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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: D50 optical detection
  2. GRB 241228B: Fermi GBM Observation
  3. GRB 241228B: Swift-XRT afterglow detection
  4. GRB 241229B: Fermi GBM Observation
  5. GRB 241229A: Swift ToO observations
  6. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  7. GRB 241228A: Mondy optical afterglow observations
  8. GRB 241229B: Swift-XRT refined Analysis
  9. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  10. Swift GRB 241229B: Global MASTER-Net observations report
  11. GRB 241229A: GOTO optical upper limits
  12. GRB 241228B: VLT/X-shooter redshift of z = 2.674
  13. GRB 241228A: NOT optical upper limits
  14. GRB 241228B: LCO optical observation
  15. GRB 241228A: Swift-BAT refined analysis
  16. GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
  17. GRB 241229B: Swift detection of a burst
  18. GRB 241229B: Fermi GBM Final Real-time Localization
  19. GRB 241229A: SVOM detection of a long burst
  20. Fermi GRB 241228B: Global MASTER-Net observations report
  21. GRB 241228A: Fermi GBM Observation
  22. GRB241228B: GROWTH-India Telescope optical observations
  23. Swift GRB 241228A: Global MASTER-Net observations report
  24. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  25. GRB 241228B: GOTO24jmz optical follow-up observations
  26. GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
  27. GRB 241228A: GROWTH-India telescope optical upper limit
  28. GRB 241228B: Swift ToO observations
  29. GRB 241228B: TRT optical counterpart confirmation
  30. GRB 241228A: Swift-XRT refined Analysis
  31. GRB 241228A: Swift/UVOT Upper Limits
  32. GRB 241228B: GOTO possible optical counterpart candidate
  33. GRB 241228A: Enhanced Swift-XRT position
  34. GRB 241228B: Fermi GBM Final Real-time Localization
  35. GRB 241228A: Swift detection of a burst
  36. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  37. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  38. GRB 241223A: GRBAlpha detection
  39. GRB 241212A: VZLUSAT-2 detection
  40. GRB 241217A/EP241217b: continued SOAR observations
  41. Fermi GRB 241226A: Global MASTER-Net observations report
  42. GRB 241226A: Fermi GBM Final Real-time Localization
  43. EP241223a: Mondy AZT-33IK optical observations
  44. GRB 241029A: LCO optical observation
  45. GRB 241223A: Swift-XRT observations
  46. LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
  47. GRB 241029A: AbAO AS-32 optical observations
  48. GRB 241223A: Fermi GBM Detection
  49. Fermi trigger No 756678579: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
  51. EP241223a
  52. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  53. IceCube Alert 241224.30: Global MASTER-Net observations report
  54. GRB 241219A: SVOM/GRM observation
  55. EP241223a: Global MASTER-Net observations report
  56. EP241223a: EP-WXT detection of a fast X-ray transient
  57. EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
  58. GRB241113A: 7DT Optical upper limits
  59. Fermi Gamma-ray Burst Monitor trigger 756678579 / 241223854 is not a GRB
  60. Fermi GRB 241223A: Global MASTER-Net observations report
  61. GRB 241223A: GOTO optical observations summary
  62. GRB 241105A: JWST photometric observations of the host galaxy
  63. GRB 241223A: Swift ToO observations
  64. EP241217a: e-MERLIN radio observations
  65. GRB 241223A: BALROG localization (Fermi Trigger 756648531 / GRB 241223506)
  66. GRB 241223A: Fermi GBM Final Real-time Localization
  67. GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
  68. The EP-WXT trigger 01709129287 is likely a flaring star
  69. Fermi trigger No 756447119: Global MASTER-Net observations report
  70. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  71. Fermi Gamma-ray Burst Monitor trigger 756447119/241221175 is not a GRB
  72. Fermi GRB 241221A: Global MASTER-Net observations report
  73. GRB 241221A: Fermi GBM Final Real-time Localization
  74. GRB 241217A/EP241217b: SOAR afterglow detection
  75. EP241217a: Liverpool Telescope optical upper limit
  76. EP241021a: VLA radio detection
  77. GRB 241218A: Mondy AZT-33IK optical upper limit
  78. EP241217a : Leavitt Observatory optical upper limit
  79. GRB 241217A/EP241217b: tentative VLT spectroscopic redshift z=1.879
  80. EP241217a: 1.6m Mephisto multi-band optical observations
  81. GRB 241217a/EP241217B: 1.6m Mephisto optical upper limits
  82. GRB 241218A: Swift/UVOT Upper Limits
  83. EP241217a: optical upper limit with the Liverpool Telescope
  84. GRB 241209B: EP-FXT afterglow detection
  85. Konus-Wind detection of GRB 241204A (short/hard)
  86. GRB 241218A: NOT optical upper limits
  87. GRB 241218A: Swift-BAT refined analysis
  88. GRB 241217A / EP241217B: GRANDMA/T1MPicduMidi optical upperlimits
  89. EP 241217a: NIR detection with P200/WIRC
  90. EP 241217a: Possible J-band detection with WINTER
  91. GRB 241217A/EP241217B: Fermi-GBM Sub-Threshold Detection
  92. EP241217a: refined EP-WXT analysis and EP-FXT follow-up observations
  93. GRB 241217A / EP241217b: Nanshan/HMT optical upper limit
  94. GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
  95. GRB 241217A / EP241217b: NOT optical upper limits
  96. GRB 241218A: REM optical upper limit
  97. GRB 241217A/EP241217b: REM optical/NIR upper limits
  98. EP241217a: REM optical/NIR upper limits
  99. GRB 241218a: Liverpool Telescope optical follow-up
  100. GRB 241217a: Liverpool Telescope optical follow-up

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