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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 251116A: Fermi GBM Final Real-time Localization
  2. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  3. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  4. GRB 251115A: Tiled Swift observations
  5. GRB 251115A: Fermi-LAT detection
  6. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  7. Fermi GRB 251115A: Global MASTER-Net observations report
  8. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  9. GRB 251115A: Fermi GBM Final Real-time Localization
  10. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  11. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  12. GRB 251113A: Glowbug gamma-ray detection
  13. GRB 251113A: AstroSat CZTI detection
  14. GRB 251114B: Fermi GBM Final Real-time Localization
  15. GRB 251112A: Swift-BAT refined analysis
  16. Konus-Wind detection of GRB 251108C
  17. Fermi trigger No 784717756: Global MASTER-Net observations report
  18. Konus-Wind detection of GRB 251103A
  19. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  20. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  21. IPN triangulation of GRB 251108C
  22. The EP-WXT trigger 01709248221 is likely a flaring star
  23. Fermi GRB 251114A: Global MASTER-Net observations report
  24. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  25. GRB 251114A: Fermi GBM Final Real-time Localization
  26. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  27. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  28. Fermi GRB 251113A: Global MASTER-Net observations report
  29. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  30. GRB 251113A: Fermi GBM Final Real-time Localization
  31. GRB 251111A: SVOM/ECLAIRs refined analysis
  32. GRB 251025B: SVOM/ECLAIRs refined analysis
  33. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  34. GRB 251112A: Swift/UVOT Upper Limits
  35. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  36. GRB 251112A: Swift-XRT refined Analysis
  37. GRB 251108C: AstroSat CZTI detection
  38. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  39. GRB 251112B: MAXI/GSC detection
  40. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  41. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  42. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  43. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  44. GRB 251108B: Glowbug gamma-ray detection
  45. Swift Trigger 1413695: a possible GRB 251112A
  46. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  47. Fermi trigger No 784621743: Global MASTER-Net observations report
  48. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  49. Fermi Gamma-ray Burst Monitor trigger 784653403/251112637 is not a GRB
  50. GRB251111A: 1.3m DFOT optical upper limit
  51. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  52. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  53. GRB 251111A: Swift-XRT afterglow detection
  54. GRB 251111A: SVOM/VT optical observations with X-band data
  55. SVOM GRB251111.42: Global MASTER-Net observations report
  56. GRB 251111A: Swift-XRT observations
  57. SVOM GRB251111.22: Global MASTER-Net observations report
  58. GRB 251111A: EP-FXT counterpart detection
  59. GRB 251013C: Chandra X-ray observations and jet break detection
  60. GRB 251111A: SVOM/VT optical observations with VHF data
  61. GRB 251111A: KAIT optical upper limit
  62. GRB 251111A: LCO optical observation
  63. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  64. GRB 251111A: SVOM detection of a soft burst
  65. GRB 251103B: Swift-BAT refined analysis
  66. GRB 251106A: Swift/UVOT Upper Limits
  67. GRB 251105B: Insight-HXMT/HE detection
  68. GRB 251106B: Insight-HXMT detection
  69. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  70. GRB 251105A: AstroSat CZTI detection
  71. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  72. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  73. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  74. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  75. GRB 251108A: Fermi GBM Final Localization Correction
  76. Fermi trigger No 784329591: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  78. Fermi trigger No 784279167: Global MASTER-Net observations report
  79. SVOM GRB251108.54: Global MASTER-Net observations report
  80. GRB 251102B: SVOM/GRM observation
  81. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  82. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  83. The EP-WXT trigger 01709248051 is likely a flaring star
  84. SVOM GRB251106.83: Global MASTER-Net observations report
  85. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  86. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  87. IPN triangulation of GRB 251105B (possible sGRB with EE)
  88. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  89. GRB 251106B: SVOM/GRM observation of a short burst
  90. GRB 251106A: Swift-XRT afterglow detection
  91. GRB 251106A: Kilonova-Catcher optical upper limit
  92. Fermi GBM Sub-Threshold Detection of GRB 251106A
  93. GRB 251106A: Swift/BAT arcminute localization of a burst
  94. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  95. GRB 251106A: MASTER optical observations
  96. GRB 251106A: SVOM detection of a burst
  97. GRB 251103B: AstroSat CZTI detection
  98. GRB 251025C: TERI Gamma-ray detection
  99. GRB 251016B: TERI Gamma-ray detection
  100. GRB 251016A: TERI Gamma-ray detection of a short burst

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