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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. Konus-Wind detection of GRB 251103A
  2. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  3. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  4. IPN triangulation of GRB 251108C
  5. The EP-WXT trigger 01709248221 is likely a flaring star
  6. Fermi GRB 251114A: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  8. GRB 251114A: Fermi GBM Final Real-time Localization
  9. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  10. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  11. Fermi GRB 251113A: Global MASTER-Net observations report
  12. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  13. GRB 251113A: Fermi GBM Final Real-time Localization
  14. GRB 251111A: SVOM/ECLAIRs refined analysis
  15. GRB 251025B: SVOM/ECLAIRs refined analysis
  16. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  17. GRB 251112A: Swift/UVOT Upper Limits
  18. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  19. GRB 251112A: Swift-XRT refined Analysis
  20. GRB 251108C: AstroSat CZTI detection
  21. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  22. GRB 251112B: MAXI/GSC detection
  23. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  24. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  25. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  26. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  27. GRB 251108B: Glowbug gamma-ray detection
  28. Swift Trigger 1413695: a possible GRB 251112A
  29. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  30. Fermi trigger No 784621743: Global MASTER-Net observations report
  31. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  32. Fermi Gamma-ray Burst Monitor trigger 784653403/251112637 is not a GRB
  33. GRB251111A: 1.3m DFOT optical upper limit
  34. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  35. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  36. GRB 251111A: Swift-XRT afterglow detection
  37. GRB 251111A: SVOM/VT optical observations with X-band data
  38. SVOM GRB251111.42: Global MASTER-Net observations report
  39. GRB 251111A: Swift-XRT observations
  40. SVOM GRB251111.22: Global MASTER-Net observations report
  41. GRB 251111A: EP-FXT counterpart detection
  42. GRB 251013C: Chandra X-ray observations and jet break detection
  43. GRB 251111A: SVOM/VT optical observations with VHF data
  44. GRB 251111A: KAIT optical upper limit
  45. GRB 251111A: LCO optical observation
  46. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  47. GRB 251111A: SVOM detection of a soft burst
  48. GRB 251103B: Swift-BAT refined analysis
  49. GRB 251106A: Swift/UVOT Upper Limits
  50. GRB 251105B: Insight-HXMT/HE detection
  51. GRB 251106B: Insight-HXMT detection
  52. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  53. GRB 251105A: AstroSat CZTI detection
  54. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  55. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  56. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  57. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  58. GRB 251108A: Fermi GBM Final Localization Correction
  59. Fermi trigger No 784329591: Global MASTER-Net observations report
  60. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  61. Fermi trigger No 784279167: Global MASTER-Net observations report
  62. SVOM GRB251108.54: Global MASTER-Net observations report
  63. GRB 251102B: SVOM/GRM observation
  64. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  65. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  66. The EP-WXT trigger 01709248051 is likely a flaring star
  67. SVOM GRB251106.83: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  69. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  70. IPN triangulation of GRB 251105B (possible sGRB with EE)
  71. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  72. GRB 251106B: SVOM/GRM observation of a short burst
  73. GRB 251106A: Swift-XRT afterglow detection
  74. GRB 251106A: Kilonova-Catcher optical upper limit
  75. Fermi GBM Sub-Threshold Detection of GRB 251106A
  76. GRB 251106A: Swift/BAT arcminute localization of a burst
  77. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  78. GRB 251106A: MASTER optical observations
  79. GRB 251106A: SVOM detection of a burst
  80. GRB 251103B: AstroSat CZTI detection
  81. GRB 251025C: TERI Gamma-ray detection
  82. GRB 251016B: TERI Gamma-ray detection
  83. GRB 251016A: TERI Gamma-ray detection of a short burst
  84. GRB 250920C: TERI Gamma-ray detection
  85. Fermi trigger No 784034269: Global MASTER-Net observations report
  86. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  87. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  88. GRB 251105A: Fermi GBM Observation
  89. GRB 251105C: Fermi GBM Final Localization Correction
  90. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  91. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  92. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  93. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  94. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  95. Fermi GBM Sub-Threshold Detection of GRB 251105B
  96. GRB 251103B: Swift/UVOT Upper Limits
  97. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  98. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  99. Fermi GRB 251105A: Global MASTER-Net observations report
  100. GRB 251105A: Fermi GBM Final Real-time Localization

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