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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. The EP-WXT trigger 01709130758 is a false trigger
  2. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  3. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  4. IPN triangulation of a bright burst from SGR 1E1841-045
  5. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  6. EP250108a: AbAO, CMO and Terskol optical upper limits
  7. Konus-Wind detection of GRB 250118B
  8. GRB 250121A: Fermi GBM Observation
  9. IPN triangulation of GRB 250118B
  10. Konus-Wind detection of GRB 250119B
  11. IPN triangulation of GRB 250119B
  12. GRB 250122A: Fermi GBM Final Real-time Localization
  13. Improved IPN triangulation of GRB 250107C
  14. GRB 250114A: Swift-BAT refined analysis
  15. GRB 250121A: INTEGRAL/SPI-ACS detection
  16. GRB 250121A: Fermi-LAT detection
  17. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  18. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  19. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  20. GRB 250121A: Fermi GBM Final Real-time Localization
  21. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  22. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  23. GRB 250119B: Fermi GBM Observation
  24. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  25. Konus-Wind detection of GRB 250117A
  26. IPN triangulation of GRB 250117A (short)
  27. ATCA detection of possible radio counterpart to GRB 250114A
  28. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  29. GRB 250119B: INTEGRAL/SPI-ACS detection
  30. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  31. EP 250108A: Late-time optical observation by LCO
  32. GRB 250117A: SVOM/GRM observation of a short burst
  33. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  34. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  35. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  36. GRB 250119C: Fermi GBM Final Real-time Localization
  37. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  38. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  39. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  40. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  41. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  42. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  43. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  44. GRB 250117A: GECAM observation of a short burst
  45. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  46. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  47. GRB 250119B: Fermi GBM Final Real-time Localization
  48. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  49. GRB 250119A: Fermi GBM Final Real-time Localization
  50. GRB 250118A: Fermi GBM Final Real-time Localization
  51. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  53. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  54. EP250108a / AT2025kg: GMG Optical Observations
  55. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  56. EP250108a / AT2025kg: VLA radio upper limit
  57. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  58. Konus-Wind detection of GRB 250116A
  59. GRB 250116A: GECAM-B detection of a long burst
  60. GRB 241217A / EP241217B: radio detection with the VLA
  61. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  62. Swift Trigger 1282245 is not a GRB
  63. GRB 250116A: Fermi-LAT detection
  64. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  65. GRB 250114B: Swift-XRT afterglow detection
  66. GRB 250114B: SVOM/VT upper limit
  67. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  68. EP250108a: MeerKAT radio upper limit
  69. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  70. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  71. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  72. Konus-Wind detection of GRB 250113A
  73. IPN triangulation of GRB 250113A
  74. GRB 250114B: Liverpool Telescope optical upper limit
  75. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  76. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  77. GRB 250114B: Swift-XRT observations
  78. GRB 250114A: LCO optical counterpart detection.
  79. GRB 250114B: OHP/T193 optical upper limit
  80. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  81. GRB 250114A: Swift-XRT refined Analysis
  82. Integral GRB250114.55: Global MASTER-Net observations report
  83. GRB 250114A: LCOGT optical afterglow i-band detection
  84. GRB 250114B : GIT optical upper limit
  85. GRB 250114B: Swift ToO observations
  86. EP250111a: SAO RAS optical upper limit
  87. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  88. GRB 250114B: a short GRB detected with INTEGRAL
  89. EP250108a: correction to GCN 38908
  90. GRB 250114A: Enhanced Swift-XRT position
  91. GRB 250113A: INTEGRAL/SPI-ACS detection
  92. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  93. GRB 250114A: REM detection of the optical and NIR counterpart
  94. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  95. Swift GRB250114A: Global MASTER-Net OT detection
  96. GRB 250114A: LCO optical observations
  97. GRB 250114A: TRT optical observations
  98. Swift GRB 250114A: Global MASTER-Net observations report
  99. GRB 250114A: Swift detection of a burst with an optical counterpart
  100. GRB 250101A: Terskol Zeiss-2000 optical observations

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