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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').

10038 results found.

  1. GRB 250327B: VIRT Optical Upper Limit
  2. GRB 250402A: Mondy optical observations
  3. EP250402a: Optical upper limit with Kinder observations
  4. GRB 250403A: SVOM/VT optical observation
  5. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  6. GRB 250402A: SVOM/VT optical counterpart
  7. GRB 250327B: Kilonova-Catcher Observations
  8. GRB250331D: AbAO optical observations
  9. GRB 250328A: AbAO AS-32 Optical Observations
  10. GRB 250322B: GRBAlpha detection
  11. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  12. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  13. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  14. GRB 250328A: Swift/UVOT Detection
  15. GRB 250331A: MAXI/GSC detection
  16. GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
  17. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
  18. GRB 250327B: ALMA detection
  19. GRB 250327B: VLA detection
  20. GRB 250329A: VLT/X-shooter redshift z = 2.921
  21. GRB 250327B: CrAO and SAO RAS Optical Observations
  22. GRB 250322A: GRANDMA/TNOT optical upper limits
  23. GRB 250327B: Las Cumbres optical counterpart detection
  24. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  25. EP250321a: Mondy AZT-33IK Continued Optical Observations
  26. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  27. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  28. GRB 250322A: Gemini-North redshift of candidate host galaxy
  29. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  30. EP250321a: Mondy AZT-33IK Optical Observations
  31. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  32. GRB 250320B: Fermi-LAT detection
  33. EP250321a: Kinder optical follow-up observations
  34. GRB 250321A: Swift detection of a burst
  35. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  36. GRB 250313A: GRBAlpha detection
  37. GRB 250317D: EIRSAT-1 GMOD Detection
  38. GRB 250317B: Mondy AZT-33IK Optical Observations
  39. GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
  40. GRB 250316A: AbAO AS-32 Optical Upper Limit
  41. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  42. GRB 250314A: EP-FXT afterglow detection
  43. GRB 250312B: GRBAlpha detection
  44. EP250315a: optical counterpart candidate detected by Gemini North
  45. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  46. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  47. GRB 250313A: CALET Gamma-Ray Burst Monitor detection
  48. GRB 250313A: SVOM/GRM observation of a bright long burst
  49. GRB 250313A: Fermi-LAT detection
  50. GRB 241213A: VIRT Optical Upper Limit
  51. GRB 241228A: VIRT Optical Upper Limit
  52. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  53. GRB 250308A: CALET Gamma-Ray Burst Monitor detection
  54. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  55. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  56. Fermi-LAT gamma-ray observations of IceCube-250309A
  57. EP250302a: Optical Observations at CrAO and SAO RAS
  58. EP250302a: Mondy Continued Optical Observations
  59. EP250304a: VLT/X-shooter redshift z = 0.200
  60. EP250302a: SVOM/VT optical observation
  61. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  62. EP250302a: SAO RAS optical observations
  63. EP250302a: Kinder optical follow-up observations
  64. EP250302a: Mondy Observations and Optical Light Curve
  65. EP250302a: VLT/MUSE optical redshift z = 1.131
  66. EP250302a: Xinglong F60B optical observation
  67. GRB 250226A: GRANDMA Optical Observations
  68. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  69. EP250228a: Optical observations with Kinder and Swift/UVOT
  70. GRB 250225B: EIRSAT-1 GMOD Detection
  71. GRB 250226A: KAO Optical Upper Limit
  72. GRB 250226A: AbAO AS-32 Optical Upper Limit
  73. GRB 250225B: VLT/HAWKI near-infrared observations
  74. EP250227a: Optical upper limits with Kinder observations
  75. GRB 250205A / EP250205A: further radio observations with the VLA
  76. EP250226a / GRB 250226A: SVOM/VT optical observations
  77. EP250226a/GRB 250226A: Kinder optical follow-up observations
  78. EP250223a: CrAO ZTSH optical observation
  79. GRB 250225B: VLT/FORS2 candidate optical afterglow
  80. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  81. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  82. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  83. EP250223a: Kinder optical follow-up observations
  84. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  85. GRB 250119B: VZLUSAT-2 detection
  86. GRB 250202B: VZLUSAT-2 detection
  87. GRB 250219A: EP-FXT afterglow detection
  88. GRB 250210A: VZLUSAT-2 detection
  89. GRB 250206A: VZLUSAT-2 detection
  90. EP250223a: SVOM/VT optical observation
  91. EP250223a: NOT redshift z = 2.756
  92. EP250223a: NOT optical afterglow candidate
  93. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  94. GRB 250221A: continued Mondy optical observations, brightening afterglow
  95. GRB 250221A: Mondy optical observations
  96. GRB 250221A: Assy optical observations
  97. GRB 250221A: VLT/X-shooter redshift z = 0.768
  98. GRB 250221A: GRANDMA/TAROT Detection
  99. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  100. EP250220a: Optical upper limit with Kinder observations

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