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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').

10039 results found.

  1. EP250220a: Optical upper limit with Kinder observations
  2. GRB 250219A: NOT optical observations
  3. GRB 250219A: SVOM/VT optical counterpart
  4. GRB 250219A: SVOM detection of a burst
  5. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
  6. SVOM/sb25021804: SVOM detection of a long X-ray transient
  7. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  8. LIGO/Virgo/KAGRA S250206dm: observation in AbAO, optical transient near NED/GLADE+ galaxy WISEA J021210.14+514821.7
  9. GRANDMA/OPD observations of GRB250215A
  10. EP250215a / GRB 250215A : NOT optical observations
  11. EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
  12. EP250207b: Xinglong optical upper limit
  13. EP250212a: Xinglong optical upper limit
  14. GRB 250213A: SVOM detection of a burst
  15. GRB 250205A: VIRT Optical Upper Limit
  16. GRB 250210A: GRBAlpha detection
  17. GRB 250205A / EP250205A: radio detection with the VLA
  18. LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
  19. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  20. GRB 241128A: VIRT Optical Upper Limit
  21. EP250207b: Gemini GMOS-N z-band observations
  22. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  23. GRB 250204B: GRBAlpha detection
  24. GRB 250204A: GRBAlpha detection
  25. LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
  26. GRB 250129A: GRANDMA Continued Afterglow Detection
  27. GRB 250206A: EIRSAT-1 GMOD Detection
  28. LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
  29. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  30. LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
  31. LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  32. GRB 250129A: Continued AbAO and Mondy optical observations
  33. LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
  34. GRB 250207B: MAXI/GSC detection
  35. The EP-WXT trigger 01709131290 is likely a flaring star
  36. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  37. EP250205a/GRB 250205A: correction to the source localization
  38. EP250205a/GRB 250205A: Einstein Probe observation
  39. GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
  40. GRB 250205A: SVOM detection of a burst
  41. GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
  42. GRB 250202C: GRBAlpha detection
  43. GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
  44. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  45. GRB 250129A: NOT optical observations of continuining activity
  46. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  47. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  48. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  49. GRB 250127A: CrAO and Terskol optical upper limits
  50. GRB 250128B: NOT optical upper limit
  51. GRB 250129A: OHP/T193 optical and spectroscopy observations
  52. GRB 250129A: NOT optical observations and redshift confirmation
  53. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  54. GRB 250127A: EP-FXT afterglow detection
  55. GRB 241223A: cubesat Avion detection
  56. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  57. GRB 250126A: MAXI/GSC detection
  58. EP250125a: Optical upper limit with Kinder observations
  59. GRB 250121A: CALET Gamma-Ray Burst Monitor detection
  60. EP250108a: AbAO, CMO and Terskol optical upper limits
  61. GRB 250114A: Swift-BAT refined analysis
  62. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  63. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  64. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  65. GRB 241217A / EP241217B: radio detection with the VLA
  66. Swift Trigger 1282245 is not a GRB
  67. GRB 250116A: Fermi-LAT detection
  68. GRB 250114B: SVOM/VT upper limit
  69. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  70. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  71. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  72. Swift GRB 250114A: Global MASTER-Net observations report
  73. GRB 250114A: Swift detection of a burst with an optical counterpart
  74. GRB 250101A: Terskol Zeiss-2000 optical observations
  75. GRB 250107A: VZLUSAT-2 detection
  76. EP250109b: optical upper limits with the Liverpool Telescope
  77. GRB 250109A / EP250109a: GRBAlpha detection
  78. GRB 250107D: GRBAlpha detection
  79. EP250111a: Mondy optical observation
  80. EP250108a: optical follow-up observations with the Liverpool Telescope
  81. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  82. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  83. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  84. GRB 250101A: CMO RC-500 optical observations
  85. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  86. EP250109a: Swift/UVOT non-detection
  87. GRB 250108B: Gemini-North likely redshift z = 2.197
  88. GRB 250108B: Swift-BAT refined analysis
  89. GRB 250101A: Terskol K-800 optical observations
  90. GRB 250108A: Swift/UVOT Upper Limits
  91. GRB 250108A: NOT optical upper limit
  92. Swift GRB 250108B: Global MASTER-Net observations report
  93. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  94. GRB 250108B: Swift/UVOT Upper Limits
  95. GRB 250108B: Swift detection of a burst
  96. GRB 241228B: Fermi-LAT detection
  97. GRB 250106A: SVOM/VT 2nd optical deep observation
  98. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  99. GRB 250103A: NOT spectroscopic redshift
  100. GRB 250103A: Montarrenti Observatory optical detection

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