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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"

8474 results found.

  1. GRB 241018A: LCO/0.4m optical upper limits
  2. GRB 241018A: Swift ToO observations
  3. GRB 241018A: X-ray afterglow candidate observed by MXT
  4. GRB 241017A: Swift-XRT observations
  5. GRB 241017A: Swift ToO observations
  6. IceCube alert 139977_2910365 retraction
  7. GRB 240916A: radio detection with the VLA
  8. GRB241013A: REM observations
  9. LIGO/Virgo/KAGRA S241009em: Updated Sky localization
  10. LIGO/Virgo/KAGRA S241011k: Updated Sky localization
  11. LIGO/Virgo/KAGRA S241011k: NED Galaxies in the Localization Volume
  12. LIGO/Virgo/KAGRA S241011k: Identification of a GW compact binary merger candidate
  13. GRB 241009A: GRANDMA optical upper limits
  14. LIGO/Virgo/KAGRA S241007bw: Updated Sky localization
  15. LIGO/Virgo/KAGRA S241009an: Updated Sky localization
  16. IceCube-241006A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 241010A: Swift detection of a burst with an optical counterpart
  18. GRB 241009A: Swift ToO observations
  19. LIGO/Virgo/KAGRA S241009l: Updated Sky localization
  20. LIGO/Virgo/KAGRA S241009em: Identification of a GW compact binary merger candidate
  21. GRB 241002B: Swift-XRT afterglow detection
  22. LIGO/Virgo/KAGRA S241009an: Identification of a GW compact binary merger candidate
  23. GRB 241002A: NOT optical upper limits
  24. LIGO/Virgo/KAGRA S241009l: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/KAGRA S241007bw: Identification of a GW compact binary merger candidate
  26. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  27. GRB 241006A: Swift detection of a burst
  28. LIGO/Virgo/KAGRA S241006k: Identification of a GW compact binary merger candidate
  29. LIGO/Virgo/KAGRA S241005bo: Retraction of GW compact binary merger candidate
  30. GRB 241002B: Swift-XRT observations
  31. GRB 241002B: Swift ToO observations
  32. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  33. GRB 241002C: Swift ToO observations
  34. Fermi-GBM Sub-Threshold Detection of GRB 241002D
  35. GRB 241002B: GOTO24gpc/AT 2024xbg follow-up observations update
  36. GRB 241002B: ULL-ASTRO-MASTER LCOGT 0.4m + QHY600 detection of the GOTO optical counterpart candidate AT 2024xbg / GOTO24gpc
  37. GRB 241002C: X-ray afterglow candidate observed by SVOM/MXT
  38. LIGO/Virgo/KAGRA S240925n: Updated Sky localization
  39. NuEm-240926A: Upper limits from a search for coincident neutrino events in IceCube
  40. LIGO/Virgo/KAGRA S241002e: Updated Sky localization
  41. GRB 241001A: GRANDMA and Kilonova-Catcher optical afterglow detection and upper limits
  42. GRB 241001A: Swift/UVOT Detection
  43. GRB 241002B: GOTO optical counterpart candidate
  44. GRB 241002C : Detection of a long soft transient by SVOM/ECLAIRs
  45. GRB 241001A: correction to GCN 37667
  46. GRB 241001A: Swift-XRT observations
  47. GRB241001A: optical afterglow candidate
  48. LIGO/Virgo/KAGRA S241002e: Identification of a GW compact binary merger candidate
  49. GRB 241002A: Swift detection of a burst
  50. LIGO/Virgo/KAGRA S240930du: Updated Sky localization
  51. GRB 241001A: Swift ToO observations
  52. EP240930a : KAIT optical upper limit
  53. GRB 241001A : Detection of a soft transient by ECLAIRs onboard SVOM
  54. EP240930a: GOTO optical upper limits
  55. LIGO/Virgo/KAGRA S240930du: Identification of a GW compact binary merger candidate
  56. IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
  57. LIGO/Virgo/KAGRA S240930df: 1 counterpart neutrino candidate event from an IceCube neutrino search
  58. LIGO/Virgo/KAGRA S240930aa: Identification of a GW compact binary merger candidate
  59. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  60. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  61. LIGO/Virgo/KAGRA S240920dw: Upper limits from Swift/BAT-GUANO
  62. LIGO/Virgo/KAGRA S240919bn: Upper limits from Swift/BAT-GUANO
  63. LIGO/Virgo/KAGRA S240925n: NED Galaxies in the Localization Volume
  64. LIGO/Virgo/KAGRA S240925n: Updated Sky localization and Source Classification
  65. LIGO/Virgo/KAGRA S240925n: Identification of a GW compact binary merger candidate
  66. LIGO/Virgo/KAGRA S240922df: Updated Sky localization
  67. LIGO/Virgo/KAGRA S240920dw: Updated Sky localization
  68. LIGO/Virgo/KAGRA S240921cw: Updated Sky localization
  69. LIGO/Virgo/KAGRA S240924a: Updated Sky localization
  70. LIGO/Virgo/KAGRA S240920bz: Updated Sky localization and Source Classification
  71. LIGO/Virgo/KAGRA S240923ct: Updated Sky localization and Source Classification
  72. LIGO/Virgo/KAGRA S240924a: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S240923ct: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo S240919bn: GOTO optical upper limits
  75. LIGO/Virgo/KAGRA S240922df: Identification of a GW compact binary merger candidate
  76. LIGO/Virgo/KAGRA S240921cw: Identification of a GW compact binary merger candidate
  77. Fermi GBM Sub-Threshold Detection of GRB240919A / EP240919a
  78. EP240919a / GRB 240919A: KAIT optical upper limit
  79. GRB 240414A: further radio observations with the VLA
  80. LIGO/Virgo/KAGRA S240920dw: Identification of a GW compact binary merger candidate
  81. GRB 240910A: radio detection with the VLA
  82. EP240919a: NOT and Gemini optical observations
  83. EP240919a: GOTO optical upper limits
  84. LIGO/Virgo/KAGRA S240920bz: Identification of a GW compact binary merger candidate
  85. LIGO/Virgo/KAGRA S240919bn: Updated Sky localization
  86. GRB 240918B: Fermi GBM Detection
  87. LIGO/Virgo/KAGRA S240917cb: Updated Sky localization and EM Bright Classification
  88. LIGO/Virgo/KAGRA S240916ar: Updated Sky localization and EM Bright Classification
  89. LIGO/Virgo/KAGRA S240919bn: Identification of a GW compact binary merger candidate
  90. GRB 240916A: Fermi GBM Observation
  91. LIGO/Virgo/KAGRA S240917cb: Identification of a GW compact binary merger candidate
  92. GRB 240821A: radio observation with the VLA
  93. GRB 240916A: Swift-XRT afterglow detection
  94. LIGO/Virgo/KAGRA S240916ar: Identification of a GW compact binary merger candidate
  95. GRB 240916A: Swift ToO observations
  96. LIGO/Virgo/KAGRA S240915b: NED Galaxies in the Localization Volume
  97. GRB 240916A: GOTO identification of two new optical sources within the GBM localisation region
  98. LIGO/Virgo/KAGRA S240915b: Coverage and upper limits from MAXI/GSC observations
  99. LIGO/Virgo/KAGRA S240915bd: Updated Sky localization
  100. LIGO/Virgo/KAGRA S240915bd: Identification of a GW compact binary merger candidate

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