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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"

2630 results found.

  1. GRB 250108A: Swift/XRT afterglow fading
  2. GRB 250109A: Fermi GBM Observation
  3. GRB 250108B: Gemini-North likely redshift z = 2.197
  4. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  5. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
  7. GRB 241228B: GOTO possible optical counterpart candidate
  8. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 241223A: GOTO optical observations summary
  10. GRB 241105A: JWST photometric observations of the host galaxy
  11. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  12. GRB 241218A: Swift-BAT refined analysis
  13. EP 241217a: NIR detection with P200/WIRC
  14. EP 241217a: Possible J-band detection with WINTER
  15. EP241217a: Kinder optical follow-up observations
  16. EP241107a: VLA Radio Observation
  17. GRB 241212A: Fermi GBM detection
  18. GRB 241206C: GRBAlpha detection
  19. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  20. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  21. EP241201a: 1.6m Mephisto Optical Upper Limits
  22. GRB 241201A: GRBAlpha detection
  23. EP241202b: Kinder optical counterpart candidate
  24. EP241201a: Kinder optical counterpart candidate
  25. Swift-XRT observations of IceCube -241127A
  26. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event
  27. EP241125a: EP detection of an X-ray transient
  28. Konus-Wind detection of GRB 241117A
  29. IPN triangulation of GRB 241117A
  30. EP241021a and EP241026b: Keck/LRIS spectroscopic observations
  31. EP trigger ID 01709065118: Keck/LRIS spectroscopic observations
  32. GRB 241120A: Mondy and AbAO optical observations
  33. GRB 241113A: Possible ATCA Radio detection
  34. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  35. EP 241113a: LBT possible optical counterpart
  36. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  37. LIGO/Virgo/KAGRA S241109bn: ATLAS observations and discovery of the potential counterpart AT2024aawt
  38. GRB 241030A: Mondy optical observations
  39. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  40. EP241101a: Possible detection of an optical counterpart with FTW
  41. GRB 241030A / EP241030a: GMG possible spectroscopic redshift at z ~ 1.4
  42. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  43. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  44. EP 241026b: LBT possible optical counterpart (brightening source)
  45. GRB 240821A: Keck/LRIS spectroscopic observations
  46. GRB 241026A: SAO RAS observations of possible optical afterglow
  47. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  48. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  49. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  50. EP240918a: Swift-XRT observation
  51. EP240918a: YAHPT Optical Upper Limit
  52. GRB 240912A: Swift-BAT refined analysis
  53. Fast X-ray Transient EP240801a: GMRT radio observations
  54. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  55. GRB 240819A as a likely X-Ray Flash
  56. GRB 240828B : Detection of a possible very soft X-ray transient by SVOM/ECLAIRs
  57. EP240801a: Keck/LRIS spectroscopic redshift confirmation
  58. IceCube-240808A - IceCube observation of a high-energy neutrino candidate track-like event
  59. The EP-WXT trigger 01709018832 on August 7th is likely a flaring star
  60. EP240801a: NOT optical observations
  61. IceCube-240725A - IceCube observation of a high-energy neutrino candidate track-like event
  62. IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event
  63. EP240708a: X-ray follow-up observations with Swift/XRT
  64. The EP-WXT source triggered on July 14th is likely a flaring star
  65. GRB 240713A: J-band upper limit from WINTER
  66. GRB240713A: X-ray follow-up observation with EP-FXT
  67. EP240708a: X-ray follow-up observations with EP/FXT and Swift/XRT
  68. EP240703a and EP240703b: Swift/XRT upper limits
  69. EP240702a: Swift/XRT upper limit
  70. EP240626a: Montarrenti Observatory optical upper limit
  71. EP240618a: NOT further optical observations
  72. X-ray transient EP240618a: Fermi/GBM non-detection
  73. EP240618a: Swift/XRT upper limit
  74. EP240617a: tentative Swift/XRT detection of the afterglow
  75. GRB 240615A: possible transient detection from Wendelstein observations
  76. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  77. Swift Trigger 1235109: a possible GRB 240606A
  78. GRB 240603B: Swift detection of a possible burst
  79. GRB 240529A: MASTER prompt OT detection
  80. The EP-WXT source triggered on June 1st is likely a flaring star
  81. EP240518a: GSP optical upper limit
  82. EP240518a: possibly identified with a flare star by EP-FXT
  83. GRB 240514E: A possible candidate BD-21 1074
  84. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  85. GRB 240514B: GOTO candidate optical counterpart
  86. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  87. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  88. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  89. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  90. GRB 240502C: GOTO possible optical counterpart candidates
  91. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  92. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  93. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  94. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  95. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  96. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  97. EP240426a: YAHPT optical upper limit
  98. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  99. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  100. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations

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