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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. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  2. GRB 251114A: Fermi GBM Final Real-time Localization
  3. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  4. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  5. Fermi GRB 251113A: Global MASTER-Net observations report
  6. GRB 251113A: BALROG localization (Fermi Trigger 784748255 / GRB 251113734)
  7. GRB 251113A: Fermi GBM Final Real-time Localization
  8. GRB 251111A: SVOM/ECLAIRs refined analysis
  9. GRB 251025B: SVOM/ECLAIRs refined analysis
  10. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  11. GRB 251112A: Swift/UVOT Upper Limits
  12. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  13. GRB 251112A: Swift-XRT refined Analysis
  14. GRB 251108C: AstroSat CZTI detection
  15. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  16. GRB 251112B: MAXI/GSC detection
  17. Fermi Gamma-ray Burst Monitor trigger 784687703/251113034 is not a GRB
  18. Fermi Gamma-ray Burst Monitor trigger 784687099/251113027 is not a GRB
  19. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  20. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  21. GRB 251108B: Glowbug gamma-ray detection
  22. Swift Trigger 1413695: a possible GRB 251112A
  23. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  24. Fermi trigger No 784621743: Global MASTER-Net observations report
  25. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  26. Fermi Gamma-ray Burst Monitor trigger 784653403/251112637 is not a GRB
  27. GRB251111A: 1.3m DFOT optical upper limit
  28. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  29. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  30. GRB 251111A: Swift-XRT afterglow detection
  31. GRB 251111A: SVOM/VT optical observations with X-band data
  32. SVOM GRB251111.42: Global MASTER-Net observations report
  33. GRB 251111A: Swift-XRT observations
  34. SVOM GRB251111.22: Global MASTER-Net observations report
  35. GRB 251111A: EP-FXT counterpart detection
  36. GRB 251013C: Chandra X-ray observations and jet break detection
  37. GRB 251111A: SVOM/VT optical observations with VHF data
  38. GRB 251111A: KAIT optical upper limit
  39. GRB 251111A: LCO optical observation
  40. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  41. GRB 251111A: SVOM detection of a soft burst
  42. GRB 251103B: Swift-BAT refined analysis
  43. GRB 251106A: Swift/UVOT Upper Limits
  44. GRB 251105B: Insight-HXMT/HE detection
  45. GRB 251106B: Insight-HXMT detection
  46. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  47. GRB 251105A: AstroSat CZTI detection
  48. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  49. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  50. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  51. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  52. GRB 251108A: Fermi GBM Final Localization Correction
  53. Fermi trigger No 784329591: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  55. Fermi trigger No 784279167: Global MASTER-Net observations report
  56. SVOM GRB251108.54: Global MASTER-Net observations report
  57. GRB 251102B: SVOM/GRM observation
  58. Fermi Gamma-ray Burst Monitor trigger 784279167/251108305 is not a GRB
  59. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  60. The EP-WXT trigger 01709248051 is likely a flaring star
  61. SVOM GRB251106.83: Global MASTER-Net observations report
  62. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  63. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  64. IPN triangulation of GRB 251105B (possible sGRB with EE)
  65. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  66. GRB 251106B: SVOM/GRM observation of a short burst
  67. GRB 251106A: Swift-XRT afterglow detection
  68. GRB 251106A: Kilonova-Catcher optical upper limit
  69. Fermi GBM Sub-Threshold Detection of GRB 251106A
  70. GRB 251106A: Swift/BAT arcminute localization of a burst
  71. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  72. GRB 251106A: MASTER optical observations
  73. GRB 251106A: SVOM detection of a burst
  74. GRB 251103B: AstroSat CZTI detection
  75. GRB 251025C: TERI Gamma-ray detection
  76. GRB 251016B: TERI Gamma-ray detection
  77. GRB 251016A: TERI Gamma-ray detection of a short burst
  78. GRB 250920C: TERI Gamma-ray detection
  79. Fermi trigger No 784034269: Global MASTER-Net observations report
  80. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  81. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  82. GRB 251105A: Fermi GBM Observation
  83. GRB 251105C: Fermi GBM Final Localization Correction
  84. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  85. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  86. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  88. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  89. Fermi GBM Sub-Threshold Detection of GRB 251105B
  90. GRB 251103B: Swift/UVOT Upper Limits
  91. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  92. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  93. Fermi GRB 251105A: Global MASTER-Net observations report
  94. GRB 251105A: Fermi GBM Final Real-time Localization
  95. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  96. GRB 251103B: Fermi GBM observation
  97. GRB 251104A: SVOM detection of a burst
  98. GRB 251028A: Insight-HXMT/HE detection
  99. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  100. EP251102a: FTW optical and NIR observations

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