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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 250119A: Fermi GBM Final Real-time Localization
  2. GRB 250118A: Fermi GBM Final Real-time Localization
  3. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  5. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  6. EP250108a / AT2025kg: GMG Optical Observations
  7. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  8. EP250108a / AT2025kg: VLA radio upper limit
  9. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  10. Konus-Wind detection of GRB 250116A
  11. GRB 250116A: GECAM-B detection of a long burst
  12. GRB 241217A / EP241217B: radio detection with the VLA
  13. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  14. Swift Trigger 1282245 is not a GRB
  15. GRB 250116A: Fermi-LAT detection
  16. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  17. GRB 250114B: Swift-XRT afterglow detection
  18. GRB 250114B: SVOM/VT upper limit
  19. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  20. EP250108a: MeerKAT radio upper limit
  21. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  22. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  23. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  24. Konus-Wind detection of GRB 250113A
  25. IPN triangulation of GRB 250113A
  26. GRB 250114B: Liverpool Telescope optical upper limit
  27. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  28. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  29. GRB 250114B: Swift-XRT observations
  30. GRB 250114A: LCO optical counterpart detection.
  31. GRB 250114B: OHP/T193 optical upper limit
  32. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  33. GRB 250114A: Swift-XRT refined Analysis
  34. Integral GRB250114.55: Global MASTER-Net observations report
  35. GRB 250114A: LCOGT optical afterglow i-band detection
  36. GRB 250114B : GIT optical upper limit
  37. GRB 250114B: Swift ToO observations
  38. EP250111a: SAO RAS optical upper limit
  39. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  40. GRB 250114B: a short GRB detected with INTEGRAL
  41. EP250108a: correction to GCN 38908
  42. GRB 250114A: Enhanced Swift-XRT position
  43. GRB 250113A: INTEGRAL/SPI-ACS detection
  44. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  45. GRB 250114A: REM detection of the optical and NIR counterpart
  46. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  47. Swift GRB250114A: Global MASTER-Net OT detection
  48. GRB 250114A: LCO optical observations
  49. GRB 250114A: TRT optical observations
  50. Swift GRB 250114A: Global MASTER-Net observations report
  51. GRB 250114A: Swift detection of a burst with an optical counterpart
  52. GRB 250101A: Terskol Zeiss-2000 optical observations
  53. EP250108a / AT 2025kg: SAO RAS optical observations
  54. EP241021a: SMA radio observation
  55. GRB 250113A: SVOM/GRM observation of a long burst
  56. GRB 250107A: VZLUSAT-2 detection
  57. EP250109b: optical upper limits with the Liverpool Telescope
  58. GRB 250109A / EP250109a: GRBAlpha detection
  59. GRB 250107D: GRBAlpha detection
  60. GRB 250106A: Swift-XRT afterglow detection
  61. Fermi trigger No 758442826: Global MASTER-Net observations report
  62. EP250111a: KAIT optical observations
  63. GRB 250109A / EP250109a: Mephisto optical upper limits
  64. EP250108a: Mephisto detection
  65. EP250111a: Mondy optical observation
  66. EP250108a / AT 2025kg: LCO optical observations
  67. EP250111a: Global MASTER-Net observations report
  68. EP250111a: Swift/XRT detection and fading
  69. EP250108a / AT 2025kg: Swift UVOT detections
  70. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  71. EP250108a: optical follow-up observations with the Liverpool Telescope
  72. EP250111a: NOT likely optical counterpart
  73. EP250111a: a new X-ray transient detected by Einstein Probe
  74. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  75. GRB 250101B: Fermi GBM Observation
  76. EP250108a: further NOT optical observations
  77. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  78. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  79. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  80. GRB 250108A: Swift/XRT afterglow fading
  81. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  82. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  83. Konus-Wind detection of GRB 250107C
  84. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  85. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  86. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  87. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  88. GRB 250101A: CMO RC-500 optical observations
  89. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  90. EP250108a: EP-FXT follow-up observation
  91. GRB 250109A: Fermi GBM Observation
  92. The EP-WXT trigger 01709130111 is likely a flaring star
  93. EP250108a: NOT optical observations
  94. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  95. GRB 250109a: GMG Optical Upper Limit
  96. EP250109a: Swift/UVOT non-detection
  97. Konus-Wind detection of GRB 250107D (short/hard)
  98. IPN triangulation of GRB 250107D (short/hard)
  99. IPN triangulation of GRB 250107C
  100. EP250108a: Liverpool Telescope likely optical counterpart

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