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

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