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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 250121A: Fermi GBM Final Real-time Localization
  2. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  3. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  4. GRB 250119B: Fermi GBM Observation
  5. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  6. Konus-Wind detection of GRB 250117A
  7. IPN triangulation of GRB 250117A (short)
  8. ATCA detection of possible radio counterpart to GRB 250114A
  9. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  10. GRB 250119B: INTEGRAL/SPI-ACS detection
  11. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  12. EP 250108A: Late-time optical observation by LCO
  13. GRB 250117A: SVOM/GRM observation of a short burst
  14. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  15. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  16. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  17. GRB 250119C: Fermi GBM Final Real-time Localization
  18. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  19. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  20. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  21. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  22. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  23. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  24. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  25. GRB 250117A: GECAM observation of a short burst
  26. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  27. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  28. GRB 250119B: Fermi GBM Final Real-time Localization
  29. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  30. GRB 250119A: Fermi GBM Final Real-time Localization
  31. GRB 250118A: Fermi GBM Final Real-time Localization
  32. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  33. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  34. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  35. EP250108a / AT2025kg: GMG Optical Observations
  36. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  37. EP250108a / AT2025kg: VLA radio upper limit
  38. Fermi Gamma-ray Burst Monitor trigger 758829338/250117747 is not a GRB
  39. Konus-Wind detection of GRB 250116A
  40. GRB 250116A: GECAM-B detection of a long burst
  41. GRB 241217A / EP241217B: radio detection with the VLA
  42. GRB 250116A: INTEGRAL/SPI-ACS and PICsIT detection
  43. Swift Trigger 1282245 is not a GRB
  44. GRB 250116A: Fermi-LAT detection
  45. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  46. GRB 250114B: Swift-XRT afterglow detection
  47. GRB 250114B: SVOM/VT upper limit
  48. Fermi Gamma-ray Burst Monitor trigger 758659047/250115776 is not a GRB
  49. EP250108a: MeerKAT radio upper limit
  50. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  51. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  52. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  53. Konus-Wind detection of GRB 250113A
  54. IPN triangulation of GRB 250113A
  55. GRB 250114B: Liverpool Telescope optical upper limit
  56. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  57. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  58. GRB 250114B: Swift-XRT observations
  59. GRB 250114A: LCO optical counterpart detection.
  60. GRB 250114B: OHP/T193 optical upper limit
  61. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  62. GRB 250114A: Swift-XRT refined Analysis
  63. Integral GRB250114.55: Global MASTER-Net observations report
  64. GRB 250114A: LCOGT optical afterglow i-band detection
  65. GRB 250114B : GIT optical upper limit
  66. GRB 250114B: Swift ToO observations
  67. EP250111a: SAO RAS optical upper limit
  68. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  69. GRB 250114B: a short GRB detected with INTEGRAL
  70. EP250108a: correction to GCN 38908
  71. GRB 250114A: Enhanced Swift-XRT position
  72. GRB 250113A: INTEGRAL/SPI-ACS detection
  73. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  74. GRB 250114A: REM detection of the optical and NIR counterpart
  75. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  76. Swift GRB250114A: Global MASTER-Net OT detection
  77. GRB 250114A: LCO optical observations
  78. GRB 250114A: TRT optical observations
  79. Swift GRB 250114A: Global MASTER-Net observations report
  80. GRB 250114A: Swift detection of a burst with an optical counterpart
  81. GRB 250101A: Terskol Zeiss-2000 optical observations
  82. EP250108a / AT 2025kg: SAO RAS optical observations
  83. EP241021a: SMA radio observation
  84. GRB 250113A: SVOM/GRM observation of a long burst
  85. GRB 250107A: VZLUSAT-2 detection
  86. EP250109b: optical upper limits with the Liverpool Telescope
  87. GRB 250109A / EP250109a: GRBAlpha detection
  88. GRB 250107D: GRBAlpha detection
  89. GRB 250106A: Swift-XRT afterglow detection
  90. Fermi trigger No 758442826: Global MASTER-Net observations report
  91. EP250111a: KAIT optical observations
  92. GRB 250109A / EP250109a: Mephisto optical upper limits
  93. EP250108a: Mephisto detection
  94. EP250111a: Mondy optical observation
  95. EP250108a / AT 2025kg: LCO optical observations
  96. EP250111a: Global MASTER-Net observations report
  97. EP250111a: Swift/XRT detection and fading
  98. EP250108a / AT 2025kg: Swift UVOT detections
  99. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  100. EP250108a: optical follow-up observations with the Liverpool Telescope

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