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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: SAO RAS optical observations
  2. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  3. GRB 241229A: SAO RAS optical observations
  4. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  5. GRB 241229B: SVOM/VT optical candidate
  6. GRB 241229A: Swift-XRT observations
  7. Konus-Wind detection of GRB 241228A
  8. GRB 241229A: EP-FXT afterglow candidates
  9. EP240702a: 7DT Optical upper limits
  10. GRB 240606B: 7DT Optical upper limits
  11. Fermi trigger No 757231333: Global MASTER-Net observations report
  12. LIGO/Virgo/KAGRA S241230bd: Identification of a GW compact binary merger candidate
  13. GRB 241229B: Swift-BAT refined analysis
  14. LIGO/Virgo/KAGRA S241225v: Updated Sky localization
  15. LIGO/Virgo/KAGRA S241225c: Updated Sky localization and EM Bright Classification
  16. Fermi Gamma-ray Burst Monitor trigger 757207662/241229978 (GRB 241229C) is not a GRB
  17. GRB241229B: UVOT upper limits
  18. GRB 241229C: Fermi GBM Final Real-time Localization
  19. GRB 241228B: D50 optical detection
  20. GRB 241228B: Fermi GBM Observation
  21. GRB 241228B: Swift-XRT afterglow detection
  22. GRB 241229B: Fermi GBM Observation
  23. GRB 241229A: Swift ToO observations
  24. GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
  25. GRB 241228A: Mondy optical afterglow observations
  26. GRB 241229B: Swift-XRT refined Analysis
  27. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  28. Swift GRB 241229B: Global MASTER-Net observations report
  29. GRB 241229A: GOTO optical upper limits
  30. GRB 241228B: VLT/X-shooter redshift of z = 2.674
  31. GRB 241228A: NOT optical upper limits
  32. GRB 241228B: LCO optical observation
  33. GRB 241228A: Swift-BAT refined analysis
  34. GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
  35. GRB 241229B: Swift detection of a burst
  36. GRB 241229B: Fermi GBM Final Real-time Localization
  37. GRB 241229A: SVOM detection of a long burst
  38. Fermi GRB 241228B: Global MASTER-Net observations report
  39. GRB 241228A: Fermi GBM Observation
  40. GRB241228B: GROWTH-India Telescope optical observations
  41. Swift GRB 241228A: Global MASTER-Net observations report
  42. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  43. GRB 241228B: GOTO24jmz optical follow-up observations
  44. GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
  45. GRB 241228A: GROWTH-India telescope optical upper limit
  46. GRB 241228B: Swift ToO observations
  47. GRB 241228B: TRT optical counterpart confirmation
  48. GRB 241228A: Swift-XRT refined Analysis
  49. GRB 241228A: Swift/UVOT Upper Limits
  50. GRB 241228B: GOTO possible optical counterpart candidate
  51. GRB 241228A: Enhanced Swift-XRT position
  52. GRB 241228B: Fermi GBM Final Real-time Localization
  53. GRB 241228A: Swift detection of a burst
  54. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  55. LIGO/Virgo/KAGRA S241225c: Two counterpart neutrino candidates from IceCube neutrino searches
  56. GRB 241223A: GRBAlpha detection
  57. GRB 241212A: VZLUSAT-2 detection
  58. GRB 241217A/EP241217b: continued SOAR observations
  59. Fermi GRB 241226A: Global MASTER-Net observations report
  60. GRB 241226A: Fermi GBM Final Real-time Localization
  61. EP241223a: Mondy AZT-33IK optical observations
  62. GRB 241029A: LCO optical observation
  63. GRB 241223A: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
  65. GRB 241029A: AbAO AS-32 optical observations
  66. GRB 241223A: Fermi GBM Detection
  67. Fermi trigger No 756678579: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S241225c: Identification of a GW compact binary merger candidate
  69. EP241223a
  70. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  71. IceCube Alert 241224.30: Global MASTER-Net observations report
  72. GRB 241219A: SVOM/GRM observation
  73. EP241223a: Global MASTER-Net observations report
  74. EP241223a: EP-WXT detection of a fast X-ray transient
  75. EP241113a: Non-detection in Radio Follow-up Observations with eMERLIN
  76. GRB241113A: 7DT Optical upper limits
  77. Fermi Gamma-ray Burst Monitor trigger 756678579 / 241223854 is not a GRB
  78. Fermi GRB 241223A: Global MASTER-Net observations report
  79. GRB 241223A: GOTO optical observations summary
  80. GRB 241105A: JWST photometric observations of the host galaxy
  81. GRB 241223A: Swift ToO observations
  82. EP241217a: e-MERLIN radio observations
  83. GRB 241223A: BALROG localization (Fermi Trigger 756648531 / GRB 241223506)
  84. GRB 241223A: Fermi GBM Final Real-time Localization
  85. GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
  86. The EP-WXT trigger 01709129287 is likely a flaring star
  87. Fermi trigger No 756447119: Global MASTER-Net observations report
  88. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  89. Fermi Gamma-ray Burst Monitor trigger 756447119/241221175 is not a GRB
  90. Fermi GRB 241221A: Global MASTER-Net observations report
  91. GRB 241221A: Fermi GBM Final Real-time Localization
  92. GRB 241217A/EP241217b: SOAR afterglow detection
  93. EP241217a: Liverpool Telescope optical upper limit
  94. EP241021a: VLA radio detection
  95. GRB 241218A: Mondy AZT-33IK optical upper limit
  96. EP241217a : Leavitt Observatory optical upper limit
  97. GRB 241217A/EP241217b: tentative VLT spectroscopic redshift z=1.879
  98. EP241217a: 1.6m Mephisto multi-band optical observations
  99. GRB 241217a/EP241217B: 1.6m Mephisto optical upper limits
  100. GRB 241218A: Swift/UVOT Upper Limits

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