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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').
  1. GRB 250117A: Fermi GBM Observation
  2. Fermi GRB 250127B: Global MASTER-Net observations report
  3. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  4. GRB 250127A: SVOM/VT upper limit
  5. GRB 250127B: Fermi GBM Final Real-time Localization
  6. IPN triangulation of GRB 250119C
  7. GRB 250127A: Swift ToO observations
  8. GRB 250127A: LCO optical upper limit
  9. GRB 241223A: cubesat Avion detection
  10. GRB 250127A: SVOM detection of a long burst
  11. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  12. EP250125A: Non-detection from Fermi-GBM Observations
  13. GRB 250126A: MAXI/GSC detection
  14. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  15. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  16. GRB 250126A: Fermi GBM Final Real-time Localization
  17. GECAM-A detection of a bright burst from SGR 1E1841-045
  18. GRB 250118A: Fermi GBM Observation
  19. EP250125a: Optical upper limit with Kinder observations
  20. EP250125a: REM optical counterpart detection
  21. GRB 250119C: Fermi GBM Observation
  22. EP250125a: Swift/XRT detection of a fading counterpart
  23. EP250125a: a new X-ray transient detected by Einstein Probe
  24. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  25. The EP-WXT trigger 01709130758 is a false trigger
  26. The EP-WXT trigger 01709130758 is a false trigger
  27. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  28. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  29. IPN triangulation of a bright burst from SGR 1E1841-045
  30. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  31. EP250108a: AbAO, CMO and Terskol optical upper limits
  32. Konus-Wind detection of GRB 250118B
  33. GRB 250121A: Fermi GBM Observation
  34. IPN triangulation of GRB 250118B
  35. Konus-Wind detection of GRB 250119B
  36. IPN triangulation of GRB 250119B
  37. GRB 250122A: Fermi GBM Final Real-time Localization
  38. Improved IPN triangulation of GRB 250107C
  39. GRB 250114A: Swift-BAT refined analysis
  40. GRB 250121A: INTEGRAL/SPI-ACS detection
  41. GRB 250121A: Fermi-LAT detection
  42. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  43. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  44. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  45. GRB 250121A: Fermi GBM Final Real-time Localization
  46. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  47. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  48. GRB 250119B: Fermi GBM Observation
  49. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  50. Konus-Wind detection of GRB 250117A
  51. IPN triangulation of GRB 250117A (short)
  52. ATCA detection of possible radio counterpart to GRB 250114A
  53. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  54. GRB 250119B: INTEGRAL/SPI-ACS detection
  55. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  56. EP 250108A: Late-time optical observation by LCO
  57. GRB 250117A: SVOM/GRM observation of a short burst
  58. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  59. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  60. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  61. GRB 250119C: Fermi GBM Final Real-time Localization
  62. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  63. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  64. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  65. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  67. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  68. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  69. GRB 250117A: GECAM observation of a short burst
  70. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  71. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  72. GRB 250119B: Fermi GBM Final Real-time Localization
  73. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  74. GRB 250119A: Fermi GBM Final Real-time Localization
  75. GRB 250118A: Fermi GBM Final Real-time Localization
  76. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  77. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  78. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  79. EP250108a / AT2025kg: GMG Optical Observations
  80. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  81. EP250108a / AT2025kg: VLA radio upper limit
  82. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  83. Konus-Wind detection of GRB 250116A
  84. GRB 250116A: GECAM-B detection of a long burst
  85. GRB 241217A / EP241217B: radio detection with the VLA
  86. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  87. Swift Trigger 1282245 is not a GRB
  88. GRB 250116A: Fermi-LAT detection
  89. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  90. GRB 250114B: Swift-XRT afterglow detection
  91. GRB 250114B: SVOM/VT upper limit
  92. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  93. EP250108a: MeerKAT radio upper limit
  94. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  95. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  96. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  97. Konus-Wind detection of GRB 250113A
  98. IPN triangulation of GRB 250113A
  99. GRB 250114B: Liverpool Telescope optical upper limit
  100. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume

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