 241207B: Swift/BAT-GUANO localization skymap of a short burst
  30. Fermi Gamma-ray Burst Monitor trigger 755277791/241207641 is not a GRB
  31. GRB 241201A: AstroSat CZTI detection
  32. GRB 241206A: DDOTI Upper Limit on the Afterglow
  33. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  34. AT2024adec: X-ray Upper Limits from EP-FXT Observation
  35. EP241206a: BOOTES Global Network optical limits
  36. GRB 241207C: MASTER optical observations
  37. Fermi trigger No 755225799: Global MASTER-Net observations report
  38. GRB 241207C: Tiled Swift observations
  39. GRB 241207C: MAXI/GSC detection
  40. GRB 241207B: Fermi GBM Final Real-time Localization
  41. Fermi trigger No 755277791: Global MASTER-Net observations report
  42. Fermi GRB 241207A: Global MASTER-Net observations report
  43. EP241206a: Global MASTER-Net observations report
  44. EP241206a: EP detection of a fast X-ray transient
  45. GRB 241206A: Fermi GBM observation
  46. GRB 241206C: SVOM/GRM observation of a likely short burst
  47. GRB 241207A: Fermi GBM Final Real-time Localization
  48. GRB 241206A: Swift/BAT-GUANO localization skymap of a burst
  49. GRB 241206B: SVOM/MXT observations: a probable flare from the QSO 1ES 1959+650
  50. GRB 241206B: GWAC-F50A optical upper limit
  51. GRB 241206B: SVOM/ECLAIRs detection of a long soft transient
  52. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  53. Fermi GRB 241206A: Global MASTER-Net observations report
  54. GRB 241206A: Fermi GBM Final Real-time Localization
  55. EP241201a: 1.6m Mephisto Optical Upper Limits
  56. GRB 241204A: COLIBRÍ Optical Upper Limit
  57. EP241202b: KAIT optical upper limit
  58. LIGO/Virgo/KAGRA S241125n: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  59. GRB 241204A: DDOTI Upper Limits on the Afterglow
  60. GRB 241204A: Fermi GBM Observation
  61. Fermi GRB 241204A: Global MASTER-Net observations report
  62. GRB 241130A: CALET Gamma-Ray Burst Monitor detection
  63. GRB 241128A : RAPAS follow-up observations
  64. GRB 241201A: GRBAlpha detection
  65. GRB 241204A: Fermi-LAT detection
  66. EP241202b: Upper limits from Fermi-GBM Observations
  67. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  68. EP241202b: Kinder optical counterpart candidate
  69. Fermi-GBM Sub-Threshold Detection of GRB 241128A
  70. GRB 241113B : RAPAS follow-up observation
  71. EP241201a: EP-FXT follow-up observations
  72. Konus-Wind detection of GRB 241130A
  73. EP241202b: Global MASTER-Net observations report
  74. EP241201a: BOOTES-5 optical upper limit
  75. EP241202b: EP detection of a fast X-ray transient
  76. EP241201a: NOT optical observations
  77. IPN triangulation of GRB 241130A
  78. GRB 241130A: EIRSAT-1 GMOD Detection
  79. GRB 241128A: Swift/UVOT Upper Limits
  80. GRB 241130A: Fermi GBM Detection
  81. IceCube-241127A: Upper limits from a search for additional neutrino events in IceCube
  82. GRB 241129A: Swift/BAT-GUANO localization skymap of a burst
  83. EP241201a: Kinder optical counterpart candidate
  84. LIGO/Virgo/KAGRA S241102br: GRAWITA wide-field optical observations
  85. EP241201a: Global MASTER-Net observations report
  86. EP241201a: EP detection of a fast X-ray transient
  87. The EP-WXT trigger 01709126243 is not a real source
  88. GRB 241127B: detection of a long GRB by SVOM/ECLAIRs
  89. GRB241201B: Fermi GBM Final Localization
  90. GRB241201B: Fermi GBM Final Localization
  91. LIGO/Virgo/KAGRA S241201ac: Updated Sky localization
  92. EP241126a: SOAR observations of the optical counterpart
  93. Fermi GRB 241201A: Global MASTER-Net observations report
  94. GRB 241201A: BALROG localization (Fermi Trigger 754757764 / GRB 241201622)
  95. GRB 241130A: Fermi GBM Final Real-time Localization
  96. GRB 241130A: Fermi GBM Final Real-time Localization
  97. EP241126a: 1.6m Mephisto Optical Upper Limits
  98. GRB 241201A: Fermi GBM Final Real-time Localization
  99. LIGO/Virgo/KAGRA S241201ac: Identification of a GW compact binary merger candidate
  100. LIGO/Virgo/KAGRA S241130be: Updated Sky localization

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