The Correlation between X-Ray Line Ionization and Optical Spectral Types of the OB Stars (2009)
Walborn, Nolan R., Nichols, Joy S., Waldron, Wayne L.
Marked correlations are reported between the ionization of the X-ray line spectra of normal OB stars, as observed by the Chandra X-Ray Observatory, and their optical spectral types. These...
An HST/NICMOS view of the prototypical giant HII region NGC604 in M33 (2009)
Barba, Rodolfo H., Apellaniz, Jesus Maiz, Perez, Enrique, Rubio, Monica, Bolatto, Alberto, Farina, Cecilia, ...
We present the first high-spatial resolution near-infrared (NIR) imaging of NGC 604, obtained with the NICMOS camera aboard the Hubble Space Telescope (HST). These NICMOS broadband images reveal new...
Spectroscopic study of the N159/N160 complex in the Large Magellanic Cloud (2009)
Fariña, Cecilia, Bosch, Guillermo L., Morrell, Nidia I., Barbá, Rodolfo H., Walborn, Nolan R.
We present a spectroscopic study of the N159/N160 massive-star forming region south of 30 Doradus in the Large Magellanic Cloud, classifying a total of 189 stars in the field of the complex. Most of...
A New Feature in the Spectrum of the Superluminous LMC Supergiant HDE 269896 (2008)
Corti, Mariela A., Walborn, Nolan R., Evans, Christopher J.
We have found strong selective emission of the N II 5000A complex in the spectrum of the LMC hypergiant HDE 269896, ON9.7 Ia$^+$. Since this object also has anomalously strong He II $\lambda$4686...
The mysterious Of?p class and the magnetic O-star Theta Ori C (2008)
Naze, Yael, Walborn, Nolan R., Martins, Fabrice
In recent years, the stars of the Of?p category have revealed a wealth of peculiar phenomena: varying line profiles, photometric changes, and X-ray overluminosity are only a few of their...
A Three-Decade Outburst of the LMC Luminous Blue Variable R127 Draws to a Close (2008)
Walborn, Nolan R., Stahl, Otmar, Gamen, Roberto C., Szeifert, Thomas, Morrell, Nidia I., Smith, Nathan, ...
The paradigmatic Luminous Blue Variable R127 in the Large Magellanic Cloud has been found in the intermediate, peculiar early-B state, and substantially fainter in visual light, signaling the final...
Townsend, Rich, Cohen, David H, Dessart, Luc, Hubrig, Swetlana, Naze, Yaël, Petit, Véronique, ...
Magnetic fields are unexpected in massive stars, due to the absence of a sub-surface convective dynamo. However, advances in instrumentation over the past three decades have led to their detection in...
The mysterious Of?p class and the magnetic O-star theta(1) Ori C: Confronting observations (2008)
Naze, Yaël, Walborn, Nolan R., Martins, Fabrice
In recent years, the stars of the Of?p category have revealed a wealth of peculiar phenomena: varying line profiles, photometric changes, and X-ray over-luminosity are only a few of their...
HD 148937: A multiwavelength study of the third galactic member of the Of?p class (2008)
Naze, Yaël, Walborn, Nolan R., Rauw, Grégor, Martins, Fabrice, Pollock, A. M. T., Bond, Howard E.
Three Galactic O-type stars belong to the rare class of Of? p objects: HD 108, HD 191612, and HD 148937. The first two stars show a wealth of phenomena, including strong X-ray emission, light...
The mysterious of?p class and the magnetic o-star _1 ori c: confronting observations (2008)
Fabrice Martins, Nolan R. Walborn, Yaël Nazé, L. Carigi, M. Peimbert
En a~nos recientes, las estrellas de la categora Of?p han revelado una multitud de fenomenos peculiares: per les de lneas variables, cambios fotometricos y exceso de luminosidad en rayos X son...
THE HOT GASEOUS HALO OF THE LMC (2007)
Elizabeth G. Jaxon, J. Chris Howk, Nolan R. Walborn, You-hua Chu, Bart P. Wakker
Interstellar C iv absorption line studies of the hot gaseous halo of the Large Magellanic Cloud (LMC) have been hindered by non-ideal selections of early-type probe stars in regions where C +3 can be...
Towards an understanding of the Of ? p star HD 191612: optical spectroscopy (2007)
Howarth, Ian D., Walborn, Nolan R., Lennon, Danny J., Puls, Joachim, Naze, Yaël, Annuk, K, ...
We present extensive optical spectroscopy of the early-type magnetic star HD 191612 (O6.5f ? pe-O8fp). The Balmer and He i lines show strongly variable emission which is highly reproducible on a...
Towards an understanding of the Of?p star HD 191612: optical spectroscopy (2007)
Howarth, Ian D., Walborn, Nolan R., Lennon, Danny J., Puls, Joachim, Naze, Yael, Annuk, K., ...
We present extensive optical spectroscopy of the early-type magnetic star HD 191612 (O6.5f?pe-O8fp). The Balmer and HeI lines show strongly variable emission which is highly reproducible on a...
The Galactic O Star Catalog V.2.0 (2007)
Sota, A., Apellániz, J. Maíz, Walborn, Nolan R., Shida, R. Y.
The Galactic O star catalog (GOS) is an ambitious project to provide as much information regarding these types of objects as possible. The first version of the catalog (GOS v1) included data for 378...
The stellar upper mass limit in the solar neighborhood (2007)
Apellániz, J. Maíz, Walborn, Nolan R., Morrell, N. I., Nelan, E. P., Niemela, V. S., Benaglia, P., ...
We are using HST GO programs 10205, 10602, and 10898 to test the stellar upper mass limit in the solar vicinity by attempting to detect optical close companions, thus lowering the calculated...
Optically observable zero-age main-sequence O stars (2007)
A list of 50 optically observable O stars that are likely on or very near the ZAMS is presented. They have been selected on the basis of five distinct criteria, although some of them exhibit more...
Pismis 24-1: The Stellar Upper Mass Limit Preserved (2006)
Apellániz, J. Maíz, Walborn, Nolan R., Morrell, N. I., Niemela, V. S., Nelan, E. P.
Is there a stellar upper mass limit? Recent statistical work seems to indicate that there is and that it is in the vicinity of 150 solar masses. In this paper we use HST and ground-based data to...
Naze, Yael, Rauw, Gregor, Pollock, A. M. T., Walborn, Nolan R., Howarth, Ian D.
We present the analysis of phase-resolved X-ray and optical observations of the peculiar hot star HD191612 (Of?p). This star is known to display line-profile variations that are recurrent with a...
Multiwavelength Systematics of OB Spectra (2006)
The systematics of OB spectra are reviewed in the optical domain, dominated by photospheric lines, and in the far ultraviolet (both IUE and FUSE ranges), in which the stellar-wind profiles dominate....
A period and a prediction for the Of ? p spectrum alternator HD 191612 (2004)
Walborn, Nolan R., Howarth, Ian D., Rauw, Grégor, Lennon, Daniel J., Bond, Howard E., Negueruela, Ignacio, ...
The observational picture of the enigmatic O-type spectrum variable HD 191612 has been sharpened substantially. A symmetrical, low-amplitude light curve with a period near 540 days has recently been...
A Period and a Prediction for the Of?p Spectrum Alternator HD 191612 (2004)
Walborn, Nolan R., Howarth, Ian D., Rauw, Gregor, Lennon, Daniel J., Bond, Howard E., Negueruela, Ignacio, ...
The observational picture of the enigmatic O-type spectrum variable HD191612 has been sharpened substantially. A symmetrical, low-amplitude light curve with a period near 540 d has recently been...
Carina's Defiant Finger: HST Observations of a Photoevaporating Globule in NGC3372 (2004)
Smith, Nathan, Barba, Rodolfo, Walborn, Nolan R.
We present HST/WFPC2 images of a prominent externally-ionized molecular globule in the Carina Nebula (NGC3372), supplemented with ground-based IR images and visual-wavelength spectra. This molecular...
A CNO Dichotomy among O2 Giant Spectra in the Magellanic Clouds (2004)
Walborn, Nolan R., Morrell, Nidia I., Howarth, Ian D., Crowther, Paul A., Lennon, Daniel J., Massey, Philip, ...
From a survey of the 3400 A region in the earliest O-type spectra, we have found that two of the four O2 giants observed in the LMC have the OIV lines there stronger than the NIV, while the other two...
Kinematics and Ultraviolet to Infrared Morphology of the Inner Homunculus of η Carinae (2004)
Smith, Nathan, Morse, Jon A., Gull, Theodore R., Hillier, D. John, Gehrz, Robert D., Walborn, Nolan R., ...
We present the first ultraviolet and optical images of η Car and itscircumstellar Homunculus nebula, obtained with the Advanced Camera forSurveys/High Resolution Camera (ACS/HRC) on board the Hubble...
Tight LMC massive star clusters R 127 and R 128 (2003)
Heydari-Malayeri, M., Meynadier, F., Walborn, Nolan R.
We study the Large Magellanic Cloud (LMC) star clusters R 127 and R 128 using imaging and spectroscopy obtained at the ESO NTT telescope. An advanced image restoration technique allows us to resolve...
Jaxon, Elizabeth G., Guerrero, Martin A., Howk, J. Chris, Walborn, Nolan R., Chu, You-Hua, Wakker, Bart P.
Interstellar C IV absorption line studies of the hot gaseous halo of the Large Magellanic Cloud (LMC) have been hindered by non-ideal selections of early-type probe stars in regions where C+3 can be...
Brandner, Wolfgang, Grebel, Eva K., Barba, Rodolfo H., Walborn, Nolan R., Moneti, Andrea
We present the detection of an intermediate-mass pre-main-sequence population embedded in the nebular filaments surrounding the 30 Doradus region in the Large Magellanic Cloud (LMC) using HST/NICMOS....
Compact star clusters of the LMC H ii region N11 C (2000)
Heydari-Malayeri, Mohammad, Royer, Pierre, Rauw, Grégor, Walborn, Nolan R
Based on imaging and spectroscopy obtained at the ESO NTT telescope and using an efficient image analysis algorithm, we study the core of the LMC OB association LH 13, particularly the two compact...
HST/WFPC2 and VLA Observations of the Ionized Gas in the Dwarf Starburst Galaxy NGC 4214 (2000)
MacKenty, John W., Maíz-Apellániz, Jesús, Pickens, Christopher E., Norman, Colin A., Walborn, Nolan R.
We present new H alpha and [O III] 5007 narrow band images of the starbursting dwarf galaxy NGC 4214, obtained with the WFPC2 onboard HST, together with VLA observations of the same galaxy. The HST...
Some spectroscopic characteristics of OB stars--[microform]. (1970)
Thesis (Ph. D.)--University of Chicago, 1970.
Some spectroscopic characteristics of the OB stars. (1970)
Thesis (Ph. D.)--University of Chicago, Dept. of Astronomy.