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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 250121A: Swift/BAT-GUANO localization skymap of a burst
  2. IPN triangulation of a bright burst from SGR 1E1841-045
  3. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  4. EP250108a: AbAO, CMO and Terskol optical upper limits
  5. Konus-Wind detection of GRB 250118B
  6. GRB 250121A: Fermi GBM Observation
  7. IPN triangulation of GRB 250118B
  8. Konus-Wind detection of GRB 250119B
  9. IPN triangulation of GRB 250119B
  10. GRB 250122A: Fermi GBM Final Real-time Localization
  11. Improved IPN triangulation of GRB 250107C
  12. GRB 250114A: Swift-BAT refined analysis
  13. GRB 250121A: INTEGRAL/SPI-ACS detection
  14. GRB 250121A: Fermi-LAT detection
  15. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  16. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  17. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  18. GRB 250121A: Fermi GBM Final Real-time Localization
  19. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  20. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  21. GRB 250119B: Fermi GBM Observation
  22. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  23. Konus-Wind detection of GRB 250117A
  24. IPN triangulation of GRB 250117A (short)
  25. ATCA detection of possible radio counterpart to GRB 250114A
  26. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  27. GRB 250119B: INTEGRAL/SPI-ACS detection
  28. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  29. EP 250108A: Late-time optical observation by LCO
  30. GRB 250117A: SVOM/GRM observation of a short burst
  31. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  32. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  33. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  34. GRB 250119C: Fermi GBM Final Real-time Localization
  35. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  36. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  37. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  38. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  40. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  41. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  42. GRB 250117A: GECAM observation of a short burst
  43. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  44. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  45. GRB 250119B: Fermi GBM Final Real-time Localization
  46. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  47. GRB 250119A: Fermi GBM Final Real-time Localization
  48. GRB 250118A: Fermi GBM Final Real-time Localization
  49. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  50. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  51. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  52. EP250108a / AT2025kg: GMG Optical Observations
  53. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  54. EP250108a / AT2025kg: VLA radio upper limit
  55. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  56. Konus-Wind detection of GRB 250116A
  57. GRB 250116A: GECAM-B detection of a long burst
  58. GRB 241217A / EP241217B: radio detection with the VLA
  59. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  60. Swift Trigger 1282245 is not a GRB
  61. GRB 250116A: Fermi-LAT detection
  62. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  63. GRB 250114B: Swift-XRT afterglow detection
  64. GRB 250114B: SVOM/VT upper limit
  65. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  66. EP250108a: MeerKAT radio upper limit
  67. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  68. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  69. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  70. Konus-Wind detection of GRB 250113A
  71. IPN triangulation of GRB 250113A
  72. GRB 250114B: Liverpool Telescope optical upper limit
  73. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  74. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  75. GRB 250114B: Swift-XRT observations
  76. GRB 250114A: LCO optical counterpart detection.
  77. GRB 250114B: OHP/T193 optical upper limit
  78. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  79. GRB 250114A: Swift-XRT refined Analysis
  80. Integral GRB250114.55: Global MASTER-Net observations report
  81. GRB 250114A: LCOGT optical afterglow i-band detection
  82. GRB 250114B : GIT optical upper limit
  83. GRB 250114B: Swift ToO observations
  84. EP250111a: SAO RAS optical upper limit
  85. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  86. GRB 250114B: a short GRB detected with INTEGRAL
  87. EP250108a: correction to GCN 38908
  88. GRB 250114A: Enhanced Swift-XRT position
  89. GRB 250113A: INTEGRAL/SPI-ACS detection
  90. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  91. GRB 250114A: REM detection of the optical and NIR counterpart
  92. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  93. Swift GRB250114A: Global MASTER-Net OT detection
  94. GRB 250114A: LCO optical observations
  95. GRB 250114A: TRT optical observations
  96. Swift GRB 250114A: Global MASTER-Net observations report
  97. GRB 250114A: Swift detection of a burst with an optical counterpart
  98. GRB 250101A: Terskol Zeiss-2000 optical observations
  99. EP250108a / AT 2025kg: SAO RAS optical observations
  100. EP241021a: SMA radio observation

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