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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. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  2. EP250108a / AT2025kg: GMG Optical Observations
  3. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  4. EP250108a / AT2025kg: VLA radio upper limit
  5. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  6. Konus-Wind detection of GRB 250116A
  7. GRB 250116A: GECAM-B detection of a long burst
  8. GRB 241217A / EP241217B: radio detection with the VLA
  9. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  10. Swift Trigger 1282245 is not a GRB
  11. GRB 250116A: Fermi-LAT detection
  12. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  13. GRB 250114B: Swift-XRT afterglow detection
  14. GRB 250114B: SVOM/VT upper limit
  15. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  16. EP250108a: MeerKAT radio upper limit
  17. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  18. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  19. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  20. Konus-Wind detection of GRB 250113A
  21. IPN triangulation of GRB 250113A
  22. GRB 250114B: Liverpool Telescope optical upper limit
  23. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  24. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  25. GRB 250114B: Swift-XRT observations
  26. GRB 250114A: LCO optical counterpart detection.
  27. GRB 250114B: OHP/T193 optical upper limit
  28. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  29. GRB 250114A: Swift-XRT refined Analysis
  30. Integral GRB250114.55: Global MASTER-Net observations report
  31. GRB 250114A: LCOGT optical afterglow i-band detection
  32. GRB 250114B : GIT optical upper limit
  33. GRB 250114B: Swift ToO observations
  34. EP250111a: SAO RAS optical upper limit
  35. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  36. GRB 250114B: a short GRB detected with INTEGRAL
  37. EP250108a: correction to GCN 38908
  38. GRB 250114A: Enhanced Swift-XRT position
  39. GRB 250113A: INTEGRAL/SPI-ACS detection
  40. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  41. GRB 250114A: REM detection of the optical and NIR counterpart
  42. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  43. Swift GRB250114A: Global MASTER-Net OT detection
  44. GRB 250114A: LCO optical observations
  45. GRB 250114A: TRT optical observations
  46. Swift GRB 250114A: Global MASTER-Net observations report
  47. GRB 250114A: Swift detection of a burst with an optical counterpart
  48. GRB 250101A: Terskol Zeiss-2000 optical observations
  49. EP250108a / AT 2025kg: SAO RAS optical observations
  50. EP241021a: SMA radio observation
  51. GRB 250113A: SVOM/GRM observation of a long burst
  52. GRB 250107A: VZLUSAT-2 detection
  53. EP250109b: optical upper limits with the Liverpool Telescope
  54. GRB 250109A / EP250109a: GRBAlpha detection
  55. GRB 250107D: GRBAlpha detection
  56. GRB 250106A: Swift-XRT afterglow detection
  57. Fermi trigger No 758442826: Global MASTER-Net observations report
  58. EP250111a: KAIT optical observations
  59. GRB 250109A / EP250109a: Mephisto optical upper limits
  60. EP250108a: Mephisto detection
  61. EP250111a: Mondy optical observation
  62. EP250108a / AT 2025kg: LCO optical observations
  63. EP250111a: Global MASTER-Net observations report
  64. EP250111a: Swift/XRT detection and fading
  65. EP250108a / AT 2025kg: Swift UVOT detections
  66. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  67. EP250108a: optical follow-up observations with the Liverpool Telescope
  68. EP250111a: NOT likely optical counterpart
  69. EP250111a: a new X-ray transient detected by Einstein Probe
  70. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  71. GRB 250101B: Fermi GBM Observation
  72. EP250108a: further NOT optical observations
  73. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  74. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  75. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  76. GRB 250108A: Swift/XRT afterglow fading
  77. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  78. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  79. Konus-Wind detection of GRB 250107C
  80. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  81. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  82. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  83. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  84. GRB 250101A: CMO RC-500 optical observations
  85. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  86. EP250108a: EP-FXT follow-up observation
  87. GRB 250109A: Fermi GBM Observation
  88. The EP-WXT trigger 01709130111 is likely a flaring star
  89. EP250108a: NOT optical observations
  90. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  91. GRB 250109a: GMG Optical Upper Limit
  92. EP250109a: Swift/UVOT non-detection
  93. Konus-Wind detection of GRB 250107D (short/hard)
  94. IPN triangulation of GRB 250107D (short/hard)
  95. IPN triangulation of GRB 250107C
  96. EP250108a: Liverpool Telescope likely optical counterpart
  97. GRB 250108B: Gemini-North likely redshift z = 2.197
  98. GRB 250108B: Swift-BAT refined analysis
  99. GRB 250108B: 1.3m DFOT upper limit
  100. GRB 250108B: REM optical/NIR upper limits

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