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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. EP250108a / AT2025kg: GMG Optical Observations
  2. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  3. EP250108a / AT2025kg: VLA radio upper limit
  4. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  5. Konus-Wind detection of GRB 250116A
  6. GRB 250116A: GECAM-B detection of a long burst
  7. GRB 241217A / EP241217B: radio detection with the VLA
  8. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  9. Swift Trigger 1282245 is not a GRB
  10. GRB 250116A: Fermi-LAT detection
  11. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  12. GRB 250114B: Swift-XRT afterglow detection
  13. GRB 250114B: SVOM/VT upper limit
  14. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  15. EP250108a: MeerKAT radio upper limit
  16. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  17. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  18. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  19. Konus-Wind detection of GRB 250113A
  20. IPN triangulation of GRB 250113A
  21. GRB 250114B: Liverpool Telescope optical upper limit
  22. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  23. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  24. GRB 250114B: Swift-XRT observations
  25. GRB 250114A: LCO optical counterpart detection.
  26. GRB 250114B: OHP/T193 optical upper limit
  27. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  28. GRB 250114A: Swift-XRT refined Analysis
  29. Integral GRB250114.55: Global MASTER-Net observations report
  30. GRB 250114A: LCOGT optical afterglow i-band detection
  31. GRB 250114B : GIT optical upper limit
  32. GRB 250114B: Swift ToO observations
  33. EP250111a: SAO RAS optical upper limit
  34. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  35. GRB 250114B: a short GRB detected with INTEGRAL
  36. EP250108a: correction to GCN 38908
  37. GRB 250114A: Enhanced Swift-XRT position
  38. GRB 250113A: INTEGRAL/SPI-ACS detection
  39. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  40. GRB 250114A: REM detection of the optical and NIR counterpart
  41. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  42. Swift GRB250114A: Global MASTER-Net OT detection
  43. GRB 250114A: LCO optical observations
  44. GRB 250114A: TRT optical observations
  45. Swift GRB 250114A: Global MASTER-Net observations report
  46. GRB 250114A: Swift detection of a burst with an optical counterpart
  47. GRB 250101A: Terskol Zeiss-2000 optical observations
  48. EP250108a / AT 2025kg: SAO RAS optical observations
  49. EP241021a: SMA radio observation
  50. GRB 250113A: SVOM/GRM observation of a long burst
  51. GRB 250107A: VZLUSAT-2 detection
  52. EP250109b: optical upper limits with the Liverpool Telescope
  53. GRB 250109A / EP250109a: GRBAlpha detection
  54. GRB 250107D: GRBAlpha detection
  55. GRB 250106A: Swift-XRT afterglow detection
  56. Fermi trigger No 758442826: Global MASTER-Net observations report
  57. EP250111a: KAIT optical observations
  58. GRB 250109A / EP250109a: Mephisto optical upper limits
  59. EP250108a: Mephisto detection
  60. EP250111a: Mondy optical observation
  61. EP250108a / AT 2025kg: LCO optical observations
  62. EP250111a: Global MASTER-Net observations report
  63. EP250111a: Swift/XRT detection and fading
  64. EP250108a / AT 2025kg: Swift UVOT detections
  65. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  66. EP250108a: optical follow-up observations with the Liverpool Telescope
  67. EP250111a: NOT likely optical counterpart
  68. EP250111a: a new X-ray transient detected by Einstein Probe
  69. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  70. GRB 250101B: Fermi GBM Observation
  71. EP250108a: further NOT optical observations
  72. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  73. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  74. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  75. GRB 250108A: Swift/XRT afterglow fading
  76. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  77. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  78. Konus-Wind detection of GRB 250107C
  79. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  80. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  81. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  82. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  83. GRB 250101A: CMO RC-500 optical observations
  84. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  85. EP250108a: EP-FXT follow-up observation
  86. GRB 250109A: Fermi GBM Observation
  87. The EP-WXT trigger 01709130111 is likely a flaring star
  88. EP250108a: NOT optical observations
  89. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  90. GRB 250109a: GMG Optical Upper Limit
  91. EP250109a: Swift/UVOT non-detection
  92. Konus-Wind detection of GRB 250107D (short/hard)
  93. IPN triangulation of GRB 250107D (short/hard)
  94. IPN triangulation of GRB 250107C
  95. EP250108a: Liverpool Telescope likely optical counterpart
  96. GRB 250108B: Gemini-North likely redshift z = 2.197
  97. GRB 250108B: Swift-BAT refined analysis
  98. GRB 250108B: 1.3m DFOT upper limit
  99. GRB 250108B: REM optical/NIR upper limits
  100. GRB 250109A /EP250109a: Fermi GBM Final Localization

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