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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. Trigger_18947: Swift ToO observations (retracted)
  2. GRB 241113B: EP-FXT afterglow detection
  3. LIGO/Virgo/KAGRA S241125n: DDOTI Optical Upper Limits
  4. LIGO/Virgo/KAGRA S241125n: Gaoyazi/GOT optical observations
  5. SVOM/GRM detection of a short burst from SGR 1830
  6. GECAM detection of a short burst from SGR 1830
  7. LIGO/VIRGO/KAGRA S241125n: GROWTH-India telescope optical observations
  8. LIGO/Virgo S241125n: Swift XRT observations, 5 X-ray sources
  9. Konus-Wind detection of GRB 241115D / EP 241115a
  10. LIGO/Virgo/KAGRA S241125n: HCT upper limit
  11. LIGO/Virgo/KAGRA S241125n: Upper limits from Konus-Wind observations
  12. GRB 241026A: radio detection with the VLA
  13. EP241125a: Optical upper limit with Kinder observations
  14. EP241125a: EP detection of an X-ray transient
  15. LIGO/Virgo/KAGRA S241125n: COLIBRÍ Upper Limits on a Optical Counterpart at the BAT Position
  16. LIGO/Virgo/KAGRA S241125n: Upper limits from Fermi-GBM Observations
  17. LIGO/Virgo/KAGRA S241125n: Updated Coincidence with External Event
  18. LIGO/Virgo/KAGRA S241125n: Kinder optical upper limit in the BAT error region
  19. LIGO/Virgo/KAGRA S241125n: Updated Sky localization
  20. LIGO/Virgo/KAGRA S241125n: Updated Coincidence with External Event
  21. LIGO/Virgo/KAGRA S241125n: No counterpart candidates in INTEGRAL SPI-ACS prompt observation, comparisong with Swift/BAT counterpart
  22. LIGO/Virgo/KAGRA S241109bn: Upper limits from a two-week IceCube neutrino search
  23. LIGO/Virgo/KAGRA S241125n: Updated Sky localization and Coincidence with External Event
  24. LIGO/Virgo/KAGRA S241125n: Swift/BAT-GUANO candidate counterpart
  25. GRB 241120A: GRBAlpha detection
  26. GRB 241113B: SVOM/VT optical afterglow observations
  27. LIGO/Virgo/KAGRA S241125n: Identification of a GW compact binary merger candidate
  28. Konus-Wind detection of GRB 241117A
  29. LIGO/Virgo/KAGRA S241122a: Updated Sky localization and Source Classification
  30. GRB 241105A: ATCA radio detection
  31. LIGO/Virgo/KAGRA S241122a: Identification of a GW compact binary merger candidate
  32. IPN triangulation of GRB 241117A
  33. GRB 241026A: VIRT Optical Upper Limit
  34. GRB 241025A: VIRT Optical Upper Limit
  35. Konus-Wind detection of GRB 241120A
  36. GRB241120A: OHP/T193 optical observations
  37. GRB 241120A: CALET Gamma-Ray Burst Monitor detection
  38. EP241021a and EP241026b: Keck/LRIS spectroscopic observations
  39. EP trigger ID 01709065118: Keck/LRIS spectroscopic observations
  40. EP-WXT trigger 01709018832: Lick/Kast spectroscopy with the 3 m Shane telescope
  41. GRB 241120A: Mondy and AbAO optical observations
  42. EP241119a: Optical upper limits with Kinder observations
  43. EP trigger ID 01709122294: the X-ray transient is likely a stellar flare event
  44. EP241119a: GIT optical upper limits
  45. GRB 241113A: Possible ATCA Radio detection
  46. EP241119a : J-band observations with WINTER
  47. GRB 241120A: Fermi GBM Observation
  48. GRB 241114B: Insight-HXMT/HE detection
  49. Integral GRB241120.25: Global MASTER-Net observations report
  50. EP241119a: Global MASTER-Net observations report
  51. EP241119a: EP detection of a fast X-ray transient
  52. GRB241120A: a long GRB detected by INTEGRAL
  53. GRB 241120A: Fermi GBM Final Real-time Localization
  54. GRB 241115A: CALET Gamma-Ray Burst Monitor detection
  55. GRB 241112B: Mephisto further optical observations
  56. GRB 241119A: Fermi GBM Final Real-time Localization
  57. GRB 241030A: J-band observations
  58. GRB 241115a: PRIME near-infrared upper limits
  59. GRB 241117A: Swift/BAT-GUANO localization skymap of a burst
  60. LIGO/Virgo/KAGRA S241116cq: Upper limits from Swift/BAT-GUANO
  61. GRB 241115B: Fermi GBM Observation
  62. LIGO/Virgo/KAGRA S241114y: Updated Sky localization
  63. Fermi GRB 241118A: Global MASTER-Net observations report
  64. GRB 241118A: Fermi GBM Final Real-time Localization
  65. Updates to IceCube realtime alert system for muon tracks
  66. GRB 241117A: SVOM/GRM observation of a short burst with extended emission
  67. GRB 241117A: Fermi GBM Detection
  68. Fermi GRB 241117B: Global MASTER-Net observations report
  69. GRB 241117B: Fermi GBM Final Real-time Localization
  70. IceCube-Cascade 241116A: Upper limits from a search for additional neutrino events in IceCube
  71. LIGO/Virgo/KAGRA S241116cq: Updated Sky localization
  72. GRB 241115B: Swift/BAT-GUANO localization skymap of a long burst
  73. Fermi GRB 241117A: Global MASTER-Net observations report
  74. GRB 241117A: Fermi GBM Final Real-time Localization
  75. GRB 241115C: Fermi GBM Observation
  76. GRB 241115A: Swift-XRT afterglow detection
  77. LIGO/Virgo/KAGRA S241116cq: Identification of a GW compact binary merger candidate
  78. EP241115a/GRB 241115D: Optical upper limits with Kinder observations
  79. GRB 241115A: Mephisto upper limits
  80. GRB 241113B: Mephisto upper limits
  81. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  82. GRB 241115D / EP 241115a: SVOM/GRM observation
  83. The EP-WXT trigger 01709120856 is likely a flaring star
  84. EP241113a: Swift XRT weak detection
  85. GRB 241115A: Fermi GBM Observation
  86. GRB 241115A: LCOGT Optical Upper Limits
  87. GRB 241115C: Swift/BAT-GUANO localization skymap of a burst
  88. Fermi GRB 241115B: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S241114bi: Updated Sky localization and EM Bright Classification
  90. EP241115a: Global MASTER-Net observations report
  91. GRB 241115B: Fermi GBM Final Real-time Localization
  92. LIGO/Virgo/KAGRA S241113p: Updated Sky localization
  93. EP241115a: EP detection of a fast X-ray transient
  94. EP241113a: No Detection in Fermi-GBM Observations
  95. Swift GRB 241115A: Global MASTER-Net observations report
  96. Fermi GRB 241115A: Global MASTER-Net observations report
  97. GRB 241115A: Swift detection of a burst
  98. GRB 241115A: Fermi GBM Final Real-time Localization
  99. EP 241113a: LBT possible optical counterpart
  100. GRB 241113B: KAIT Optical Afterglow Candidate

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