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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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. Swift GRB 250129A: Global MASTER-Net OT detection
  2. GRB 250128B: Swift-XRT refined Analysis
  3. GRB 250128B: Fermi GBM Observation
  4. GRB 250128B: GOTO optical upper limit
  5. Swift GRB 250128B: Global MASTER-Net observations report
  6. EP250125a: Upper limits from Swift/BAT-GUANO
  7. GRB 250128B: LCO optical observations
  8. GRB 250128B: Swift detection of a short burst
  9. GRB 250128B: Fermi GBM Final Real-time Localization
  10. GRB 250127A: Swift-XRT observations
  11. GRB 250127B: DDOTI Upper Limit on the Afterglow
  12. Fermi-LAT Gamma-ray Observations of IceCube-250102A
  13. GRB 250127A: EP-FXT afterglow detection
  14. Fermi GRB 250128A: Global MASTER-Net observations report
  15. GRB 250128A: Fermi GBM Final Real-time Localization
  16. GRB 250117A: Fermi GBM Observation
  17. Fermi GRB 250127B: Global MASTER-Net observations report
  18. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  19. GRB 250127A: SVOM/VT upper limit
  20. GRB 250127B: Fermi GBM Final Real-time Localization
  21. IPN triangulation of GRB 250119C
  22. GRB 250127A: Swift ToO observations
  23. GRB 250127A: LCO optical upper limit
  24. GRB 241223A: cubesat Avion detection
  25. GRB 250127A: SVOM detection of a long burst
  26. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  27. EP250125A: Non-detection from Fermi-GBM Observations
  28. GRB 250126A: MAXI/GSC detection
  29. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  30. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  31. GRB 250126A: Fermi GBM Final Real-time Localization
  32. GECAM-A detection of a bright burst from SGR 1E1841-045
  33. GRB 250118A: Fermi GBM Observation
  34. EP250125a: Optical upper limit with Kinder observations
  35. EP250125a: REM optical counterpart detection
  36. GRB 250119C: Fermi GBM Observation
  37. EP250125a: Swift/XRT detection of a fading counterpart
  38. EP250125a: a new X-ray transient detected by Einstein Probe
  39. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  40. The EP-WXT trigger 01709130758 is a false trigger
  41. The EP-WXT trigger 01709130758 is a false trigger
  42. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  43. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  44. IPN triangulation of a bright burst from SGR 1E1841-045
  45. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  46. EP250108a: AbAO, CMO and Terskol optical upper limits
  47. Konus-Wind detection of GRB 250118B
  48. GRB 250121A: Fermi GBM Observation
  49. IPN triangulation of GRB 250118B
  50. Konus-Wind detection of GRB 250119B
  51. IPN triangulation of GRB 250119B
  52. GRB 250122A: Fermi GBM Final Real-time Localization
  53. Improved IPN triangulation of GRB 250107C
  54. GRB 250114A: Swift-BAT refined analysis
  55. GRB 250121A: INTEGRAL/SPI-ACS detection
  56. GRB 250121A: Fermi-LAT detection
  57. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  58. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  59. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  60. GRB 250121A: Fermi GBM Final Real-time Localization
  61. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  62. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  63. GRB 250119B: Fermi GBM Observation
  64. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  65. Konus-Wind detection of GRB 250117A
  66. IPN triangulation of GRB 250117A (short)
  67. ATCA detection of possible radio counterpart to GRB 250114A
  68. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  69. GRB 250119B: INTEGRAL/SPI-ACS detection
  70. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  71. EP 250108A: Late-time optical observation by LCO
  72. GRB 250117A: SVOM/GRM observation of a short burst
  73. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  74. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  75. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  76. GRB 250119C: Fermi GBM Final Real-time Localization
  77. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  78. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  79. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  80. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  82. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  83. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  84. GRB 250117A: GECAM observation of a short burst
  85. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  86. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  87. GRB 250119B: Fermi GBM Final Real-time Localization
  88. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  89. GRB 250119A: Fermi GBM Final Real-time Localization
  90. GRB 250118A: Fermi GBM Final Real-time Localization
  91. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  92. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  93. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  94. EP250108a / AT2025kg: GMG Optical Observations
  95. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  96. EP250108a / AT2025kg: VLA radio upper limit
  97. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  98. Konus-Wind detection of GRB 250116A
  99. GRB 250116A: GECAM-B detection of a long burst
  100. GRB 241217A / EP241217B: radio detection with the VLA

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