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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"

27323 results found.

  1. GRB 250114B: Swift-XRT afterglow detection
  2. EP250108a: MeerKAT radio upper limit
  3. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  4. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  5. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  6. IPN triangulation of GRB 250113A
  7. GRB 250114B: Liverpool Telescope optical upper limit
  8. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  9. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  10. GRB 250114B: Swift-XRT observations
  11. GRB 250114A: LCO optical counterpart detection.
  12. GRB 250114B: OHP/T193 optical upper limit
  13. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  14. GRB 250114A: Swift-XRT refined Analysis
  15. GRB 250114A: LCOGT optical afterglow i-band detection
  16. GRB 250114B : GIT optical upper limit
  17. EP250111a: SAO RAS optical upper limit
  18. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  19. GRB 250114B: a short GRB detected with INTEGRAL
  20. GRB 250114A: Enhanced Swift-XRT position
  21. GRB 250114A: REM detection of the optical and NIR counterpart
  22. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  23. Swift GRB250114A: Global MASTER-Net OT detection
  24. GRB 250114A: LCO optical observations
  25. GRB 250114A: TRT optical observations
  26. GRB 250114A: Swift detection of a burst with an optical counterpart
  27. GRB 250101A: Terskol Zeiss-2000 optical observations
  28. EP250108a / AT 2025kg: SAO RAS optical observations
  29. EP241021a: SMA radio observation
  30. GRB 250113A: SVOM/GRM observation of a long burst
  31. GRB 250107A: VZLUSAT-2 detection
  32. EP250109b: optical upper limits with the Liverpool Telescope
  33. GRB 250106A: Swift-XRT afterglow detection
  34. EP250111a: KAIT optical observations
  35. GRB 250109A / EP250109a: Mephisto optical upper limits
  36. EP250108a: Mephisto detection
  37. EP250111a: Mondy optical observation
  38. EP250108a / AT 2025kg: LCO optical observations
  39. EP250108a / AT 2025kg: Swift UVOT detections
  40. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  41. EP250111a: NOT likely optical counterpart
  42. GRB 250101B: Fermi GBM Observation
  43. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  44. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  45. GRB 250108A: Swift/XRT afterglow fading
  46. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  47. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  48. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  49. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  50. GRB 250101A: CMO RC-500 optical observations
  51. GRB 250109A: Fermi GBM Observation
  52. EP250108a: NOT optical observations
  53. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  54. GRB 250109a: GMG Optical Upper Limit
  55. EP250109a: Swift/UVOT non-detection
  56. IPN triangulation of GRB 250107D (short/hard)
  57. EP250108a: Liverpool Telescope likely optical counterpart
  58. GRB 250108B: Swift-BAT refined analysis
  59. GRB 250108B: 1.3m DFOT upper limit
  60. GRB 250108B: REM optical/NIR upper limits
  61. GRB 250101A: Terskol K-800 optical observations
  62. EP250109a: Swift/XRT non-detection
  63. GRB 250108A: Swift/UVOT Upper Limits
  64. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  65. GRB 250108A: NOT optical upper limit
  66. EP250108a: EP-WXT detection of an X-ray transient
  67. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  68. GRB 250108B: Swift-XRT refined Analysis
  69. GRB 250103A: 1.6m Mephisto optical observations
  70. GRB 250108A: Swift-XRT afterglow detection
  71. GRB 250108A:SVOM/VT optical candidate
  72. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  73. GRB 250108B: Swift/UVOT Upper Limits
  74. GRB 250103A: Swift-XRT afterglow detection
  75. GRB 250108B: Enhanced Swift-XRT position
  76. GRB 250108B: Swift detection of a burst
  77. GRB 250107A: Fermi GBM Observation
  78. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  79. GRB 250106A: SVOM/VT 2nd optical deep observation
  80. GRB 250101A: J band upper limit by SYSU 80cm telescope
  81. EPWXT01709129925: Xinglong optical observations
  82. GRB 250106A: NOT optical observations
  83. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  84. GRB 250103B: REM optical/NIR upper limits
  85. GRB 250101A: REM optical/NIR counterpart detection
  86. GRB 250106A: Swift-XRT observations
  87. GRB 250106A: SVOM/VT optical candidate
  88. The EP-WXT trigger 01709129925 is likely a flaring star
  89. GRB 250103B: Swift-XRT refined Analysis
  90. GRB 250103B: LCO/1m optical afterglow candidate detection
  91. GRB 250103A: Bassano Bresciano Observatory upper limit
  92. GRB 250103A: Swift-XRT observations
  93. GRB 250101A: 1.3m DFOT optical afterglow detection
  94. GRB 241229A: 1.3m DFOT upper limit
  95. GRB 241228B: 1.3m DFOT Optical observations
  96. GRB 241228A: 1.3m DFOT upper limit
  97. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  98. GRB 250103A: Montarrenti Observatory optical detection
  99. GRB 250101A: further LCOGT optical afterglow observations
  100. GRB 250103A: TSHAO optical upper limit

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