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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 250814A: Possible afterglow candidate from P200/WIRC
  2. GRB 250813B: Fermi GBM Observation
  3. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  4. Fermi trigger No 776818276: Global MASTER-Net observations report
  5. Swift GRB250814.32: Global MASTER-Net observations report
  6. GRB 250814A: J-band upper limit from WINTER
  7. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 250813B: NOT observations of the optical afterglow
  9. GRB 250813B: SVOM/VT optical observations
  10. Subject GRB 250813B: SVOM/MXT refined analysis
  11. GRB 250814A: COLIBRÍ optical upper limit
  12. GRB 250814B: Fermi GBM Final Real-time Localization
  13. GRB 250813A: AstroSat CZTI detection
  14. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  15. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  16. GRB 250814A: DDOTI Optical Upper Limit
  17. GRB 250813B: EP-FXT counterpart detection
  18. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  19. GRB 250813B: Swift-XRT afterglow detection
  20. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  21. GRB 250814A: Fermi GBM Final Real-time Localization
  22. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  23. GRB 250813B: Ondrejov D50 fast decay
  24. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  25. GRB 250813B: Ondrejov D50 optical afterglow detection
  26. GRB 250813B: SVOM detection of a bright long burst
  27. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  28. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  29. EP250812a: Nickel optical upper limit
  30. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  31. GRB 250812A: NTT spectroscopic redshift z = 2.57
  32. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  33. EP250812a: NOT, NTT, and GS observations
  34. GRB 250812A: Swift/UVOT Detection
  35. GRB 250813A: Fermi GBM Final Localization
  36. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  37. EP250812a: Liverpool Telescope upper limits
  38. EP250812a: SVOM/VT optical counterpart
  39. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  40. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  41. IceCube Alert 250813.14: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  43. GRB 250812A: EP-FXT counterpart detection
  44. GRB 250812A: Swift ToO observations
  45. GRB 250807B: Swift-BAT refined analysis
  46. EP 250812a: GOTO optical upper limit
  47. GRB 250812A: Kilonova-Catcher optical afterglow detection
  48. EP250812a: Swift-XRT counterpart detection
  49. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  50. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  51. EP250812a: Einstein Probe detection of an X-ray transient
  52. GRB 250812A: SVOM/VT optical afterglow confirmation
  53. GRB 250812A: Swift-XRT afterglow detection
  54. GRB 250812A: TRT likely optical counterpart detection
  55. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 250812A: SVOM detection of a faint long burst
  57. GRB 250809A: Swift-BAT refined analysis
  58. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  59. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  60. GRB 250807A: Swift-BAT refined analysis
  61. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  62. GRB 250809A: Swift/UVOT Detection
  63. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  64. Corrected Swift-XRT Refined Analysis of GRB 250809A
  65. GRB 250809A: Swift-XRT refined Analysis
  66. GRB 250807B: SVOM/VT optical observation
  67. EP250807a: EP-FXT follow-up observation upper limit
  68. GRB 250809A: LCOGT Optical Upper Limits
  69. GRB 250702B: Chandra X-ray Detection
  70. EP250807a: Global MASTER-Net observations report
  71. Fermi GRB 250808A: Global MASTER-Net observations report
  72. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  73. GRB 250808A: VLT X-shooter candidate counterpart
  74. GRB 250809A: Prompt enhanced Swift-XRT position
  75. GRB 250809A: Swift detection of a gamma ray burst
  76. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  77. GRB 250808A: Fermi GBM Observation
  78. GRB 250808A: Swift-XRT candidate counterpart detection
  79. GRB 250807A: SVOM/VT optical continued observation
  80. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  81. GRB 250808A: SVOM detection of a long burst
  82. GRB 250808A: Fermi GBM Final Real-time Localization
  83. Konus-Wind detection of GRB 250807A
  84. GRB 250807B: Swift/UVOT Detection
  85. GRB 250807B: Kilonova-Catcher optical afterglow detection
  86. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 250807A: Swift/UVOT Detection
  88. GRB 250807A: Swift-XRT refined Analysis
  89. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  90. GRB 250806A: SVOM/MXT refined analysis
  91. GRB 250806A: SVOM/ECLAIRs refined analysis
  92. EP250807a: NTT z-band optical upper limit
  93. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  94. GRB 250804B: Insight-HXMT detection
  95. GRB 250807A: SVOM/GRM observation
  96. Swift GRB250807.45: Global MASTER-Net observations report
  97. GRB 250807A: AstroSat CZTI detection of bright long burst
  98. GRB 250807B: Swift-XRT refined Analysis
  99. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  100. GRB 250807B: NTT optical observations

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