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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 241223A: cubesat Avion detection
  2. GRB 250127A: SVOM detection of a long burst
  3. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  4. EP250125A: Non-detection from Fermi-GBM Observations
  5. GRB 250126A: MAXI/GSC detection
  6. EP250108a / SN 2025kg: Refined Analysis of EP-WXT Detection
  7. GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
  8. GRB 250126A: Fermi GBM Final Real-time Localization
  9. GECAM-A detection of a bright burst from SGR 1E1841-045
  10. GRB 250118A: Fermi GBM Observation
  11. EP250125a: Optical upper limit with Kinder observations
  12. EP250125a: REM optical counterpart detection
  13. GRB 250119C: Fermi GBM Observation
  14. EP250125a: Swift/XRT detection of a fading counterpart
  15. EP250125a: a new X-ray transient detected by Einstein Probe
  16. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  17. The EP-WXT trigger 01709130758 is a false trigger
  18. The EP-WXT trigger 01709130758 is a false trigger
  19. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  20. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  21. IPN triangulation of a bright burst from SGR 1E1841-045
  22. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  23. EP250108a: AbAO, CMO and Terskol optical upper limits
  24. Konus-Wind detection of GRB 250118B
  25. GRB 250121A: Fermi GBM Observation
  26. IPN triangulation of GRB 250118B
  27. Konus-Wind detection of GRB 250119B
  28. IPN triangulation of GRB 250119B
  29. GRB 250122A: Fermi GBM Final Real-time Localization
  30. Improved IPN triangulation of GRB 250107C
  31. GRB 250114A: Swift-BAT refined analysis
  32. GRB 250121A: INTEGRAL/SPI-ACS detection
  33. GRB 250121A: Fermi-LAT detection
  34. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  35. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  36. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  37. GRB 250121A: Fermi GBM Final Real-time Localization
  38. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  39. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  40. GRB 250119B: Fermi GBM Observation
  41. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  42. Konus-Wind detection of GRB 250117A
  43. IPN triangulation of GRB 250117A (short)
  44. ATCA detection of possible radio counterpart to GRB 250114A
  45. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  46. GRB 250119B: INTEGRAL/SPI-ACS detection
  47. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  48. EP 250108A: Late-time optical observation by LCO
  49. GRB 250117A: SVOM/GRM observation of a short burst
  50. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  51. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  52. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  53. GRB 250119C: Fermi GBM Final Real-time Localization
  54. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  55. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  56. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  57. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  59. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  60. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  61. GRB 250117A: GECAM observation of a short burst
  62. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  63. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  64. GRB 250119B: Fermi GBM Final Real-time Localization
  65. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  66. GRB 250119A: Fermi GBM Final Real-time Localization
  67. GRB 250118A: Fermi GBM Final Real-time Localization
  68. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  69. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  70. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  71. EP250108a / AT2025kg: GMG Optical Observations
  72. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  73. EP250108a / AT2025kg: VLA radio upper limit
  74. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  75. Konus-Wind detection of GRB 250116A
  76. GRB 250116A: GECAM-B detection of a long burst
  77. GRB 241217A / EP241217B: radio detection with the VLA
  78. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  79. Swift Trigger 1282245 is not a GRB
  80. GRB 250116A: Fermi-LAT detection
  81. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  82. GRB 250114B: Swift-XRT afterglow detection
  83. GRB 250114B: SVOM/VT upper limit
  84. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  85. EP250108a: MeerKAT radio upper limit
  86. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  87. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  88. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  89. Konus-Wind detection of GRB 250113A
  90. IPN triangulation of GRB 250113A
  91. GRB 250114B: Liverpool Telescope optical upper limit
  92. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  93. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  94. GRB 250114B: Swift-XRT observations
  95. GRB 250114A: LCO optical counterpart detection.
  96. GRB 250114B: OHP/T193 optical upper limit
  97. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  98. GRB 250114A: Swift-XRT refined Analysis
  99. Integral GRB250114.55: Global MASTER-Net observations report
  100. GRB 250114A: LCOGT optical afterglow i-band detection

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