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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"

24353 results found.

  1. GRB 260708A: LCO further optical observations show supernova features
  2. GRB 260803A: Fermi GBM Final Real-time Localization
  3. Fermi GRB 260802B: Global MASTER-Net observations report
  4. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  5. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  6. GRB 260802A: SVOM/VT optical upper limits from VHF data
  7. GRB 260802A: LCO optical upper limits
  8. GRB 260802B: Fermi GBM Final Localization
  9. The EP-WXT trigger 01709277420 is likely a flaring star
  10. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  11. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  12. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  13. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  14. EP260731a: COLIBRÍ optical upper limit
  15. EP260731a: NOT optical upper limit
  16. GRB 260730B: NuSTAR detection of prompt emission
  17. GRB 260727A: SVOM/ECLAIRs refined analysis
  18. GRB 260726A: SVOM/ECLAIRs refined analysis
  19. GRB260730A: Fermi GBM Final Localization
  20. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  21. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  22. EP260728a: EP-FXT follow-up observation
  23. GRB 260726A: EP-FXT follow-up observations
  24. GRB 260727A: SVOM/GRM observation
  25. GRB 260726A: Fermi GBM Observation
  26. EP260727a: 1.5m OSN optical counterpart detection
  27. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  28. Konus-Wind detection of GRB 260727A
  29. EP260727a: NUTTELA-TAO Early Optical Limits
  30. GRB 260728A: Fermi GBM Final Localization
  31. GRB 260727A: EP/FXT follow-up observations
  32. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  33. GRB 260727A: J-band upper limit with WINTER
  34. GRB 260726A: SVOM/VT optical candidate
  35. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  36. GRB 260727A: LCO optical upper limits
  37. GRB 260727B: Fermi GBM Final Real-time Localization
  38. Fermi GRB 260726A: Global MASTER-Net observations report
  39. GRB 260727A: SVOM detection of a bright long burst
  40. GRB 260726A: SVOM detection of a burst
  41. GRB 260726A: Fermi GBM Final Real-time Localization
  42. EP260723a: further EP-FXT follow-up observation
  43. EP260725a: EP-WXT detection of an X-ray transient
  44. GRB 260616A: cubesat Avion detection
  45. GRB 260602B: cubesat Avion detection
  46. GRB 260601A: cubesat Avion detection
  47. EP260723a: EP-FXT follow-up observation
  48. IPN triangulation of GRB 260706B
  49. GRB 260718A: SVOM/ECLAIRs refined analysis
  50. EP260723a: SVOM/VT optical observation
  51. EP260723a: NOT optical conterpart confirmation
  52. GRB 260723A: Fermi GBM Final Localization
  53. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  54. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  55. IceCube Alert 260722A: Global MASTER-Net observations report
  56. Konus-Wind detection of GRB 260721A
  57. GRB 260722A: Fermi GBM Final Real-time Localization
  58. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  59. GRB 260721A: NuSTAR detection of prompt emission
  60. Konus-Wind detection of GRB 260714B
  61. GRB 260718A: EP-FXT follow-up observation
  62. Fermi trigger No 806104130: Global MASTER-Net observations report
  63. Fermi GRB 260718A: Global MASTER-Net observations report
  64. GRB 260718A: LCO optical upper limits
  65. GRB 260710A: SVOM/GRM observation
  66. GRB 260718A: Fermi GBM Observation
  67. GRB 260718A : GRANDMA and KNC upper limits
  68. GRB 260718A: SVOM/VT optical upper limits
  69. GRB 260718A: SVOM/VT optical upper limits from VHF data
  70. GRB 260718A: SVOM detection of a burst
  71. GRB 260714B: SVOM/GRM observation
  72. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  73. GRB 260714B: GECAM-B observation of a burst
  74. GRB 260618B: EP-FXT follow-up observation upper limit
  75. GRB 260714B: COLIBRÍ optical counterpart candidate
  76. SVOM sb26071506: Global MASTER-Net observations report
  77. sb26071506: SVOM detection of a X-ray transient
  78. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  79. GRB 260715A: Fermi GBM Final Real-time Localization
  80. GRB 260714B: Fermi-LAT detection
  81. GRB 260714B: Fermi GBM Detection
  82. GRB 260714B: BALROG localization (Fermi Trigger 805746211 / GRB 260714766)
  83. IceCube-260712A: Upper limits from a search for additional neutrino events in IceCube
  84. GRB 260714B: Fermi GBM Final Real-time Localization
  85. GRB 260714A: Fermi GBM Final Real-time Localization
  86. GRB 260619A: SVOM/VT continuous optical observations
  87. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  88. GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
  89. EP260711a: EP-FXT follow-up observation
  90. GRB 260708A: GRANDMA Optical Observations
  91. Fermi-LAT Gamma-ray Observations of IceCube-260712A
  92. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  93. Fermi-LAT Gamma-ray Observations of IceCube-260704A
  94. IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
  95. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  96. GRB 260708A: LCO optical observations
  97. GRB 260710A: Fermi GBM Detection
  98. GRB 260709A: SVOM/GRM detection
  99. GRB 260709A: GECAM-B observation
  100. The EP-WXT trigger 01709274666 is likely a new outburst of the CV SS Cyg

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