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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"

26922 results found.

  1. GRB 260807A: SVOM/ECLAIRs refined analysis
  2. GRB260808B: MAO/AZT-22 optical observations
  3. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  4. GRB 260809A: J-band upper limit with WINTER
  5. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  6. GRB 260806A: Glowbug gamma-ray detection
  7. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  8. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  9. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  10. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  11. The EP-WXT trigger 01709278015 is likely a flaring star
  12. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  13. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  14. GRB 260809A: NOT optical observations
  15. GRB260809A: MAO/AZT-22 optical observations
  16. GRB260809A: OHP/T193 optical observations
  17. GRB 260809A: SVOM/VT optical counterpart
  18. EP260809a: J-band upper limit with WINTER
  19. GRB 260808B: J-band upper limit with WINTER
  20. GRB 260808B: SVOM/ECLAIRs refined analysis
  21. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  22. GRB 260809A: SVOM detection of a faint burst
  23. GRB 260808B: Liverpool Telescope optical observations
  24. GRB 260808B: NOT optical observations
  25. GRB 260808B: LCO optical observations
  26. EP260809a: COLIBRÍ optical observations
  27. EP260809a: LCO optical observation
  28. EP260809a: OHP/T193 optical observations
  29. GRB260808B: OHP/T193 optical observations
  30. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  31. EP260809a: Einstein Probe detection of an X-ray transient
  32. GRB 260808B: SVOM/VT optical afterglow confirmation
  33. GRB 260808C: Fermi GBM Final Real-time Localization
  34. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  35. GRB 260808B: SVOM/VT optical candidate from VHF data
  36. GRB 260808B: SVOM detection of a faint burst
  37. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  38. Fermi GRB 260808A: Global MASTER-Net observations report
  39. GRB 260808A: Fermi GBM Final Real-time Localization
  40. IceCube Alert 260807A: Global MASTER-Net observations report
  41. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. GRB 260807A: SVOM possible detection of a faint burst
  43. EP260806a: COLIBRÍ optical observations
  44. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  45. EP260806a: SVOM/VT optical observation
  46. EP260806a: OSIRIS+/GTC redshift z=0.089
  47. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  48. EP260806a: LCO likely optical counterpart
  49. EP260806a: Einstein Probe detection of an X-ray transient
  50. SN 2026stf / GRB 260708A: ATLAS forced photometry
  51. Fermi GRB 260805A: Global MASTER-Net observations report
  52. GRB 260805B: Fermi GBM Final Localization
  53. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  54. GRB 260805A: Fermi GBM Final Localization
  55. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  56. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  57. GRB 260804A: Fermi GBM Final Real-time Localization
  58. GRB 260708A: LCO further optical observations show supernova features
  59. GRB 260803A: Fermi GBM Final Real-time Localization
  60. Fermi GRB 260802B: Global MASTER-Net observations report
  61. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  62. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  63. GRB 260802A: SVOM/VT optical upper limits from VHF data
  64. GRB 260802A: LCO optical upper limits
  65. GRB 260802B: Fermi GBM Final Localization
  66. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  67. The EP-WXT trigger 01709277420 is likely a flaring star
  68. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  69. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  70. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  71. GRB 260731A: AstroSat CZTI detection of a long burst
  72. EP260731a: COLIBRÍ optical upper limit
  73. EP260731a: NOT optical upper limit
  74. EP260731a: Einstein Probe detection of an X-ray transient
  75. GRB 260727A: SVOM/ECLAIRs refined analysis
  76. GRB 260726A: SVOM/ECLAIRs refined analysis
  77. GRB260730A: Fermi GBM Final Localization
  78. EP260728a: COLIBRÍ optical upper limit
  79. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  80. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  81. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  82. EP260729a: Einstein Probe detection of an X-ray transient
  83. GRB 260727A: AbAO and SAO RAS optical observations
  84. EP260728a: EP-FXT follow-up observation
  85. GRB 260726A: EP-FXT follow-up observations
  86. EP260728a: Einstein Probe detection of a fast X-ray transient
  87. GRB 260727A: SVOM/GRM observation
  88. GRB 260726A: Fermi GBM Observation
  89. EP260727a: 1.5m OSN optical counterpart detection
  90. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  91. EP260727a: OHP/T193 optical observations
  92. GRB 260726A: Liverpool Telescope optical observations
  93. GRB 260727A: Liverpool Telescope optical upper limits
  94. EP260727a: NUTTELA-TAO Early Optical Limits
  95. GRB 260728A: Fermi GBM Final Localization
  96. GRB 260727A: EP/FXT follow-up observations
  97. EP260727a: Einstein Probe detection of an X-ray transient
  98. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  99. GRB 260726A: J-band upper limit with WINTER
  100. GRB 260727A: J-band upper limit with WINTER

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