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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 250114A: Swift-XRT refined Analysis
  2. Integral GRB250114.55: Global MASTER-Net observations report
  3. GRB 250114A: LCOGT optical afterglow i-band detection
  4. GRB 250114B : GIT optical upper limit
  5. GRB 250114B: Swift ToO observations
  6. EP250111a: SAO RAS optical upper limit
  7. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  8. GRB 250114B: a short GRB detected with INTEGRAL
  9. EP250108a: correction to GCN 38908
  10. GRB 250114A: Enhanced Swift-XRT position
  11. GRB 250113A: INTEGRAL/SPI-ACS detection
  12. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  13. GRB 250114A: REM detection of the optical and NIR counterpart
  14. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  15. Swift GRB250114A: Global MASTER-Net OT detection
  16. GRB 250114A: LCO optical observations
  17. GRB 250114A: TRT optical observations
  18. Swift GRB 250114A: Global MASTER-Net observations report
  19. GRB 250114A: Swift detection of a burst with an optical counterpart
  20. GRB 250101A: Terskol Zeiss-2000 optical observations
  21. EP250108a / AT 2025kg: SAO RAS optical observations
  22. EP241021a: SMA radio observation
  23. GRB 250113A: SVOM/GRM observation of a long burst
  24. GRB 250107A: VZLUSAT-2 detection
  25. EP250109b: optical upper limits with the Liverpool Telescope
  26. GRB 250109A / EP250109a: GRBAlpha detection
  27. GRB 250107D: GRBAlpha detection
  28. GRB 250106A: Swift-XRT afterglow detection
  29. Fermi trigger No 758442826: Global MASTER-Net observations report
  30. EP250111a: KAIT optical observations
  31. GRB 250109A / EP250109a: Mephisto optical upper limits
  32. EP250108a: Mephisto detection
  33. EP250111a: Mondy optical observation
  34. EP250108a / AT 2025kg: LCO optical observations
  35. EP250111a: Global MASTER-Net observations report
  36. EP250111a: Swift/XRT detection and fading
  37. EP250108a / AT 2025kg: Swift UVOT detections
  38. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  39. EP250108a: optical follow-up observations with the Liverpool Telescope
  40. EP250111a: NOT likely optical counterpart
  41. EP250111a: a new X-ray transient detected by Einstein Probe
  42. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  43. GRB 250101B: Fermi GBM Observation
  44. EP250108a: further NOT optical observations
  45. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  46. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  47. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  48. GRB 250108A: Swift/XRT afterglow fading
  49. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  50. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  51. Konus-Wind detection of GRB 250107C
  52. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  53. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  54. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  55. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  56. GRB 250101A: CMO RC-500 optical observations
  57. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  58. EP250108a: EP-FXT follow-up observation
  59. GRB 250109A: Fermi GBM Observation
  60. The EP-WXT trigger 01709130111 is likely a flaring star
  61. EP250108a: NOT optical observations
  62. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  63. GRB 250109a: GMG Optical Upper Limit
  64. EP250109a: Swift/UVOT non-detection
  65. Konus-Wind detection of GRB 250107D (short/hard)
  66. IPN triangulation of GRB 250107D (short/hard)
  67. IPN triangulation of GRB 250107C
  68. EP250108a: Liverpool Telescope likely optical counterpart
  69. GRB 250108B: Gemini-North likely redshift z = 2.197
  70. GRB 250108B: Swift-BAT refined analysis
  71. GRB 250108B: 1.3m DFOT upper limit
  72. GRB 250108B: REM optical/NIR upper limits
  73. GRB 250109A /EP250109a: Fermi GBM Final Localization
  74. EP250109a: SVOM/VT optical candidate
  75. EP250109a: Global MASTER-Net observations report
  76. GRB 250107C: SVOM/GRM observation
  77. GRB 250101A: Terskol K-800 optical observations
  78. EP250109a: GOTO optical upper limits
  79. EP250109a: Swift/XRT non-detection
  80. GRB 250108A: Swift/UVOT Upper Limits
  81. EP250108a: Global MASTER-Net observations report
  82. EP250109a: EP-WXT detection of an X-ray transient
  83. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  84. GRB 250108A: NOT optical upper limit
  85. EP250108a: EP-WXT detection of an X-ray transient
  86. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  87. GRB 250108B: Swift-XRT refined Analysis
  88. Swift GRB 250108B: Global MASTER-Net observations report
  89. Fermi Gamma-ray Burst Monitor trigger 758061038/250108855 is not a GRB
  90. LIGO/Virgo/KAGRA S250108ha: Retraction of GW compact binary merger candidate
  91. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  92. GRB 250103A: 1.6m Mephisto optical observations
  93. GRB 250108A: Swift-XRT afterglow detection
  94. GRB 250108A:SVOM/VT optical candidate
  95. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  96. GRB 250108B: Swift/UVOT Upper Limits
  97. GRB 250103A: Swift-XRT afterglow detection
  98. GRB 250108B: Enhanced Swift-XRT position
  99. GRB 250108B: Swift detection of a burst
  100. GRB 250108A: Swift ToO observations

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