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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"

27447 results found.

  1. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  2. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  3. GRB 260813A: Fermi GBM Final Real-time Localization
  4. EP260812a: NOT and Liverpool Telescope upper limits:
  5. EP260812a: SVOM/C-GFT optical upper limit
  6. EP260812b: COLIBRÍ optical observations
  7. EP260812b: SVOM/VT optical observation
  8. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  9. Fermi GBM Sub-Threshold Detection of GRB 260809A
  10. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  11. GRB 260808B: SVOM/VT optical re-brightening at day 3
  12. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  13. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 260807A: SVOM/ECLAIRs refined analysis
  15. GRB260808B: MAO/AZT-22 optical observations
  16. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  17. GRB 260809A: J-band upper limit with WINTER
  18. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  19. GRB 260806A: Glowbug gamma-ray detection
  20. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  21. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  22. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  23. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  24. The EP-WXT trigger 01709278015 is likely a flaring star
  25. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  26. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  27. GRB 260809A: NOT optical observations
  28. GRB260809A: MAO/AZT-22 optical observations
  29. GRB260809A: OHP/T193 optical observations
  30. GRB 260809A: SVOM/VT optical counterpart
  31. EP260809a: J-band upper limit with WINTER
  32. GRB 260808B: J-band upper limit with WINTER
  33. GRB 260808B: SVOM/ECLAIRs refined analysis
  34. GRB 260809A: SVOM detection of a faint burst
  35. GRB 260808B: Liverpool Telescope optical observations
  36. GRB 260808B: NOT optical observations
  37. GRB 260808B: LCO optical observations
  38. EP260809a: COLIBRÍ optical observations
  39. EP260809a: LCO optical observation
  40. EP260809a: OHP/T193 optical observations
  41. GRB260808B: OHP/T193 optical observations
  42. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  43. GRB 260808B: SVOM/VT optical afterglow confirmation
  44. GRB 260808C: Fermi GBM Final Real-time Localization
  45. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  46. GRB 260808B: SVOM/VT optical candidate from VHF data
  47. GRB 260808B: SVOM detection of a faint burst
  48. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  49. Fermi GRB 260808A: Global MASTER-Net observations report
  50. GRB 260808A: Fermi GBM Final Real-time Localization
  51. IceCube Alert 260807A: Global MASTER-Net observations report
  52. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  53. GRB 260807A: SVOM possible detection of a faint burst
  54. EP260806a: COLIBRÍ optical observations
  55. EP260806a: SVOM/VT optical observation
  56. EP260806a: OSIRIS+/GTC redshift z=0.089
  57. EP260806a: LCO likely optical counterpart
  58. SN 2026stf / GRB 260708A: ATLAS forced photometry
  59. Fermi GRB 260805A: Global MASTER-Net observations report
  60. GRB 260805B: Fermi GBM Final Localization
  61. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  62. GRB 260805A: Fermi GBM Final Localization
  63. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  64. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  65. GRB 260804A: Fermi GBM Final Real-time Localization
  66. GRB 260708A: LCO further optical observations show supernova features
  67. GRB 260803A: Fermi GBM Final Real-time Localization
  68. Fermi GRB 260802B: Global MASTER-Net observations report
  69. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  70. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  71. GRB 260802A: SVOM/VT optical upper limits from VHF data
  72. GRB 260802A: LCO optical upper limits
  73. GRB 260802B: Fermi GBM Final Localization
  74. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. The EP-WXT trigger 01709277420 is likely a flaring star
  76. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  77. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  78. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  79. GRB 260731A: AstroSat CZTI detection of a long burst
  80. EP260731a: COLIBRÍ optical upper limit
  81. EP260731a: NOT optical upper limit
  82. GRB 260727A: SVOM/ECLAIRs refined analysis
  83. GRB 260726A: SVOM/ECLAIRs refined analysis
  84. GRB260730A: Fermi GBM Final Localization
  85. EP260728a: COLIBRÍ optical upper limit
  86. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  87. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  88. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  89. GRB 260727A: AbAO and SAO RAS optical observations
  90. EP260728a: EP-FXT follow-up observation
  91. GRB 260726A: EP-FXT follow-up observations
  92. GRB 260726A: Fermi GBM Observation
  93. EP260727a: 1.5m OSN optical counterpart detection
  94. EP260727a: OHP/T193 optical observations
  95. GRB 260726A: Liverpool Telescope optical observations
  96. GRB 260727A: Liverpool Telescope optical upper limits
  97. EP260727a: NUTTELA-TAO Early Optical Limits
  98. GRB 260728A: Fermi GBM Final Localization
  99. GRB 260727A: EP/FXT follow-up observations
  100. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart

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