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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 250128A: Fermi GBM Final Real-time Localization
  2. GRB 250117A: Fermi GBM Observation
  3. Fermi GRB 250127B: Global MASTER-Net observations report
  4. Fermi-LAT Gamma-ray Observations of IceCube-250101A
  5. GRB 250127A: SVOM/VT upper limit
  6. GRB 250127B: Fermi GBM Final Real-time Localization
  7. IPN triangulation of GRB 250119C
  8. GRB 250127A: Swift ToO observations
  9. GRB 250127A: LCO optical upper limit
  10. GRB 241223A: cubesat Avion detection
  11. GRB 250127A: SVOM detection of a long burst
  12. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  13. EP250125A: Non-detection from Fermi-GBM Observations
  14. GRB 250126A: MAXI/GSC detection
  15. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  16. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  17. GRB 250126A: Fermi GBM Final Real-time Localization
  18. GECAM-A detection of a bright burst from SGR 1E1841-045
  19. GRB 250118A: Fermi GBM Observation
  20. EP250125a: Optical upper limit with Kinder observations
  21. EP250125a: REM optical counterpart detection
  22. GRB 250119C: Fermi GBM Observation
  23. EP250125a: Swift/XRT detection of a fading counterpart
  24. EP250125a: a new X-ray transient detected by Einstein Probe
  25. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  26. The EP-WXT trigger 01709130758 is a false trigger
  27. The EP-WXT trigger 01709130758 is a false trigger
  28. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  29. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  30. IPN triangulation of a bright burst from SGR 1E1841-045
  31. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  32. EP250108a: AbAO, CMO and Terskol optical upper limits
  33. Konus-Wind detection of GRB 250118B
  34. GRB 250121A: Fermi GBM Observation
  35. IPN triangulation of GRB 250118B
  36. Konus-Wind detection of GRB 250119B
  37. IPN triangulation of GRB 250119B
  38. GRB 250122A: Fermi GBM Final Real-time Localization
  39. Improved IPN triangulation of GRB 250107C
  40. GRB 250114A: Swift-BAT refined analysis
  41. GRB 250121A: INTEGRAL/SPI-ACS detection
  42. GRB 250121A: Fermi-LAT detection
  43. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  44. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  45. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  46. GRB 250121A: Fermi GBM Final Real-time Localization
  47. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  48. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  49. GRB 250119B: Fermi GBM Observation
  50. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  51. Konus-Wind detection of GRB 250117A
  52. IPN triangulation of GRB 250117A (short)
  53. ATCA detection of possible radio counterpart to GRB 250114A
  54. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  55. GRB 250119B: INTEGRAL/SPI-ACS detection
  56. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  57. EP 250108A: Late-time optical observation by LCO
  58. GRB 250117A: SVOM/GRM observation of a short burst
  59. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  60. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  61. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  62. GRB 250119C: Fermi GBM Final Real-time Localization
  63. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  64. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  65. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  66. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  67. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  68. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  69. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  70. GRB 250117A: GECAM observation of a short burst
  71. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  72. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  73. GRB 250119B: Fermi GBM Final Real-time Localization
  74. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  75. GRB 250119A: Fermi GBM Final Real-time Localization
  76. GRB 250118A: Fermi GBM Final Real-time Localization
  77. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  79. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  80. EP250108a / AT2025kg: GMG Optical Observations
  81. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  82. EP250108a / AT2025kg: VLA radio upper limit
  83. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  84. Konus-Wind detection of GRB 250116A
  85. GRB 250116A: GECAM-B detection of a long burst
  86. GRB 241217A / EP241217B: radio detection with the VLA
  87. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  88. Swift Trigger 1282245 is not a GRB
  89. GRB 250116A: Fermi-LAT detection
  90. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  91. GRB 250114B: Swift-XRT afterglow detection
  92. GRB 250114B: SVOM/VT upper limit
  93. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  94. EP250108a: MeerKAT radio upper limit
  95. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  96. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  97. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  98. Konus-Wind detection of GRB 250113A
  99. IPN triangulation of GRB 250113A
  100. GRB 250114B: Liverpool Telescope optical upper limit

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