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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 241229B: Swift detection of a burst
  2. GRB 241229B: Fermi GBM Final Real-time Localization
  3. GRB 241229A: SVOM detection of a long burst
  4. Fermi GRB 241228B: Global MASTER-Net observations report
  5. GRB 241228A: Fermi GBM Observation
  6. GRB241228B: GROWTH-India Telescope optical observations
  7. Swift GRB 241228A: Global MASTER-Net observations report
  8. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  9. GRB 241228B: GOTO24jmz optical follow-up observations
  10. GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
  11. GRB 241228A: GROWTH-India telescope optical upper limit
  12. GRB 241228B: Swift ToO observations
  13. GRB 241228B: TRT optical counterpart confirmation
  14. GRB 241228A: Swift-XRT refined Analysis
  15. GRB 241228A: Swift/UVOT Upper Limits
  16. GRB 241228B: GOTO possible optical counterpart candidate
  17. GRB 241228A: Enhanced Swift-XRT position
  18. GRB 241228B: Fermi GBM Final Real-time Localization
  19. GRB 241228A: Swift detection of a burst
  20. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  21. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  22. GRB 241223A: GRBAlpha detection
  23. GRB 241212A: VZLUSAT-2 detection
  24. GRB 241217A/EP241217b: continued SOAR observations
  25. Fermi GRB 241226A: Global MASTER-Net observations report
  26. GRB 241226A: Fermi GBM Final Real-time Localization
  27. EP241223a: Mondy AZT-33IK optical observations
  28. GRB 241029A: LCO optical observation
  29. GRB 241223A: Swift-XRT observations
  30. LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
  31. GRB 241029A: AbAO AS-32 optical observations
  32. GRB 241223A: Fermi GBM Detection
  33. Fermi trigger No 756678579: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
  35. EP241223a
  36. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  37. IceCube Alert 241224.30: Global MASTER-Net observations report
  38. GRB 241219A: SVOM/GRM observation
  39. EP241223a: Global MASTER-Net observations report
  40. EP241223a: EP-WXT detection of a fast X-ray transient
  41. EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
  42. GRB241113A: 7DT Optical upper limits
  43. Fermi Gamma-ray Burst Monitor trigger 756678579 / 241223854 is not a GRB
  44. Fermi GRB 241223A: Global MASTER-Net observations report
  45. GRB 241223A: GOTO optical observations summary
  46. GRB 241105A: JWST photometric observations of the host galaxy
  47. GRB 241223A: Swift ToO observations
  48. EP241217a: e-MERLIN radio observations
  49. GRB 241223A: BALROG localization (Fermi Trigger 756648531 / GRB 241223506)
  50. GRB 241223A: Fermi GBM Final Real-time Localization
  51. GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
  52. The EP-WXT trigger 01709129287 is likely a flaring star
  53. Fermi trigger No 756447119: Global MASTER-Net observations report
  54. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  55. Fermi Gamma-ray Burst Monitor trigger 756447119/241221175 is not a GRB
  56. Fermi GRB 241221A: Global MASTER-Net observations report
  57. GRB 241221A: Fermi GBM Final Real-time Localization
  58. GRB 241217A/EP241217b: SOAR afterglow detection
  59. EP241217a: Liverpool Telescope optical upper limit
  60. EP241021a: VLA radio detection
  61. GRB 241218A: Mondy AZT-33IK optical upper limit
  62. EP241217a : Leavitt Observatory optical upper limit
  63. GRB 241217A/EP241217b: tentative VLT spectroscopic redshift z=1.879
  64. EP241217a: 1.6m Mephisto multi-band optical observations
  65. GRB 241217a/EP241217B: 1.6m Mephisto optical upper limits
  66. GRB 241218A: Swift/UVOT Upper Limits
  67. EP241217a: optical upper limit with the Liverpool Telescope
  68. GRB 241209B: EP-FXT afterglow detection
  69. Konus-Wind detection of GRB 241204A (short/hard)
  70. GRB 241218A: NOT optical upper limits
  71. GRB 241218A: Swift-BAT refined analysis
  72. GRB 241217A / EP241217B: GRANDMA/T1MPicduMidi optical upperlimits
  73. EP 241217a: NIR detection with P200/WIRC
  74. EP 241217a: Possible J-band detection with WINTER
  75. GRB 241217A/EP241217B: Fermi-GBM Sub-Threshold Detection
  76. EP241217a: refined EP-WXT analysis and EP-FXT follow-up observations
  77. GRB 241217A / EP241217b: Nanshan/HMT optical upper limit
  78. GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
  79. GRB 241217A / EP241217b: NOT optical upper limits
  80. GRB 241218A: REM optical upper limit
  81. GRB 241217A/EP241217b: REM optical/NIR upper limits
  82. EP241217a: REM optical/NIR upper limits
  83. GRB 241218a: Liverpool Telescope optical follow-up
  84. GRB 241217a: Liverpool Telescope optical follow-up
  85. EP241217a: Liverpool Telescope optical follow-up
  86. GRB 241218A: Swift-XRT refined Analysis
  87. EP241217a: NOT optical observations
  88. EP241217a: GROWTH-India Telescope optical observations
  89. GRB 241218A: NUTTelA-TAO / BSTI Optical Limits
  90. EP241119a: 7DT Optical upper limits
  91. EP241217b: Global MASTER-Net observations report
  92. GRB 241209A: ATCA radio follow-up observations
  93. EP241217a: Xinglong optical follow-up observations
  94. EP241217b/GRB 241217A: EP detection of the prompt X-ray emssion
  95. GRB 241218A: LCOGT Optical Upper Limit
  96. GRB 241218A: Enhanced Swift-XRT position
  97. EP241217a: Global MASTER-Net observations report
  98. GRB 241217A: GMG Optical Upper Limit
  99. GRB 241218A: Swift detection of a burst
  100. GRB 241217A : SVOM/VT optical afterglow detection

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