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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. EP trigger ID 01709061302: the X-ray transient is likely a stellar flare event
  2. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-240926A
  3. Konus-Wind detection of GRB 240905B
  4. GRB 240529A: FRAM-ORM early optical afterglow observations reveal plateau and rebrightening
  5. GW S240915b and S240919bn : Swift UVOT follow-up
  6. EP240919a / GRB 240919A: SVOM/VT upper limit
  7. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  8. EP240918b and EP240918c: EP-FXT follow-up observations
  9. LIGO/Virgo/KAGRA S240925n: Updated Sky localization and Source Classification
  10. Insight-HXMT ToO observations of X-ray bursts from SGR 1E 1841-045 / Kes 73
  11. GRB 240716A: Swift/BAT-GUANO localization skymap of a long burst
  12. LIGO/Virgo/KAGRA S240925n: Identification of a GW compact binary merger candidate
  13. Konus-Wind detection of GRB 240918B
  14. IPN triangulation of GRB 240918B
  15. GRB 240905B: VZLUSAT-2 detection
  16. LIGO/Virgo/KAGRA S240922df: Updated Sky localization
  17. LIGO/Virgo/KAGRA S240920dw: Updated Sky localization
  18. LIGO/Virgo/KAGRA S240921cw: Updated Sky localization
  19. LIGO/Virgo/KAGRA S240924a: Updated Sky localization
  20. LIGO/Virgo/KAGRA S240920bz: Updated Sky localization and Source Classification
  21. LIGO/Virgo/KAGRA S240923ct: Updated Sky localization and Source Classification
  22. EP trigger ID 01709059262: correction to the observation start time and source localization
  23. EP trigger ID 01709059262: the X-ray transient is likely a stellar flare event
  24. LIGO/Virgo/KAGRA S240924a: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/KAGRA S240923ct: Identification of a GW compact binary merger candidate
  26. LIGO/Virgo S240919bn: GOTO optical upper limits
  27. LIGO/Virgo S240919bn: Swift XRT observations, 10 X-ray sources
  28. GRB 240918B: AstroSat CZTI detection
  29. LIGO/Virgo/KAGRA S240922df: Identification of a GW compact binary merger candidate
  30. LIGO/Virgo/KAGRA S240921cw: Identification of a GW compact binary merger candidate
  31. EP240919a: EP-FXT follow-up observation update
  32. EP240913A/GRB 240913C: AbAO optical upper limit
  33. EP240919a / GRB 240919A: Mondy optical upper limit
  34. EP240913a/GRB 240913C: 1.6m Mephisto observations
  35. EP240918a: SVOM/VT upper limit
  36. Fermi GBM Sub-Threshold Detection of GRB240919A / EP240919a
  37. EP240919a / GRB 240919A: REM optical and NIR upper limits
  38. EP240919a / GRB 240919A: KAIT optical upper limit
  39. EP240918b and EP240918c: Optical upper limits with Kinder observations
  40. GRB 240414A: further radio observations with the VLA
  41. EP240919a: Optical upper limit with Kinder observations
  42. GRB 240919A / EP240919a: SVOM/GRM observation
  43. EP240919a: INTEGRAL SPI-ACS confirmation of reported high-energy counterpart
  44. EP240919a: INTEGRAL SPI-ACS confirmation of reported high-energy counterpart
  45. LIGO/Virgo/KAGRA S240920dw: Identification of a GW compact binary merger candidate
  46. EP EP240919a: Global MASTER-Net observations report
  47. GRB 240910A: radio detection with the VLA
  48. EP240918a: 1.6m Mephisto multi-band Optical Upper Limit
  49. EP240919a: NOT and Gemini optical observations
  50. EP240919a: GOTO optical upper limits
  51. EP240919a: JinShan optical upper limits
  52. EP240919a is likely a GRB event (duplicate submission of 37563)
  53. EP240919a is likely a GRB event
  54. LIGO/Virgo/KAGRA S240920bz: Identification of a GW compact binary merger candidate
  55. EP240919a: EP-WXT detection of a fast X-ray transient
  56. GRB 240918A and GRB 240918B : INTEGRAL SPI ACS LIGHT CURVE
  57. LIGO/Virgo/KAGRA S240919bn: Updated Sky localization
  58. GRB 240918B: Fermi GBM Detection
  59. LIGO/Virgo/KAGRA S240917cb: Updated Sky localization and EM Bright Classification
  60. LIGO/Virgo/KAGRA S240916ar: Updated Sky localization and EM Bright Classification
  61. EP240918b and EP240918c: EP-WXT detection of two fast X-ray transients
  62. EP240918a: EP observation update
  63. GRB 240910A: further Swift observations and confirmation of afterglow
  64. LIGO/Virgo/KAGRA S240919bn: Identification of a GW compact binary merger candidate
  65. EP240918a: Swift-XRT observation
  66. Fermi GRB 240918A: Global MASTER-Net observations report
  67. GRB 240918A: Fermi GBM Final Real-time Localization
  68. EP EP240918a: Global MASTER-Net observations report
  69. EP240918a: JinShan optical upper limits
  70. EP240918a: YAHPT Optical Upper Limit
  71. EP240918a: Optical upper limits with Kinder observations
  72. EP240918a: GMG Optical Upper Limit
  73. GRB 240916A: GRBAlpha detection
  74. GRB 240914B: GRBAlpha detection
  75. EP240918a: an X-ray transient detected by Einstein Probe
  76. GRB 240916A: NOT optical observation
  77. GRB 240912A: Swift-BAT refined analysis
  78. IPN triangulation of GRB 240913C / EP 240913a
  79. GRB 240825A: INTEGRAL SPI ACS LIGHT CURVE
  80. GRB 240825A: The nature of the afterglow motivates the search of the associated supernova
  81. GRB 240916A: Fermi GBM Observation
  82. LIGO/Virgo/KAGRA S240917cb: Identification of a GW compact binary merger candidate
  83. GRB 240821A: radio observation with the VLA
  84. GRB 240916A (AT 2024vlp / GOTO24fzn): VLT/X-shooter redshift
  85. GRB 240916A: Swift-XRT afterglow detection
  86. LIGO/Virgo/KAGRA S240916ar: Identification of a GW compact binary merger candidate
  87. GRB 240916A: Swift ToO observations
  88. LIGO/Virgo/KAGRA S240915b: NED Galaxies in the Localization Volume
  89. LIGO/Virgo S240915b: Swift XRT observations, 8 X-ray sources
  90. GRB 240916A: JinShan optical decay in one of the two GOTO candidates
  91. GRB 240916B: Fermi GBM Final Real-time Localization
  92. GRB 240914B: Fermi GBM Final Localization
  93. The EP-WXT triggers 01709047257 and 01709047278 are not real sources
  94. GRB 240916A: GOTO identification of two new optical sources within the GBM localisation region
  95. EP EP240913a: Global MASTER-Net observations report
  96. LIGO/Virgo/KAGRA S240915b: Coverage and upper limits from MAXI/GSC observations
  97. GRB 240916A INTEGRAL SPI ACS LIGHT CURVE
  98. GRB 240916A: Fermi GBM Final Real-time Localization
  99. Fermi Gamma-ray Burst Monitor trigger 748124309/240915846 is not a GRB
  100. LIGO/Virgo/KAGRA S240915bd: Updated Sky localization

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