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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 241228B: Fermi GBM Final Real-time Localization
  2. GRB 241228A: Swift detection of a burst
  3. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  4. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  5. GRB 241223A: GRBAlpha detection
  6. GRB 241212A: VZLUSAT-2 detection
  7. GRB 241217A/EP241217b: continued SOAR observations
  8. Fermi GRB 241226A: Global MASTER-Net observations report
  9. GRB 241226A: Fermi GBM Final Real-time Localization
  10. EP241223a: Mondy AZT-33IK optical observations
  11. GRB 241029A: LCO optical observation
  12. GRB 241223A: Swift-XRT observations
  13. LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
  14. GRB 241029A: AbAO AS-32 optical observations
  15. GRB 241223A: Fermi GBM Detection
  16. Fermi trigger No 756678579: Global MASTER-Net observations report
  17. LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
  18. EP241223a
  19. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  20. IceCube Alert 241224.30: Global MASTER-Net observations report
  21. GRB 241219A: SVOM/GRM observation
  22. EP241223a: Global MASTER-Net observations report
  23. EP241223a: EP-WXT detection of a fast X-ray transient
  24. EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
  25. GRB241113A: 7DT Optical upper limits
  26. Fermi Gamma-ray Burst Monitor trigger 756678579 / 241223854 is not a GRB
  27. Fermi GRB 241223A: Global MASTER-Net observations report
  28. GRB 241223A: GOTO optical observations summary
  29. GRB 241105A: JWST photometric observations of the host galaxy
  30. GRB 241223A: Swift ToO observations
  31. EP241217a: e-MERLIN radio observations
  32. GRB 241223A: BALROG localization (Fermi Trigger 756648531 / GRB 241223506)
  33. GRB 241223A: Fermi GBM Final Real-time Localization
  34. GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
  35. The EP-WXT trigger 01709129287 is likely a flaring star
  36. Fermi trigger No 756447119: Global MASTER-Net observations report
  37. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  38. Fermi Gamma-ray Burst Monitor trigger 756447119/241221175 is not a GRB
  39. Fermi GRB 241221A: Global MASTER-Net observations report
  40. GRB 241221A: Fermi GBM Final Real-time Localization
  41. GRB 241217A/EP241217b: SOAR afterglow detection
  42. EP241217a: Liverpool Telescope optical upper limit
  43. EP241021a: VLA radio detection
  44. GRB 241218A: Mondy AZT-33IK optical upper limit
  45. EP241217a : Leavitt Observatory optical upper limit
  46. GRB 241217A/EP241217b: tentative VLT spectroscopic redshift z=1.879
  47. EP241217a: 1.6m Mephisto multi-band optical observations
  48. GRB 241217a/EP241217B: 1.6m Mephisto optical upper limits
  49. GRB 241218A: Swift/UVOT Upper Limits
  50. EP241217a: optical upper limit with the Liverpool Telescope
  51. GRB 241209B: EP-FXT afterglow detection
  52. Konus-Wind detection of GRB 241204A (short/hard)
  53. GRB 241218A: NOT optical upper limits
  54. GRB 241218A: Swift-BAT refined analysis
  55. GRB 241217A / EP241217B: GRANDMA/T1MPicduMidi optical upperlimits
  56. EP 241217a: NIR detection with P200/WIRC
  57. EP 241217a: Possible J-band detection with WINTER
  58. GRB 241217A/EP241217B: Fermi-GBM Sub-Threshold Detection
  59. EP241217a: refined EP-WXT analysis and EP-FXT follow-up observations
  60. GRB 241217A / EP241217b: Nanshan/HMT optical upper limit
  61. GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
  62. GRB 241217A / EP241217b: NOT optical upper limits
  63. GRB 241218A: REM optical upper limit
  64. GRB 241217A/EP241217b: REM optical/NIR upper limits
  65. EP241217a: REM optical/NIR upper limits
  66. GRB 241218a: Liverpool Telescope optical follow-up
  67. GRB 241217a: Liverpool Telescope optical follow-up
  68. EP241217a: Liverpool Telescope optical follow-up
  69. GRB 241218A: Swift-XRT refined Analysis
  70. EP241217a: NOT optical observations
  71. EP241217a: GROWTH-India Telescope optical observations
  72. GRB 241218A: NUTTelA-TAO / BSTI Optical Limits
  73. EP241119a: 7DT Optical upper limits
  74. EP241217b: Global MASTER-Net observations report
  75. GRB 241209A: ATCA radio follow-up observations
  76. EP241217a: Xinglong optical follow-up observations
  77. EP241217b/GRB 241217A: EP detection of the prompt X-ray emssion
  78. GRB 241218A: LCOGT Optical Upper Limit
  79. GRB 241218A: Enhanced Swift-XRT position
  80. EP241217a: Global MASTER-Net observations report
  81. GRB 241217A: GMG Optical Upper Limit
  82. GRB 241218A: Swift detection of a burst
  83. GRB 241217A : SVOM/VT optical afterglow detection
  84. GRB 241217A: Swift-XRT afterglow detection
  85. GRB 241217A: LCO optical upper limit
  86. GRB 241217A: GRANDMA/TAROT optical upperlimits
  87. EP241217a: Swift-XRT Detection
  88. EP241217A: Non-detection from Fermi-GBM Observations
  89. GRB 241217A : SVOM/ECLAIRs,GRM,MXT detection of a long burst with a bright X-ray afterglow candidate
  90. EP241217a: Gemini-North spectroscopic redshift z = 4.59
  91. EP241217a: Kinder optical follow-up observations
  92. GRB 241214A: GRBAlpha detection
  93. GRB 241213A (EP241213a): GRBAlpha detection
  94. GRB 241209D: GRBAlpha detection
  95. EP241217A: LCO optical observations
  96. EP241217a: Gemini-North detection of the likely optical counterpart
  97. EP241217a: EP detection of an X-ray transient
  98. The EP-WXT trigger 01709129023 is likely a flaring star
  99. EP241107a: VLA Radio Observation
  100. GRB 241213A: Swift-BAT refined analysis

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