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

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